Genetic spectrum of retinal dystrophies in Tunisia

Sci Rep. 2020 Jul 8;10(1):11199. doi: 10.1038/s41598-020-67792-y.

Abstract

We report the molecular basis of the largest Tunisian cohort with inherited retinal dystrophies (IRD) reported to date, identify disease-causing pathogenic variants and describe genotype-phenotype correlations. A subset of 26 families from a cohort of 73 families with clinical diagnosis of autosomal recessive IRD (AR-IRD) excluding Usher syndrome was analyzed by whole exome sequencing and autozygosity mapping. Causative pathogenic variants were identified in 50 families (68.4%), 42% of which were novel. The most prevalent pathogenic variants were observed in ABCA4 (14%) and RPE65, CRB1 and CERKL (8% each). 26 variants (8 novel and 18 known) in 19 genes were identified in 26 families (14 missense substitutions, 5 deletions, 4 nonsense pathogenic variants and 3 splice site variants), with further allelic heterogeneity arising from different pathogenic variants in the same gene. The most common phenotype in our cohort is retinitis pigmentosa (23%) and cone rod dystrophy (23%) followed by Leber congenital amaurosis (19.2%). We report the association of new disease phenotypes. This research was carried out in Tunisian patients with IRD in order to delineate the genetic population architecture.

MeSH terms

  • ATP-Binding Cassette Transporters / genetics
  • Adolescent
  • Adult
  • Child
  • Child, Preschool
  • Cohort Studies
  • DNA Mutational Analysis
  • Exome Sequencing
  • Eye Proteins / genetics
  • Female
  • Genetic Testing / statistics & numerical data*
  • Humans
  • Infant
  • Male
  • Membrane Proteins / genetics
  • Middle Aged
  • Mutation
  • Nerve Tissue Proteins / genetics
  • Pedigree
  • Phosphotransferases (Alcohol Group Acceptor) / genetics
  • Prevalence
  • Retinal Dystrophies / congenital
  • Retinal Dystrophies / diagnosis
  • Retinal Dystrophies / epidemiology
  • Retinal Dystrophies / genetics*
  • Tunisia / epidemiology
  • Young Adult
  • cis-trans-Isomerases / genetics

Substances

  • ABCA4 protein, human
  • ATP-Binding Cassette Transporters
  • CRB1 protein, human
  • Eye Proteins
  • Membrane Proteins
  • Nerve Tissue Proteins
  • Phosphotransferases (Alcohol Group Acceptor)
  • ceramide kinase
  • retinoid isomerohydrolase
  • cis-trans-Isomerases