Ntl protein expression starts at the dorsal side of the late blastula. (A) Blastula (4.0 h, animal pole view) stained with an antiserum raised against the Ntl protein shows asymmetrical distribution at the margin. (B) Double staining of gsc RNA (blue) and Ntl protein (brown) demonstrates that Ntl protein is expressed first at the dorsal side of the zebrafish blastula (animal pole view). (C) Histological section through the dorsal margin of an embryonic shield stage embryo after double staining as in (B) shows that some cells, but not all, express both gsc RNA (blue) in the cytoplasm and Ntl protein (yellow) in the nucleus. The arrowhead marks the epiblast.
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