Genetically modified mice are of considerable value for understanding the molecular basis of human disease and for the development of new diagnostic and therapeutic approaches. In this project we propose to construct transgenic mice which will serve as mode/e for tumourigenesis, or for human developmental disorders.
First generation transgenics did not mimic a "natural" mutational event, because of the effect of random integration of the transgene, the use of heterologous promoters, and the presence of two non-mutated endogenous alleles. Similarly, first generation knock-outs were mostly aimed at obtaining a complete loss of function of the targeted gene, often resulting in non-informative early lethal phenotypes.
The approach described in this project is a substantial step forward with respect to the above techniques, since it is aimed at obtaining mice bearing the exact replicas of naturally occurring genetic lesions in man. We will activate (or partially inactivate) genes by introducing point mutations in the targeted sequence by homologous recombination, without perturbing the endogenous pattern of expression. The targets will be four receptor tyrosine kineses (RTKs) known for their oncogenic potential, and for being involved in development Met, Ret, PDGFR, and Trk.
The introduction of gain of function mutations in receptor genes should induce the appearance of a variety of tumors in the transgenic animals (oncomice). Such oncomice will be, first of all, of diagnostic va/ue, since the development of tumors in specific tissues will pinpoint the cell types susceptible to oncogenic transformation for each receptor. Furthermore, they will make it possible to explore in-vivo the multi-step nature of tumourigenesis, for example by testing the effect of the mutation in different mouse strains, or by crossing the mice with transgenics carrying inactivating mutations in tumor suppressor genes. Finally, these animals will represent ideal tools to test the efficacy of a family of anti-cancer drugs currently being developed by pharmacological industries, based on the inhibition of tyrosine kinase activity or signal transduction.
The loss of function mutations are likely to yield a phenotype in the heterozygous condition, due the dominant negative effect caused by receptor dimerization. The defects of these animals should be milder than those found in the corresponding knock-outs (embryonal or perinatal lethal for Met, Ret, and PDGFR). Such partial loss of function phenotypes may thus provide additional information with respect to the knock-out, and may help linking a partial loss of function of Met and PDGFR (for which,at present, there no corresponding pathology) with human developmental disorders.
Funding SchemeCSC - Cost-sharing contracts
751 24 Uppsala
CB2 2QQ Cambridge