MZ myo1g mutants present stage-specific endosomal trafficking defects. a, b MZ myo1g mutants present an increased number of SARA-negative AcvrIIAa endosomes (white arrowheads). Animal pole views of germ ring stage blastoderm cells. Scale bars: 10 µm. c, d Quantifications of AcvrIIAa/SARA-positive endosomes in WT control and MZ myo1g mutant cells in the germ ring stage blastoderm (c) and the 12 somites stage Lateral Plate Mesoderm (d, see also Supplementary Fig. 12c, d). Left panels: Mean number of AcvrIIAa-GFP and mRFP-SARA double-positive endosomes per cell. Middle panels: Percentage of the total number of AcvrIIAa endosomes per cell that are SARA-negative. Right panels: Number of SARA endosomes per cell. The absolute number of AcvrIIAa+SARA double-positive endosomes decreases and the fraction of SARA-negative AcvrIIAa endosomes increases both in the early blastoderm (c) and later lateral plate mesoderm (d). In contrast, the mean number of SARA endosomes per cell remains unchanged in MZ myo1g mutants at the early germ ring stage while being significantly decreased at 12 somites. In c, d data points represent the mean number of endosomes per cell for a particular embryo and lines indicate the overall mean ± SEM. e Eight-somites stage SARA morphants (MO sara) present a reduction in the antero-posterior extension of forebrain lft1 expression. Dorsal views of the brain, anterior up. Scale bar: 100 µm. Box plots in e indicate mean values ± SD. All p values were obtained using non-directional statistical tests. Complete numerical and statistical information for all experiments are provided in the Source Data files.
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