Biology subjects

Owen, C. M.

Publications and source records attributed to Owen, C. M..

4 recordsLinked to original sources

bioRxiv2026

Conditional replacement of the mouse LH receptor with GFP, enabling imaging of cell migration during ovulation

To facilitate the investigation of signaling by the luteinizing hormone receptor (LHR), we created a mouse line called Lhr-COIN. This line allows for the conditional replacement of the Lhr coding sequence with enhanced green fluorescent protein (eGFP), resulting in both a conditional knockout line and a reporter line. By breeding these mice with mice expressing Cre recombinase, we generated mice in which either one or both Lhr alleles were replaced with eGFP. Notably, mice in which one Lhr allele in the granulosa cells was replaced with eGFP exhibited normal LH responsiveness. This enabled live imaging of LH-induced migration of LH-receptor-expressing granulosa cells within preovulatory ovarian follicles. The Lhr-COIN mouse line holds significant potential for future research on LHR function and localization in the ovary and other tissues.

developmental biology↗

bioRxiv2023

Luteinizing hormone stimulates ingression of granulosa cells within the mouse preovulatory follicle.

Luteinizing hormone (LH) induces ovulation by acting on its receptors in the mural granulosa cells that surround a mammalian oocyte in an ovarian follicle. However, much remains unknown about how activation of the LH receptor modifies the structure of the follicle such that the oocyte is released and the follicle remnants are transformed into the corpus luteum. The present study shows that the preovulatory surge of LH stimulates LH receptor-expressing granulosa cells, initially located almost entirely in the outer layers of the mural granulosa, to rapidly extend inwards, intercalating between other cells. The cellular ingression begins within 30 minutes of the peak of the LH surge, and the proportion of LH receptor-expressing cell bodies in the inner half of the mural granulosa layer increases until the time of ovulation, which occurs at about 10 hours after the LH peak. During this time, many of the initially flask-shaped cells appear to detach from the basal lamina, acquiring a rounder shape with multiple filipodia. Starting at about 4 hours after the LH peak, the mural granulosa layer at the apical surface of the follicle where ovulation will occur begins to thin, and the basolateral surface develops invaginations and constrictions. Our findings raise the question of whether LH stimulation of granulosa cell ingression may contribute to these changes in the follicular structure that enable ovulation. Summary sentenceLH-induced ingression of LH receptor-expressing cells within the mural granulosa layer of the ovarian follicle is a new component in the complex sequence of structural changes that lead to ovulation.

developmental biology↗

bioRxiv2020

Cellular heterogeneity of the LH receptor and its significance for cyclic GMP signaling in mouse preovulatory follicles

Meiotic arrest and resumption in mammalian oocytes are regulated by two opposing signaling proteins in the cells of the surrounding follicle: the guanylyl cyclase NPR2, and the luteinizing hormone receptor (LHR). NPR2 maintains a meiosis-inhibitory level of cyclic GMP (cGMP) until LHR signaling causes dephosphorylation of NPR2, reducing NPR2 activity, lowering cGMP to a level that releases meiotic arrest. However, the signaling pathway between LHR activation and NPR2 dephosphorylation remains incompletely understood, due in part to imprecise information about the cellular localization of these two proteins. To investigate their localization, we generated mouse lines in which HA epitope tags were added to the endogenous LHR and NPR2 proteins, and used immunofluorescence and immunogold microscopy to localize these proteins with high resolution. The results showed that the LHR protein is absent from the cumulus cells and inner mural granulosa cells, and is present in only 13-48% of the outer mural granulosa cells. In contrast, NPR2 is present throughout the follicle, and is more concentrated in the cumulus cells. Less than 20% of the NPR2 is in the same cells that express the LHR. These results suggest that to account for the LH-induced inactivation of NPR2, LHR-expressing cells send a signal that inactivates NPR2 in neighboring cells that do not express the LHR. An inhibitor of gap junction permeability attenuates the LH-induced cGMP decrease in the outer mural granulosa cells, consistent with this mechanism contributing to how NPR2 is inactivated in cells that do not express the LHR.

cell biology↗

bioRxiv2019

Follicle-stimulating hormone and luteinizing hormone increase Ca2+ in the granulosa cells of mouse ovarian follicles

Summary sentenceBoth FSH and LH increase Ca2+ in the granulosa cells of intact ovarian follicles from mice expressing genetically encoded sensors.\n\nABSTRACTIn mammalian ovarian follicles, follicle stimulating hormone (FSH) and luteinizing hormone (LH) signal primarily through the G-protein Gs to elevate cAMP, but both of these hormones can also elevate Ca2+ under some conditions. Here we investigate FSH- and LH-induced Ca2+ signaling in intact follicles of mice expressing genetically encoded Ca2+ sensors, Twitch-2B and GCaMP6s. At a physiological concentration (1 nM), FSH elevates Ca2+ within the granulosa cells of preantral and antral follicles. The Ca2+ rise begins several minutes after FSH application, peaks at ~10 minutes, remains above baseline for another ~10 minutes, and depends on extracellular Ca2+. However, suppression of the FSH-induced Ca2+ increase by reducing extracellular Ca2+ does not inhibit FSH-induced phosphorylation of MAP kinase, estradiol production, or the acquisition of LH responsiveness. Like FSH, LH also increases Ca2+, when applied to preovulatory follicles. At a physiological concentration (10 nM), LH elicits Ca2+ oscillations in a subset of cells in the outer mural granulosa layer. These oscillations continue for at least 6 hours and depend on the activity of Gq family G-proteins. Suppression of the oscillations by Gq inhibition does not inhibit meiotic resumption, but does slightly attenuate ovulation. In summary, both FSH and LH increase Ca2+ in the granulosa cells of intact follicles, but the functions of these Ca2+ rises are only starting to be identified.

cell biology↗