Biomaterial Database

Poly(A) length, cytoplasmic adenylation and synthesis of poly(A)+ RNA in early mouse embryos. 1983

K B Clegg, and L Pikó

The poly(A) content of early mouse embryos fluctuates widely: after a transient increase in the one-cell embryo, there is a 70% drop in the two-cell and an approximately fivefold increase between the two-cell and early blastocyst stages (L. Pikó and K. B. Clegg, 1982, Dev. Biol. 89, 362-378). To shed light on the significance of these changes, we analyzed the size distribution of total poly(A) from embryos at different stages of development by gel electrophoresis and hybridization with [3H]poly(U). The number-average size of poly(A) tracts varies only slightly, from 61 to 77 nucleotides, indicating that the changes in poly(A) content are due primarily to changes in the number of poly(A) sequences, i.e., the number of poly(A)+ mRNA. From these data, the number of poly(A)+ mRNA can be estimated as follows: ovulated egg, 1.7 x 10(7); one-cell embryo, 2.4 x 10(7); late two-cell, 0.7 x 10(7); late eight-cell, 1.3 x 10(7); and early blastocyst, 3.4 x 10(7). These results suggest the elimination of the bulk of maternal poly(A)+ mRNA at the two-cell stage, to be replaced by newly synthesized mRNA derived from the embryonic genome. To study the synthesis of poly(A)+ mRNA, we cultured mouse embryos in vitro with [3H]adenosine and analyzed the labeled poly(A)+ RNA as to molecular size, length of the poly(A) tail, and relative distribution of label in poly(A) vs internal locations. We observed an active incorporation of label into large-molecular-weight (average size about 2 kb) poly(A)+ RNA at all stages from the one-cell to the blastocyst. However, in the one-cell embryo, about 70% of the label was localized in the poly(A) tail, suggesting cytoplasmic polyadenylation, and only about 30% was localized in the remainder of the molecule, suggesting the complete new synthesis of a small amount of poly(A)+ RNA. Differences in the size distribution of the labeled poly(A) as compared with the total poly(A) in the one-cell embryo indicate that the labeling is not due to a general turnover of poly(A) tails, but rather to the polyadenylation of previously nonpolyadenylated, stored RNA. Significant new synthesis of poly(A)+ RNA is evident from the two-cell stage onward and most likely accounts for the sharp rise in the number of poly(A)+ RNA molecules by the early blastocyst stage.

UI	MeSH Term	Description	Entries
D008970	Molecular Weight	The sum of the weight of all the atoms in a molecule.	Molecular Weights,Weight, Molecular,Weights, Molecular
D009693	Nucleic Acid Hybridization	Widely used technique which exploits the ability of complementary sequences in single-stranded DNAs or RNAs to pair with each other to form a double helix. Hybridization can take place between two complimentary DNA sequences, between a single-stranded DNA and a complementary RNA, or between two RNA sequences. The technique is used to detect and isolate specific sequences, measure homology, or define other characteristics of one or both strands. (Kendrew, Encyclopedia of Molecular Biology, 1994, p503)	Genomic Hybridization,Acid Hybridization, Nucleic,Acid Hybridizations, Nucleic,Genomic Hybridizations,Hybridization, Genomic,Hybridization, Nucleic Acid,Hybridizations, Genomic,Hybridizations, Nucleic Acid,Nucleic Acid Hybridizations
D011061	Poly A	A group of adenine ribonucleotides in which the phosphate residues of each adenine ribonucleotide act as bridges in forming diester linkages between the ribose moieties.	Adenine Polynucleotides,Polyadenylic Acids,Poly(rA),Polynucleotides, Adenine
D001755	Blastocyst	A post-MORULA preimplantation mammalian embryo that develops from a 32-cell stage into a fluid-filled hollow ball of over a hundred cells. A blastocyst has two distinctive tissues. The outer layer of trophoblasts gives rise to extra-embryonic tissues. The inner cell mass gives rise to the embryonic disc and eventual embryo proper.	Embryo, Preimplantation,Blastocysts,Embryos, Preimplantation,Preimplantation Embryo,Preimplantation Embryos
D003593	Cytoplasm	The part of a cell that contains the CYTOSOL and small structures excluding the CELL NUCLEUS; MITOCHONDRIA; and large VACUOLES. (Glick, Glossary of Biochemistry and Molecular Biology, 1990)	Protoplasm,Cytoplasms,Protoplasms
D004591	Electrophoresis, Polyacrylamide Gel	Electrophoresis in which a polyacrylamide gel is used as the diffusion medium.	Polyacrylamide Gel Electrophoresis,SDS-PAGE,Sodium Dodecyl Sulfate-PAGE,Gel Electrophoresis, Polyacrylamide,SDS PAGE,Sodium Dodecyl Sulfate PAGE,Sodium Dodecyl Sulfate-PAGEs
D004622	Embryo, Mammalian	The entity of a developing mammal (MAMMALS), generally from the cleavage of a ZYGOTE to the end of embryonic differentiation of basic structures. For the human embryo, this represents the first two months of intrauterine development preceding the stages of the FETUS.	Embryonic Structures, Mammalian,Mammalian Embryo,Mammalian Embryo Structures,Mammalian Embryonic Structures,Embryo Structure, Mammalian,Embryo Structures, Mammalian,Embryonic Structure, Mammalian,Embryos, Mammalian,Mammalian Embryo Structure,Mammalian Embryonic Structure,Mammalian Embryos,Structure, Mammalian Embryo,Structure, Mammalian Embryonic,Structures, Mammalian Embryo,Structures, Mammalian Embryonic
D000241	Adenosine	A nucleoside that is composed of ADENINE and D-RIBOSE. Adenosine or adenosine derivatives play many important biological roles in addition to being components of DNA and RNA. Adenosine itself is a neurotransmitter.	Adenocard,Adenoscan
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia
D001483	Base Sequence	The sequence of PURINES and PYRIMIDINES in nucleic acids and polynucleotides. It is also called nucleotide sequence.	DNA Sequence,Nucleotide Sequence,RNA Sequence,DNA Sequences,Base Sequences,Nucleotide Sequences,RNA Sequences,Sequence, Base,Sequence, DNA,Sequence, Nucleotide,Sequence, RNA,Sequences, Base,Sequences, DNA,Sequences, Nucleotide,Sequences, RNA