Vestibular Dysfunction in the Epistatic circler Mouse Is Caused by Phenotypic Interaction of One Recessive Gene and Three Modifier Genes

Vestibular dysfunction is a frequent clinical problem, leading to dizziness and imbalance. Genes play an important role in its etiology, but the genetics are complex and poorly understood. In this study we have analyzed the complex inheritance pattern in the Epistatic circler mouse, which shows circling behavior indicative of vestibular dysfunction in the mouse. This phenotype exists in a proportion of the F2-generation from an intercross between C57L/J and SWR/J mouse strains. Genetic investigation indicates that the circling behavior is caused by a major recessively inherited gene derived from the SWR/J strain (the Ecs-gene) in combination with at least three different modifier genes derived from C57L/J (the Ecl-genes). Genetic mapping made it possible to localize the Ecs-gene to chromosome 14 and the Ecl-genes to chromosome 3, 4, and 13. This study illustrates the feasibility of identifying genes for multifactorial traits in mice

Mutations in the WFS1 gene that cause low-frequency sensorineural hearing loss are small non-inactivating mutations

Hereditary hearing impairment is an extremely heterogeneous trait, with more than 70 identified loci. Only two of these loci are associated with an auditory phenotype that predominantly affects the low frequencies (DFNA1 and DFNA6/14). In this study, we have completed mutation screening of the WFS1 gene in eight autosomal dominant families and twelve sporadic cases in which affected persons have low-frequency sensorineural hearing impairment (LFSNHI). Mutations in this gene are known to be responsible for Wolfram syndrome or DIDMOAD (diabetes insipidus, diabetes mellitus, optic atrophy, and deafness), which is an autosomal recessive trait. We have identified seven missense mutations and a single amino acid deletion affecting conserved amino acids in six families and one sporadic case, indicating that mutations in WFS1 are a major cause of inherited but not sporadic low-frequency hearing impairment. Among the ten WFS1 mutations reported in LFSNHI, none is expected to lead to premature protein truncation, and nine cluster in the C-terminal protein domain. In contrast, 64% of the Wolfram syndrome mutations are inactivating. Our results indicate that only non-inactivating mutations in WFS1 are responsible for non-syndromic low-frequency hearing impairment