Zipping up the Synaptonemal Complex: Pathways to Homologous Chromosome Synapsis.

The synaptonemal complex (SC), a hallmark of meiosis, is a zipper-like protein assembly that links homologous chromosomes to regulate their recombination and segregation. With its characteristic ladder-like structure bridging paired homologs, the SC possesses unique biochemical and biophysical properties that influence both the number and distribution of crossovers. Although its ultrastructure is strikingly similar across eukaryotes, the molecular mechanisms underlying SC assembly and regulation are remarkably diverse, reflecting both conserved principles and evolutionary innovation. In this review, we synthesize current knowledge of the pathways that promote homologous synapsis across diverse model organisms. We focus on how synapsis initiation is coordinated with other meiotic processes, particularly homolog pairing and recombination, and highlight emerging themes, including the spatial and temporal regulation of SC assembly and the conserved molecular modules that couple SC assembly to recombination sites.