A novel marker of early epidermal differentiation: cDNA subtractive cloning starting on a single explant of Xenopus laevis gastrula epidermis.

To understand the molecular mechanism underlying in the earliest steps of the embryonic ectoderm subdivision into epidermis and neuroectoderm, it would be important to isolate differentially expressed genes in presumptive neuroectoderm and epidermis at the gastrula stage, the period of the divergence of the two adjacent ectodermal compartments. Meanwhile, the most direct approach for such a task, i.e. subtractive enrichment of cDNA from neuroectodermal and epidermal explants with differentially expressed gene sequences, was difficult to realize because of the high number of explants needed for this technique. In the present paper we report a novel effective and quite simple method of cDNA subtractive enrichment, based on amplification of cDNA in vitro by polymerase chain reaction (PCR) and allowing to use a very small amount of initial cDNA samples. With this method we have cloned cDNA of a novel gene of Xenopus laevis, which was named XEP-1 for its specific expression in the presumptive epidermis starting from the midgastrula stage.