REVIEW article

Front. Genet., 07 June 2019

Sec. Genetics of Common and Rare Diseases

Volume 10 - 2019 | https://doi.org/10.3389/fgene.2019.00507

Genetic and Epigenetic Studies in Diabetic Kidney Disease

  • Center for Pathophysiology, School of Basic Medicine and Clinical Pharmacy, China Pharmaceutical University, Nanjing, China

Abstract

Chronic kidney disease is a worldwide health crisis, while diabetic kidney disease (DKD) has become the leading cause of end-stage renal disease (ESRD). DKD is a microvascular complication and occurs in 30–40% of diabetes patients. Epidemiological investigations and clinical observations on the familial clustering and heritability in DKD have highlighted an underlying genetic susceptibility. Furthermore, DKD is a progressive and long-term diabetic complication, in which epigenetic effects and environmental factors interact with an individual’s genetic background. In recent years, researchers have undertaken genetic and epigenetic studies of DKD in order to better understand its molecular mechanisms. In this review, clinical material, research approaches and experimental designs that have been used for genetic and epigenetic studies of DKD are described. Current information from genetic and epigenetic studies of DKD and ESRD in patients with diabetes, including the approaches of genome-wide association study (GWAS) or epigenome-wide association study (EWAS) and candidate gene association analyses, are summarized. Further investigation of molecular defects in DKD with new approaches such as next generation sequencing analysis and phenome-wide association study (PheWAS) is also discussed.

Introduction

Diabetes is a major public health problem that is approaching epidemic proportions globally. According to the latest report from the IDF, the prevalence of diabetes will increase from 425 million persons in 2017 to 629 million by 2045 (IDF 20171). Diabetic kidney disease (DKD, previously termed diabetic nephropathy, DN) is a microvascular complication and progresses gradually over many years in approximately 30–40% of individuals with T1D and T2D mellitus (; Thomas et al., 2015; ). DKD is now the main cause of chronic kidney disease (CKD) worldwide and the leading cause of end-stage-renal disease (ESRD) requiring renal replacement therapy (dialysis or transplantation). The presence of CKD is the single strongest predictor of mortality for persons with diabetes (; ). Pathological findings in DKD include glomerular hypertrophy, mesangial matrix expansion, reduced podocyte number, glomerulosclerosis, tubular atrophy and tubulointerstitial fibrosis. Clinical criteria used to diagnose the subjects with DKD are urine ACR higher than 300 mg/g, while microalbuminuria is diagnosed when ACR is between 30–300 mg/g (). Accumulating evidence has indicated that podocyte loss and epithelial dysfunction play important roles in DKD pathogenesis with further progression associated with inflammation but the exact molecular mechanisms responsible for DKD are not fully known (; ; ).

Both clinical and epidemiological studies have demonstrated that there is familial aggregation of DKD in different ethnic groups, indicating that genetic factors contribute to development of the disease. Furthermore, genetic risk factors in DKD interact with the environmental factors (for example, lifestyle, diet and medication) (; ; Thomas et al., 2012; ). Figure 1 is a schematic diagram representing the relationship between genetic, epigenetic and environmental factors that are involved in the development and progression of DKD. Genetic studies of DKD are mainly focused on association analyses between genomic DNA variation (for example, single nucleotide polymorphisms, SNPs, copy number variants, CNVs, and microsatellites) and clinical phenotypes of the disease (; ; Thomas et al., 2012; ). Epigenetics studies of DKD examine potentially heritable changes in gene expression that occur without variation in the original DNA nucleotide sequence (Villeneuve and Natarajan, 2010; ; Thomas, 2016; ). Therefore, epigenetic studies of DKD may provide information to help understand how environmental factors modify the expression of genes that are involved in DKD progression. Combined genetic, epigenetic and phenotypic studies together may generate information to understand new pathogenic pathways and to search for new biomarkers for early diagnosis and prediction as part of prevention programs in DKD. The results may also be useful in finding novel targets for the treatment of DKD.

FIGURE 1

SNPs are the most common form of genomic DNA variation. The updated dbSNP database of more than 500 million reference SNPs (rs) with allele frequency data2 has provided fundamental information for genetic studies of complex diseases including, DKD. The genetic studies in DKD have implicated previously unsuspected biological pathways and subsequently improved our knowledge for understanding of the genetic basis of the disease. For most common traits studied in DKD, however, the identified genes and their SNPs only explain a fraction of associated risk, suggesting that human genomic DNA variations are only a part of underlying susceptibility to DKD. This has led to evolving interest in epigenetics to help explain some of the missing heritability of DKD. Epigenetic mechanisms mainly consist of DNA methylation, chromosome histone modification and non-coding RNA (ncRNA) regulation (; ). Epigenetic related ncRNAs include miRNA, siRNA, piRNA, and lncRNA (). There are more than 30,000 identified CpG islands in the human genome. Detailed information for these CpG islands can be found in the public database3. The CpG islands are defined as stretches of DNA > 200 bp long with a GC percentage greater than 50% and an observed-to-expected CpG ratio of more than 60%. The CpG islands are often found at promoters and contain the 5′ end of the transcript, while DNA methylation occurs at 5′-cytosines of “CpG” dinucleotides4 (). In DKD, the effects of DNA methylation have been studied in terms of transgenerational inheritance of the disease to explore environmental and other non-genetic factors that may influence epigenetic modifications in the genes involved in DKD (; ). Identification of differentially methylated CpG sites in promoters or other functional regions of genes and the analysis of the DNA methylation changes that are associated with DKD have become the most common approaches used in epigenetic studies of the disease (Villeneuve and Natarajan, 2010; ; Thomas, 2016). Furthermore, ncRNAs, particularly long ncRNAs are known to be involved in epigenetic processes. ncRNAs certainly play an important role in chromatin formation, histone modification, DNA methylation and consequently gene transcription silencing.

Genetic and epigenetic studies of DKD, initially using candidate gene approaches and more recently at genome-wide scale (known as GWAS and EWAS), have been undertaken to identify many genes conferring susceptibility or resistance to DKD. In this review, clinical phenotypes, research approaches and experimental designs that have been used for genetic and epigenetic studies of DKD are described. These research approaches and experimental designs can also be used for study of CKD. Current information from genetic and epigenetic studies of DKD is summarized. Further investigation of molecular defects in DKD with new generation sequencing analyses and phenome-wide association studies (PheWAS) are discussed.

