Syngeneic antisera have been produced in mouse strain 129/Sv-CP males against the primitive cells of teratocarcinoma. These sera react specifically with the primitive cells and are negative on various types of differentiated teratoma cells derived from the same original tumor. They are negative on all other mouse cells tested, with the exception of male germ cells and cleavage-stage embryos. Thus, teratoma cells possess cell-surface antigens in common with normal cleavage-stage embryos.
Expression of cytokeratin endo A has been analyzed during mouse blastocyst formation and embryonal carcinoma cell differentiation. To study the regulation of endo A expression, nuclease S1 mapping experiments have been performed on RNA extracted from two-cell to 7.5-day embryos. Low levels of endo A mRNA begin to be detectable in eight-cell embryos. The amount of this mRNA increases at the blastocyst stage, suggesting that endo A expression is regulated at the mRNA level during blastocyst formation. At this stage, in situ hybridization studies show that endo A mRNA is present in the trophectoderm but not in the inner cell mass. In 7.5-day embryos, endo A mRNAs are also detectable in the endoderm layer and in the amnion.
A cDNA from the Hox-3.1 locus, isolated from a 10.5-day postcoitum (p.c.) mouse embryo cDNA library, and the putative encoded protein are described. The spatial distribution of Hox-3.1 gene transcripts from late gastrulation to embryonic day 14.5 p.c. was monitored by in situ hybridization, using a cDNA probe. When first detectable in 8.5-day p.c. embryos, the transcripts are distributed in all the tissues of the posterior end. At later stages, the distribution becomes progressively spatially restricted and tissue specific. By 12.5 days p.c., transcription is localized most intensely in the neural tube region lying above the heart. The early transcription pattern thus appears to be compatible with a regionalizing role for the Hox-3.1 gene.
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