Changes in the relative abundance of mRNA transcripts for insulin-like growth factor (IGF-I and IGF-II) ligands and their receptors (IGF-IR/IGF-IIR) in preimplantation bovine embryos derived from different in vitro systems.
The aim of this study was to determine the relative abundance of mRNAs for the insulin-like growth factor I (IGF-I) and IGF-II ligands, and for the IGF receptors (IGF-IR and IGF-IIR) in in vitro preimplantation bovine embryos from the oocyte to the hatched blastocyst stage using two different culture systems: TCM-199 supplemented with oestrous cow serum, or synthetic oviduct fluid supplemented with polyvinyl alcohol. Development to the two- to four-cell stage and blastocyst stage was significantly higher (P < or = 0.05) in embryos cultured in TCM supplemented with oestrous cow serum than in those cultured in synthetic oviduct fluid supplemented with polyvinyl alcohol (61 and 25% versus 55 and 17%, respectively). A semi-quantitative RT-PCR assay did not detect IGF-I transcripts at any stage of preimplantation bovine development, including the hatched blastocyst stage. In both culture systems, IGF-IR, IGF-II and IGF-IIR were expressed throughout preimplantation development up to the hatched blastocyst stage in a varying pattern. The expression patterns of IGF-IR, IGF-II and IGF-IIR in embryos generated in the two culture systems were not significantly different, except at the expanded blastocyst stage, at which significantly higher amounts of IGF-IIR were observed in the TCM system than in the synthetic oviduct fluid system. These results indicate that transcripts of IGF-IR and IGF-IIR follow the standard pattern in which maternal stores of mRNA in the oocyte are slowly depleted up to the 16-cell stage and then re-established at the onset of embryonic expression of these genes. The lack of detectable IGF-I transcripts in the bovine embryo indicates a predominantly paracrine mode of action. The bovine embryo is capable of producing IGF-II, IGF-IIR and IGF-IR in large amounts, particularly after hatching, which may be important for the formation of the filamentous conceptus. Results indicate an autocrine mechanism for IGF-II and modulation of IGF family expression by culture conditions.
Yaseen
M A
MA
Department of Biotechnology, Institut für Tierzucht und Tierverhalten, Mariensee, 31535 Neustadt, Germany.
Wrenzycki
C
C
Herrmann
D
D
Carnwath
J W
JW
Niemann
H
H
D000704:Analysis of Variance; D000818:Animals; D001755:Blastocyst / Q000378:metabolism*; D002417:Cattle; D003470:Culture Media; D017931:DNA Primers; D005307:Fertilization in Vitro / Q000379:methods*; D007334:Insulin-Like Growth Factor I / Q000032:analysis; D007335:Insulin-Like Growth Factor II / Q000235:genetics*; D009866:Oogenesis; D016133:Polymerase Chain Reaction / Q000379:methods; D012333:RNA, Messenger / Q000032:analysis / Q000378:metabolism*; D017526:Receptor, IGF Type 1 / Q000235:genetics; D017527:Receptor, IGF Type 2 / Q000235:genetics; D017451:Receptors, Somatomedin / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction
D003470:Culture Media; D017931:DNA Primers; D012333:RNA, Messenger; D017527:Receptor, IGF Type 2; D017451:Receptors, Somatomedin; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II; D017526:Receptor, IGF Type 1