5 GE essentially as described . full protocol described in. Embryos were always find useful information dissected on ice in PBS and de capitated. The brain was removed, the hemispheres separated, and the lateral and medial ganglionic emi nences removed with fine forceps. GE cells were mech anically dissociated with a fire polished Pasteur pipette and plated out in cell culture flasks with 100,000 cells per milliliter in NS Medium with B27 supplement, penicillin/streptomycin, human EGF and human bFGF. NS were incubated in suspension at 37 C, 5% CO2 for 1 week and fed on the 5th day with an equal volume of NS medium. For differentiation, 7 day old NS were collected into 50 ml tubes and centrifuged for 3 minutes at 100xg.

The NS were mechanically dissociated using a fire polished Pasteur pipette and plated out with 150,000 cells per cm2 in petri dishes in NS medium without EGF and with 1% fetal calf serum, a medium that supports the differentiation of both neurons and astrocytes. After 2. 5 days of incubation the medium was changed to NS medium without bFGF and EGF but with 1% FCS. The following pharmacological reagents were added in different experiments 10, 25 or 50nM trichostatin A, recombinant BMP2, 6 h, 24 h. Immunocytofluorescence Neurospheres were cultured as described above, treated with 50nM trichostatin A, recombinant BMP2, or both reagents for 24 hours before bFGF withdrawal, cultured for another 4. 5 days, and fixed with 4% PFA for 10 min. Cultures were stained as described with the following antibodies TuJ1, O4, anti GFAP, and DAPI. Confocal analysis was per formed on a Nikon A1Rsi microscope.

RNA Isolation Total RNA was isolated from neurosphere culture 6, 12, and 24hours after treatment using RNeasy Mini Kit according to the manufacturers instructions. RNA quality was examined by agarose gel electro phoreses and concentration was determined by UV ab sorbance. Affymetrix Arrays were performed with RNA samples from untreated and 6 h and 24 h TSA and BMP2 treated cultures. RNA from cultures treated with TSA or BMP2 from all three time points were used for quantitative real time PCR. Biotin labeled cDNA transcription and Affymetrix gene chip hybridization Total RNA samples obtained after 6 h and 24 h treat ment were labeled and hybridized to an Affymetrix Gene ChipW Mouse Genom 420 2. 0 according to manufacturers protocol.

Biotin labled cRNA transcription and Affyme trix gene chip hybridization was performed by the Gen omic Core Facility of EMBL, Heidelberg. Analysis of gene expression data Raw data obtained from Affymetrix gene chip were ana lyzed using dChip software. Samples were normalized using rank based normalization. Genes were considered Drug_discovery to be signifi cantly regulated if expression had changed more than two fold and absolute difference of normalized values exceeded 100 comparing treated and mock treated samples with a confidence greater than 90%. Data was submitted to GEO.