Meiotic expression of human ornithine transcarbamylase in the testes of transgenic mice

Brain growth retardation due to the expression of human insulin like growth factor binding protein-1 in transgenic mice: an in vivo model for the analysis of igf function in the brain

Three lines of transgenic (Tg) mice carrying a fusion gene linking the mouse metallothionein-I promoter to a cDNA encoding human insulin-like growth factor binding protein-1 (hIGFBP-1) were found to express the transgene in brain. As judged by comparing Tg brain weights to those of non-transgenic littermates, adult hemizygotic Tg mice of each line exhibited brain growth retardation (16.2%, 14.4% and 8.1% reductions in weight, respectively in each line). In two lines, total brain DNA and protein content were decreased. Further analysis indicated that the brain growth retardation was manifested in the second week of postnatal life. Given that the insulin-like growth factors (IGFs) stimulate cell proliferation and/or survival in neural cultures and that hIGFBP-1, when present in a molar excess, inhibits IGF interactions with their cell surface receptors, the brain growth retardation in hIGFBP-1 Tg mice likely results from hIGFBP-1 inhibition of IGF-stimulated growth-promoting actions. These hIGFBP-1 Tg mice should prove useful in defining IGF actions during postnatal brain maturation.

Metal-inducible pathology in the liver, pancreas, and kidney of transgenic mice expressing SV40 early region genes

Transgenic mice (SV-202) that carry the SV40 early region genes under the control of an inverted metallothionein promoter developed islet cell adenomas, hepatocellular carcinomas, and a generalized peripheral neuropathy. Both the islet cell adenomas and the hepatocellular carcinomas developed from the proliferation of T antigen-positive cells. However, T antigen expression was not seen in either the peripheral or central nervous systems. Stimulation of the metallothionein promoter with heavy metals altered the temporal onset of hepatic expression and broadened the distribution of oncogene expression to include exocrine pancreas and renal tubular epithelium. Although solid tumors were not seen in the exocrine pancreas or kidneys of SV-202 mice, all immunopositive tissues developed histologic changes. These results indicate that metallothionein-directed T antigen expression can induce abnormal cellular growth in a variety of tissues, and the distribution of these tissues can be manipulated with heavy metals.