Developmental Expression of Two Cloned Sequences Coding for Rare Sea Urchin Embryo Messages

Abstract

Measurements are presented of the number of transcripts in sea urchin embryos and in adult intestine cells complementary to two cloned genomic single copy sequences. These sequences apparently code for maternal mRNAs stored in the egg. About 1000 and 1400 transcripts are stored per egg, close to the average value for maternal mRNAs. RNAs complementary to the cloned sequences are also found in the polysomal message of early embryos. The number of polysomal transcripts representing each cloned sequence is typical of the "complex" or "rare" class of message in sea urchin embryos. Expression of these putative complex class structural genes is regulated developmentally. Thus, polysomal transcripts of both sequences essentially disappear by the blastula stage. One sequence is again represented at a low level in adult intestine cytoplasmic RNA while the other is absent. However, in all the developmental stages examined, the number of nuclear transcripts of the cloned sequences remains about the same as for any average single copy sequence transcript.

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