05-P015 Developmental regulatory targets of the homeobox transcription factor HESX1

(Shaked etal., PLoS ONE 2008). To further investigate this finding, several different approaches have been taken. First, the expression of HDAC-regulated candidate genes responsible for controlling neurogenesis has been examined through quantitative realtime RT-PCR. TSA-based inhibition of HDAC activity resulted in upregulation of Bmp2, Stat1, Stat3, Ngn1 and Ngn2 in neural precursors from both cortex and striatum. In contrast, the expression of Smad7, an inhibitor of BMP2/4 signaling, decreased as a result of HDAC inhibition. This suggested that HDACs control neurogenesis by inhibiting the BMP2/4 signaling pathway, with additional involvement of JAK/STAT signaling and the Ngn transcription factors. Second, in order to ascertain which HDAC family members influenced neurogenesis, the expression of individual HDAC genes was inhibited via RNA interference. Expression of HDAC 1, 2, 4 and 5 could be effectively downregulated, as seen on the mRNA level. The effect of the knockdown on neurogenesis and astrogliogenesis will be elucidated. Third, the expression patterns of individual HDACs in developing brain tissue will be presented.