Figure 4.

Laminar fate of GABAergic interneurons is independent from the environment of the last mitosis. a–c illustrates the laminar fate acquired by BrdU-positive rat β-actin-GFP interneurons generated by P7 donors transplanted to E15 (a), P1 (b), and P7 (c) wild-type rat recipients. The nucleotide analog was administered in the first 24 h after transplantation. d–m, The phenotype and distribution of these donor cells (examples are depicted in g–i) match those of endogenous interneurons born on the day of transplantation (Fig. 2e, one-way ANOVA with Bonferroni's multiple comparisons, p > 0.05). P7 rat β-actin GFP-derived interneurons transplanted to P1 hosts, which captured BrdU administered 8 h (d, j, k) (61 cells/8 cases) or 24 h (e, l, m) (64 cells/6 cases) before dissection, also reached laminar positions consistent with the host age (one-way ANOVA with Bonferroni's multiple comparisons, p = 0.43; both conditions were significantly different from the laminar position occupied by interneurons born at P7; Student's t test, p < 0.0001). Similar results were obtained with fluorescence-activated cell-sorted P7 Gad67-GFP postmitotic donor cells, which also acquired host-specific phenotypes [e.g., basket neurons in the molecular layer (ML) (n), and Lugaro cells in the granular layer (GL) (o); the inset shows that this cell is not immunopositive for parvalbumin] and positions (f; Student's t test vs endogenous interneurons born at P0, p = 0.12, vs endogenous interneurons born at P5, p < 0.0001). In all instances, the recipient animals were killed 1 month after transplantation. PCL, Purkinje cell layer. Scale bars: (h–l, n), 20 μm; (g, m, o), 50 μm.