The mechanism of somite formation in mice.

Somitogenesis is a series of dynamic morphogenetic events that involve cyclical signaling. The periodicity of somitogenesis is controlled by segmentation clock operating in the presomitic mesoderm (PSM), the precursor of somites. Notch signaling plays important roles not only in the segmentation clock mechanism but also as an output signal of the clock to induce Mesp2 transcription that controls somite formation. In the present review, recent advances in the understanding of the molecular mechanisms underlying the translation of clock information into the spatial patterning of segmental somites in mice are discussed. Particular attention is paid to the interplay between two the distinct signaling pathways of Notch and FGF and the Mesp2 transcription factor acting as an effector molecule during mouse somitogenesis.