Biological Material, Research Approaches and Study Designs Used in Genetic and Epigenetic Investigations of Diabetic Kidney Disease

Two major research approaches either at genome-wide scale or focused on candidate gene(s) have been widely used for comparative studies between cases (patients with DKD) and controls (diabetes patients without DKD). Case-control studies by recruiting large numbers of subjects can increase the statistical power of reported associations. The aim is to discover the genes presented differentially in genomic structure or genetic expression. Genome-wide or epigenome-wide association studies (GWAS or EWAS) are hypothesis-generating approaches (; ; ). These study designs have benefited from rapid development of human genome research, including the creation of publicly available databases of SNPs, haplotypes and CpG islands and the rapid technical improvements in analyzing genomic variation using high-throughput techniques and high-density SNP or CpG arrays. Another approach is to focus on candidate genes and study a more limited number of genes potentially involved in the pathogenesis of DKD based upon our known knowledge or hypothesis. In genetic and epigenetic studies of DKD, DNA samples used are commonly extracted from peripheral blood samples because they are clinically accessible. have comparatively analyzed DNA methylation changes related to BMI by using both approaches of whole-blood DNA methylation profiling and adipose tissue specific methylation measurement. Data suggests that analysis of blood DNA methylation is worthwhile because the results can reflect the DNA methylation changes in relevant tissues for a particular phenotype. Nevertheless, there is still limited information concerning the correlation between whole blood DNA methylation profiles and kidney tissue specific DNA methylation changes in part due to the heterogeneity of cell types within the kidney. To improve the tissue specific DNA methylation analysis of kidney diseases, including DKD, it is necessary to construct biobanks of renal biopsies. Karolinska Institutet has established a biobank in KaroKidney with more than 750 renal biopsies5. The advantages and limitations of these two approaches, as well as the clinical materials and experimental design used in genetic and epigenetic studies of DKD are summarized in Table 1.

Table 1

StudyAdvantageDisadvantage
Clinical materialBlood or salivaClinical accessiblePossible bias from mixed cell types
Kidney tissuesGene specific methylation and expression can be analyzedDifficult to access
Renal cell linesIntervention and mechanism studyIn vitro experiment
Research approachCandidate gene DNA variation or methylation analysisStudy of candidate genes with potential biological functionsLess information on the studied genes
Global genomic DNA variation or methylation analysesGeneral information of DNA polymorphisms and methylation in genome wide scaleAnalysis of repeated sequence alteration and methylation changes Lack of gene specific information
Genome or epigenome-wide association studiesNumerous SNP, CNV or CpG sites methylation information in genome wide scaleHigher cost Strict validation is needed
Experimental designCase-control studyMany cohorts existDifficult to control genetic and environmental confounders
Twin studyControl for geneticsFew large cohorts
Family studyStudy of potential inheritanceFew large cohorts
Longitudinal studyDetermine causalityTime consuming

Clinical material, research approaches and experimental designs used in genetic and epigenetic studies of diabetic kidney disease.

CNV, copy-number variation; CpG sites, the regions of DNA where a cytosine nucleotide is followed by a guanine nucleotide in the linear sequence of bases along its 5′ → 3′ direction; SNP, single-nucleotide polymorphism.

Recent Data From Genetic Studies in Diabetic Kidney Disease

Considerable amounts of data from genetic studies in DKD have accumulated. A list of the genes that are reported to be associated with susceptibility or resistance to DKD are summarized in Table 2. The genes are listed in alphabetical order. Surprisingly, there are more than 150 genes. Most of them have been identified by genetic association studies employing candidate gene approaches over the past 20 years. Furthermore, a number of GWAS in DKD have been published in the last 10 years. By using GWAS approaches, approximately 33 genes have been found to be associated with the DKD, i.e., ABCG2, AFF3, AGER, APOL1, AUH, CARS, CERS2, CDCA7/SP3, CHN2, CNDP1, ELMO1, ERBB4, FRMD3, GCKR, GLRA3, KNG1, LIMK2, MMP9, NMUR2, MSRB3/HMGA2, MYH9, PVT1, RAET1L, RGMA/MCTP2, RPS12, SASH1, SCAF8/CNKSR3, SHROOM3, SLC12A3, SORBS1, TMPO, UMOD, and ZMIZ1 (; , ; ; Thameem et al., 2013; ; ; ; Teumer et al., 2016; ; ; ; van Zuydam et al., 2018). However, most of these genes (∼80%) reportedly associated with DKD still need to be confirmed by further replication studies and detailed analysis of their functional role in DKD in experimental models. Polymorphisms in these candidate genes association with DKD studies are listed in Table 2A, while their potential biological relevance and genetic effects in DKD are briefly described. Of them, 34 genes are originally predicted by GWAS and the statistical association with DKD summarized in Table 2B.

