her9 is expressed in hindbrain progenitor populations at late embryonic stages. (A-A″,B-B″) Tg[BCP:H2BGFP] in situ hybridized with her9 and sox2 (A′) or fabp7a (B,B′) probes at the indicated stages. Arrowheads indicate the position of the hindbrain boundaries. (D-D″) Embryos at 72 hpf hybridized with her9 and fabp7a probes and immunostained with anti-pH3. (C,F-F′) Tg[BCP:H2BGFP] embryos at the indicated stages assayed for EdU incorporation to detect cells in S phase (n=6/6 at 48 hpf and n=5/5 at 72 hpf). Turquoise and red arrowheads indicate the position of mitotic or proliferating cells in lateral and medial domains, respectively. (A-F,A′-F′,A″,D″) Dorsal maximum intensity projections of the hindbrain with anterior to the left. (E,G) Plots showing the number of mitotic cells or S-phase cells in her9-expressing domains (E: 8±3.5 cells in the medial versus 6±2.5 cells in the lateral domain, n=9; G: 63.8±7.9 cells in the medial versus 44.8±11.1 cells in the lateral domain, n=5]. (H) Plot showing the percentage of S-phase cells in hindbrain domains (23.7±5.6% in the her9-expressing lateral versus 34.5±8% in her9-expressing medial versus 41.9±10.5% in the her9-negative domain, n=5). (I,J) Embryos treated with DMSO or LY411575 from 60 hpf to 72 hpf, and in situ hybridized with her9 probe (DMSO n=7/7; LY411575 n=6/6). (K-N) Embryos injected with control-MO and her9-MO, and in situ hybridized with sox2 probe or immunostained with anti-Sox2 at 72 hpf. Note that sox2 expression domain (K-M) was decreased in the her9-MO embryo (L, n=6/7; N, n=8/9) compared to the control (K, n=7/7; M, n=8/8). (a-a″,b-b′,c,d-d′,f-f′,I-N) Transverse projections of r4/r5 boundary. Asterisks indicate the position of the her9-expressing lateral domains. Dotted line delimitates the contour of the neural tube. BCP, boundary cell population; hpf, hours post-fertilization; MO, morpholino. Scale bars: 50 µm.
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