A very large protein with diverse functional motifs is deficient in rjs (runty, jerky, sterile) mice.

Three radiation-induced alleles of the mouse p locus, p6H, p25H, and pbs, cause defects in growth, coordination, fertility, and maternal behavior in addition to p gene-related hypopigmentation. These alleles are associated with disruption of the p gene plus an adjacent gene involved in the disorders listed. We have identified this adjacent gene, previously named rjs (runty jerky sterile), by positional cloning. The rjs cDNA is very large, covering 15,264 nucleotides. The predicted rjs-encoded protein (4,836 amino acids) contains several sequence motifs, including three RCC1 repeats, a structural motif in common with cytochrome b5, and a HECT domain in common with E6-AP ubiquitin ligase. On the basis of sequence homology and conserved synteny, the rjs gene is the single mouse homolog of a previously described five- or six-member human gene family. This family is represented by at least two genes, HSC7541 and KIAA0393, from human chromosome 15q11-q13. HSC7541 and KIAA0393 lie close to, or within, a region commonly deleted in most Prader-Willi syndrome patients. Previous work has suggested that the multiple phenotypes in rjs mice might be due to a common neuroendocrine defect. In addition to this proposed mode of action, alternative functions of the rjs gene are evaluated in light of its known protein homologies.

The mouse pale ear (ep) mutation is the homologue of human Hermansky-Pudlak syndrome.

The recessive mutation at the pale ear (ep) locus on mouse chromosome 19 was found to be the homologue of human Hermansky-Pudlak syndrome (HPS). A positional cloning strategy using yeast artificial chromosomes spanning the HPS locus was used to identify the HPS gene and its murine counterpart. These genes and their predicted proteins are highly conserved at the nucleotide and amino acid levels. Sequence analysis of the mutant ep gene revealed the insertion of an intracisternal A particle element in a protein-coding 3' exon. Here we demonstrate that mice with the ep mutation exhibit abnormalities similar to human HPS patients in melanosomes and platelet-dense granules. These results establish an animal model of HPS and will facilitate biochemical and molecular analyses of the functions of this protein in the membranes of specialized intracellular organelles.