Fig. 3. (A) Numbers of neurospheres from E10.5 rostral telencephalic vesicles of wild type (WT) or tenascin C (TNC) null mice (K/O) grown for seven days in the presence of either fibroblast growth factor (FGF2) or epidermal growth factor (EGF) (20 ng/ml). Note the lack of EGF-responsive neural stem cells in TNC null cells as demonstrated by the absence of neurosphere formation in EGF. Results represent mean±s.e.m. of three independent experiments (Student's t-test: ^*P<0.001). (B) E10.5 neurospheres were grown for 5 days from heterozygous (+/–) or TNC null (–/–) cells in the presence of FGF2 (20 ng/ml) and 0 or 10 µg/ml TNC as indicated. The Figure shows 4 gel lanes from the same Western blot analysis of neurosphere proteins using antibodies against the EGFR, with a long exposure required to visualise the low levels of EGFR protein at this developmental stage. Note that EGFR is detected in heterozygous cells either with or without added TNC (lanes 1-2). By contrast, FGF2 alone was not sufficient to induce EGFR expression in the null cells after 5 days (lane 3), and that EGFR expression was rescued by the addition of exogenous TNC for the duration of the experiment (lane 4).