Developmental regulation of a gastrula-specific gene injected into fertilized Xenopus eggs.

To study the transcriptional regulation of genes during early Xenopus development, we have isolated a gene that is first transcribed at the mid-blastula transition. Transcription of this gene, called GS17, stops at mid-gastrula and the mRNA is rapidly degraded. Consequently, transcripts of GS17 are only present for a brief period, primarily during gastrulation. When the GS17 gene is injected into fertilized eggs, transcription from the injected DNA mimics the expression pattern of the endogenous gene, i.e., both the switch-on and switch-off of transcription are correctly regulated. The injected DNA is not significantly amplified and remains extrachromosomal. The correct expression of genes injected into Xenopus eggs will make it possible to investigate maternal factors involved in activating the embryonic genome.