Limbs develop from limb buds composed of a core of limb progenitor cells covered by the surface ectoderm. Cell trac- king experiments in chick showed that the limb progenitors located at the distal tip of the limb bud progressively res- trict their developmental potential in the proximo-distal axis. The mechanisms and models by which the limb progeni- tors acquire progressively more distal fates are subject to intense investigation and debate. To shed light into this issue we have generated expression profiles for each of the progressive differentiation step by RNA-seq. In parallel we have also generated the temporal transcriptome of the distal ectoderm including the Apical ectodermal ridge (the AER). We seek to unravel expression pattern specific of each of the progressive stages of the limb progenitors and of the AER trying to identify essential descriptors of their biological state (morphogenetic potential). Of 46,480 Ensembl-anno- tated genes, 3,416 were differentially expressed between ectoderm and mesoderm. Intriguingly, we observed that the number of genes changing between stages is similar between ectoderm and mesoderm, with the bulk of changes occurring from E9.5 to E10.5. Expression pattern validation was confirmed by in situ hybridization and trustful pre- viously published data. Gene Ontology analysis revealed, in general terms, a downregulation of transcription factors and an upregulation of extracellular molecules with age. We have identified a specific expression of HoxC genes in the limb ectoderm, which is currently on evaluation.

Resumen del póster presentado al 11th Meeting Spanish Society for Developmental Biology, celebrado en Girona del 19 al 21 de octubre de 2016.

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