etsrp colocalizes with and regulates the expression of both scl isoforms in angioblasts of the PLPM. (A-F) Double fluorescent in situ hybridization on wild-type embryos at 14 hpf, flatmount, anterior to left. Arrowheads denote the rostral PLPM (A-D,F), and arrows denote the medial caudal PLPM (A-D,F). (C) Overlay of etsrp (A, green) and scl expression detected by scl-3′ probe (B, red), with coexpression shown in yellow. (F) Overlay of etsrp (D, green) and gata1 (E, red) expression. (G-N) scl expression detected by scl-3′ probe (G-J) and scl-5′ probe (K-N) at 14 hpf in control (G,K), etsrp MO (H,L), tbx16 MO (I,M), and etsrp MO + tbx16 MO (J,N), flatmount, anterior to left. Arrowheads denote the rostral PLPM (G,I,K,M), note that the scl expression in rostral PLPM detected by scl-3′ probe is much stronger than that detected by scl-5′ probe (compare G with K and I with M). Arrows denote the caudal PLPM (G-H,K-L). (O-P) qPCR analysis of scl-α and scl-α and -β transcripts on RNA samples from control or embryos overexpressing etsrp mRNA (etsrp OE) at 10 hpf (O), and from control or etsrp morphants (etsrp MO) at 14 hpf (P). The average fold changes of expression are represented by the bar graphs. Error bars plotted are SEM, and asterisks indicate significant changes at P < .05 on the basis of independent Student t tests.