Fig. 4

Transcriptional conversion of fused fusion competent myoblast (FCM) nuclei to founder cell (FC) identity. FISH against nascent duf (A, C) or sns (E, G) transcripts (green), staining for Mef2 (red), and Col (blue) to visualise the DA3, DT1 and LL1 FC nuclei at stage 12 (A, E) and the DA3 muscle at stage 14 (C, G), wt embryos. Double FISH against nascent col (red) and either duf (B, D) or sns (F, H) transcripts (green) and Col staining (blue) of the DA3 FC at stage 12 (B, F) and DA3 muscle at stage 14 (D, H). (I, I’) Double FISH against nascent duf (red) and sns transcripts (green) and Col staining, stage 14 DA3 muscle; (I’) blue channel only. (H, I, I’) sns transcription (yellow arrow) is detected in "no Col" nuclei. (J, K) Box plots showing the number of nuclei transcribing either col or duf, or col and duf, relative to the total number of DA3 nuclei (J), and either col or sns only (K). Two adjacent hemisegments are shown in (A, C, E, G), section projections; a single hemisegment in (B, D, F, H, I), single confocal sections. L Schematic representation of the transcriptional FCM to generic FC identity switch, post fusion