Altering Notch activity affects the heterochrony of BMP response between sister cells.

(A) Percentage of cell division generating two Tg(BMPRE-AAV.Mlp:EGFP)mw29 + cells (2 Bre+) or a single Tg(BMPRE-AAV.Mlp:EGFP)mw29 + cell and an ø cell (Bre+/ø) in WT and Tg(hsp70l:dnXla.Rbpj-MYC)vu21 (Notch KD) embryos. No statistical difference was observed between the Tg(hsp70l:dnXla.Rbpj-MYC)vu21 and the WT embryos using a chi-squared test (p = 0.70). n indicates the number of successfully tracked cells from 12 WT and 8 Notch-impaired embryos. (B) Scheme explaining the timing variables extracted from time-lapse datasets as well as the color code used for the different types of 2 Bre+ divisions: blue for Δt > 0, orange for t1 = t2 = Δt = 0, and purple for t1 = t2 ≠ 0. The red circles indicate nuclei from Bre- cells, whereas green circles represent Bre+ cell nuclei. (C) Percentage of 2 Bre+ divisions belonging to the symmetric and asymmetric categories. The difference between the WT and Tg(hsp70l:dnXla.Rbpj-MYC)vu21 backgrounds was determined to be significant using a chi-squared test (p = 0.0374). n indicates the number of successfully tracked cells from 4 WT and 6 Notch-impaired embryos. (D-M) Frames from a time-lapse dataset obtained in a WT embryo showing an example of an asymmetric 2 Bre+ division. The frames shown in F and G correspond to t1 and t2, respectively. (N-W) Frames from a time-lapse dataset obtained in a Tg(hsp70l:dnXla.Rbpj-MYC)vu21 embryo showing an example of a symmetric 2 Bre+ division. The Tg(BMPRE-AAV.Mlp:EGFP)mw29 transgene is expressed in the progenitor prior to division. Scale bar represents 15 μm. The time of division was set as a zero. Anterior is to the top. n indicates the number of successfully tracked cells. Nuclei expressing Histone2B:RFP are shown in gray, and the Tg(BMPRE-AAV.Mlp:EGFP)mw29 transgene is shown in green. Underlying data can be found in S1 Data. BMP, bone morphogenetic protein; KD, knock-down; n.s., not significant; WT, wild type.