The murine SCP3 gene is required for synaptonemal complex assembly, chromosome synapsis, and male fertility

During meiosis, the homologous chromosomes pair and recombine. An evolution arily conserved protein structure, the synaptonemal complex (SC), is locate d along the paired meiotic chromosomes. We have studied the function of a s tructural component in the axial/lateral lateral element of the SC, the syn aptonemal complex protein 3 (SCP3). A null mutation in the SCP3 gene was ge nerated, and we noted that homozygous mutant males were sterile due to mass ive apoptotic cell death during meiotic prophase. The SCP3-deficient male m ice failed to form axial/lateral elements and SCs, and the chromosomes in t he mutant spermatocytes did not synapse. While the absence of SCP3 affected the nuclear distribution of DNA repair and recombination proteins (Rad51 a nd RPA), as well as synaptonemal complex protein 1 (SCP1), a residual chrom atin organization remained in the mutant meiotic cells.