ObjectiveTo observe the gene mutations and clinical phenotypes in patients with Usher syndrome type 2 (USH2) and retinitis pigmentosa (RP).Methods From August 2018 to January 2019, 4 patients and 11 normal family members from 3 families of USH2 and RP who visited Henan Eye Hospital were enrolled in the study. Detailed medical history was obtained and visual acuity, fundus color photography, OCT, visual field, full field ERG examination were performed. Among the three families, pedigree 1 was diagnosed with USH2, pedigree 2 and pedigree 3 were diagnosed with RP. The peripheral venous blood of patients and their family members were collected, and the whole genomic DNA was extracted. Targeted capture next generation sequencing analysis was performed on these members, and Sanger sequencing and family co-segregation were verified.ResultsIn the family F1, the proband had symptoms of RP and sensorineural deafness. Sequencing revealed two heterozygous frameshift variants: c.13877-13880 del AGAC (p. Q4626P) in exon 64 and c.798 del T (p. F266L) in exon 5 of USH2A. Both patients of family 2 and 3 showed RP signs without deafness. Two heterozygous variants c.15178T＞C (p. S5060 P) in exon 70 and c.6986C＞A (p. P2329H) in exon 37, and a pathogenic heterozygous variant c.5836C＞T (p. R1946X) in exon 29 of USH2A were identified in family F2. A heterozygous missense variant c.14951C＞T (p. P4984L) in exon 68 and a variant c.11156G＞A (p. R3719H) in exon 57 of USH2A were found in family F3. The results of conservation analysis showed that the corresponding amino acid sites of USH2A p.Q4626P, p.F266L, p.S5060P, p.P2329H and p.P4984L were highly conserved in many species. Among these 7 pathogenic variants detected, M1-M4 and M6 were novel.ConclusionsMutation USH2A gene are the main cause of USH2 and non-syndromic RP. Different variants affect protein translation and synthesis, consequently causing different clinical phenotypes.
ObjectiveTo identify the causative gene in a family affected with Usher syndrome (USH) with retinitis pigmentosa sine pigmento (RPSP) and to analyze the genotype-phenotype correlation.MethodsA retrospective clinical study. A 9-year-old girl with RPSP type 1F USH diagnosed in the ophthalmology clinic of Henan Provincial People's Hospital in November 2019 and her parents were included in the study. The patient had bilateral night blindness for more than 4 years, she suffered from hearing loss 7 years, and is currently binaural sensorineural deafness. The best corrected visual acuity in both eyes was 0.5+. There was showed no obvious pigmentation on the fundus. The visual acuity of the peripheral field of vision decreased. Optical coherence tomography showed that the outer layer of the peripheral retina became thinner and the ellipsoid band disappeared. On electroretinogram examination, the rod and cone system response was severely decreased. The clinical phenotype of the parents of the child were normal. The peripheral venous blood of the child and his parents were extracted, the whole genome DNA was extracted, the custom developed targeted capture kit (PS400) was used, and the next-generation sequencing technology was used to detect genetic mutations. The suspected pathogenic mutation sites were verified by Sanger; co-segregation was performed among family members. The pathogenicity of variants were evaluated according to the interpretation standards and guidelines of sequence variants. Bioinformatics techniques were used to assess the impact of variants on encoded proteins.ResultsThe results of genetic testing showed that the proband detected the PCDH15 gene c.4109dupA (p.K1370fs) (M1), c.17dupA (p.Y6_L7delinsX) (M2) compound heterozygous mutation sites, verified by Sanger sequencing, the mutations were in the family in a state of co-segregation. According to the evaluation of sequence variation interpretation standards and guidelines, M1 and M2 were pathogenic variants of the PCDH15 gene. M1 led to a complete change in the transmembrane structure of the encoded protein, and M2 caused the gene to only translate 6 amino acids, which predicted that the PCDH15 protein cannot be synthesized. According to the clinical phenotype, gene mutation pathogenicity and protein structure prediction, the final clinical diagnosis was PCDH15-related type 1F.ConclusionsPCDH15 genes c.4109dupA and c.17dupA are the pathogenic mutation sites of USH in this family. These compound heterozygous new mutations lead to the failure of normal synthesis of PCDH15 protein, which leads to ocular and ear manifestations.