Table 2A

Gene symbolGenomic DNA polymorphismsDisease
ABCG2rs2231142T2D-uric acid
ACACBrs2268388T2D-DKD
ACErs4646994 (289bp Alu I/D), rs4343, rs1799752, rs1800764, rs12449782T1D-DKD, T2D-DKD, T2D-ESRD
ADPOQrs266729, rs17300539, rs2241766, rs1063537, rs2241767, rs2082940T1D-DKD, T2D-DKD
ADRB2Arg16Gly, Gln27GluT2D-eGFR
AFF3rs7583877T1D-ESRD
AGERrs2070600, rs2071288T2D-DKD
AGTrs5050, rs4762, Met235ThrT2D-DKD
AGTR1rs5186, +1166A/C, -106C/T, rs12695897T1D-DKD, T2D-ESRD
AGTR2+1675G/A, +1818A/TT1D-DKD
AKR1B1rs759853T2D-DKD, T2D-ESRD
ALOX12rs14309T2D-DKD+CVD
APOEe4 allele, e2/e3 allelesT2D-DKD
APOL1rs136161, rs713753, rs767855, Ser342Gly, Ile384MetT2D-ESRD
AUHrs773506T2D-ESRD
BIDrs181390T1D-ESRD
CALD1rs3807337T1D-DKD
CARSrs452041, rs739401T1D-DKD, T2D-DKD
CASRrs3804594T2D-DKD
CATrs1001179T2D-ESRD
CERS2rs267734, rs267738T1D-DKD, T2D-DKD
CDH13rs11646213, rs3865188T1D-ESRD
CFHrs379489T2D-ESRD
CHN2rs39059T1D-DKD
CNDP1(CTG)5, rs4892249, rs6566815, rs2346061, rs1295330, rs6566810, rs11151964, rs17817077T2D-dialysis, T2D-DKD, T1D-ESRD, T2D-ESRD
CNDP2rs7577, rs4892247T2D-ESRD
CYP11B2-344T/CT2D-DKD
COQ5rs1167726, rs614226, rs1167725T1D-ESRD
COX6A1rs12310837T1D-ESRD
COX10rs7213412T1D-ESRD
CUBNrs1801239T1D-albuminuria, T2D-ESRD
CYBArs4673, rs9932581T1D-ESRD, T2D-DKD
eNOS-786C/T, +786T/C, +894G/T, Glu298AspT1D-DKD, T2D-DKD
ELMO1rs741301, rs1345365, rs11769038, rs10951509, rs1882080, rs6462776, rs6462777T1D-DKD, T1D-ESRD, T2D-DKD
ENPP1rs1044498, rs7754586, rs1974201T1D-DKD, T2D-DKD, T2D-ESRD
EPHX2rs751141T2D-DKD
EPOrs1617640T1D-ESRD, T2D-DKD
ERBB4rs7588550T1D-DKD
ESR1rs12197043, rs11964281, rs1569788, rs9340969T2D-DKD
FNDC5rs16835198T2D-DKD
FRMD3rs1888747, rs10868025, rs942280, rs942278, rs942263, rs1535753, rs2378658, rs13288659T1D-ESRD, T2D-DKD
GAS6Intron 8, c.834+7G/AT2D-DKD
GATCrs2235222, rs7137953T1D-ESRD
GCKrs730947T2D-ESRD
GCKRrs1260326T2D-eGFR
GFPT2Ile147ValT2D-DKD
GLRA3rs1564939T1D-AER
GPX1rs3448T1D-DKD
GREM1rs1129456T1D-DKD
GSTP1rs1695 (Ile105Val)T2D-DKD, T2D-ESRD
H19-IGF2 clusterrs2839698, rs10732516, rs201858505T2D-DKD
HIF1αrs11549465 (Pro582Ser)T1D-DKD, T2D-DKD
HO1-413T/AT2D-DKD
HSP70rs2763979, rs2227956T2D-DKD
ICAM1rs5498T1D-DKD, T2D-DKD
IGFBP1rs1065780, rs3828998, rs3793344, rs4619T2D-DKD
IGF2BP2rs4402960T2D-DKD
IL1α-889C/TT2D-DKD
IL1βrs16944, -511C/TT2D-DKD
IL6-634G/C, -174G/C, rs1800796, rs1524107, rs1800795, rs1800796T2D-DKD
IL10-819T/C, -592A/C, -1082A/GT2D-DKD
IL18rs360719T2D-DKD
INSRrs2059806T2D-DKD
IRAK4rs4251532T2D-DKD
KCNQ1I/D in intron 12, rs2237897T2D-eGFR, T2D-DKD
KLRA1rs2168749T1D-ESRD
KNG1+7965C/TT1D-DKD
LIMK2rs2106294T2D-ESRD
LTAThr60AsnT1D-DKD
LRP2rs17848169T2D-ESRD
MAPRE1P2rs1670754T1D-ESRD
MCF2L2Leu359IleT1D-DKD
MGP-138T/CT2D-DKD
MMErs3796268, rs3773885T1D-DKD
MMP12rs1277718, rs652438, Asn357SerT1D-DKD
MMP9(CA)n in promoter, rs481480, rs2032487, rs4281481, rs3752462, rs3918242T2D-ESRD, T2D-DKD
NMUR2rs982715, rs4958531, rs4958532, rs4958535T1D-DKD
MSCrs9298190T1D-ESRD
MT2Ars28366003T2D-DKD
MTHFRrs1801133T1D-DKD, T2D-DKD
MTORrs7212142T2D-DKD
MyD88rs6853T2D-DKD
MYH9rs5750250T2D-ESRD
NCALDrs1131863, +999T/A, +1298A/C, +1307A/GT2D-DKD
near IRS2rs1411766T1D-DKD, T1D-ESRD, T2D-DKD
NOS2rs1137933T2D-DKD
NOS3rs3918188, Glu298Asp, Gly894ThrT1D-DKD, T2D-DKD
NQO1rs1800566T2D-DKD
NPHS1rs35238405T2D-ESRD
NPYLeu7ProT1D-DKD
PACRGrs2147653, rs1408705T1D-ESRD
PAI14G/5GT2D-DKD
PARK2rs4897081T2D-DKD
PARP1C410T, G1672A, Val762AlaT2D-DKD
PFKFB2rs17258746, rs11120137T2D-DKD
PLEKHH2rs1368086, rs725238, rs11886047T1D-DKD
PLXDC2rs1571942, rs12219125T1D-DKD
PON1Leu55Met, Gln192ArgT1D-DKD, T2D-ACR
PON2rs12704795T2D-DKD
PPARGrs1805192, rs1801282T1D-DKD, T2D-DKD
PPARG2Pro12AlaT2D-eGFR, T2D-DKD
PPARGC1AGly482SerT2D-DKD
PRKAA2rs2746342, rs10789038T2D-DKD
PROX1rs340841T2D-DKD
PSMD9rs1043307, rs14259, +460A/G, +437T/C, Glu197GlyT2D-DKD
PRKCB1-1504C/T, -546C/T, -348A/G, -278C/T, -238C/GT1D-DKD, T2D-eGFR
PTX3rs2305619, rs2120243T2D-DKD
PVT1rs2648875, rs2720709T2D-ESRD
RAGE-429T/C, -374T/A, +2184A/GT1D-ESRD, T2D-DKD
RAET1Lrs1543547T1D-DKD
RBP4rs3758538, rs10882278, rs7094671, rs12766992T2D-eGFR
RENrs41317140T2D-DKD
RREB1rs9379084, rs41302867T2D-ESRD
TOP1MTrs7387720, 724037T1D-ESRD
TXNRD2rs17745445, rs17745433, rs5992495, rs5992493T1D-ESRD
RPS12rs7769051T2D-ESRD
RTN1rs1952034, rs12431381, rs12434215T2D-ESRD
SASH1rs6930576T2D-ESRD
SCAF8/CNKSR3rs12523833T2D-DKD
SEMA6D/SLC24A5rs12917114T1D-ESRD
SERPINB7rs1720843T2D-DKD
SERPINE14G/5G polymorphismT2D-DKD
SHROOM3rs1739721T2D-eGFR
SIK1rs2838302T1D-ESRD
SIRT1rs4746720T2D-DKD
SLC2A1rs3820589, HaeIII polymorphismT1D-DKD, T2D-DKD
SLC2A2+16459C/TT1D-DKD
SLC2A9rs11722228, rs3775948T2D-uric acid
SLC12A3rs11643718T2D-DKD, T2D-ESRD
SOD1rs2234694T1D-DKD
SOD2Ala9Val, Val16AlaT1D-DKD
SORBS1rs1326934T1D-DKD
SOX2rs11915160T1D-DKD
SPTLC2rs176903T1D-ESRD
SUMO4rs237025T2D-DKD
SUV39H2rs17353856T1D-DKD
TCF7L2rs7903146T2D-DKD
TGFβ1rs1800470T1D-DKD, T2D-DKD
THPrs12444268T1D-DKD
TMPOrs4762495T1D-ESRD
TNFαrs1800629, rs1800470, rs1800469, rs1800630, rs1799964T2D-DKD, T2D-ESRD
TRAF6rs16928973T2D-DKD
TRIB3rs2295490T2D-DKD
UMODrs12917707, rs13333226T2D-DKD
VDRRaql variantT2D-DKD
VEGF-1499C/T, rs2010963T1D-DKD, T2D-DKD
VEGFArs3025021T1D-DKD
WNT4/ZBTB40rs12137135T1D-ESRD
ZMIZ1rs1749824T1D-ESRD
miRNA-146ars2910164T1D-DKD, T2D-DKD
miRNA-125rs12976445T2D-DKD

