Zic2a regulates proliferation, but not apoptosis or differentiation of PT precursors. Embryos were injected singly or co-injected with zic2aMO and p53MO and stained out for expression of arx, an early PT marker at 15 somites (A–C), dlx2a, a late PT marker, at Prim-7 (D–F), or gfp (G, H). (A) p53 morphants show normal expression of arx (26/26 embryos, 2 exp.). (B) Embryos injected with zic2aMO alone show a strong reduction of arx expression at 15s (13/17 embryos, 2 exp.). (C) Co-injection of zic2aMO and p53MO leads to a similar reduction of arx expression (11/16 embryos, 2 exp.). (D) p53MO-injected embryos show no patterning defect at Prim-7 (29/30 embryos, 2 exp.). (E) zic2aMO-injected, or (F) zic2aMO and p53MO co-injected embryos show equivalent loss of dlx2a expression at Prim-7 (19/26 embryos, 2 exp. and 33/45 embryos, 2 exp. respectively). (G, H) Transgenic Tg(HuC:gfp) embryos express gfp in post-mitotic neurons. (G) conMO-injected transgenic embryos show no evidence of gfp-positive post-mitotic cells in the PT at 12s. (H) zic2aMO morphants do not contain prematurely differentiating cells in the PT at 12s (17/17 embryos, 3 exp.). (I) Ratios of BrdU positive cells/total cells in conMOs and zic2aMOs at 10s and 17s. 10s analysis revealed no significant difference between conMO-injected (n = 5) and zic2aMO-injected (n = 4) embryos. 17s analysis showed a significant difference (p = 0.005) between conMOs (n = 5) and zic2aMOs (n = 4). (J–M) Representative confocal sections of MO-injected embryos, showing BrdU-positive cells in yellow and BrdU-negative nuclei in green. White outlines the approximate prethalamic area determined by arx expression at the same stages. Embryos are shown in lateral view, anterior to the left. Arrows mark the PT.
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