Figure 4.

zswim4-6 is a target of BMP signaling with bilaterally symmetric expression and encodes a nuclear protein.

(A) Maximum likelihood phylogeny shows that Nematostella ZSWIM4-6 clusters with ZSWIM4, ZSWIM5, and ZSWIM6 from zebrafish, frog, and mouse. (B–F’) Nematostella zswim4-6 expression follows the dynamic BMP signaling domain (see Figure 1D for comparison). Double ISH shows zswim4-6 and chd transcripts localize to the opposite sides of the directive axis. (G–I) Mosaic expression of ZSWIM4-6-EGFP under the control of the ubiquitously active EF1α promoter in F0 transgenic animals demonstrates that ZSWIM4-6 is a nuclear protein. Full-length ZSWIM4-6-EGFP is translocated into the nuclei (G), while ZSWIM4-6ΔNLS-EGFP missing the predicted nuclear localization signal NLS remains cytoplasmic (H), similar to the EGFP control (I). Exposure time was the same in all images. (J–L) Microinjection of ZSWIM4-6-EGFP mRNA results in a weak EGFP signal detectable in the nuclei of the early blastula (J), which progressively disappears towards late gastrula (K). EGFP translated from EGFP mRNA remains readily detectable (L). To visualize the weak signal in (J–K), the exposure had to be increased in comparison to (L). Asterisks mark the oral side; scale bars 100 µm.