*2.7. Cortical Progenitor Cultures and Immunofluorescence*

Cortical progenitor cells were cultured as described previously [26]. Briefly, cortices were dissected from TCTP-cKO and littermate control embryos at E14.5–E15.5. Cortices were mechanically dissociated by trituration, and cell aggregates were plated on polyornithine-coated 4-well dishes and cultured in media containing Neurobasal medium (Invitrogen), 0.5 mM glutamine, 0.5 % penicillin–streptomycin, 1% N2 supplement (Invitrogen), 2% B27 supplement (Invitrogen), and 10 ng/mL NGF-2. On day 1, the medium was replaced with fresh medium. Immunofluorescence or immunohistochemistry experiments were performed 3 days after culture. Cultured cells were fixed in 4% paraformaldehyde for 20 min at room temperature and further processed for immunostaining. Cells were permeabilized with 0.1% Triton X-100, blocked for 1 h in 5% bovine serum albumin–5% goa<sup>t</sup> serum, and incubated with primary antibodies, rabbit TCTP, and anti-nestin. After incubation overnight, cells were washed with PBS followed by 2 h of incubation with secondary antibodies, conjugated FITC, or rhodamine. Cells were counterstained for 30 s with DAPI for double immunofluorescence.

### *2.8. Cell Survival Assay and MTT Reduction Assay*

Quantitative measurements of cortical progenitor cell survival were performed using the 3-[4, 5-dimethylthiazol-2-yl]-2, 5-duphenyltetrazolium bromide (MTT) reduction assay. The MTT reduction assay measures mitochondrial function as an index for cell survival. Cells were incubated in culture medium with MTT at a final concentration of 0.5 mg/mL MTT for 2 h; afterwards, the culture medium was replaced with 500 mL of dimethyl sulfoxide. Absorbance at 570 nm was determined by an ELISA reader.

## *2.9. Statistical Analysis of the Data*

The experimental results are expressed as the mean and standard error of the mean (mean ± SEM) accompanied by the number of observations. Data were analyzed by Student's unpaired *t*-test, taking *p*-values of <0.05 as significant. Data obtained from 3 or more groups were compared by one-way ANOVA; *p*-values of <0.05 were considered statistically significant. Because the sample sizes involved in each experiment were di fferent, they were included in the figures and/or figure legends.
