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Id2 cDNA was isolated from a subtractive screen of stage-12 quail caudal somites. In situ hybridisation analysis identified the previously un-described expression of Id2 mRNA in distinct medial and lateral domains of the somitic dermamyotome in both quail and chick embryos. Id2 expression in somites was highly dynamic being first initiated in the lateral domain of the dermamyotome of stage-8-10 embryos, followed by expression in a separate medial domain. Id2 mRNA during subsequent embryonic development could be detected in both medial and lateral domains in the anterior to mid regions while the posterior, recently segmented somites, showed expression only in the lateral domain, which was eventually down regulated in the anterior-most somites. Tissue manipulation studies revealed that Id2 expression in somites required positive signalling from not only axial structures and lateral plate mesoderm but also surface ectoderm. In addition, Id2 expression was also observed in anterior and posterior domains of developing avian limb buds and interdigital tissue.