Biallelic sequence and structural variants in RAX2 are a novel cause for autosomal recessive inherited retinal disease

Genet Med. 2019 Jun;21(6):1319-1329. doi: 10.1038/s41436-018-0345-5. Epub 2018 Oct 31.

Abstract

Purpose: RAX2 encodes a homeobox-containing transcription factor, in which four monoallelic pathogenic variants have been described in autosomal dominant cone-dominated retinal disease.

Methods: Exome sequencing in a European cohort with inherited retinal disease (IRD) (n = 2086) was combined with protein structure modeling of RAX2 missense variants, bioinformatics analysis of deletion breakpoints, haplotyping of RAX2 variant c.335dup, and clinical assessment of biallelic RAX2-positive cases and carrier family members.

Results: Biallelic RAX2 sequence and structural variants were found in five unrelated European index cases, displaying nonsyndromic autosomal recessive retinitis pigmentosa (ARRP) with an age of onset ranging from childhood to the mid-40s (average mid-30s). Protein structure modeling points to loss of function of the novel recessive missense variants and to a dominant-negative effect of the reported dominant RAX2 alleles. Structural variants were fine-mapped to disentangle their underlying mechanisms. Haplotyping of c.335dup in two cases suggests a common ancestry.

Conclusion: This study supports a role for RAX2 as a novel disease gene for recessive IRD, broadening the mutation spectrum from sequence to structural variants and revealing a founder effect. The identification of biallelic RAX2 pathogenic variants in five unrelated families shows that RAX2 loss of function may be a nonnegligible cause of IRD in unsolved ARRP cases.

Keywords: RAX2; homeobox-containing transcription factor; loss of function; novel ARRP gene; retinitis pigmentosa.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • DNA Mutational Analysis / methods
  • European Continental Ancestry Group / genetics
  • Eye Proteins / genetics*
  • Eye Proteins / metabolism
  • Eye Proteins / physiology
  • Female
  • Genes, Recessive / genetics
  • Genetic Association Studies / methods
  • Genotype
  • Haplotypes / genetics
  • Homeodomain Proteins / genetics*
  • Homeodomain Proteins / metabolism
  • Homeodomain Proteins / physiology
  • Humans
  • Male
  • Middle Aged
  • Mutation / genetics
  • Mutation, Missense / genetics
  • Pedigree
  • Phenotype
  • Retina / metabolism
  • Retina / pathology
  • Retinal Diseases / genetics
  • Retinitis Pigmentosa / genetics*
  • Transcription Factors / genetics*
  • Transcription Factors / metabolism
  • Transcription Factors / physiology

Substances

  • Eye Proteins
  • Homeodomain Proteins
  • RAX protein, human
  • Transcription Factors