These mice carry a &#946-Geo fusion reporter inserted into the mouse immunoglobulin-like domain containing receptor 1 gene (Ildr1). The gene trap creates a null allele and produces &#946-galactiosidase in targeted cells. ILDR1 has been shown to perform two distinct functions. In the small intestine, ILDR1 functions as a lipoprotein receptor that mediates the fat-stimulated secretion of cholecystokinin (CCK). CCK promotes satiety, and mice homozygous for this &#946-Geo gene trap allele fail to secrete CCK, following orogastric administration of fatty acids.

Secondly, ILDR1 is also present in tricellular tight junctions that contribute to the ultrastructure of the inner ear and regulate permeability of distal renal tubules. In humans, ILDR1 has been linked to autosomal recessive nonsyndromic deafness 42 (DFNB42). Ildr1 null mice (referred to as Ildr1w-/-) develop severe hearing loss by 2 weeks of age with no measurable auditory brainstem response (ABR) by 8 weeks of age. Outer hair cells are absent by one month of age and inner hair cells by 2 months of age; by P13 outer hair cells show a mosaic pattern of degeneration and stereocilia bundles develop a partial loss of shorter-row stereocilia along with fusion of stereocilia with the apical membrane of hair cells. Tricellulin, a tricellular tight junction protein, mislocalizes at the tricellular tight junctions in the organ of Corti from P6-P10 and is absent from the top portion of the tight junction by P11. In the kidneys, null mice exhibit a 5.8-fold increase in urinary volume output, a 9-fold increase in water intake, a 74% reduction in urinary osmolality, and a 2.1-fold increase in fecal water volume excretion. Microperfusion of the thick ascending limb of the loop of Henle results in an 8-fold higher water permeation velocity thereby reducing the inner medullary interstitial osmolality of the kidney. This strain may be useful for studying water homeostasis, cochlear hair cell degeneration, and gastrointestinal hormone secretion.

Ildr1 null mice carry the &beta;-Geo fusion reporter inserted into the mouse immunoglobulin-like domain containing receptor 1 gene. Ildr1 null mice exhibit hearing loss, polyuria, polydipsia and fail to secrete fat-stimulated cholecystokinin. This strain may be useful for studying water homeostasis, cochlear hair cell degeneration and gastrointestinal hormone secretion.

This strain is hosted by NIH's MMRRC, which partners with JAX for the distribution of this and other strains. For additional information and to purchase, please visit the MMRRC site.