Nuclear progesterone receptor expression, localization and function during bovine oocyte growth.

Area of Science:

• Reproductive Biology
• Cell Biology
• Molecular Endocrinology

Background:

• Nuclear progesterone receptor (nPR) signaling is crucial for bovine oocyte developmental competence.
• Previous studies indicated nPR's role in oocyte maturation, but its function during oocyte growth was unclear.

Purpose of the Study:

• To characterize the expression, localization, and functional role of nPR during bovine oocyte growth.
• To investigate the association between nPR and mitochondria in developing oocytes.

Main Methods:

• Immunohistochemistry and immunofluorescence were used to analyze nPR expression and localization in bovine oocytes and follicle cells.
• In-silico analysis identified potential nPR target genes containing progesterone response elements (PREs) in their promoters.
• MitoTracker labeling assessed mitochondrial activity and its colocalization with nPR.

Main Results:

• Continuous nPR expression was observed in both oocytes and follicular cells throughout follicle development.
• In-silico analysis revealed that 20% of genes upregulated during oocyte growth contained PREs and were involved in nuclear and mitochondrial pathways.
• nPR colocalized extensively with mitochondria in smaller oocytes with high mitochondrial activity.

Conclusions:

• nPR is expressed throughout bovine oocyte growth and is associated with mitochondrial function.
• These findings suggest a novel role for nPR in regulating mitochondrial pathways essential for oocyte development and competence.