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Presenting Author(s) Susana Pascoal
Abstract Title Temporal control of limb bud development: evidences of a molecular clock.
Full author List Carvalho C.(1), Rodriguez-Léon J.(1), Pascoal S. (1,2), Delphini MC.(3), Vieira C.(1), Thorsteinsdóttir, S.(1), Duprez D.(3), Belmonte JC.(1), Palmeirim I(1,2)
Text of abstract

The limb bud is asymmetric along its three development axes, P-D, A-P and D-V, and its formation requires a precise orchestration of cell proliferation and differentiation in both space and time. Among the three cardinal axes, the mechanisms that lead to cell fate specification along the P-D axis are the least understood.

In 1997, Palmeirim et al., presented evidence for the existence of a molecular clock underlying the process of chick somitogenesis by describing a dynamic expression pattern of hairy1 gene in presomitic cells. These authors showed that presomitic mesoderm (PSM) cells undergo several cycles of hairy1 expression, with a 90 minute periodicity, corresponding to the time required to form one somite-pair. Other genes presenting cyclic gene expression in the chick PSM are hairy2, lunatic fringe, and hey2.

In this study, we analyzed the expression pattern of hairy2 during limb development. We found that hairy2 transcripts are detected in ZPA and AER signalling centres and we investigated the regulation of hairy2 expression in those structures. Surprisingly, we found that hairy2 presents a dynamic expression pattern not only along the P-D axis of the distal mesenchyme, but also along the D-V axis, in the dorsal and ventral mesenchymal masses of the limb. We propose that the molecular clock underlying the process of somitogenesis is not an exclusive property of PSM cells, but a more general way to count time and to provide positional information during vertebrate embryonic development.
Which session is your work most relevant to: Limb patterning