YR3: The Role of the NotchNumb Interaction in Promoting Skeletal Muscle Repair

YR3: The Role of the NotchNumb Interaction in Promoting Skeletal Muscle Repair The Role of the Notch/Numb Interaction in Promoting Skeletal Muscle Repair Skeletal muscle repair is dependent on the balance between self-renewal of endogenous stem cells, called satellite cells, and their differentiation into muscle fibers. Numb, an adaptor protein that participates in protein ubiquitination and receptor-mediated endocytosis, is associated with asymmetric segregation of daughter cells and the regulation of binary cell fates in a broad set of developing tissues. The pattern of Numb expression in activated satellite cells predicts a similar role for the gene in regulating skeletal muscle repair. To directly test this, we propose to conditionally inactivate Numb in mice and use both in vitro and in vivo approaches to examine its impact on satellite cell proliferation and differentiation. Numb will be inactivated postnatally in mice using a tamoxifen inducible CAGGCre-ERTM transgene to direct recombination of the floxed Numbtm1Zili allele. We have also bred the Numbtm1Zili allele into the brachyury(T) Cre to generate mice that will have Numb deleted in all cells of the somites, the anlage of skeletal muscle. Muscle repair will be measured following experimentally induced injury by examining the rate and extent of muscle fiber regeneration and the number and distribution of active and reserve satellite cells. The effects on satellite cell proliferation and differentiation will be examined in vitro using satellite cell cultures derived from CAGGCre-ERTM:Numbtm1Zili/tm1Zili mice. The establishment of genetically corrected populations of satellite cells represents a viable approach to treating some forms of muscular dystrophy. Enhancing the self-renewal capabilities of engrafted satellite cells will significantly contribute to the regenerative potential of this therapeutic approach.