Current data from genetic association studies in diabetic kidney disease by using candidate gene approach.

Table 2B

Gene symbolGenomic DNA polymorphismsP-valueDiseaseReferences
ABCG8rs4148217P = 0.003T2D-ESRD
AFF3rs7583877, rs7562121P = 1.2 × 10(-8) and <1 × 10(-6)T1D-ESRD,
AGERrs2070600, rs2071288P < 0.001T2D-DKD
AGTR1rs12695897P = 0.032T2D-ESRD
APOL1rs136161, rs713753, rs767855P = 0.006–0.037T2D-ESRD
AUHrs7735506P = 2.57 × 10(-4)T2D-ESRD
BIDrs181390P = 0.006T1D-ESRD
CARSrs452041, rs739401P = 3.1 × 10(-6)T1D-DKD, T2D-DKD
CERS2rs267734, rs267738P = 0.0013 and 0.0015T1D-DKD, T2D-DKD
CDCA7-SP3rs4972593P = 5 × 10(-8)T1D-ESRD in women
CHN2rs17157914P = 0.029T2D-ESRD
CNDP1rs4892249, rs6566815P = 0.0043 and 0.0076T2D-ESRD
CNTNAP2rs1989248P < 1 × 10(-6)T1D-ESRD
ELMO1rs741301 rs1345365, rs11769038, rs10951509, rs1882080, rs6462776, rs6462777P = 0.004T2D-DKDWu et al., 2013
ERBB4rs7588550P = 2.1 × 10(-7)T1D-DKD
FRMD3rs942278, rs1888747, rs10868025, rs942280, rs942263, rs1535753, rs2378658, rs13288659P = 5.0 × 10(-7)T1D-ESRD, T2D-ESRD;
GABRR1rs9942471P = 4.5 × 10(-8)T2D-DKDvan Zuydam NR
GCKRrs1260326P = 3.23 × 10(-3)T2D-eGFR
GLRA3rs1564939P = 0.0013T1D-AER
KLKBrs4253311P = 5.5 × 10(-8)Plasma renin activity
KNG1rs5030062P = 0.001Plasma renin activity
LIMK2rs2106294, rs4820043P = 7.49E-04 and 0.001T2D-ESRD
MMP9rs481480, rs2032487, rs4281481P = 0.038, 0.045 and 0.048 P = 0.053, 0.054 and 0.055T2D-ESRD T2D-DKD;
MYH9rs5750250, rs92280P = 4.3 × E(-4) P = 3 × 10(-7)T2D-ESRD;
PTPN13rs61277444P < 1 × 10(-6)T1D-DKD
PVT1rs2648875, rs2720709P = 1.8–2.1 × (-7)T2D-ESRD
RAET1Lrs1543547P = 1 × 10(-5)T1D-DKD
RGMA-MCTP2rs12437854P = 2 × 10(-9)T1D-ESRD
RPS12rs9493454P = 8.79 × 10(-4)T2D-ESRD
SHROOM3rs1739721P = 3.18 × 10(-3)T2D-eGFR
SLC12A3rs11643718P = 0.021T2D-DKD, T2D-ESRDTanaka et al., 2003
TMPOrs4762495P = 0.0006T1D-ESRD
UMODrs12917707P = 8.84 × 10(-4)T2D-eGFR
ZMIZ1rs1749824P = 8.1 × 10(-5)T1D-ESRD

Current data from genetic association studies in diabetic kidney disease by using genome wide association approach.

