The PHOX2B c.428A>G missense variant affects post-transcriptional control thus likely explaining the absence of neural crest-derived tumors in Congenital Central Hypoventilation Syndrome

Tiziana Bachetti¹Simona Bagnasco²Giuseppe Santamaria²Maria Francesca Bedeschi³Francesca Menni³Igor Catalano⁴Luigina Spaccini⁵Francesco Cavigioli⁵Francesco Morandi⁶Isabella Ceccherini^2*

• ¹San Martino Hospital (IRCCS), Genova, Liguria, Italy
• ²Giannina Gaslini Institute (IRCCS), Genoa, Italy
• ³IRCCS Ca 'Granda Foundation Maggiore Policlinico Hospital, Milan, Lombardy, Italy
• ⁴Pediatric Palliative Care Service, VIDAS ODV, Milan, Italy
• ⁵Buzzi Children’s Hospital, Milan, Lombardy, Italy
• ⁶Italian Association for Congenital Central Hypoventilation Syndrome (A.I.S.I.C.C.), Firenze, Italy

Heterozygous mutations in the Paired-like homeobox 2b (PHOX2B) gene cause congenital central hypoventilation syndrome (CCHS). While polyalanine expansions are quite exclusively associated with isolated CCHS, missense, nonsense and frameshift mutations are mainly identified in syndromic CCHS, presenting with Hirschsprung disease (CCHS+HSCR) alone and/or together with neuroblastoma (CCHS+HSCR+NB). CCHS-associated missense mutations occur in the PHOX2B homeo-domain, such that impaired transcriptional activity has been suggested for their functional effects. However, the molecular pathogenesis underlying their association with HSCR- and/or NB-associated CCHS has never been investigated so far. Here we demonstrate that the missense c.428A>G variant, reported by us and by others in a set of CCHS+HSCR but never associated with NB, in addition to cause the aminoacidic p.Q143R change, disrupts the intron 2 splice donor site, thus producing aberrant mRNA transcript and likely aberrant hypomorphic protein. We therefore propose that, in the presence of splicing defects of PHOX2B, a loss-of-function mechanism could underlie CCHS+HSCR and may explain the lack of neural crest-derived tumors.