Welcome to the new version of CaltechAUTHORS. Login is currently restricted to library staff. If you notice any issues, please email coda@library.caltech.edu
Published September 1988 | public
Journal Article

Mosaic Incorporation and Regulated Expression of an Exogenous Gene in the Sea Urchin Embryo

Abstract

A fusion gene construct in which the bacterial chloramphenicol acetyltransferase (CAT) gene is controlled by CyIIIa actin gene cis-regulatory sequences was injected into unfertilized eggs of the sea urchin Strongylocentrotus purpuratus. The distribution of CAT DNA sequences was measured directly by in situ hybridization in squashed 24-hr blastula preparations derived from these eggs. Earlier studies had shown that stable mosaic incorporation of the exogenous DNA occurs during cleavage, after which the exogenous sequences replicate at approximately the pace of the host cell genomes. The fractions of embryonic cells observed in this study to include CAT DNA sequences imply that their stable incorporation into a replicating, nuclear form occurs most often in a single cell at the 3rd or 4th cleavage stages, though it may occur as early as 2nd cleavage, or as late as 7th cleavage. Corroborative measurements were carried out by the same method on squashed preparations of embryos at earlier stages, and by in situ hybridizations of CAT mRNA, both in dissociated embryos and in cytological sections of 72-hr pluteus-stage embryos. Hybridizations to CAT mRNA and to CAT DNA were carried out on alternate sections of several embryos. The results confirm unequivocally that although CAT mRNA appears only in the aboral ectoderm in embryos derived from eggs injected with the CyIIIa · CAT fusion gene, the exogenous sequences are indeed present, though silent, in the various other cell types of the late embryo.

Additional Information

© 1988 Academic Press, Inc. Accepted March 15, 1988. We thank Drs. Roberta Franks and Donna Livant for their expert and enthusiastic collaboration in carrying out the microinjection experiments. This research was supported by NIH Grant HD05753.

Additional details

Created:
August 19, 2023
Modified:
October 18, 2023