Data were extracted from more than 300 references in PubMed and most studies were carryout with genetic association study of candidate gene(s). CNVs, Copy Number Variants; DKD, Diabetic Kidney Disease; eGFR, estimated Glomerular Filtration Rate; T1D, Type 1 Diabetes Mellitus; T2D, Type 2 Diabetes Mellitus; ABCG, ATP Binding Cassette Subfamily G; ACACB, Acetyl-CoA Carboxylase Beta; ACE, Angiotensin I Converting Enzyme; ADPOQ, Adiponectin; ADRB2, Adrenoceptor Beta 2; AFF3, AF4/FMR2 Family Member 3; AGER, Advanced Glycosylation End-Product Specific Receptor; AGT, Angiotensinogen; AGTR, Angiotensin II Receptor; AKR1B1, Aldo-Keto Reductase Family 1 Member B; ALOX12, Arachidonate 12-Lipoxygenase, 12S Type; ApoE, Apolipoprotein E; APOL1, Apolipoprotein L1; AUH, AU RNA Binding Methylglutaconyl-CoA Hydratase; BID, BH3 Interacting Domain Death Agonist; CALD1, Caldesmon 1; CaSR, Calcium-Sensing Receptor; CARS, Cysteinyl-TRNA Synthetase; CAT, Catalase; CERS2, Ceramide Synthase 2; CDCA7, Cell Division Cycle Associated 7; CDH13, Cadherin 13; CHN2, Chimerin 2; CNDP, Carnosine Dipeptidase; COQ5, Coenzyme Q5, Methyltransferase; COX6A1, Cytochrome C Oxidase Subunit 6A1; COX10, COX10, Heme A:Farnesyltransferase Cytochrome C Oxidase Assembly Factor; CUBN, Cubilin; CYBA, Cytochrome B-245 Alpha Chain; CYP11B2, Cytochrome P450 Family 11 Subfamily B Member 2; ELMO1, Engulfment And Cell Motility 1; eNOS, Nitric Oxide Synthase; ENPP1, Ectonucleotide Pyrophosphatase/Phosphodiesterase 1; EPO, Erythropoietin; EPHX2, Epoxide Hydrolase 2; ERBB4, Erb-B2 Receptor Tyrosine Kinase 4; ESR1, Estrogen Receptor 1; FRMD3, FERM Domain Containing 3; FNDC5, Fibronectin Type III Domain Containing 5; GAS6, Growth Arrest Specific 6; GATC, Glutamyl-TRNA Amidotransferase Subunit C; GCK, Glucokinase; GCKR, Glucokinase Regulator; GFPT2, Glutamine-Fructose-6-Phosphate Transaminase 2; GLRA3, Glycine Receptor Alpha 3; GPX1, Glutathione Peroxidase 1; GREM1, Gremlin 1, DAN Family BMP Antagonist; GSTP1, Glutathione S-Transferase Pi 1; HIF1α, Hypoxia Inducible Factor 1 Subunit Alpha; H19, H19, Imprinted Maternally Expressed Transcript; HMGA2, High Mobility Group AT-Hook 2; HO1, Heme Oxygenase 1; HSP70, Heat Shock Protein 70; ICAM1, Intercellular Adhesion Molecule 1; IGF2, Insulin Like Growth Factor 2; IGFBP1, Insulin Like Growth Factor Binding Protein 1; IL, Interleukin; IRAK4, Interleukin 1 Receptor Associated Kinase 4; INSR, Insulin Receptor; IRS2, Insulin Receptor Substrate 2; KCNQ1, Potassium Voltage-Gated Channel Subfamily Q Member 1; KLRA1, Killer Cell Lectin Like Receptor A1; KNG1, Kininogen 1; LTA, Lymphotoxin Alpha; LIMK2, LIM Domain Kinase 2; MAPRE1P2, MAPRE1 Pseudogene 2; MCF2L2, MCF.2 Cell Line Derived Transforming Sequence-Like 2; MGP, Matrix Gla Protein; MME, Membrane Metalloendopeptidase; MMP, Matrix Metallopeptidase; MSC, Musculin; MTHFR, Methylenetetrahydrofolate Reductase; MT2A, Metallothionein 2A; MSRB3, Methionine Sulfoxide Reductase B3; MTOR, Mechanistic Target of Rapamycin Kinase; MyD88, Myeloid Differentiation Primary Response 88; MYH9, Myosin Heavy Chain 9; NCALD, Neurocalcin Delta; NOS, Nitric Oxide Synthase; NQO1, NAD(P)H Quinone Dehydrogenase 1; NPHS1, NPHS1, Nephrin; NPY, Neuropeptide Y; PACRG, Parkin Coregulated; PAI1, Plasminogen Activator Inhibitor 1; PARK2, Parkin RBR E3 Ubiquitin Protein Ligase; PFKFB2, 6-Phosphofructo-2-Kinase/Fructose-2,6-Biphosphatase 2; PLXDC2, Plexin Domain Containing 2; PLEKHH2, Pleckstrin Homology, MyTH4 and FERM Domain Containing H2; PON, Paraoxonase; PPARG, Peroxisome Proliferators-Activated Receptor Gamma; PPARGC1A, Peroxisome Proliferators-Activated Receptor Gamma Co-activator 1 alpha; PRKAA2, Protein Kinase AMP-Activated Catalytic Subunit Alpha 2; PROX1, Prospero Homeobox 1; PSMD9, Proteasome 26S Subunit, Non-ATPase 9; PRKCB1, Protein Kinase C Beta; PTX3, Pentraxin 3; PVT1, Pvt1 Oncogene; RAGE, Advanced Glycosylation End-Product Specific Receptor; RAET1L, Retinoic Acid Early Transcript 1L; RBP4, Retinol Binding Protein 4; REN, Renin; RGMA, Repulsive Guidance Molecule BMP Co-Receptor A; RREB1, Ras Responsive Element Binding Protein 1; TOP1MT, DNA Topoisomerase I Mitochondrial; RPS12, Ribosomal Protein S12; RTN1, Reticulon 1; SASH1, SAM And SH3 Domain Containing 1; SCAF8, SR-Related CTD Associated Factor 8; SEMA6D, Semaphorin 6D; SERPINB, Serpin Family; SHROOM3, Shroom Family Member 3; SIK1, Salt Inducible Kinase 1; SIRT1, Sirtuin 1; SLC2A, Solute Carrier Family 2; SLC12A3, Solute Carrier Family 12 Member 3; SOD, Superoxide Dismutase; SOX2, SRY-Box 2; SORBS1, Sorbin and SH3 Domain Containing 1; SP3, Sp3 Transcription Factor; SUMO4, Small Ubiquitin-Like Modifier 4; SUV39H2, Suppressor Of Variegation 3-9 Homolog 2; TCF7L2, Transcription Factor 7 Like 2; TGFβ1, Transforming Growth Factor Beta 1; TMPO, Thymopoietin; TNFα, Tumor Necrosis Factor alpha; THP, Tamm-Horsfall protein; TRAF6, TNF Receptor Associated Factor 6; TRIB3, Tribbles Pseudokinase 3; UMOD, Uromodulin; VEGF, Vascular Endothelial Growth Factor; VEGFA, Vascular Endothelial Growth Factor A; VDR, Vitamin D Receptor; WNT4, Wnt Family Member 4; ZBTB40, Zinc Finger and BTB Domain Containing 40; ZMIZ1, Zinc Finger MIZ-Type Containing 1.

The CNDP1 (carnosine dipeptidase 1) gene is located in chromosome 18q22.3 and contains 5-leucine (CTG) trinucleotide repeat length polymorphism (D18S880) in the coding region (Wanic et al., 2008). This trinucleotide repeat polymorphism is found to have gender specificity and to confer the susceptibility for DKD and ESRD in T2D (). Furthermore, serum carnosinase (CN-1) activity is negatively correlated with time on hemodialysis (). In addition, several SNPs in this gene are also associated with DKD and ESRD (; ; ; ; ; ; ; ). Interestingly, an experimental study in BTBR ob/ob mice has demonstrated that treatment with carnosine as the target of CNDP1 improves glucose metabolism and albuminuria, suggesting that carnosine may be a novel therapeutic strategy to treat patients with DKD ().

