Sternal ossification defects and formation of pre-axial polydactylous triphalangeal thumbs preferentially in the hind limbs have been described in two different mouse models of Meckel-Gruber syndrome gene Mks1—kerouac and Mksdel64-323 and demonstrated to be caused by disruptions in Hh signaling [39, 40]. This evidence concerns the gene MKS1 and Meckel syndrome, type 1.