DISTINCT PATTERN OF EMBRYONIC EXPRESSION OF THE SEA-URCHIN CYI ACTIN GENE IN TRIPNEUSTES GRATILLA

Cloning and sequencing of Tripneustes gratilla genomic DNA and cDNA en coding a developmentally regulated, embryonic messenger RNA, referred to as Tg616, revealed an actin-encoding gene orthologous to the CyI ac tin gene described from Strongylocentrotus purpuratus. Tg616 and SpCyl share: (1) 150 nucleotides of highly conserved sequence 5' of the tra nscription start site, (2) 95% nucleotide sequence identity in the pro tein encoding regions, which specify identical amino acid residues in 375 of 377 positions, and (3) extensive nucleotide sequence identity i n the 3' untranslated region of their messenger RNAs. Tg616 was theref ore designated TgCyI. In situ hybridization shows sequential activatio n of TgCyI in various cells of the embryo. TgCyI mRNA becomes abundant in primary and secondary mesenchyme cells as they prepare to enter th e blastocoel, in prospective aboral ectoderm cells at blastula stage, in gut cells during gut differentiation, and in oral ectoderm at plute us stage. This pattern of embryonic gene expression is more complex th an any of the major patterns of developmentally upregulated genes obse rved in S. purpuratus embryos and is distinct from SpCyI expression wh ich is progressively restricted to the gut and oral ectoderm. (C) 1994 Academic Press, Inc.