title: Genetic Analyses of a Three Generation Family Segregating Hirschsprung Disease and Iris Heterochromia.
abstract: We present the genetic analyses conducted on a three-generation family (14 individuals) with three members affected with isolated-Hirschsprung disease (HSCR) and one with HSCR and heterochromia iridum (syndromic-HSCR), a phenotype reminiscent of Waardenburg-Shah syndrome (WS4). WS4 is characterized by pigmentary abnormalities of the skin, eyes and/or hair, sensorineural deafness and HSCR. None of the members had sensorineural deafness. The family was screened for copy number variations (CNVs) using Illumina-HumanOmni2.5-Beadchip and for coding sequence mutations in WS4 genes (EDN3, EDNRB, or SOX10) and in the main HSCR gene (RET). Confocal microscopy and immunoblotting were used to assess the functional impact of the mutations. A heterozygous A/G transition in EDNRB was identified in 4 affected and 3 unaffected individuals. While in EDNRB isoforms 1 and 2 (cellular receptor) the transition results in the abolishment of translation initiation (M1V), in isoform 3 (only in the cytosol) the replacement occurs at Met91 (M91V) and is predicted benign. Another heterozygous transition (c.-248G/A; -predicted to affect translation efficiency-) in the 5'-untranslated region of EDN3 (EDNRB ligand) was detected in all affected individuals but not in healthy carriers of the EDNRB mutation. Also, a de novo CNVs encompassing DACH1 was identified in the patient with heterochromia iridum and HSCR Since the EDNRB and EDN3 variants only coexist in affected individuals, HSCR could be due to the joint effect of mutations in genes of the same pathway. Iris heterochromia could be due to an independent genetic event and would account for the additional phenotype within the family.
authors.affiliation: Department of Surgery, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China.
authors.forename: Long
authors.initials: L
authors.lastname: Cui
authors.forename: Emily Hoi-Man
authors.initials: EH
authors.lastname: Wong
authors.forename: Guo
authors.initials: G
authors.lastname: Cheng
authors.forename: Manoel
authors.initials: M
authors.lastname: Firmato de Almeida
authors.forename: Man-Ting
authors.initials: MT
authors.lastname: So
authors.forename: Pak-Chung
authors.initials: PC
authors.lastname: Sham
authors.forename: Stacey S
authors.initials: SS
authors.lastname: Cherny
authors.forename: Paul Kwong-Hang
authors.initials: PK
authors.lastname: Tam
authors.forename: Maria-Mercè
authors.initials: MM
authors.lastname: Garcia-Barceló
mesh_terms: D056915:DNA Copy Number Variations; D019334:Endothelin-3 / Q000235:genetics; D005260:Female; D005799:Genes, Dominant; D006627:Hirschsprung Disease / Q000235:genetics*; D006801:Humans; D040582:Inheritance Patterns; D007499:Iris Diseases / Q000235:genetics*; D008297:Male; D009154:Mutation; D010375:Pedigree; D010859:Pigmentation Disorders / Q000235:genetics*; D044023:Receptor, Endothelin B / Q000235:genetics; D055757:SOXE Transcription Factors / Q000235:genetics
chemical_list: C000588595:EDN3 protein, human; C000588596:EDNRB protein, human; D019334:Endothelin-3; D044023:Receptor, Endothelin B; C527923:SOX10 protein, human; D055757:SOXE Transcription Factors