RAC1 and osteopetrosis: Interestingly, RAC1 and Cdc42 proteins bear consensus substrate motifs (RxRxxS) for PKCs and protein kinases with motifs similar to PKCs.93 In supporting these studies, Cdc42-deficient and Cdc42 downstream WASP KO mice also showed severe osteopetrosis phenotypes.60,94 Osteoclasts lacking WASP spread over a much larger surface area and are highly polykaryotic.