INTERLEUKIN-7 IS TROPHIC FOR EMBRYONIC NEURONS AND IS EXPRESSED IN DEVELOPING BRAIN

Interleukin-7 (IL7) is a hematopoietic cytokine with critical function s in both B- and T-lymphocyte development. In this study, we find that IL7 exhibits trophic properties in the developing brain as well. Trea tment of cultures of embryonic brain with exogenous IL7 increases neur onal survival and results in greater numbers of cells manifesting neur ite outgrowth. As demonstrated with single-cell cultures, IL7 acts dir ectly to promote neuronal survival. Expression of the mRNA encoding th e high-affinity IL7 receptor (IL7R) is observed in vitro in neurons as well as in subventricular zone progenitor cells. Phosphorylation of p 59(fyn), which is activated by IL7 in pre-B cells and is thought to be important in neural development, occurs rapidly following IL7 treatme nt of cultured embryonic neurons. Additionally, the expression of c-my c mRNA, which is modulated by IL7 in lymphoid cells, is upregulated by IL7 in the same CNS cultures. Finally, the messenger RNAs encoding IL 7 and IL7R are expressed in vivo in developing brain. The direct neuro trophic properties of IL7 combined with the expression of ligand and r eceptor in developing brain suggest that IL7 may be a neuronal growth factor of physiological significance during central nervous system (CN S) ontogeny. (C) 1996 Academic Press, Inc.