Fig. 6

Defects in the vegetal localization of wnt8a mRNA and Sybu protein.

(A-D) Off-center shift of wnt8a mRNA is affected in hec mutants. Whole mount in situ hybridization of wild-type embryos (A,C) and hec mutant embryos (B,D) at the 1- (A,B, 30 mpf) and 4- (C,D, 60 mpf) cell stages. Images show representative embryos. A majority of wild-type embryos showed a clear off-center shift (85%, n = 27 at 30 mpf and 74%, n = 47 at 60 mpf). A majority of hec mutant embryos showed vegetal localization without a shift at 30 mpf (79%, n = 33, remaining embryos show no localization) and absence of localization at 60 mpf (89%, n = 38, remaining embryos show reduced vegetal localization without a shift). The apparent label at the base of the blastodisc is observed in a majority of mutant embryos (71%, n = 38) but not in wild-type (C) or control embryos labeled with other probes (not shown) and may reflect remaining wnt8a mRNA that has lost anchoring at the vegetal pole and has moved animally through the action of axial streamers [83]. E–I) Localization of Sybu protein is affected in hec mutants. Whole mount immunofluorescence to detect Sybu protein of untreated wild-type (E,G) and hec mutant (F,H,) embryos and nocodazole-treated wild-type embryos (I) at the indicated stages. In wild-type embryos, an off-center shift in Sybu protein can be observed starting at 30 mpf (G). In hec mutants, Sybu protein becomes undetectable levels by this same time point (H). Patterns of localization of Sybu protein at 10 mpf and 20 mpf time points (combined n: 32 WT, 19 mutant for 10–20 mpf), and 30 mpf and 40 mpf time points were similar and have been combined. 59% (n = 32) of wild-type and 63% (n = 19) of hec mutant embryos showed centered vegetal localization during 10–20 mpf. At 30–40 mpf, the percent of embryos that showed vegetal localization, now with an off-center shift, was reduced to 25% (n = 28) in wild-type, and 0% (n = 25) of hec mutants showed any localization at these time points. Treatment of wild-type embryos with nocodazole inhibits the shift but does not result in delocalization from the vegetal cortex (I, embryo at 40 mpf), as previously shown [6]. Magnification bars in (D) and (I) correspond to 100 µm for panels sets (A-D) and (E-I), respectively.