Fig. 2. Math1-negative progenitors give rise to Math1-expressing cells. (A) Math1^EGFP expression is restricted to the external granule layer of the cerebellum at E14.5 and overlaps with endogenous Math1 expression. (B) FACS subdivides the Math1^EGFP-negative fraction from the Math1^EGFP-positive cells. (C) The unsorted cells, as well as the Math1^EGFP-negative cells, give rise to neurospheres, whereas the Math1^EGFP-positive cells do not form neurospheres. (D,E) FACS of neurospheres derived from Math1^EGFP-negative cells plated on a feeder layer reveals the upregulation of Math1^EGFP after 2 days in culture. The perdurance of the EGFP allows the double-labeling of Math1^EGFP-positive neurons expressing Tuj-1 (E).