Developmental abnormalities in mouse embryos lacking the HDL receptor SR-BI.

Area of Science:

• Developmental biology
• Molecular biology
• Genetics

Background:

• The scavenger receptor class B member I (SR-BI) is a lipoprotein receptor primarily expressed in the liver and steroidogenic tissues.
• Disruption of the SR-BI gene in mice and mutations in humans affect lipoprotein metabolism and fertility.
• SR-BI is present in murine yolk sac and placenta during development, and in human trophoblast cells and placenta, but its embryonic role is unclear.

Purpose of the Study:

• To investigate the role of SR-BI in embryonic development, particularly concerning intrauterine demise observed in SR-BI-null mice.
• To elucidate the cause of embryonic demise in SR-BI-deficient mice, focusing on potential roles in maternal-fetal transport and developmental processes.
• To characterize the expression pattern of SR-BI during murine development and its impact on embryonic development.

Main Methods:

• Generation and analysis of SR-BI-null mouse models.
• Phenotypic analysis of embryos, including assessment for exencephaly and growth parameters.
• Immunolocalization studies to determine SR-BI expression patterns during embryonic development.
• Biochemical analysis of cholesterol levels in SR-BI-null embryos.

Main Results:

• SR-BI-null embryos exhibit a high incidence of exencephaly, with a female sex bias.
• SR-BI is not expressed in early embryonic stages but is localized in cells mediating maternal-fetal nutrient transport.
• SR-BI-null embryos show reduced cholesterol levels compared to wild-type littermates.
• Newborn SR-BI-deficient pups display intrauterine growth restriction.

Conclusions:

• SR-BI in extraembryonic tissues is essential for maternal-fetal cholesterol and lipid transport.
• SR-BI plays a critical role in neural tube closure and overall fetal growth.
• The absence of SR-BI leads to embryonic demise, likely due to impaired nutrient transport and subsequent developmental defects.