Amounts, synthesis, and some properties of intracisternal A particle-related RNA in early mouse embryos.
Early mouse embryos express two morphological subtypes of intracisternal A-type particles, one resembling those occurring in mouse tumors (referred to as IAP) and the other apparently specific for early embryos [referred to as IAP(epsilon)]. Using cloned fragments of IAP genes as labeled probes in dot-hybridization experiments, we detected IAP-related RNA sequences in mouse oocytes and preimplantation embryos. IAP RNA is relatively abundant in ovarian oocytes, is reduced in amount to approximately equal to 1/10th in the ovulated egg, and increases approximately equal to 100 times (from approximately equal to 1.3 X 10(3) to approximately equal to 1.5 X 10(5) molecules per embryo) between the one-cell stage and late blastocyst stage. Most of the IAP RNA consists of a single size class of about 5.4 kilobases, and a major fraction of this RNA is polyadenylylated. Quantitative considerations suggest that only a few percent of the IAP RNA in embryos are associated with particles. In two-cell embryos, the number of IAP RNA molecules is less than 1/10th the number of IAP(epsilon) particles, suggesting that IAP(epsilon) is genetically distinct from IAP and presumably represents a family of as yet unidentified retrovirus-like elements.
D000818:Animals; D004274:DNA, Recombinant; D005260:Female; D007181:Inclusion Bodies, Viral / Q000648:ultrastructure*; D051379:Mice / Q000196:embryology*; D008970:Molecular Weight; D009693:Nucleic Acid Hybridization; D009865:Oocytes / Q000502:physiology*; D012367:RNA, Viral / Q000096:biosynthesis / Q000502:physiology*; D012190:Retroviridae / Q000502:physiology*
D004274:DNA, Recombinant; D012367:RNA, Viral