The ELMO1 (engulfment and cell motility 1) gene is located on chromosome p14.1 and encodes a member of the engulfment and cell motility protein family. The protein interacts with dedicator of cytokinesis proteins and subsequently promotes phagocytosis and cell migration. Increased expression of ELMO1 and dedicator of cytokinesis 1 may promote glioma cell invasion (). Furthermore, several SNPs in this gene are found to be associated with DKD in both T1D and T2D (, ; ; ; ; ; Wu et al., 2013; ; ; ; ; ). The variants associated with DKD, however, are different in the several populations studied, suggesting the presence of allelic heterogeneity probably resulting from the diverse ancestral genetic backgrounds of the different racial groups.

The FRMD3 (FERM domain containing 3) gene is located in chromosome 9q21.32. The FRMD3 gene is expressed in adult brain, fetal skeletal muscle, thymus, ovaries, and podocytes (). have demonstrated that FRMD3 expression in kidneys of a DKD mouse model is decreased as compared with non-diabetic mice. Genetic polymorphisms in the FRMD3 gene are associated with DKD and ESRD in T1D and T2D (; ). Furthermore, the members of the bone morphogenetic protein (BMP) interact with FRMD3, which implies that FRMD3 may influence the risk of DKD through regulation of the BMP pathway (; ).

The MMP9 (matrix metallopeptidase 9) gene is located in chromosome 20q13.12. The MMP family members are involved in the breakdown of extracellular matrix (ECM) in physiological processes, such as tissue remodeling, reproduction and embryonic development, while MMP9 is the ninth member in the family. MMP9 may play an essential role in local proteolysis of the extracellular matrix and in leukocyte migration. Moreover, MMPs, including MMP9, are zinc-dependent endopeptidases and the major proteases in ECM degradation. There are common variants such as rs3918242 (-1562C/T) and microsatellites (CA)n in the promoter region and several SNPs rs481480, rs2032487, rs4281481, rs3752462 and rs3918242 are found to be associated with the susceptibility to DKD (; ; ; ; ; Zhang et al., 2015; ).

Both UMOD (uromodulin) and SLC12A3 (solute carrier family 12 member 3) genes are located in the same chromosome but in short and long arms, respectively, i.e., 16p12.3 and 16q13. SLC12A3 is also known as thiazide-sensitive sodium-chloride cotransporter in kidney distal convoluted tubules, which is important for electrolyte homeostasis. Mutations in this gene are characterized by hypokalemic alkalosis combined with hypomagnesemia, low urinary calcium, but increased renin activity. Tanaka et al. (2003) performed a GWAS in Japanese T2D subjects and reported that the SLC12A3 Arg913Gln polymorphism was associated with reduced risk of DKD. then conducted another 10-year longitudinal study in the same population. The results confirmed that the 913Gln allele of SLC12A3 Arg913Gln polymorphism conferred a protective effect in DKD (). More recently, performed a further genetic study of SLC12A3 polymorphisms in a Malaysian population, including the meta-analysis of the association between the SLC12A3 Arg913Gln polymorphism and DKD from all the previous studies. SLC12A3 Arg913Gln polymorphism was found to be associated with T2D (P = 0.028, OR = 0.772, 95% CI = 0.612–0.973) and DKD (P = 0.038, OR = 0.547, 95% CI = 0.308–0.973) in the Malaysian cohort. The meta-analysis confirmed the protective effects of the SLC12A3 913Gln allele in DKD (Z-value = -1.992, P = 0.046, OR = 0.792). In addition, the authors investigated the role of slc12a3 expression in the progress of DKD with db/db mice and in kidney development with zebrafish embryos. With knockdown of zebrafish ortholog, slc12a3 led to structural abnormality of kidney pronephric distal duct at 1-cell stage. Slc12a3 mRNA and protein expression levels were upregulated in kidneys of db/db mice from 6, 12, and 26 weeks at the age. The authors thus concluded that SLC12A3 is a susceptibility gene in DKD, while allele 913Gln but not allele Arg913 has a preventive effect in the disease (). This association of the SLC12A3 Arg913Gln polymorphism with DKD has been very recently replicated in a Chinese population (Zhang et al., 2018). The UMOD gene encoded glycoprotein is synthesized exclusively in renal tubular cells and released into urine. Furthermore, UMOD may prevent urinary tract infection and inhibit formation of liquid containing supersaturated salts and subsequent formation of salt crystals. SNPs rs4293393 and rs1297707 in the UMOD gene are found to be associated with the susceptibility to DKD in T2D (; ; van Zuydam et al., 2018).

The Human Genome Project has revealed that there are more than twenty thousand protein coding genes, and probably more than one million of RNA genes6. Genetic association studies of RNA gene polymorphisms with DKD are very limited. Up to date, only two SNPs, i.e., rs2910164 and rs12976445 in the genes for miRNA-146a and miRNA-125 have been found to be associated with DKD in T1D and T2D (; ). Further investigation of RNA genetic variation conferring susceptibility to DKD needs to be undertaken.

Current Information From Epigenetic Studies in Diabetic Kidney Disease

Similar to genetic association studies, epigenome-wide (EWAS) and candidate gene DNA methylation analyses have been used for epigenetic studies of DKD. Current information from epigenetic studies in DKD are represented in Table 3. An EWAS suggested that several genes, including SLC22A12, TRPM6, AQP9, HP, AGTX, and HYAL2, may have epigenetic effects in DKD (VanderJagt et al., 2015). Interestingly, SLC22A12 encodes for urate anion transporter 1 (URAT1), which is a kidney-specific urate transporter that transports urate across the apical membrane of the proximal tubule in kidneys. Loss-of-function SLC22A12 mutations are associated with renal hypouricaemia and affected persons can develop exercise-induced acute kidney injury and are at increased risk of developing urate stones (). TRPM6 is a member of transient receptor potential superfamily of cation channels. This gene is widely expressed in the body, including kidneys along the nephron. The TRPM6 channels are mainly located in the renal distal convoluted tubule, the site of active transcellular calcium and magnesium transport in the kidney (). As described previously, several studies have implicated UMOD genetic polymorphisms in the susceptibility to DKD (; ; van Zuydam et al., 2018). A recent study has demonstrated that UMOD regulates renal magnesium homeostasis through TRPM6 (). Furthermore, analyses of the candidate genes such as IGFBP1 and MTHFR have also provided evidence that DNA methylation changes in these genes may be involved in the pathogenesis of DKD (, ; Yang et al., 2016). Combining and analyzing data from genetic and epigenetic studies together may help understand some of the pathophysiology in DKD.

