Infertility in POMC-deficient mice

Abstract

The pro-opiomelanocortin (POMC) gene is expressed in the hypothalamus and pituitary and its product is cleaved into several peptides including the melanocyte stimulating hormones (α, β, or γ-MSH), adrenocorticotropic hormone (ACTH), and beta-endorphin. Alpha-MSH is involved in regulating appetite, sexual behavior, and melanin, while ACTH regulates secretion of glucocorticoids from the adrenal cortex. Humans who have a POMC mutation either produce an abnormally short version of POMC or are missing the protein completely and therefore lack these hormones. This has biological consequences including red hair and fair skin, early-onset obesity (due to severe hyperphagia), and potentially hypothyroidism, hypogonadism, and infertility. Many of these same effects are seen with mice containing this deficiency. We are interested in studying infertility through a mouse model of hypothalamic-specific POMC-deficiency. These mice also experience early-onset obesity and infertility. Estradiol is a key reproductive hormone that is essential for fertility. POMC deficiency may lead to hypogonadism, which can cause low levels of estrogen so we hypothesize that POMC-deficient mice have reduced estrogen levels, which may contribute to their infertility. To test this hypothesis, we will measure estrogen levels in POMC-deficient mice at different stages of the estrus cycle using an estradiol ELISA kit. We expect the POMC-deficient mice to have lower estrogen levels than control mice. We also plan to use liquid chromatography mass spectrometry (LC-MS) to measure estrogen levels. Before collecting the blood samples, vaginal cell samples are obtained and viewed under a microscope to analyze the ratio of cells and determine which stage the females were in—proestrus, estrus, metestrus, or diestrus. Blood samples are then collected into 1.5 mL microcentrifuge tubes with 10 microliters of 0.5 M EDTA to prevent blood clotting. After blood is collected, it is centrifuged at 2,000 g for 20 minutes at 4 degrees Celsius. The plasma is then stored at -80 degrees Celsius until analysis. Based on preliminary results we expect the POMC deficient mice to have reduced estrogen and/or altered levels throughout the cycle. So far, our results have indicated that POMC-deficient female mice have abnormal estrus cycles and also reduced uterine weights. The conclusions from this study will help us understand more about the causes of infertility in POMC-deficient mice, which may also lead to greater understanding on how to treat humans with infertility due to a POMC mutation. Support for this research was provided by IRACDA grant NIHK12GM111725 to Z.T. and UVU Scholarly Activities Grant to A.G. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.