Biallelic null variants in C19orf44 cause a unique late onset retinal dystrophy phenotype characterized by patchy perifoveal chorioretinal atrophy.

Abstract

Purpose: To identify the genetic cause for disease in individuals affected with inherited retinal disease (IRD), to characterize their retinal phenotype and the properties of the underlying gene.

Methods: Participants underwent a comprehensive ophthalmological evaluation, including best-corrected visual acuity, visual field testing, fundus autofluorescence, optical coherence tomography and electroretinography. Genetic analyses included exome, genome and Sanger sequencing. Gene expression pattern was analyzed by reverse transcription-PCR. Localization of the encoded protein in cells and in the human retina was examined by immunofluorescence staining.

Results: Four different pathogenic variants in C19orf44 were identified in 15 biallelic individuals from 11 unrelated families. The most common variant was c.549_550del p.(Ser185ProfsTer2). Most individuals were affected with a unique clinical phenotype characterized by late onset patchy perifoveal chorioretinal atrophy and electroretinographic features of rod-cone degeneration. C19orf44 is expressed in various human tissues, including the retina, where it was found in the outer nuclear layer and in the outer plexiform layer. In cultured cells (hTERT RPE-1 and HeLa) and in human primary fibroblasts C19orf44 is found in the nucleus, and it is down-regulated during mitosis.

Conclusion: Based on our results, C19orf44 is crucial for normal human retinal function and pathogenic variants in this gene are associated with autosomal recessive IRD.