Localization of the gene responsible for the op (osteopetrotic) defect in rats on chromosome 10.

Osteopetrosis, a skeletal disorder of inadequate bone resorption with an abnormal increase in skeletal mass, results from a variety of independent single gene mutations that affect osteoclast differentiation and/or function. The osteopetrotic defect, op, is one of four spontaneous, nonallelic mutations in rats that result in osteopetrosis. In intercross progeny of (BN/SsN x LEW/SsN. +/op) F1 carriers, we mapped this locus by linkage analysis with microsatellite markers to rat chromosome 10. The linkage group contained, as well as op, 15 anonymous DNA loci and 9 DNA loci associated with genes (interleukin-3, myosin heavy chain [skeletal, embryonic], asialoglycoprotein receptor [hepatic lectin]-1, vesicle-associated membrane protein [synaptobrevin-2], sex hormone binding globulin, aldolase C, nitric oxide synthase [inducible], erythroblastic leukemia avian viral oncogene homolog-2, and proline-rich protein). The markers for these loci include nine not previously reported. The op locus mapped to the end of the chromosome 10 linkage group, within 1 cM of the anonymous DNA locus, D10Mit6. Based on its location, the op gene is likely to be distinct from seven described mutations in mice as well as three other mutations in rats. These results may permit a positional cloning strategy to be undertaken to identify the gene and mutation underlying the op defect.