[P2.23]: SNF2L‐mediated control of cell number in the developing brain

identified fourmicroRNAs in foetal neural stem(NSC) andprogenitor (NPC) cells, miR9, 21, 153 and 335, which were specifically suppressed by the neuroteratogen, ethanol [Sathyan et al., 2007, J. Neurosci. 27(32): 8546–8557]. Moreover, the sensitivity of these microRNAs collectively explained many of ethanol’s effects on NSC renewal andmaturation.We found thatmir335particularly,playsan important role in NSC/NPC survival and proliferation. MiR335 is coded within the MEST gene locus, which is implicated in the aetiology of the Russell–Silver syndrome, as well as in the spatial patterning of the emerging cerebral cortex. In situ hybridization and immuno-fluorescence analyses indicate that bothmir335 andMEST localize to the apical cells of the fetal ventricular zone, further suggesting that the MEST/miR335 locus controls the proliferation and maturation of NSCs. To further study miR335’s impact on NSC/ NPC maturation, we cultured foetal mouse neuroepithelial cells as non-adherent neurospheres. We used microarray approach to identify key genes targeted by miR-335. Our results indicate that 214 genes encompassingMAPKinase, steroid biosynthesis and actin cytoskeleton reorganization pathways were significantly up-regulated followingmiR335 knockdown. Preliminary data indicates that FGF, which controls NSC renewal, also promotes the expression of miR335. These data collectively suggest that miR335 is an integral part of a complex signalling web that controls the growth and maturation of foetal NSCs. Its teratogen-sensitivity further supports the conclusion that microRNAs represent windows of vulnerability that render the developing foetus susceptible to environmental disrupters. Supported by a grant from NIAAA (AA13440) to RCM.