# Cytoplasmic Maturation in Mouse Oocytes

> **NIH NIH R01** · UNIVERSITY OF CONNECTICUT SCH OF MED/DNT · 2020 · $352,600

## Abstract

PROJECT SUMMARY
The objective of this project is to understand mechanisms by which immature egg cells, or oocytes, become
developmentally competent. Mammalian oocytes are stored in the ovary, arrested at meiotic prophase, for
extended periods of time (decades in women). Following puberty, oocytes enter a period of growth in which
they synthesize proteins needed for the maturation process. They are stimulated to mature by signals from the
pituitary. Oocytes undergo many cytoplasmic changes during oocyte maturation, the period between prophase
I and metaphase II. These include a dramatic reorganization of the endoplasmic reticulum (ER) in which the
ER becomes concentrated in the egg cortex. Ca2+ uptake into the ER also occurs, and that is necessary for
the egg to release intracellular Ca2+ from the ER at fertilization, a critical event required for early embryonic
development. Oocytes also undergo changes that permit them to undergo cortical granule exocytosis at
fertilization, an important event that renders the fertilized egg impermeable to more than one sperm and thus
serves as a polyspermy prevention mechanism. Many questions remain about these events. Aim 1 will
investigate whether changes in ER structure and the formation of ER-plasma membrane (ER-PM) contacts are
required for developmental competence, as well as mechanisms that regulate ER reorganization, formation of
ER-PM contacts, and Ca2+ uptake during maturation. Aim 2 will identify proteins that are needed for
constitutive exocytosis as well as the Ca2+-regulated exocytosis of cortical granules. These experiments will
make use of protein degradation methods to study the role of specific proteins, alone or in combination with
other candidate proteins, using isolated or follicle-enclosed oocytes. Importantly, we will use a newly
developed method for the rapid and acute degradation of endogenous proteins. Oocytes will be injected with
fluorescent molecules that allow the visualization of the ER and ER-PM contacts, or with
antibodies/siRNAs/morpholinos to specifically deplete proteins. The conclusions reached from these studies
will be applicable to understanding oocyte development in women. Currently, the ability to mature human
oocytes in vitro is an area of high importance, but methods for maturing oocytes are imperfect. A complete
knowledge of all aspects of oocyte development could lead to improved culturing methods that will increase the
success of assisted reproduction.

## Key facts

- **NIH application ID:** 9885809
- **Project number:** 1R01HD096037-01A1
- **Recipient organization:** UNIVERSITY OF CONNECTICUT SCH OF MED/DNT
- **Principal Investigator:** LISA M MEHLMANN
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $352,600
- **Award type:** 1
- **Project period:** 2020-03-02 → 2025-02-28

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9885809

## Citation

> US National Institutes of Health, RePORTER application 9885809, Cytoplasmic Maturation in Mouse Oocytes (1R01HD096037-01A1). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/9885809. Licensed CC0.

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