USH2A, also known as usherin, is a gene with significant importance. It encodes a protein that is crucial for the normal function of the retina and inner ear. Mutations in this gene disrupt its normal function, which is associated with pathways related to maintaining the integrity of photoreceptor cells in the retina and the function of hair cells in the inner ear. Its proper functioning is vital for normal vision and hearing [2,4].

Biallelic variants in USH2A can cause Usher syndrome type 2 and non-syndromic retinitis pigmentosa [2]. In a study of Chinese patients, 230 variants in USH2A were identified, with 90 (39.13%) being novel. Patients with biallelic truncating variants had an earlier age at initial clinical visit and symptom onset compared to those with missense variants. Also, USH2 patients had an earlier onset of visual decline compared to non-syndromic retinitis pigmentosa patients [1]. Another study found that the prevalence of USH2A mutations in a cohort of Chinese patients with inherited retinal disease was 15.75%, with hotspots at c.8559-2A > G and c.2802T > G. USH2 patients had earlier and more serious visual function decline and retinal structure damage in the first 10 years compared to retinitis pigmentosa patients [3].

In conclusion, USH2A is essential for the normal function of the retina and inner ear. Studies on patients with USH2A-related diseases have provided insights into the genotype-phenotype correlations. Understanding USH2A's role through these studies is crucial for the development of potential therapies for Usher syndrome type 2 and non-syndromic retinitis pigmentosa [1,2,3].

References:

1. Zhu, Tian, Chen, De-Fu, Wang, Lei, Jin, Zi-Bing, Sui, Ruifang. 2020. USH2A variants in Chinese patients with Usher syndrome type II and non-syndromic retinitis pigmentosa. In The British journal of ophthalmology, 105, 694-703. doi:10.1136/bjophthalmol-2019-315786. https://pubmed.ncbi.nlm.nih.gov/32675063/

2. Toualbi, Lyes, Toms, Maria, Moosajee, Mariya. 2020. USH2A-retinopathy: From genetics to therapeutics. In Experimental eye research, 201, 108330. doi:10.1016/j.exer.2020.108330. https://pubmed.ncbi.nlm.nih.gov/33121974/

3. Gao, Feng-Juan, Wang, Dan-Dan, Chen, Fang, Chang, Qing, Wu, Ji-Hong. 2020. Prevalence and genetic-phenotypic characteristics of patients with USH2A mutations in a large cohort of Chinese patients with inherited retinal disease. In The British journal of ophthalmology, 105, 87-92. doi:10.1136/bjophthalmol-2020-315878. https://pubmed.ncbi.nlm.nih.gov/32188678/

4. McGee, Terri L, Seyedahmadi, Babak Jian, Sweeney, Meredith O, Dryja, Thaddeus P, Berson, Eliot L. 2010. Novel mutations in the long isoform of the USH2A gene in patients with Usher syndrome type II or non-syndromic retinitis pigmentosa. In Journal of medical genetics, 47, 499-506. doi:10.1136/jmg.2009.075143. https://pubmed.ncbi.nlm.nih.gov/20507924/