Novel homozygous mutations in the transcription factor cause non-syndromic retinitis pigmentosa.

PURPOSE

To describe the clinical phenotype and genetic basis of non-syndromic retinitis pigmentosa (RP) in one family and two sporadic cases with biallelic mutations in the transcription factor neural retina leucine zipper (.

METHODS

Exome sequencing was performed in one affected family member. Microsatellite genotyping was used for haplotype analysis. PCR and Sanger sequencing were used to confirm mutations in and screen other family members where they were available. The SMART tool for domain prediction helped us build the protein schematic diagram.

RESULTS

For family MM1 of Pakistani origin, whole-exome sequencing and microsatellite genotyping revealed homozygosity on chromosome 14 and identified a homozygous stop-loss mutation in , NM_006177.5: c.713G>T, p.238Lext57, which is predicted to add an extra 57 amino acids to the normal protein chain. The variant segregated with disease symptoms in the family. For case RP-3051 of Spanish ancestry, clinical exome sequencing focusing on the morbid genome highlighted a homozygous nonsense mutation in , c.238C>T, p.Gln80, as the most likely disease candidate. For case RP-1553 of Romanian ethnicity, targeted-exome sequencing of 73 RP/LCA genes identified a homozygous nonsense mutation in , c.544C>T, p.Gln182*. The variants were either rare or absent in the gnomAD database.

CONCLUSIONS

mutations predominantly cause dominant retinal disease, but there have been five published reports of mutations causing recessive disease. Here, we present three further examples of recessive RP due to mutations. The phenotypes observed are consistent with those in the previous reports, and the observed mutation types and distribution further confirm distinct patterns for variants in causing recessive and dominant diseases.