GPR143 genotypic and ocular phenotypic characterisation in a Chinese cohort with ocular albinism

Ocular albinism type I (OA1) is caused by mutations in the GPR143 gene. The purpose of this study was to describe the clinical and genetic findings in 13 patients from 12 unrelated Chinese pedigrees with a pathogenic variant of the GPR143 gene.

Most patients underwent clinical examination, including best-corrected visual acuity (BCVA), slit-lamp biomicroscopy, fundus examination, spectral domain optical coherence tomography, and full-field electroretinograms (ERG). A combination of molecular screening procedures, consisting of Sanger-DNA sequencing of GPR143 and targeted next-generation sequencing, was performed to identify each mutation. In silico programs were utilized to evaluate the pathogenicity of all the variants.

The 13 patients (mean age 21.75 ± 16.63 years, range 1-54 years) all presented with congenital nystagmus, different extents of visual impairment, and severe foveal hypoplasia. Their BCVA was between 0.05 and 0.3 (decimal notation). The patients and obligate carriers exhibited different extents of mild depigmentation of the iris and fundus. We detected 11 distinct mutations in this patient cohort, including 7 novel mutations. Most (82%) were null mutations and included frameshift indel, nonsense, splicing effect, and large genomic DNA deletions, while missense mutations only accounted for 18%.

Patients with GPR143 mutations all have congenital nystagmus, visual impairment, and foveal hypoplasia, whereas hypopigmentation in their iris and fundus is mild. They exhibit no evident genotype-phenotype correlations. GPR143 mutation screening is very important for establishing a precise diagnosis and for providing genetic counseling for patients and their families.