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. Author manuscript; available in PMC: 2010 May 25.
Published in final edited form as: Cell. 2009 Nov 12;139(5):907–919. doi: 10.1016/j.cell.2009.10.039

Figure 8. A model for homolog pairing and synapsis.

Figure 8

A nucleus containing a single pair of chromosomes is shown for simplicity. In early meiosis, the NE proteins SUN-1 (orange) and ZYG-12 (green) concentrate by association with individual PCs. Motion of the patches and associated chromosomes is facilitated by microtubules, and promotes encounters between chromosomes. In addition to mediating chromosome encounters, the NE bridge components SUN-1 and ZYG-12 also collaborate to inhibit initiation of synapsis between transiently associated chromosomes. Homology between associated chromosomes is assessed by dynein, acting tangentially at the NE surface. Non-homologous chromosomes normally separate rapidly. However, when dynein exerts force opposing the association between homologous PCs, the resulting tension overcomes a thermodynamic barrier to license synapsis initiation; once initiated, the SC polymerizes processively along the chromosomes, completing their alignment.