Cloned Embryo mRNAs Not Detectably Expressed in Adult Sea Urchin Coelomocytes

Abstract

A set of 455 cloned pluteus cDNAs was analyzed by colony hybridization to radioactive cDNAs transcribed from cytoplasmic poly(A) RNA of pluteus embryos and adult coelomocytes. The prevalence of transcripts corresponding to each of the clones was estimated by use of cloned standards having known transcript prevalences. While 46% of the clones correspond to transcripts present at more than 105 copies/ng poly(A) RNA (about 5 copies/cell) in plutei, only 5.5% are that prevalent in the coelomocyte. The most prevalent pluteus transcripts are frequently also prevalent in coelomocytes, but more than 85% of the moderately prevalent pluteus transcripts are below the limit of detection of about 1 copy/cell in coelomocytes. None of the clones corresponding to rare transcripts in the pluteus is represented by prevalent transcripts in coelomocytes. The data suggest that the expression of the majority of genes giving rise to moderately prevalent messenger RNAs in embryos must be regulated during the life cycle of the sea urchin, while some very prevalent transcripts may be ubiquitous.

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