Behavioral phenotypes revealed during reversal learning are linked with novel genetic loci in diversity outbred mice.

Impulsive behavior and impulsivity are heritable phenotypes that are strongly associated with risk for substance use disorders. Identifying the neurogenetic mechanisms that influence impulsivity may also reveal novel biological insights into addiction vulnerability. Our past studies using the BXD and Collaborative Cross (CC) recombinant inbred mouse panels have revealed that behavioral indicators of impulsivity measured in a reversal-learning task are heritable and are genetically correlated with aspects of intravenous cocaine self-administration.

High-throughput measurement of fibroblast rhythms reveals genetic heritability of circadian phenotypes in diversity outbred mice and their founder strains.

Circadian variability is driven by genetics and Diversity Outbred (DO) mice is a powerful tool for examining the genetics of complex traits because their high genetic and phenotypic diversity compared to conventional mouse crosses. The DO population combines the genetic diversity of eight founder strains including five common inbred and three wild-derived strains. In DO mice and their founders, we established a high-throughput system to measure cellular rhythms using in vitro preparations of skin fibroblasts.

Characterization of genetically complex Collaborative Cross mouse strains that model divergent locomotor activating and reinforcing properties of cocaine.

Rationale: Few effective treatments exist for cocaine use disorders due to gaps in knowledge about its complex etiology. Genetically defined animal models provide a useful tool for advancing our understanding of the biological and genetic underpinnings of addiction-related behavior and evaluating potential treatments. However, many attempts at developing mouse models of behavioral disorders were based on overly simplified single gene perturbations, often leading to inconsistent and misleading results in pre-clinical pharmacology studies.

Deletion of a Long-Range Enhancer Disrupts Inner Ear Development in Mice.

Distal enhancers are thought to play important roles in the spatiotemporal regulation of gene expression during embryonic development, but few predicted enhancer elements have been shown to affect transcription of their endogenous genes or to alter phenotypes when disrupted. Here, we demonstrate that a 123.6-kb deletion within the mouse gene is associated with reduced transcription of , a gene located 660 kb away.

Hearing loss without overt metabolic acidosis in ATP6V1B1 deficient MRL mice, a new genetic model for non-syndromic deafness with enlarged vestibular aqueducts.

Mutations of the human ATP6V1B1 gene cause distal renal tubular acidosis (dRTA; OMIM #267300) often associated with sensorineural hearing impairment; however, mice with a knockout mutation of Atp6v1b1 were reported to exhibit a compensated acidosis and normal hearing. We discovered a new spontaneous mutation (vortex, symbol vtx) of Atp6v1b1 in an MRL/MpJ (MRL) colony of mice. In contrast to the reported phenotype of the knockout mouse, which was developed on a primarily C57BL/6 (B6) strain background, MRL-Atp6v1b1vtx/vtx mutant mice exhibit profound hearing impairment, which is associated with enlarged endolymphatic compartments of the inner ear.

Effects of Cdh23 single nucleotide substitutions on age-related hearing loss in C57BL/6 and 129S1/Sv mice and comparisons with congenic strains.

A single nucleotide variant (SNV) of the cadherin 23 gene (Cdh23), common to many inbred mouse strains, accelerates age-related hearing loss (AHL) and can worsen auditory phenotypes of other mutations. We used homologous recombination in C57BL/6 NJ (B6N) and 129S1/SvImJ (129S1) embryonic stem cells to engineer mouse strains with reciprocal single base pair substitutions (B6-Cdh23 and 129S1-Cdh23). We compared ABR thresholds and cochlear pathologies of these SNV mice with those of congenic (B6.

A hypomorphic mutation of the gamma-1 adaptin gene (Ap1g1) causes inner ear, retina, thyroid, and testes abnormalities in mice.

Adaptor protein (AP) complexes function in the intracellular sorting and vesicular transport of membrane proteins. The clathrin-associated AP-1 complex functions at the trans-Golgi network and endosomes, and some forms of this complex are thought to mediate the sorting of proteins in plasma membranes of polarized epithelial cells. A null mutation of the mouse Ap1g1 gene, which encodes the gamma-1 subunit of the AP-1 complex, causes embryonic lethality when homozygous, indicating its critical importance in early development but precluding studies of its possible roles during later stages.

A QTL on Chr 5 modifies hearing loss associated with the fascin-2 variant of DBA/2J mice.

Inbred mouse strains serve as important models for human presbycusis or age-related hearing loss. We previously mapped a locus (ahl8) contributing to the progressive hearing loss of DBA/2J (D2) mice and later showed that a missense variant of the Fscn2 gene, unique to the D2 inbred strain, was responsible for the ahl8 effect. Although ahl8 can explain much of the hearing loss difference between C57BL/6J (B6) and D2 strain mice, other loci also contribute.

