![]() Previous research has been shown that mutations of USH2A could cause nonsyndromic recessive RP. In mammalian photoreceptors, the usherin are expressed specifically in the connecting cilia and involved in the cargo delivery from the inner segment to the outer segment. The protein usherin, encoded by the isoform b of USH2A, is presumed with 5202 amino acids and anchored on the cell membrane. To date, all 72 exons of USH2A isoform b have been carried out plenty of mutational analyses and found many pathogenic mutations (including splicing mutations at splice sites). The shorter USH2A isoform was first identified in 1998 and the much longer USH2A isoform b was identified by van Wijk et al. USH2A gene is located on chromosome 1q41 and has two alternatively spliced isoforms. USH2A gene is the major pathogenic gene for USH2 and responsible for more than 74% USH2 cases. Up to now, 16 genes have been identified that may cause USH ( ), three genes of them ( USH2A (usherin), ADGRV1 (Adhesion G Protein-Coupled Receptor V1) and DFNB31 (autosomal recessive deafness 31) ) are the USH2 genes. They usually show a gradual loss of their hearing and vision. USH3 patients are not born deaf and blind. USH2 is the most common form of USH and USH2 patients account for more than 50% of all USH patients. Different from the USH1 patients defined as having congenital deafness and blindness within the first decade of life, patients with USH2 exhibit congenital mild-moderate hearing and vision loss in the second decade of life, and generally show normal vestibular function in all their lives. USH1 is the most serious form in the three types, patients with USH1 have congenital profound hearing loss and begin to lose their vision early in life. Besides, approximately 20–30% cases are categorized as atypical USH. Up to now, it is unavailability of a therapy for the USH.Ĭlinically, according to the severity and progression of vision and hearing loss of patients, USH classified into USH type I (USH1), USH type II (USH2), and USH type III (USH3). In worldwide, the general prevalence of USH approximately ranges from 3.3 to 6.4 per 100,000 individuals. It is the most prevailing cause of the human hereditary deafness and blindness. ![]() USH is characterized by retinitis pigmentosa (RP), bilateral sensorineural hearing impairment and intact vestibular responses. Usher syndrome (USH), an autosomal recessive disorder, is a clinically and genetically heterogeneous disease. It expands the spectrum of USH2A variants in USH. We identified five heterozygous pathogenic variants in the USH2A gene in Chinese patients diagnosed with Usher syndrome type 2, two of which were not reported. In addition, three reported mutations (c.8559-2A > G, c.8232G > C and c.11389 + 3A > T) were also found in this study. Two novel variants c.4217C > A (p.Ser1406X) and c.11780A > G (p.Asp3927Gly)) were predicted deleterious by computer prediction algorithms. Two patients were found to have two-mutations and two patients only have one. Resultsįive heterozygous pathogenic variants were detected in four patients. Silico prediction tools were used to predict the pathogenicity of the variants identified in these patients. Sanger sequencing was used to study alleles. Genomic DNA was extracted from peripheral blood of unrelated Chinese USH2 patients, we designed specific primers for amplifying the coding region (exons 2–72) of the USH2A gene. For expanding the spectrum of USH2A mutations and further revealing the role of USH2A in USH2, we performed the USH2A gene variant screening in Chinese patients with USH2. USH type II (USH2) is the most common form of USH, and USH2A is the major pathogenic gene for USH2. Usher syndrome (USH) is the most prevalent cause of the human genetic deafness and blindness.
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