Kinesin drive meiotic chromosome dynamics via interaction with the KASH5-LINC complex

Area of Science:

• Cell Biology
• Molecular Biology
• Genetics

Background:

• Rapid chromosome movements (RPMs) are essential for homologous chromosome pairing during meiotic prophase.
• The cytoskeleton generates these movements, transmitted via the LINC complex, but cytoplasmic force generators are poorly understood.

Purpose of the Study:

• To identify cytoplasmic motor proteins involved in generating forces for meiotic chromosome movements.
• To elucidate the role of kinesins, particularly KIF5B, in the LINC complex-mediated transmission of forces to telomeres.

Main Methods:

• Proteomic screening of mouse spermatocytes to identify microtubule-associated motor proteins.
• Co-immunoprecipitation and yeast two-hybrid assays to test interactions with the LINC complex component KASH5.
• Total internal reflection fluorescence microscopy and microtubule sedimentation assays with recombinant proteins.
• In vivo studies in cultured somatic cells and mouse spermatocytes to validate KIF5B-KASH5 interactions and KIF5B function.

Main Results:

• KIF5B and KIF2B were identified as specific interactors of KASH5, a component of the LINC complex.
• Direct interaction between purified KASH5 and KIF5B on microtubules was demonstrated.
• KASH5's N-terminal EF-hand domains mediate KIF5B binding.
• In vivo evidence confirmed KIF5B recruitment to the nuclear envelope via KASH5-SUN1 and its association with telomeres and microtubules in mouse spermatocytes.
• Inhibition of kinesins reduced telomere-led chromosome motions.

Conclusions:

• Kinesins, particularly KIF5B, are identified as novel components of the force-generating machinery for meiotic chromosome movements.
• KIF5B acts through KASH5 as a specific nuclear membrane adaptor to drive chromosome motion during meiotic prophase I.
• These findings advance the understanding of the molecular mechanisms underlying chromosome dynamics in meiosis.