MEMBERS OF THE JAK STAT PROTEINS ARE EXPRESSED AND REGULATED DURING DEVELOPMENT IN THE MAMMALIAN FOREBRAIN/

The presence and activation of members of the Janus Kinases/Signal Tra nsducers and Activator of Transcription proteins ill response to speci fic cytokines is currently the focus of intense investigation in the h ematopoietic system. Although some evidence suggests that cytokines mi ght play an important role in brain development and brain pathologies, very limited information is available on the presence of the JAK/STAT proteins in the Central Nervous System. Here we provide Western blot and immunohystochemistry data on the presence of Jak2 in vivo in the i mmature brain, its expression being greater in early stages of the emb ryonic life and gradually diminishing towards adulthood. Conversely, J ak1 was found expressed at a lower level compared to Jak2 and not modu lated during brain maturation. Western blot data also show that specif ic members of the STAT family, the cytoplasmic substrates of the Janus Kinases, are present in vivo and that the extent of their expression is modulated differently at various stages. In particular, Stat6 prote in levels were markedly attenuated at advanced stages of differentiati on, as well as in the adult brain, with respect to early embryonic lif e. On the contrary, Stat3 levels did not vary, Analysis of Stat1 and S tat5 proteins showed a more complex expression pattern, These data ind icate that members of the JAK/STAT proteins are present and modulated in vivo in the embryonic and postnatal brain, therefore supporting the ir role in the modulation of gene expression during the different stag es of brain maturation. (C) 1998 Wiley-Liss, Inc.