Novel pathogenic splicing mutation in COL11A1 in a patient with Stickler syndrome verified by minigene splicing assay

YAXIN HUANG¹Jie Zhang^2*Yafei Deng¹Xiaochun Yang³Hong Shi⁴Yuecheng Yang⁵Tao Lv⁶Yuanlong Yan⁶Ming He^7*Fang Liu^2*

• ¹昆明理工大学医学院, 昆明市, China
• ²云南省第一人民医院医学遗传科, 昆明市, China
• ³云南省第一人民医院眼科, 昆明市, China
• ⁴昆明理工大学灵长类生物医学重点实验室, 昆明市, China
• ⁵昆明医科大学第二附属医院, 昆明市, China
• ⁶国家卫生健康委员会西部地区孕前健康与优生重点实验室, 昆明市, China
• ⁷昆明医科大学基础医学院生物化学与分子生物学系, 昆明市, China

Background Stickler syndrome (STL) is a group of related connective tissue disorders characterized by heterogeneous clinical presentations with varying degrees of orofacial, ocular, skeletal, and auditory abnormalities. However, this condition is difficult to diagnose on the basis of clinical features because of phenotypic variability.Thus, expanding the variant spectrum of this disease will aid in achieving a firm definitive diagnosis of STL.Methods Comprehensive examinations, including ophthalmology, otology, and orthopedic evaluations, were performed to identify the disease phenotype of the proband. Furthermore, whole-exome sequencing (WES) and Sanger sequencing were performed to identify the molecular basis of the disease. In silico analysis and a minigene splicing assay were conducted to verify the pathogenicity of the splice site variant. The clinical phenotypes of the reported STL patients were then reviewed.The proband presented mild symptoms with early-onset high myopia and mild scoliosis. A novel de novo splicing variant (NM_080629.3: c.4069-1G>T), in the COL11A1 gene was identified in the proband via WES and confirmed via Sanger sequencing. Minigene splicing assays verified that this variant resulted in abnormal splicing of the COL11A1 transcripts because of the skipping of exon 54 and retention of 21 bp in intron 53. The literature review revealed that the most common phenotypes associated with STL type 2 include myopia and hearing impairment.We identified a novel acceptor splice site variant causing aberrant splicing of COL11A1. Our findings expand the variant spectrum of this gene and provide a precise genetic diagnosis of STL that could be helpful in genetic counseling, reproductive prevention, and treatment of long-term complications of this disorder.