Transient structure associated with the spindle pole body directs meiotic microtubule reorganization in S. pombe

Area of Science:

• Cell Biology
• Molecular Biology
• Genetics

Background:

• Cytoskeletal assemblies drive chromosome movements essential for sexual differentiation and meiotic recombination.
• Fission yeast transforms cytoplasmic microtubule (MT) arrays into a single radial MT (rMT) array at the spindle pole body (SPB) during meiotic prophase.
• Mechanisms governing these dynamic MT rearrangements remain unclear.

Purpose of the Study:

• To elucidate the structural and molecular mechanisms underlying dynamic microtubule rearrangements during meiotic differentiation in fission yeast.
• To identify the components and regulation of the novel microtubule organizing center (MTOC) involved in rMT array formation.

Main Methods:

• Electron tomography was used to visualize the ultrastructure of the SPB and identify novel structures.
• Immunofluorescence and biochemical assays were employed to analyze the localization and regulation of key proteins.
• Genetic approaches were used to investigate the function of meiosis-specific SPB components.

Main Results:

• A novel amorphous structure, termed the rMTOC, was identified at the cytoplasmic side of the SPB, emanating the rMT array.
• The rMTOC is enriched in γ-tubulin and its formation depends on the meiosis-specific SPB component Hrs1/Mcp6.
• Hrs1/Mcp6 downregulation via proteasome-dependent degradation and phosphorylation inactivates the rMTOC, enabling bipolar spindle formation for meiosis I.

Conclusions:

• The study reveals the molecular basis for the transient generation of a novel MTOC (rMTOC) during meiotic differentiation.
• This novel MTOC triggers essential microtubule rearrangements for successful meiotic progression.
• Understanding the rMTOC regulation provides insights into the broader mechanisms of microtubule organization and cell division.