A Natural Occurring Mouse Model with Adgrv1 Mutation of Usher Syndrome 2C and Characterization of its Recombinant Inbred Strains

Abstract

Background/Aims: Our laboratory discovered a Kunming mouse with enormous electroretinogram (ERG) defects. Its auditory brainstem response (ABR) threshold was significantly elevated and closely resembled the features of Usher syndrome (USH). This study sought to cross these USH-like mice (named KM^ush/ush mice) with CBA/CaJ mice to establish recombinant inbred strains and identify their phenotypes and genotypes. Methods: KM^ush/ush mice were crossed with CBA/CaJ mice to establish inbred strains by sibling mating. ERG, ABR, ocular fundus morphology, histological examinations of the retina and inner ear, quantitative real-time polymerase chain reaction, western blotting, and exon sequencing were performed to assess the phenotypes and genotypes of the offspring strains. Results: The F1 hybrids from crossing KM^ush/ush and CBA/CaJ mice had normal ERG and ABR responses. The F2 offspring from intercrossing the F1 mice showed a segregation of the retinitis pigmentosa (RP) and hearing loss phenotypes. The CBA-1^ush/ush mice had an RP phenotype that was characterized by a vanished ERG waveform and loss of the outer nuclear layer. Their Pde6b gene had a nonsense mutation that resulted in the failure of protein production in western blotting. However, the ABR threshold of this strain of mice was normal. The CBA-2^ush/ush mice had normal retinal function and architecture. Their ABR threshold was increased, with a dramatic degeneration of the stereocilia bundles in the outer hair cells of the inner ear. Whole exome sequencing and exon sequencing revealed a deletion of one base pair in exon 31 of the Adgrv1 gene, which would result in the premature termination of protein encoding. The level of Adgrv1 mRNA was reduced in the CBA-2^ush/ush mice. The CBA-3^ush/ush mice had phenotypes of RP, elevated ABR threshold, and degeneration of the stereocilia bundles in the outer hair cells. They were closely associated with the nonsense mutations of Pde6b and Adgrv1, respectively. Conclusion: We isolated a mouse strain with hearing loss from inbred mice with retinal degeneration and established it as a recombinant inbred strain with a spontaneous mutation in Adgrv1, the human Usher syndrome 2C gene. The retinal degeneration was cause by a mutation in Pde6b, while the hearing loss was caused by a mutation in Adgrv1.

Proband Whole-Exome Sequencing Identified Genes Responsible for Autosomal Recessive Non-Syndromic Hearing Loss in 33 Chinese Nuclear Families

“…In family HL1121, we detected a novel c.G3232T (p.E1078X) nonsense variant and a novel c.2057_2063del (p.A686fs) frameshift variant in ADGRV1 , which segregated with hearing loss in this family. ADGRV1 , a gene that is crucial for the development of hair cells, can result in Usher syndrome 2C, which is characterized by congenital moderate-to-severe hearing loss, retinal degeneration in the second decade of life or later, and normal vestibular function (Yan et al, 2018). This intriguing finding may be associated with the fact that these affected members might be too young to present retinal degeneration, which generally begins to appear in patients with Usher syndrome during puberty.…”

USH2A-retinopathy: From genetics to therapeutics

“…Several point mutations were identified in the Ush2a gene, suggesting a causative role in the KM USH/USH usher-like phenotype. However, further studies showed that a single base deletion occurring in Adgrv1 was responsible for the hearing loss phenotype of this model ( Yan et al, 2018 ).…”

Protection of retinal function and morphology in MNU-induced retinitis pigmentosa rats by ALDH2: an in-vivo study

“…OCT scanning was conducted with the same method as stated previously [23]. Rats, which remained anaesthetized after the ERG recording, were placed on a platform to keep fixed in place.…”