Induction and early development of the hematopoietic and immune systems in Xenopus.

This paper reviews several aspects of the development of the hematopoietic and lymphoid systems in Xenopus. The developmental biology of hematopoietic stem cells and the early development of the thymus and B-cells are discussed. Recent advances in the development of molecular indices of the hematopoietic program are also considered. Previous studies as well as new data demonstrate that the hematopoietic program is initiated at the time of gastrulation. Recent advances suggest that both positive and negative regulation is necessary for the appropriate spatial and temporal expression of the hematopoietic program during development.