Figure 2
- ID
- ZDB-FIG-240531-91
- Publication
- Torcq et al., 2024 - Tuning apicobasal polarity and junctional recycling in the hemogenic endothelium orchestrates the morphodynamic complexity of emerging pre-hematopoietic stem cells
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Immature HE is not polarized and controls membrane delivery of intra-cytosolic vesicular pools. (A) Tg(Kdrl:Gal4;UAS:RFP;4xNR:eGFP-podxl2) embryo imaged using spinning disk confocal microscopy. Black and white images show eGFP-podxl2 only. Images (single z-planes) were obtained from a time-lapse sequence (initiated at 35 hpf) lasting for 435 min (7.25 hr), with intervals of 15 min between each z-stack. Example of an HE cell with equal partitioning of eGFP-podxl2 between luminal and abluminal membranes (at t=0 min), with eGFP-podxl2 containing intra-cytosolic vesicles (one labeled with a green asterisk) and undergoing mitosis at t=30 min (HE cell 1’ and HE cell 1’’ are daughter cells). Note the inheritance of the largest micropinocytic-like vacuole by HE cell 1’ and its maintenance over time until EHT emergence initiation at t=180 min (green asterisk in 1.5 x magnified areas at t=60 and 90 min). At t=360 min (green box) EHT is proceeding and both fluorescence channels are shown; bottom panel: green (eGFP-podxl2), magenta (soluble RFP). The magenta arrow points at the basal side of the EHT pol+ cell (EHT cell 1’, on the right) that does not contain any detectable eGFP-podxl2; on the contrary, eGFP-podxl2 is enriched at the luminal/apical membrane (note that exocytosis of the large vacuolar structure may have contributed to increase the surface of the apical/luminal membrane [the green asterisk is surrounded by the apical/luminal membrane of the EHT pol+ cell]). The green arrow points at the abluminal membrane of the EHT cell derived from HE cell 1’’ (EHT cell 1’’) and that contains eGFP-podxl2 (with no evidence of a significant expansion of a luminal/apical membrane); this indicates that this cell is more likely to be an EHT pol- cell that did not sort the vesicular cargo to the luminal/apical membrane. Scale bar = 10 µm. (B) Hypothetical model summarizing the evolution of HE cells involving the tuning of apicobasal polarity to lead to cells competent for giving birth to either EHT pol+ or EHT pol- cells (including the release of large vesicular macropinocytic-like vacuoles preferentially toward the luminal membrane of future EHT pol+ cells). The polarity status of HE cells is proposed to evolve asynchronously throughout the entire EHT time window, leading to place-to-place ability to give birth to EHT cells (emergence of EHT pol+ and EHT pol- cells are both observed until 72 hpf, see main text). |