Analysis of WT and <i>Abl</i> muscle growth at RT and HT.

Abstract

<p>A) Muscle cell numbers per single-embryo culture from stage 10 WT and <i>Abl</i> embryos incubated at RT and HT. At RT, abundant muscle cells were present in <i>Abl</i> cultures but nearly absent in WT cultures (***p<0.001, rank test). HT-incubation greatly increased the number of muscle cells in WT cultures (***p<0.0001, rank test) while exerted little effect on <i>Abl</i> cultures. Similar proportions between muscle cells isolated from cell clusters and those still associated with clusters were observed among HT WT cultures, RT <i>Abl</i> cultures, and HT <i>Abl</i> cultures (57%, 41%, and 57% isolated muscle cells, respectively, for the 3 cultures). Error bars, SEM. Sample sizes for A (number of coverslips (C) and number of muscle cells (N) for each culture): WT RT, C = 17, N = 20; WT HT, C = 6, N = 633; <i>Abl</i> RT, C = 6, N = 238; <i>Abl</i> HT, C = 7, N = 371. Note that muscles cells in WT RT cultures were nearly absent (arrows). B) Average number of lamellipodia per muscle cell. The number for <i>Abl</i> RT was greater than both WT RT and WT HT. C) Increased degree of muscle fusion by HT incubation and <i>Abl</i> mutations. A majority of muscle cells in each culture type were multinucleated, except for WT RT cultures, in which very few muscle cells were encountered (total 20 in 17 cultures) and they were exclusively mononucleated (arrows). The fusion rate is significantly increased after HT incubation (WT, p<0.0001; <i>Abl,</i> p<0.03, χ² test). The identical cell samples from the same cultures were analyzed for B & C (number of muscle cells (N) and number of lamellipodia (n): WT RT, N = 20, n = 0; WT HT, N = 296, n = 39; <i>Abl</i> RT, N = 228, n = 60; <i>Abl</i> HT, N = 92, n = 44). Same cultures shown in A were analyzed. All cultures were derived from stage 10 embryos and incubated 2–5 days.</p