CONTROL OF N-CAM BY HOX AND PAX GENES IN TRANSGENIC MICE

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Cell adhesion molecules (CAMs) play important roles in embryonic tissues and in maintaining the structure and function of adult tissues. Changes in CAM expression accompany a number of disease states, and it has been shown that they are involved in both regenerative and degenerative processes including nerve and muscle. We propose to study the function of CAMs in vivo by microinjecting into mouse embryos the gene for the chicken liver cell adhesion molecule L-CAM under the control of promoters that will cause it to be expressed in transgenic mice in locations where L-CAM is not normally seen. In addition we are making constructs to locations where L- CAM is not normally seen. In addition we are making constructs to truncate, mutate, and delete the endogenous gene for the neural cell adhesion molecule, N-CAM, by transfection of embryonicstem (ES) cells and transplantation into mouse blastocysts to produce transgenic mice. DNA constructs that include the chicken L-CAM gene coupled to the insulin promoter, the neurofilament promoter, and the crystallin promoter have been used in initial experiments in this laboratory to make transgenic mice. Those with the insulin promoter express chicken L-CAM in the beta-cells of the pancreas with some apparent perturbation of cell function. Cultures of ES cells have been established and mouse N-CAM genomic clones have been isolated. Production of mice ectopically expressing L-CAM under control of tissue specific promoters should provide opportunities to locally perturb function by L-CAM expression in the beta-cells of the pancreas, in neurons and in lens cells. These tissues do not express L-CAM normally but express other CAMs, can be assessed. Our preliminary studies show that some of these animals survive and can be used to look for the influence of L-CAM on regenerative processes (eg. nerve-muscle interactions) and degenerative processes that accompany aging. Alteration or ablation of the endogenous N-CAM gene should provide a detailed analysis of the role of each form of the molecule in development, regeneration, and degeneration in vivo. These studies should have extensive implications for a variety of birth defects and genetic defects, and provide important data for assessing the role of CAMs in events associated with aging.