Skin Manifestations of Tuberous Sclerosis

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DESCRIPTION (provided by applicant): Skin Manifestations of Tuberous Sclerosis This application focuses on the mechanisms of pathogenesis of tuberous sclerosis (TS) and associated angiogenesis. Tuberous sclerosis is one of the most common autosomal dominant disorders in humans, occuring at a frequency of 1/6000 in the population. Thus, in the United States, one child is born every day with TS. In childhood, the major causes of morbidity and mortality are seizures and mental retardation, while with increasing age, benign and malignant tumors of the brain, kidney and skin become highly problematic. Two genes have been found to be causative for tuberous sclerosis. The first one cloned is tsd (hamartin), localized to chromosome 9, and the second one is tsc2 (tuberin), localized to chromosome 16. While some of the lesions in this disorder show the classic loss of heterozygosity for tumor suppressor genes, many other lesions do not. In this proposal, I wish to explore other mechanisms of hamartoma formation. These mechanisms include dominant mutations in tuberin, as well as contribution of modifying genes to the TS phenotype. In order to address dominant negative mutations in tuberin, my laboratory has created a transgenic mouse model by expressing a dominant negative tuberin, analogous to mutations observed in human TS, behind a constitutive promoter. Interestingly, this transgenic mouse develops a unique phenotype of skin and brain hamartomas not previously observed in other mouse models. We have also shown that this dominant negative allele of tuberin (delta/ARG allele) aberrantly activates akt and reactive oxygen signaling, which have been implicated in human TS. Thus, our model allows us to examine the effect of upstream mediators (receptor tyrosine kinase signaling) and downstream mediators (other genetic events) on a fixed genetic background. Knowledge of how these upstream and downstream events impact on the TS phenotype may lead to therapies that can prevent or ameliorate the phenotype of TS and other skin disorders in humans. Hypothesis: Cutaneous manifestations of tuberous sclerosis are caused by specific signaling abnormalities: Specific Aim 1. To determine whether TS-related cell lines demonstrate aberrant receptor tyrosine kinase signaling. Specific Aim 2. To determine the role of activation of reactive oxygen and akt pathways in pathogenesis of cutaneous lesions of TS through the use of dominant negative signal transduction genes and pharmacologic inhibition. Specific Aim 3. To determine whether dysregulation of p16ink4a and PTCH (patched) acts as a modifier of theTS phenotype in transgenic mice expressing dominant negative tuberin.