No abstract

Pulmonary fibrosis is a disease of significant morbidity, with no effective therapeutics and an as yet incompletely defined genetic basis. The chemotherapeutic agent bleomycin induces pulmonary fibrosis in susceptible C57BL/6J mice but not in mice of the C3H/HeJ strain, and this differential strain response has been used in prior studies to map bleomycin-induced pulmonary fibrosis susceptibility loci named Blmpf1 and Blmpf2. In this study we isolated the quantitative trait gene underlying Blmpf2 initially by histologically phenotyping the bleomycin-induced lung disease of sublines of congenic mice to reduce the linkage region to 13 genes. Of these genes, Trim16 was identified to have strain-dependent expression in the lung, which we determined was due to sequence variation in the promoter. Over-expression of Trim16 by plasmid injection increased pulmonary fibrosis, and bronchoalveolar lavage levels of both interleukin 12/23-p40 and neutrophils, in bleomycin treated B6.C3H-Blmpf2 subcongenic mice compared to subcongenic mice treated with bleomycin only, which follows the C57BL/6J versus C3H/HeJ strain difference in these traits. In summary we demonstrate that genetic variation in Trim16 leads to its strain-dependent expression, which alters susceptibility to bleomycin-induced pulmonary fibrosis in mice.

Loss of heterozygosity (LOH) at human chromosome bands 1p32-36 and 10q23-26 is frequent in various human tumors, including breast cancers, and is thought to reflect the loss of tumor-suppressor genes (TSGs). To map such genes, high-resolution LOH analysis was performed on 93 Erbb2-induced mammary tumors from (BALB/c x C57BL/6) F1 MMTV/Erbb2 transgenic mice. A panel of 24 microsatellite markers specific to the region of mouse chr4, homologous to human 1p31-36, and 16 markers specific to the mouse chr19 region, homologous to human 10q23-26 were used. In addition, lower-density mapping was performed on the remaining portion of mouse chr4 [homologous to human 9p13, 9p21-24, 9q21-22, 9q31-34 (12 markers)] and chr19 [homologous to 9q21, 9p24, 11q12-13 (9 markers)]. Several distinct, discrete, and discontinuous LOH regions flanked by areas of heterozygosity were identified, 22 on chr4 and 14 on chr19. Among these, 13 were mapped in the region of homology with human 1p31-36 (between D4Mit153 and D4Mit254) and 9 in the region of homology with human 10q23-26 (between D19Mit46 and D19Mit6). Although several LOH loci span a large interval, many are relatively short (1-4 Mb), and a few span an interval of <1 Mb. This allelotyping represents the highest density of LOH loci yet mapped in these chromosomal regions. The presence of numerous LOH regions in alternation with regions of heterozygosity, consistent with mitotic recombination as a mechanism for generating such a mosaic pattern, suggests the presence of several TSGs in these regions and should facilitate their identification.