Fig. 5: Cdkn1c function is required for nascent cortical projection neuron survival.

Analysis of developing cerebral cortex in MADM-7 (MADM-7^GT/TG;Emx1^Cre/+) (a–e), Cdkn1c-MADM-7 (MADM-7^GT/TG,Cdkn1c;Emx1^Cre/+) with maternal deletion (f–j), Cdkn1c-MADM-7 (MADM-7^GT/TG,Cdkn1c;Emx1^Cre/+) with paternal deletion (k–o), and cKO-Cdkn1c-MADM-7 (MADM-7^{GT,Cdkn1c/TG,Cdkn1c};Emx1^Cre/+) (p–t) at E13. The parent, from which the MADM cassettes and with recombined Cdkn1c-flox allele (Cdkn1c) (f–t) was inherited, is indicated in the respective genotypes in pink (mother) and blue (father). Schematics (a, f, k, p) depict green (GFP⁺), red (tdT⁺), yellow (GFP⁺/tdT⁺) and unlabeled MADM cells with UPD (red, green) and control cells (yellow, unlabeled). Imprinting (arrow, expression; ball on stick, repression) and expression (0×, 1×, 2×) status is indicated. Conditional deletion of Cdkn1c is marked with red cross. Parental origin of chromosome is indicated (M maternal, P paternal). MADM-labeling in overview (GFP⁺, green; tdT⁺, red; GFP⁺/tdT⁺, yellow) (b, g, l, q) and G/R ratio (geometric mean) of single MADM-labeled cortical projection neurons (c, h, m, r) in MADM-7 (b, c), Cdkn1c-MADM-7 with maternal deletion (g, h), Cdkn1c-MADM-7 with paternal deletion (l, m), and cKO-Cdkn1c-MADM-7 (q, r) at E13 indicate emerging microcephaly. Note the equipotency of cells with matUPD and patUPD in (c) and (r) but decreased numbers of Cdkn1c^−/− cells when compared to Cdkn1c^+/+ cells in (h) and (m) regardless of the UPD status. Labeling of apoptotic Caspase-3⁺ cells (white) in MADM tissue (GFP⁺, green; tdT⁺, red; GFP⁺/tdT⁺, yellow) (d, i, n, s); and quantification of Caspase-3⁺/DAPI⁺ coloc (%) (e, j, o, t) in MADM-7 (d, e), Cdkn1c-MADM-7 with maternal deletion (i, j), Cdkn1c-MADM-7 with paternal deletion (n, o), and cKO-Cdkn1c-MADM-7 (s, t) at E13. Note that in MADM-7 almost no Caspase-3⁺ cells are detected. Yellow arrows indicate GFP⁺ remnants of Cdkn1c^−/− mutant cells. All bars indicate mean. Error bars represent SEM (e, j, o, t). Data points indicate individual animals (n = 3). Nuclei were stained using DAPI (blue). NCX neocortex. Scale bar, 200 μm (b, g, l, q) and 20 μm (d, i, n, s). Source data are provided as a Source Data file.