Prostaglandins limit nuclear actin to control nucleolar function during oogenesis.

Area of Science:

• Reproductive Biology
• Cellular Biology
• Molecular Signaling

Background:

• Prostaglandins (PGs) are crucial lipid signals regulating female reproduction and oocyte development.
• The precise cellular mechanisms of PG action, particularly on the nucleolus, are not fully understood.
• Nucleolar morphology changes are linked to altered nucleolar function, including ribosomal RNA (rRNA) transcription.

Purpose of the Study:

• To elucidate the roles and downstream mechanisms of PGs in regulating the nucleolus during *Drosophila* oogenesis.
• To investigate how PGs influence nucleolar morphology and function, specifically rRNA transcription and protein translation.

Main Methods:

• Utilized *in vivo* *Drosophila* oogenesis as a model system.
• Analyzed nucleolar morphology and rRNA transcription in response to PG signaling loss.
• Investigated the role of nuclear actin, including its levels and form, in PG-mediated nucleolar regulation.
• Manipulated PG signaling, nuclear actin levels (NLS-actin), and Exportin 6 to assess effects on nucleolar activity.

Main Results:

• Loss of PGs leads to altered nucleolar morphology, not due to reduced, but increased rRNA transcription and protein translation.
• PGs modulate nucleolar function by regulating nuclear actin, which is enriched in the nucleolus.
• Increased nuclear actin levels (via PG loss or NLS-actin overexpression) result in rounder nucleoli and enhanced RNAPI-dependent transcription.

Conclusions:

• PGs maintain nucleolar homeostasis by balancing nuclear actin levels and forms.
• This regulation controls nucleolar activity, specifically rRNA transcription, essential for producing fertilization-competent oocytes.
• Nuclear actin is a key mediator of prostaglandin signaling in the nucleolus during oogenesis.