Fig. 2

FEVPs proliferate at the LPM.

A to C shows dorsal view of etsrp⁺ cells at 4, 8, and 12 som. Two lateral stripes of etsrp⁺ cells evenly distributed on either side of the midline at 4s (A). At 8 som, an asymmetric break is noticed (B, blue asterisks) in the cells of LPM resulting in two etsrp⁺ cell populations that show distinct behavior (B and C, green and yellow arrows). A and B contain insets of etsrp⁺ cells at LPM marked by red dots, which was quantified in panel D, red bars. (D) show quantitation of etsrp⁺ cells as indicated by red dots in panel (B) across each stage indicated in the graph. Error bars represent SEM (qPCR, n = 9; cell count, n = 10). Red bars indicate absolute cell number and blue bars indicate etsrp transcript fold change. Samples for analysis were collected at the indicated stages. (E-G) Developing embryos (1 som) were treated with BrdU (10 mM) in embryonic buffer, and subsequent staining was performed with DAB substrate. The BrdU incorporated cells appear in the developing somites at the midline (black arrows) and in the two lateral stripes of etsrp⁺ cells at the LPM (red arrows) in E, F, and G. We confirmed the identity of BrdU⁺ cell at 10 som by ISH with etsrp AS probe (H), immunostaining of GFP in Tg(fli1a:nEGFP) embryos (I) and EdU incorporation assay (J) post 10 μm cross-section of the embryos at 10 som. White arrows in J show EdU⁺ cells at 10 som. (K) and (L) shows double immunostaining sections of Tg(fli1a:EGFP) 10 som embryos stained for EGFP (green), and phospho-histone H3 antibody (p-H3, red). Arrows indicate merged yellow cells stained for both markers. Blue color is from DAPI staining. Cartoon of 10 som embryos with different section plains for panels H-L are indicated.