Hearing impairment in hypothyroid dwarf mice caused by mutations of the thyroid peroxidase gene.

Thyroid hormone (TH) is essential for proper cochlear development and function, and TH deficiencies cause variable hearing impairment in humans and mice. Thyroid peroxidase (TPO) catalyzes key reactions in TH synthesis, and TPO mutations have been found to underlie many cases of congenital hypothyroidism in human patients. In contrast, only a single mutation of the mouse TPO gene has been reported previously (Tpo(R479C)) but was not evaluated for auditory function.

CLIC5 stabilizes membrane-actin filament linkages at the base of hair cell stereocilia in a molecular complex with radixin, taperin, and myosin VI.

Chloride intracellular channel 5 protein (CLIC5) was originally isolated from microvilli in complex with actin binding proteins including ezrin, a member of the Ezrin-Radixin-Moesin (ERM) family of membrane-cytoskeletal linkers. CLIC5 concentrates at the base of hair cell stereocilia and is required for normal hearing and balance in mice, but its functional significance is poorly understood. This study investigated the role of CLIC5 in postnatal development and maintenance of hair bundles.

Mutations of the mouse ELMO domain containing 1 gene (Elmod1) link small GTPase signaling to actin cytoskeleton dynamics in hair cell stereocilia.

Stereocilia, the modified microvilli projecting from the apical surfaces of the sensory hair cells of the inner ear, are essential to the mechanoelectrical transduction process underlying hearing and balance. The actin-filled stereocilia on each hair cell are tethered together by fibrous links to form a highly patterned hair bundle. Although many structural components of hair bundles have been identified, little is known about the signaling mechanisms that regulate their development, morphology, and maintenance.

Genetic background effects on age-related hearing loss associated with Cdh23 variants in mice.

Inbred strain variants of the Cdh23 gene have been shown to influence the onset and progression of age-related hearing loss (AHL) in mice. In linkage backcrosses, the recessive Cdh23 allele (ahl) of the C57BL/6J strain, when homozygous, confers increased susceptibility to AHL, while the dominant allele (Ahl+) of the CBA/CaJ strain confers resistance. To determine the isolated effects of these alleles on different strain backgrounds, we produced the reciprocal congenic strains B6.

A modifier gene alleviates hypothyroidism-induced hearing impairment in Pou1f1dw dwarf mice.

Thyroid hormone has pleiotropic effects on cochlear development, and genomic variation influences the severity of associated hearing deficits. DW/J-Pou1f1dw/dw mutant mice lack pituitary thyrotropin, which causes severe thyroid hormone deficiency and profound hearing impairment. To assess the genetic complexity of protective effects on hypothyroidism-induced hearing impairment, an F1 intercross was generated between DW/J-Pou1f1dw/+ carriers and an inbred strain with excellent hearing derived from Mus castaneus, CAST/EiJ.

Association of a citrate synthase missense mutation with age-related hearing loss in A/J mice.

We previously mapped a locus (ahl4) on distal Chromosome 10 that contributes to the age-related hearing loss of A/J strain mice. Here, we report on a refined genetic map position for ahl4 and its association with a mutation in the citrate synthase gene (Cs). We mapped ahl4 to the distal-most 7 megabases (Mb) of chromosome 10 by analysis of a new linkage backcross and then further narrowed the interval to 5.

The R109H variant of fascin-2, a developmentally regulated actin crosslinker in hair-cell stereocilia, underlies early-onset hearing loss of DBA/2J mice.

The quantitative trait locus ahl8 is a key contributor to the early-onset, age-related hearing loss of DBA/2J mice. A nonsynonymous nucleotide substitution in the mouse fascin-2 gene (Fscn2) is responsible for this phenotype, confirmed by wild-type BAC transgene rescue of hearing loss in DBA/2J mice. In chickens and mice, FSCN2 protein is abundant in hair-cell stereocilia, the actin-rich structures comprising the mechanically sensitive hair bundle, and is concentrated toward stereocilia tips of the bundle's longest stereocilia.

Separate and combined effects of Sod1 and Cdh23 mutations on age-related hearing loss and cochlear pathology in C57BL/6J mice.

Both the ahl allele of Cdh23 and the null mutation of Sod1 have been shown to contribute to age-related hearing loss (AHL) in mice, but mixed strain backgrounds have confounded analyses of their individual and combined effects. To test for the effects of Sod1 deficiency independently from those of Cdh23(ahl), we produced mice with four digenic genotypes: Sod1(+/+)Cdh23(ahl)(/ahl), Sod1(+/+)Cdh23(+/+), Sod1(-/-)Cdh23(ahl)(/ahl), and Sod1(-/-)Cdh23(+/+), all on a uniform C57BL(/)6J strain background. We assessed hearing loss by ABR threshold measurements and evaluated cochlear pathologies in age-matched mice of each digenic combination.

