Biology subjects

Lowther, K. M.

Publications and source records attributed to Lowther, K. M..

3 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

Phosphatases modified by LH signaling in rat ovarian follicles and their role in regulating the NPR2 guanylyl cyclase

In response to luteinizing hormone, multiple proteins in rat and mouse granulosa cells are rapidly dephosphorylated, but the responsible phosphatases remain to be identified. Because the phosphorylation state of phosphatases can regulate their interaction with substrates, we searched for phosphatases that might function in LH signaling by using quantitative mass spectrometry. We identified all proteins in rat ovarian follicles whose phosphorylation state changed detectably in response to a 30-minute exposure to LH, and within this list, identified protein phosphatases or phosphatase regulatory subunits that showed changes in phosphorylation. Phosphatases in the PPP family were of particular interest because of their requirement for dephosphorylating the natriuretic peptide receptor 2 (NPR2) guanylyl cyclase in the granulosa cells, which triggers oocyte meiotic resumption. Among the PPP family regulatory subunits, PPP1R12A and PPP2R5D showed the largest increases in phosphorylation, with 4-10 fold increases in signal intensity on several sites. Although follicles from mice in which these phosphorylations were prevented by serine-to-alanine mutations in either Ppp1r12a or Ppp2r5d showed normal LH-induced NPR2 dephosphorylation, these regulatory subunits and others could act redundantly to dephosphorylate NPR2. Our identification of phosphatases and other proteins whose phosphorylation state is rapidly modified by LH provides clues about multiple signaling pathways in ovarian follicles. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=150 SRC="FIGDIR/small/544636v2_ufig1.gif" ALT="Figure 1"> View larger version (38K): org.highwire.dtl.DTLVardef@2622cdorg.highwire.dtl.DTLVardef@1b6eef7org.highwire.dtl.DTLVardef@102da9borg.highwire.dtl.DTLVardef@5e3221_HPS_FORMAT_FIGEXP M_FIG C_FIG Summary sentenceQuantitative mass spectrometric analysis of phosphatases whose phosphorylation state is rapidly modified by luteinizing hormone provides clues about how LH signaling dephosphorylates NPR2 as well as a resource for future studies.

cell biology↗

bioRxiv2019

SNAP23 is required for the maintenance of meiotic arrest and cortical granule exocytosis in mouse oocytes

Mammalian oocytes are stored in the ovary for prolonged periods, arrested in meiotic prophase. During this period, their plasma membranes are constantly being recycled by endocytosis and exocytosis. However, the function of this membrane turnover is unknown. Here, we investigated the requirement for exocytosis in the maintenance of meiotic arrest. Using a newly developed method for rapidly and specifically depleting proteins in oocytes, we have identified the SNARE protein, SNAP23, to be required for meiotic arrest. Degradation of SNAP23 causes premature meiotic resumption in follicle-enclosed oocytes. The reduction in SNAP23 is associated with loss of gap junction communication between the oocyte and surrounding follicle cells. Reduction of SNAP23 protein also inhibits cortical granule exocytosis in response to a Ca2+ stimulus, as measured by lectin staining and cleavage of ZP2. Our results show an essential role for SNAP23 in two key processes that occur in mouse oocytes and eggs. SummaryThe SNARE protein, SNAP23, is required to maintain gap junction communication between the oocyte and follicle cells that is needed to maintain oocyte meiotic arrest, as well as for cortical granule exocytosis at fertilization.

cell biology↗