 Without LBX1, limb muscles will fail to form properly; studies have shown that hindlimb muscles are severely affected by this deletion while only flexor muscles form in the forelimb muscles as a result of ventral muscle migration.c-Met is a tyrosine kinase receptor that is required for the survival and proliferation of migrating myoblasts.A lack of c-Met disrupts secondary myogenesis and—as in LBX1—prevents the formation of limb musculature.