Preimplantation mouse blastocysts fail to express CYP genes required for estrogen biosynthesis.
Implantation is initiated on day 4 in the mouse and on day 13 in the pig. The preimplantation pig blastocyst synthesizes steroid hormones, but whether preimplantation rodent embryos also have this ability has remained unresolved for the last two decades. In this study, the mRNAs encoding NADPH-cytochrome P450 reductase (P450-reductase), adrenodoxin, lanosterol 14-demethylase P450 (CYP51), 17 alpha-hydroxylase P450 (CYP17), cholesterol side-chain cleavage P450 (CYP11A1), sterol 27-hydroxylase P450 (CYP27), and aromatase P450 (CYP19) were examined in day 4 mouse blastocysts (day 1 = vaginal plug) and in day 13 and 16 pig blastocysts using reverse transcription-polymerase chain reaction (RT-PCR). In mouse blastocysts, mRNAs of P450-reductase, adrenodoxin, and CYP51, but not CYP17, CYP11A1, CYP27, and CYP19, were detected. In agreement with this finding, no aromatase protein could be detected by immunohistochemistry. By contrast, all these mRNAs were detected in the pig blastocyst. Furthermore, both the ovarian and placental types of aromatase (CYP19) mRNAs were detected in the pig blastocyst on days 13 and 16 of pregnancy, although the ovarian form was more abundant. Both forms of aromatase were much higher in day 13 than in day 16 pig blastocysts. The results provide definitive evidence that the preimplantation mouse blastocyst, as opposed to the pig blastocyst, has no ability to synthesize estrogen and no steroidogenic capacity. Maternal estrogen synthesis is essential for implantation of the mouse blastocyst.
Strömstedt
M
M
Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-0146, USA.
Keeney
D S
DS
Waterman
M R
MR
Paria
B C
BC
Conley
A J
AJ
Dey
S K
SK
D000325:Adrenodoxin / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D001141:Aromatase / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D001755:Blastocyst / Q000378:metabolism; D053493:Cholestanetriol 26-Monooxygenase; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics / Q000378:metabolism; D017931:DNA Primers; D047108:Embryonic Development; D004967:Estrogens / Q000096:biosynthesis; D005260:Female; D015870:Gene Expression; D008099:Liver / Q000196:embryology* / Q000378:metabolism; D008297:Male; D051379:Mice; D008969:Molecular Sequence Data; D009247:NADH, NADPH Oxidoreductases / Q000235:genetics / Q000378:metabolism; D009251:NADPH-Ferrihemoprotein Reductase; D010053:Ovary / Q000196:embryology* / Q000378:metabolism; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism*; D011247:Pregnancy; D013254:Steroid 17-alpha-Hydroxylase / Q000235:genetics / Q000378:metabolism; D013250:Steroid Hydroxylases / Q000235:genetics / Q000378:metabolism; D058886:Sterol 14-Demethylase; D013552:Swine
D017931:DNA Primers; D004967:Estrogens; D000325:Adrenodoxin; D003577:Cytochrome P-450 Enzyme System; D010088:Oxidoreductases; D013250:Steroid Hydroxylases; D001141:Aromatase; C548415:Cyp51 protein, mouse; D058886:Sterol 14-Demethylase; D013254:Steroid 17-alpha-Hydroxylase; D053493:Cholestanetriol 26-Monooxygenase; C506832:Cyp27a1 protein, mouse; D009247:NADH, NADPH Oxidoreductases; D009251:NADPH-Ferrihemoprotein Reductase