Rebuilding MTOCs upon centriole loss during mouse oogenesis

Area of Science:

• Cell Biology
• Developmental Biology
• Reproductive Biology

Background:

• Most animal cells utilize canonical centrosomes with centrioles as microtubule-organizing centers.
• Vertebrate oocytes uniquely lose centrioles during oogenesis, replacing centrosomes with acentriolar microtubule-organizing centers (MTOCs).
• Mechanisms of MTOC metabolism and microtubule organization during oocyte growth remain poorly understood.

Purpose of the Study:

• Investigate microtubule organization and intracellular architecture in growing mouse oocytes after centrosome disassembly.
• Elucidate the role of pericentriolar material (PCM) in microtubule dynamics during oocyte growth.
• Characterize the reorganization of MTOCs and microtubules preceding meiotic resumption.

Main Methods:

• Immunofluorescence microscopy to visualize microtubule structures and PCM.
• Live-imaging techniques to observe dynamic microtubule rearrangements in real-time.
• Coupled approaches to analyze microtubule organization and MTOC formation in mouse oocytes.

Main Results:

• Growing oocytes exhibit dispersed PCM that drives microtubule assembly throughout the cell.
• PCM foci enlarge, forming perinuclear MTOCs and large microtubule asters near the nucleus in competent oocytes.
• During meiosis resumption, perinuclear MTOCs reorganize around the nuclear envelope in a microtubule- and dynein-dependent manner before nuclear envelope breakdown (NEBD).

Conclusions:

• The dynamic reorganization of MTOCs and microtubules is a hallmark of mouse oocyte competency.
• This process is essential for preparing the oocyte for meiotic divisions.
• The findings shed light on the unique mechanisms governing microtubule organization in oocytes lacking canonical centrosomes.