Table 3

AnalysisGene symbol/ TargetMaterial and methodsResultsReferences
DNA methylationAKR1B1, TIMP-2T2DM-DKDHypomethylation of the genes are associated with albuminuria
AKR1B1, IGF1, SLC12A3T2DM-DKD and ESRDThose genes implicated in DKD based upon the inter-individual epigenetic differences
CTGFT2DM-DKD Glomerular and mesangial cellsHypomethylation through the decreased Dnmt3a binding in the gene promoterZhang et al., 2014
IGFBP1T1DM-DKDHypermethylation
IL13RA1, IL15, EDG3, INHAHemodialyzed patients with DKDHypermethylation
MTHFRDiabetic complications, including DKDHypermethylation
MTHFRT2DM-DKDDemethylationYang et al., 2016
MIOXHuman and mouseHypomethylation
PIK3C2BGlomeruli in DKDUp-regulated with methylation in glomeruliWang et al., 2018
POLR2G, DDB1, ZNF230Down-regulated with methylation in glomeruli
SLC30A8T2DM-DKDHypermethylation
SLC22A12, TRPM6, AQP9, HP, AGXT, HYAL2Pre-diabetes and T2DM-DNHypermethylation found in 174 of 694 CpG sitesVanderJagt et al., 2015
TAMM41, PMPCB, TSFM, AUHT1DM-DKDDNA methylation changes in these genes and influence with mitochondrial function
UNC13BT1DM-DKDAn intronic polymorphism rs13293564 in the gene is associated with DKD DNA methylation levels in 19 CpG sites are changed
KLF4Glomerular podocytes in human and mouseDNA methylation levels in the promoters of genes encoding mesenchymal markers are increased
aPCPodocytesaPC epigenetically controls p66(Shc) expression
egfrCultured proximal tubule (normal rat kidney) cellsInhibition of histone deacetylase in eGFR
pxrdb/db mice and proximal tubular cellsDemethylation of DNAWatanabe et al., 2018
dnmt1db/db miceHypomethylationZhang et al., 2017
agt, abcc4, cyp4a10, glut5db/m mouseHypomethylation
kif20b, cldn18, slco1a1Hypomethylation
sglt2, pck1, g6pc, hnf4adb/db miceDemethylated in the proximal tubules
tgfb1, tet2db/db miceDecreased DNA methylationYang et al., 2018
Histone modificationMTHFRT2D with DNMTHFR regulates histone modification rs1801133 C677T in the gene is associated with DNZhou et al., 2015
TGFB1Glomerular and mesangial cellsTGF-β1 increases expression of the H3K4 methyltransferase SET7/9
12/15-LOGlomerular and mesangial cellsUp-regulation of histone lysine modificationsYuan et al., 2016
h3k9/14ac, at1rGlomerular and mesangial cells db/db miceLosartan attenuated increased H3K9/14Ac at RAGE, PAI-1 and MCP-1 promoters, while the chromatin state at these genes are mediated in part by AT1R
h3k9, h3k23db/db and C57BL/6 miceAcetylation
h3k4 in serine 10Demethylation and phosphorylation
h3k9/14acdb/+ miceLosartan reversed permissive epigenetic changes in renal glomeruli
set7/9db/db miceInduced histone modification and mcp-1 expression
xbp1db/db miceXBP1s-mediated of histone SET7/9 and consequently decreased MCP-1 expression
opn/h3k27me3Sur1-E1506K miceHistone modification with opn
txnip, h3k9ac, h3k4me3, h3k4me1, h3k27me3Sur1-E1506K miceHistone acetylation changes
egfrCultured proximal tubule (normal rat kidney) cellsInhibition of histone deacetylase in eGFR
grp78/histone h4Diabetic ratsAcetylation changes
mfn2Diabetic ratsHistone acetylation at collagen IV promoter
h3 and hsp-27, map kinase p28Sprague-Dawley ratsDephosphorylation and acetylation of h3Tikoo et al., 2008
Non-coding RNA dysregulationmiR-9-3, miR34a, miR-137DKD and diabetic retinopathyDNA methylation changes
miR-199b-5p, klothoT2DM-DKD and STZ miceIncreased serum klotho levels are mediated by miR-199b-5p
microRNA Let-7a-3T2DM with DKDDNA methylation levels in the promoter are increased by targeting UHRF1
microRNA 1207-5PGlomerular and mesangial cellsThis PVT1-derived microRNA is upregulated by glucose and TGF-β1
creb1, miR-10aHFD/STZ miceThis microRNA regulate epigenetic modification by targeting creb1

Current information from epigenetic studies in diabetic kidney disease.

DKD, Diabetic Kidney Disease; T1D, Type 1 Diabetes; T2DM, Type 2 Diabetes. The genes predicted by epigenome-wide association analysis are shown in bold, while genes from rodent studies are shown in lower case. AKR1B1, Aldo-Keto Reductase family 1, member B1; aPC, activated Protein C; AQP9, Aquaporin; AT1R, Angiotensin II Receptor type 1; AUH, AU RNA binding protein/enoyl-CoA hydratase; EGFR, epidermal growth factor receptor; CTGF, Connective Tissue Growth Factor; DDB1, Damage Specific DNA Binding Protein 1; EDG3, Endothelial Differentiation G-protein coupled receptor 3; DNMT1, DNA methyltransferase 1; HFD, High Fat Diet; IGF1, Insulin like Growth Factor 1; IGFBP1, Insulin-like Growth Factor Binding Protein 1; IL13RA1, interleukin 13 receptor subunit alpha 1; IL15, Interleukin 15; INHA, Inhibin alpha; KLF4, Kkruppel-like factor 4; MTHFR, Methylenetetrahydrofolate Reductase; MIOX, Myo-Inositol Oxygenase; PIK3C2B, Phosphatidylinositol-4-Phosphate 3-Kinase Catalytic Subunit Type 2 Beta; PMPCB, Peptidase, Mitochondrial Processing beta subunit; POLR2G, RNA Polymerase II Subunit G; SLC12A3, Solute Carrier family 12 member 3; SLC22A12, Solute Carrier family 22 member 12; SLC30A8, Solute Carrier family 30 member 8; TAMM41, TAM41 Mitochondrial translocator assembly and maintenance homolog; tet2, tet methylcytosine dioxygenase 2; TIMP2, TIMP metallopeptidase inhibitor 2; TRPM6, Transient Receptor Potential cation channel subfamily M member 6; TSFM, Ts translation elongation Factor, Mitochondrial; UHRF1, Ubiquitin like with PHD and Ring Finger domains 1; UNC13B, Unc-13 homolog B member 3; XBP1, X-Box Binding Protein 1; ZNF230, Zinc Finger Protein 230; 12/15-LO, 12/15-lipoxygenase; TGFB1, Transforming Growth Factor Beta 1.

