We cloned the Xenopus homologue of cadherin-11 and studied its spatiotemporal expression pattern during early development. The messenger RNA is present from the mid-gastrulation through embryo development. It is expressed in different neural crest cell populations, during their migration and differentiation. This pattern, unexpected for an adhesion molecule, reinforces the idea of novel functions for type II cadherins.

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Thymotaxin, an 11-kilodalton protein chemotactic for rat bone marrow hematopoietic precursors, was purified from media conditioned by a rat thymic epithelial cell line. The NH2-terminal sequence of thymotaxin was identical to that of rat beta 2-microglobulin (beta 2m). Antibodies to beta 2m removed thymotaxin activity from the fraction containing the 11-kilodalton protein. Chemotactic activity was observed with rat plasma beta 2m, human beta 2m, and mouse recombinant beta 2m, further supporting the identity of thymotaxin with beta 2m. The directional migration, as opposed to random movement, of the cells was also confirmed. The only rat bone marrow cells that migrated toward beta 2m were Thy1+ immature lymphoid cells devoid of T cell, B cell, and myeloid cell differentiation markers.

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