EXPRESSION OF FLT3 TYROSINE KINASE RECEPTOR GENE IN MOUSE HEMATOPOIETIC AND NERVOUS TISSUES

The Flt3 gene encodes a tyrosine kinase receptor highly related to the Kit and Fms gene products. We have studied the expression of Flt3 by using in situ hybridization of mouse tissue sections. The results show that Flt3 RNAs are present in certain regions of lymphohematopoietic organs, placenta and nervous system. Flt3 is expressed in the medullar y area of fetal and newborn thymus, in the paracortical regions of lym ph nodes and in the red pulp of spleen. In placenta, labyrinthine trop hoblasts express Flt3. Finally, Flt3 RNAs are found in several re ions of the brain and in cerebellar Purkinje cells. Western-blot analysis showed that the FLT3 protein is present in the tissues positive for Fl t3 RNA expression. Our observations allow for a comparison with the di stribution of the Kit gene and analysis of a possible redundancy betwe en KIT and FLT3 receptors.