Faithful meiotic segregation requires pairwise alignment of the homologous chromosomes and their synaptonemal complex (SC) mediated stabilization. Here, we investigate factors that promote and coordinate these events during C. elegans meiosis. We identify BRA-2 (BMP Receptor Associated family member 2) as an interactor of HIM-17, previously shown to promote double-strand break formation. We found that loss of bra-2 impairs synapsis elongation without affecting homolog recognition, chromosome movement or SC maintenance. Epistasis analyses reveal previously unrecognized activities for HIM-17 in regulating homolog pairing and SC assembly in a partially overlapping manner with BRA-2. We show that removing bra-2 or him-17 restores nuclear clustering, recruitment of PLK-2 at the nuclear periphery, and abrogation of ectopic synapsis in htp-1 mutants, suggesting intact CHK-2-mediated signaling and presence of a barrier that prevents SC polymerization in the absence of homology. Our findings shed light on the regulatory mechanisms ensuring faithful pairing and synapsis.

Department of Biology Faculty of Medicine Masaryk University Brno Czech Republic

Department of Biology Faculty of Science McGill University Montreal QC Canada

Department of Biology University of Iowa Iowa City IA USA

Department of Biomedical Informatics University of Pittsburgh School of Medicine Pittsburgh PA USA

Department of Obstetrics Gynecology and Reproductive Sciences University of Pittsburgh School of Medicine Pittsburgh PA USA

Magee Womens Research Institute Pittsburgh PA USA

Max Perutz Labs Vienna Biocenter Campus Vienna Biocenter Vienna Austria

University of Vienna Max Perutz Labs Department of Chromosome Biology Vienna Biocenter Vienna Austria

Vienna Biocenter PhD Program a Doctoral School of the University of Vienna and the Medical University of Vienna Vienna Austria

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