A BMP signaling pathway involved in DV identity restricts <i>wnt1</i> expression to the posterior.

(A) FISH detecting wnt1 expression in animals following 14 days of homeostatic control RNAi and 10, 14, or 18 days bmp4 RNAi. Inhibition of bmp4 expanded wnt1 expression toward the anterior. Increased time of bmp4 inhibition results in further anterior expression of wnt1. The wnt1 domain expanded anteriorly and eventually had reduced expression in the posterior tip (yellow arrows show ectopic wnt1+ cells, white arrows show absence of wnt1+ cells relative to controls). (B) wnt1 expression domain size was reduced in nog1;nog2(RNAi) animals treated with dsRNA for 18 days of homeostasis (yellow boxes, magnified insets). (C) Top: FISH of wnt1 following 14 days of control, smad1, or smad4 RNAi. Bottom: FISH detecting wnt1 after 18 days of control, tbx2/3, or nlg8 RNAi. Inhibition of these BMP signaling components resulted in anterior expansion of wnt1 expression. (A-C) White scale bars represent 150 μm, and yellow brackets indicate wnt1 AP expression domain size. Box plots showing the distance from the posterior tip of the animal to the most anterior wnt1 expression relative to body length after indicated treatments. N ≥ 4 animals. Box plots show median values (middle bars) and first-to-third interquartile ranges (boxes); whiskers indicate 1.5× the interquartile ranges, and dots are data points from individual animals. *p(D) Pathway model for components acting in DV determination and control of wnt1.