ncRNAs regulate gene expression at the post-transcriptional level and are involved in chromatin histone modification. Most of studies concerning histone modification and ncRNA dysregulation have been performed in diabetic animal models, while a few studies have been undertaken in subjects with DKD (Table 3). have analyzed histone modification profiles in genes associated with DKD pathology and the modified regulation of these genes following treatment with the angiotensin II type 1 receptor (AT1R) blocker losartan. The data indicate that losartan attenuates key parameters of DKD and modifies gene expression, and reverses some epigenetic changes in db/db mice. Losartan also attenuates increased H3K9/14Ac at RAGE, PAI-1, and MCP-1 promoters in mesangial cells cultured under diabetic conditions (). In a recent study of subjects of T2D and diabetic complications (including DKD) () the methylation profiles of miR gene were compared and related to the presence of diabetic complications. Results indicated that miRs can modulate the expression of a variety of genes and methylation changes of miR-9-3, miR-34a, and miR-137 were found to be associated with diabetic complications (). These two studies provide evidence suggesting that therapies targeting epigenetic regulators might be beneficial in the treatment of DKD.

Summary and Perspectives

Researchers have made major efforts to undertake well powered genetic and epigenetic studies in DKD to help understand its pathogenesis. The data, however, need to be confirmed by several strategies, for instance, replication studies could be performed with better selection of subjects with similar genetic background to limit influences from migration; intermarriage; cultural preferences; coupled with further investigation of DNA variation and methylation changes in RNA regulation genes and biological experiments to determine functional impact of these variants. Furthermore, new technologies for DNA and ncRNA sequencing analysis such as third generation sequencing and a PheWAS approach have recently been developed.

New Generation Sequencing

DNA sequencing analysis is used for determining the accurate order of nucleotides along chromosomes and genomes. Second-generation sequencing, commonly known as next-generation sequencing (NGS), has presently become popular in DNA sequencing analysis because NGS can enable a massively-paralleled approach capable of producing large numbers of reads at high coverages along the genome and therefore dramatically reduce the cost of DNA sequencing analysis (Treangen and Salzberg, 2011; ; ). Today, third-generation sequencing (often called as long-read sequencing) is a new generation sequencing method, which works by reading the nucleotide sequences at single molecule level in contrast to the first and second generations of DNA sequencing (van Dijk et al., 2018). Moreover, it is necessary to develop the molecular instruments for whole genome sequencing to make this new generation sequencing commercially available. The advanced sequencing technologies will improve genetic and epigenetic studies in DKD in the near future.

ncRNA Genetic and Epigenetic Studies

In the human genome, RNA genes are much more abundant than protein coding genes, while ncRNAs mainly include miRNAs and lncRNAs. Both forms of ncRNAs have been found to be involved in chromatin histone modifications, and subsequently can have epigenetic effects on the target genes. Therefore, identification of RNA genetic variation and investigation of biological alteration of these RNA genes should be included in research plans. Kato has very recently pointed out a hypothesis that transforming growth factor-β (TGF1β) may play an important role in early stage development of DKD, while some miRNAs and lncRNAs regulate the key molecules in the TGF1β pathway. These ncRNAs may be served as biomarkers for predicting the potential targets for prevention and treatment in DKD (). Furthermore, have compared Sanger sequencing and NGS to validate the five top ranked miRNAs that are predicted to be associated with DKD by EWAS. This study suggests that targeted NGS may offer a more cost-effective and sensitive approach and implied that the methylated miR-329-2, in which region SNP rs10132943 is located, and miR-429 where SNPs rs7521584 and rs112695918 exist, are associated with DKD (). Although these two studies are preliminary, they may be good examples to help direct further DKD research.

Phenome-Wide Association Study (PheWAS)

PheWAS is a new approach to analyze many phenotypes in comparison with a single genetic variant. This approach was originally described using electronic medical record (EMR) data from EMR-linked with a DNA biobank and also can be combined with GWAS and EWAS. Therefore, PheWAS has become a powerful tool to investigate the impact of genetic variation on drug response among many individuals and may expand our knowledge of new drug targets and effects (; ; ). Clearly, combined with GWAS and EWAS, PheWAS will provide us with the possibility to discover the associations with drug effects, including therapeutic response and side effect profiles in DKD ().

Taken together, application of these advanced studies in DKD will be very useful not only for evaluating current data from genetic and epigenetic studies but also for generating new knowledge for dissecting the complexity of this disease.

Statements

Author contributions

The author confirms being the sole contributor of this work and has approved it for publication.

Funding

The study was supported by the Start Grant from China Pharmaceutical University.

Conflict of interest

The author declares that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Abbreviations

  • ACR

    albumin-to-creatinine ratio

  • ADA

    American Diabetes Association

  • BMI

    body mass index

  • CNV

    copy number variant

  • DKD

    diabetic kidney disease

  • ESRD

    end-stage renal disease

  • EWAS

    epigenome-wide association study

  • GFR

    glomerular filtration rate

  • GWAS

    genome-wide association study

  • IDF

    International Diabetes Federation

  • IHME

    Institute for Health Metrics and Evaluation

  • LD

    Linkage disequilibrium

  • PheWAS

    phenome-wide association study

  • SNP

    single nucleotide polymorphism

  • T1D

    type 1 diabetes

  • T2D

    type 2 diabetes

  • UAE

    urinary albumin excretion

References

Summary

Keywords

diabetic kidney disease, diabetes, end-stage renal disease, genetics, epigenetics, phenotypes

Citation

Gu HF (2019) Genetic and Epigenetic Studies in Diabetic Kidney Disease. Front. Genet. 10:507. doi: 10.3389/fgene.2019.00507

Received

03 December 2018

Accepted

08 May 2019

Published

07 June 2019

Volume

10 - 2019

Edited by

Calli Dendrou, Wellcome Centre for Human Genetics (WT), United Kingdom

Reviewed by

Alexander Peter Maxwell, Queen’s University Belfast, United Kingdom; Taku Miyagawa, Tokyo Metropolitan Institute of Medical Science, Japan

Updates

Copyright

*Correspondence: Harvest F. Gu,

This article was submitted to Genetic Disorders, a section of the journal Frontiers in Genetics

Disclaimer

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article or claim that may be made by its manufacturer is not guaranteed or endorsed by the publisher.

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