Expression of a secreted transplantation antigen gene during murine embryogenesis.

Abstract

We examined the midgestation mouse embryo for transcripts related to the secreted transplantation antigen Q10 and show here that this gene is transcribed in the endoderm of the visceral yolk sac. Its level of expression is highest at day 14 and then declines as development proceeds. Concurrently with the decrease in yolk sac expression, the amount of transcripts accumulating in the fetal liver increases during late embryogenesis.The murine major histocompatibility complex encodes different classes of proteins that regulate the immune response. The analysis of class I-related cDNA clones derived from adult mouse liver RNA has recently led to the description of a novel class I antigen (5). The cDNA sequence of one clone predicted a protein which would have several polar amino acid substitutions followed by nonsense codons in the normally hydrophobic transmembrane domain and would therefore lack the carboxy-terminal cytoplasmic domain (12). Because of these considerations it was reasoned that if such a protein was synthesized, it would be secreted rather than membrane bound. Using antibodies raised against a peptide that would be derived from the modified transmembrane domain, a class I-related protein of the molecular weight predicted from the sequence was immunoprecipitated from adult mouse serum (15), and its synthesis was shown to be restricted to the liver (6, 15). Other studies mapped the gene to the Q10 locus of the Qa region in the major histocompatibility complex (18,19).Since the liver is not well developed until about day 12 in mouse embryonic development and does not mature until later in gestation (21), we were interested in whether another tissue might synthesize the Q10 antigen during embryogenesis. The visceral yolk sac (VYS) seemed a likely candidate since it is one of the first tissues to differentiate (8) and is known to synthesize a number of liver proteins (1,7,10,17). These properties cease in the latter stages of gestation and are then taken over by the developing liver. We report here that RNAs which show homology to a probe specific for the secreted class I antigen, Q10, are present in the VYS of the midgestation mouse embryo. MATERIALS AND METHODSDissection of mouse conceptuses. Mature female CD-1 mice (Charles River Breeding Laboratories, Inc., Wilmington, Mass.) were injected intraperitoneally with 1 IU of pregnant mare serum gonadotropin (Diosynth, Inc., Chicago, Ill.). Two days later, they were injected with 5 IU of human chorionic gonadotropin (Organon, West Orange, N.J.) and mated. The morning that a vaginal plug was found was considered day 1 of pregnancy. This amount of pregnant mare serum gonadotropin synchronized the estrous cycle without inducing superovulation and thereby increased the number of successful matings. * Corresponding author.At the appropriate day, conceptuses were dissected free of the uterus in phosphate-buffered saline. Each conceptus was then separated into placenta, parietal yolk sac (PYS) (trophectoderm and parietal endoderm), and VYS (visceral endoderm [VE] ...

Expression of the murine apolipoprotein E gene is coupled to the differentiated state of F9 embryonal carcinoma cells.

“…This difference is similar to that seen in the apoE mRNA contents of VE-like and PE-like F9 cells (Table 1) although the absolute values of apoE mRNA are lower in the F9 cells. Separation of the visceral yolk sac into its component tissues showed that apoE mRNA was present mostly in the VE and not the extraem- 16.4 ± 0.7 Embryonic tissues were isolated as described (37). Each value is the mean ± SD of four measurements from 25-50 pooled embryos.…”