Experimental study of MAP kinase phosphatase-3 (Mkp3) expression in the chick neural tube in relation to Fgf8 activity

Mitogen-activated protein kinase (MAPK) pathways are well known to be involved in signal transduction from extracellular to intracellular compartments in all eukaryotes. The activation of this cascade will have an effect on cell proliferation, differentiation, and apoptosis. In this study, we describe the cloning of the chick Mkp3 gene that is highly homologous to the mammalian gene and are both expressed in several embryo regions with demonstrated morphogenetic activity. In early developmental stages, Mkp3 and Fgf8 have similar expression patterns. Differences in the activation of Mkp3 transcription in the isthmus and the repression with FGF receptor inhibition suggest that Fgf8 protein controls Mkp3 transcription. Ectopically, expression of Fgf8 protein induces Mkp3 in a short period of time in the diencephalon, indicating a positive regulation of Mkp3 by Fgf8. Moreover, we show a distinct tissue competence to express Mkp3 rostrally and caudally to the zona limitans intrathalamica (ZLI).