(a) Schematic diagram of BrdU incorporation experiment. At E12.5, intraperitoneal injection of BrdU was performed and cells in S-phase (progenitors) incorporated BrdU. At E13.5 postmitotic neurons generated from BrdU-labelled progenitors can also be labelled with BrdU. The number and the position of BrdU-labelled GABAergic interneurons and Purkinje cells predicts a general distribution of PIPs and PCPs at E12.5, respectively. (b,c) Examples of immunostaining of E13.5 wild-type cerebellum using antibodies for BrdU, Lhx1/5 and (b) Pax2 or (c) Corl2. Immunostaining of Lhx1/5 enables the distinction of BrdU-labelled postmitotic neurons from BrdU-labelled mitotic progenitors. (d,e) Representative images of plots of indicated cells in wild-type and Olig1/2 dKO cerebella. (f) The ratio of BrdU-labelled Pax2 + INs or Purkinje cells to BrdU-labelled GABAergic neurons in wild-type and Olig1/2 dKO cerebella (n =3, ***P<0.001 by t-test, mean±s.e.m.). (g,h) Short-term lineage tracing analyses using (g) heterozygotes and (h) homozygotes of Olig1/2 dKO line. Arrowheads indicate GFP-positive Pax2 INs. Scale bars represent (b,c) 100 μm, (g,h) 25 μm.