Developmental biology and etiology of axial skeleton: Lessons from a mouse model of spondylocostal dysostosis and spondylothoracic dysostosis

Skeletal patterning is tightly linked to embryonic morphogenesis. Accumulated evidence on genotype–phenotype analyses in model animals and human has uncovered molecular signals that participate in skeletal size, shape, and spatial organization. Embryonic morphogenesis endows morphological information to groups of skeletal precursors. Accordingly, some of the congenital skeletal disorders are manifested as defects in embryogenesis prior to skeletal tissue differentiation and pathologically categorized as dysostosis. Spondylocostal dysostosis (SCDO) and spondylothoracic dysostosis (STDO) are skeletal disorders that are highly specific to the axial skeleton, vertebrae, and ribs, whose embryonic origin is the segmented mesodermal structure called somite. The genes responsible for these diseases have recently been identified and are operated during somite formation. Current investigations on organogenesis of mouse models of SCDO and STDO uncovered the existence of more complicated regulatory steps for the spatiotemporal organization of the axial skeleton than the original view of direct link between morphogenesis and skeletal patterning. Molecular and cellular findings in axial skeleton development are expected to contribute to develop more efficient therapeutic strategies against common medical problems.