Stage- and adult tissue-specific expression of a homeobox gene in embryo and adult Parechinus angulosus sea urchins.

We report the isolation of a gene (PaHbox6), encoding a homeobox-containing protein of the South African sea urchin, Parechinus angulosus. Sequencing identified an Antennapedia-class gene encoding a homeobox that is the homologue of the Hawaiian sea urchin Tripneustes gratilla homeobox gene. Extensive restriction-fragment length polymorphism surrounds the gene. RNase-protection analyses revealed expression of PaHbox6 in mesenchyme blastula embryos at maximal levels of 44 +/- 8 transcripts/embryo. Four adult tissues examined (testes, ovary, intestines, Aristotle's lantern) showed expression of PaHbox6, though at greatly differing levels, with testes highest at eleven transcripts/10 pg RNA. Two transcripts of 5.2 and 5.7 kb were identified in adult tissue.