Temporal and spatial pattern of expression of the HDL receptor SR-BI during murine embryogenesis.

Hatzopoulos AK, Rigotti A, Rosenberg RD, Krieger M
J Lipid Res. 1998 39 (3): 495-508

PMID: 9548583

During rodent fetal development, maternal lipoproteins can be sources of cholesterol for the membrane synthesis required for tissue growth in the developing embryo and for steroid hormone production in the extraembryonic tissues. Although the mechanisms underlying the maternal-fetal lipoprotein cholesterol transport system are not well defined, the placenta and yolk sac seem to play major roles in this process, serving as functionally active interfaces between maternal circulation and the embryo. In rodents, the principal cholesterol transporter in the plasma is HDL, and the HDL receptor SR-BI is a physiologically important mediator of cholesterol uptake in adult liver and steroidogenic tissues. To begin to investigate SR-BI's role in maternal cholesterol uptake by the fetus, we used immunofluorescence microscopy to determine the pattern of SR-BI expression during murine embryogenesis. At day E7.5 in gestation, there was significant SR-BI expression in endothelial cells of the decidua, but little in intraembryonic and extraembryonic tissues. By day E8.5, there was a dramatic increase in SR-BI expression in the trophoblast cells which surround the developing embryo. Beginning at day E10, SR-BI was expressed in both the placenta and yolk sac. The expression in these extraembryonic tissues was correlated with significant uptake of fluorescent dye by the yolk sac visceral endodermal cells from DiI-labeled HDL injected into pregnant mice. Within the embryo proper, SR-BI expression appeared by day E14.5 at high levels in the adrenal gland. SR-BI expression was not detected in the embryonic liver through day E17.5 of gestation; however, it could be observed in neonatal livers. These findings suggest that SR-BI may play a role in the rodent maternal-fetal lipoprotein cholesterol transport system, supplying HDL cholesterol for either membrane or steroid hormone synthesis, or both.

MeSH Terms (23)

Animals Biological Transport Carbocyanines CD36 Antigens Cholesterol Embryonic and Fetal Development Female Fluorescent Dyes Gene Expression Membrane Proteins Mice Mice, Inbred BALB C Mice, Inbred C57BL Microscopy, Fluorescence Placenta Placentation Pregnancy Receptors, Immunologic Receptors, Lipoprotein Receptors, Scavenger Scavenger Receptors, Class B Time Factors Yolk Sac

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