Functional analysis of a novel homeodomain missense mutation that abrogates HMX1 protein function; confirming the molecular basis of oculo- auricular syndrome

Autor: 1. Gillespie RL Urquhart J Lovell SC Schorderet DF Lloyd IC Clayton-Smith J Black GC.
Rok vydání: 2015
Zdroj: Invest. Ophthalmol Vis Sci
DOI: 10.1167/iovs.14-15861
Popis: PURPOSE: To define the phenotypic manifestation confirm the genetic basis and delineate the pathogenic mechanisms underlying an oculoauricular syndrome (OAS). METHODS: Two individuals from a consanguineous family underwent comprehensive clinical phenotyping and electrodiagnostic testing (EDT). Genome wide microarray analysis and Sanger sequencing of the candidate gene were used to identify the likely causal variant. Protein modelling Western blotting and dual luciferase assays were used to assess the pathogenic effect of the variant in vitro. RESULTS: Complex developmental ocular abnormalities of congenital cataract anterior segment dysgenesis iris coloboma early onset retinal dystrophy and abnormal external ear cartilage presented in the affected family members. Genetic analyses identified a homozygous c.650A>C; p.(Gln217Pro) missense mutation within the highly conserved homeodomain of the H6 family homeobox 1 (HMX1) gene. Protein modelling predicts that the variant may have a detrimental effect on protein folding and/or stability. In vitro analyses were able to demonstrate that the mutation has no effect on protein expression but adversely alters function. CONCLUSIONS: Oculoauricular syndrome is an autosomal recessive condition that has a profound effect on the development of the external ear anterior segment and retina leading to significant visual loss at an early age. This study has delineated the phenotype and confirmed HMX1 as the gene causative of OAS enabling the description of only the second family with the condition. HMX1 is a key player in ocular development possibly in both the pathway responsible for lens and retina development and via the gene network integral to optic fissure closure
Databáze: OpenAIRE