Differential induction of Pax genes by NGF and BDNF in cerebellar primary cultures.

The Pax genes encode sequence-specific DNA binding transcription factors that are expressed in embryonic development of the nervous system. Primary neuronal cell cultures derived from the cerebellar cortex of embryonic day 14, newborn and 7-d old mice, were used to investigate the cell-type specific expression patterns of three members of the murine paired box containing gene family (Pax gene family), in vitro. Cell types which express Pax-2, Pax-3, and Pax-6 RNA in primary cultures correspond to those found in regions of the cerebellum which show RNA signals in sections of the developing mouse brain. To find mechanisms regulating Pax gene expression during cerebellar development, the differential regulation of Pax-2, Pax-3, and Pax-6 by NGF and BDNF, two structurally related neurotrophins, was studied in such primary cultures. Pax-2 and Pax-6 RNA increased slightly by 1 h and remained elevated throughout a 24-h treatment with BDNF and NGF. Pax-3 RNA was not detected in newborn cultures, but underwent a rapid (1 h) and transient (2 h) induction upon treatment with either BDNF or NGF. No response was seen with EGF or FGF. Cycloheximide treatment amplified Pax-3 induction and prolonged the signal. Thus, Pax-3 induction resembles that of the immediate-early gene c-fos, which transduces growth factor signals during the development of particular neuronal/glial cell types. The changes in Pax expression were inductive rather than trophic.