Mutations in Grxcr1 are the basis for inner ear dysfunction in the pirouette mouse.

Recessive mutations at the mouse pirouette (pi) locus result in hearing loss and vestibular dysfunction due to neuroepithelial defects in the inner ear. Using a positional cloning strategy, we have identified mutations in the gene Grxcr1 (glutaredoxin cysteine-rich 1) in five independent allelic strains of pirouette mice. We also provide sequence data of GRXCR1 from humans with profound hearing loss suggesting that pirouette is a model for studying the mechanism of nonsyndromic deafness DFNB25.

A locus on distal chromosome 11 (ahl8) and its interaction with Cdh23 ahl underlie the early onset, age-related hearing loss of DBA/2J mice.

The DBA/2J inbred strain of mice is used extensively in hearing research, yet little is known about the genetic basis for its early onset, progressive hearing loss. To map underlying genetic factors we analyzed recombinant inbred strains and linkage backcrosses. Analysis of 213 mice from 31 BXD recombinant inbred strains detected linkage of auditory brain-stem response thresholds with a locus on distal chromosome 11, which we designate ahl8.

A missense mutation in the conserved C2B domain of otoferlin causes deafness in a new mouse model of DFNB9.

Mutations of the otoferlin gene have been shown to underlie deafness disorders in humans and mice. Analyses of genetically engineered mice lacking otoferlin have demonstrated an essential role for this protein in vesicle exocytosis at the inner hair cell afferent synapse. Here, we report on the molecular and phenotypic characterization of a new ENU-induced missense mutation of the mouse otoferlin gene designated Otof(deaf5Jcs).

Targeted knockout and lacZ reporter expression of the mouse Tmhs deafness gene and characterization of the hscy-2J mutation.

The Tmhs gene codes for a tetraspan transmembrane protein that is expressed in hair cell stereocilia. We previously showed that a spontaneous missense mutation of Tmhs underlies deafness and vestibular dysfunction in the hurry-scurry (hscy) mouse. Subsequently, mutations in the human TMHS gene were shown to be responsible for DFNB67, an autosomal recessive nonsyndromic deafness locus.

Congenital hypothyroidism, dwarfism, and hearing impairment caused by a missense mutation in the mouse dual oxidase 2 gene, Duox2.

Dual oxidases generate the hydrogen peroxide needed by thyroid peroxidase for the incorporation of iodine into thyroglobulin, an essential step in thyroid hormone synthesis. Mutations in the human dual oxidase 2 gene, DUOX2, have been shown to underlie several cases of congenital hypothyroidism. We report here the first mouse Duox2 mutation, which provides a new genetic model for studying the specific function of DUOX2 in the thyroid gland and in other organ systems where it is hypothesized to play a role.

The chloride intracellular channel protein CLIC5 is expressed at high levels in hair cell stereocilia and is essential for normal inner ear function.

Although CLIC5 is a member of the chloride intracellular channel protein family, its association with actin-based cytoskeletal structures suggests that it may play an important role in their assembly or maintenance. Mice homozygous for a new spontaneous recessive mutation of the Clic5 gene, named jitterbug (jbg), exhibit impaired hearing and vestibular dysfunction. The jbg mutation is a 97 bp intragenic deletion that causes skipping of exon 5, which creates a translational frame shift and premature stop codon.

A missense mutation in the previously undescribed gene Tmhs underlies deafness in hurry-scurry (hscy) mice.

Mouse deafness mutations provide valuable models of human hearing disorders and entry points into molecular pathways important to the hearing process. A newly discovered mouse mutation named hurry-scurry (hscy) causes deafness and vestibular dysfunction. Scanning electron microscopy of cochleae from 8-day-old mutants revealed disorganized hair bundles, and by 50 days of age, many hair cells are missing.

New intragenic deletions in the Phex gene clarify X-linked hypophosphatemia-related abnormalities in mice.

X-linked hypophosphatemic rickets (XLH) in humans is caused by mutation in the PHEX gene. Previously, three mutations in the mouse Phex gene have been reported: Phex(Hyp), Gy, and Phex(Ska1). Here we report analysis of two new spontaneous mutation in the mouse Phex gene, Phex(Hyp-2J) and Phex(Hyp-Duk).

Mouse models of USH1C and DFNB18: phenotypic and molecular analyses of two new spontaneous mutations of the Ush1c gene.

We mapped two new recessive mutations causing circling behavior and deafness to the same region on chromosome 7 and showed they are allelic by complementation analysis. One was named 'deaf circler' (allele symbol dfcr) and the other 'deaf circler 2 Jackson' (allele symbol dfcr-2J). Both were shown to be mutations of the Ush1c gene, the mouse ortholog of the gene responsible for human Usher syndrome type IC and for the non-syndromic deafness disorder DFNB18.