ro. The four factors SDF-1, PTN, IGF2, and EFNB1 were sufficient to induce hESC to differentiate to DA neurons. were used for 810 days for CM collection. CM that had been frozen at 220uC for up to one month was also used. Co-culture of BG01V2 with feeder cell lines For co-culture experiments, the cell lines were grown to confluence in 6-well tissue culture plates in their 84573-16-0 biological activity respective growth media as previously described. Media was replaced with hESC differentiation medium, comprised of Glasgow Minimum Essential Medium supplemented with 10% knockout serum replacement, 0.1 mM nonessential amino acids, 1 mM sodium pyruvate, and 0.1 mM b-mercaptoethanol. MEFs and stromal cells were cultured in 0.1% gelatin and collagen type-I coated plates, respectively. The PA6 subtype PA6-X exhibited rapid cell division and a lack of contact inhibition of growth. Upon confluency, PA6X feeder layers retracted and detached from the plates. 21505263 To avoid detachment, cells were inactivated with 10 mg/ml mitomycin-c for one hr followed by three washes with 
fresh medium and permitted to recover overnight. BG01V2 colonies were dissociated from the MEF feeder layer by enzymatic treatment and added to the feeders at a density of 50100 small colonies/well corresponding to 500010000 cells/cm2. The culture medium was changed on day four and every other day thereafter. The hESC were allowed to grow and differentiate on the feeder layers for 12 days. Immunocytochemistry Materials and Methods Cell lines Mitotically-inactivated MEF feeder layers were cultured in cell culture dishes coated with 0.1% gelatin with high-glucose Dulbecco’s Modified Eagle’s Medium , supplemented with 10% fetal bovine serum and 50 U/ml Penn-Strep. The MM55K mouse kidney cell line was purchased from American Type Culture Collection and cultured with high-glucose DMEM containing 10% fetal bovine serum and 50 U/ml Penn-Strep. The PA6 mouse stromal cell line was obtained from Riken BioResource Center Cell Bank. MS5 cells were kindly provided by Dr Caruz. The stromal cell lines were cultured in aminimum essential medium supplemented with 10% fetal bovine serum and 50 U/ml Penn-Strep. Sub-culturing of these cell 17984313 lines was accomplished by trypsinization using 0.5 1 ml 0.05% trypsin-EDTA for 23 min. hESC lines used were: BG01V2, BG02, and BG03, derived by BresaGen. The BG01V2 hESC line is a variant of the hESC line BG01. Mitotically-inactivated MEFs were used as feeder cells to maintain BG01V2 in an undifferentiated state. The hESC culture medium consisted of DMEM/nutrient mixture, supplemented with 10% Knockout serum replacement, 2 mM L-glutamine, 1 mM nonessential amino acids, 4 ng/ ml bFGF, 50 U/ml Penn-Strep, and 0.1 mM b-mercaptoethanol. The culture media was changed daily with routine passage of hESC on fresh MEF layers carried out once a week. hESC colonies were isolated from the MEF feeder layers with 1 mg/ml collagenase type IV treatment for approximately 1 hr. Feeder-free cultures of BG01V2 were grown on human fibronectin, 20 mg/ml, in MEF conditioned medium. MEF-CM was collected daily, filtered and supplemented with an additional 16 ng/ml of bFGF before feeding hESC. MEF cells Cultures were fixed in 4% paraformaldehyde in PBS and then incubated with the primary antibodies in blocking buffer at room temperature for two hr. The following primary antibodies were used: mouse anti-Oct 3/4, rabbit anti-TH, mouse anti-TH, rabbit antib III-tubulin, mouse anti-nestin, rabbit anti-GFAP, mouse antiMAP-2, and
