Abstract
Meiosis yields haploid gametes following two successive divisions of a germ cell in the absence of intervening DNA replication. Balanced segregation of homologous chromosomes in Meiosis I is aided by a proteinaceous structure, the synaptonemal complex (SC). The objective of this study was to determine total average autosomal SC lengths in spermatocytes in three commonly used mouse strains (129S4/SvJae, C57BL/6J, and BALB/c). Our experiments revealed that the total autosomal SC length in BALB/c spermatocytes is 9% shorter than in the two other strains. Shorter SCs are also observed in spermatocytes of (BALB/c × 129S4/SvJae) and (C57BL/6J × BALB/c) F1 hybrids suggesting a genetic basis of SC length regulation. Along these lines, we studied expression of a selected group of genes implicated in meiotic chromosome architecture. We found that BALB/c testes express up to 6-fold less of Rec8 mRNA and 4-fold less of REC8 protein. These results suggest that the mechanism that defines the SC length operates via a REC8‑dependent process. Finally, our results demonstrate that genetic background can have an effect on meiotic studies in mice.
Highlights
Generation of haploid gametes from diploid germ cells is accomplished by way of meiosis, a specialized process comprised of two cell divisions lacking intervening replication of the genome.Precise segregation of homologous chromosomes poses a major logistical challenge for the germ cell.This difficult problem is elegantly solved by bringing homologs in physical proximity and cementing their associations by means of the synaptonemal complex (SC) [1,2,3,4,5]
We focused on mouse spermatocytes and, on the physical length of the SC, a proteinaceous structure prominently featuring between homologous chromosomes in pachynema of meiotic prophase I
Meiotic spreads were prepared from pooled testicular cell suspensions of two age-matched males of each of 129S4/SvJae, C57BL/6J, and BALB/c strains, and probed with antibodies to SYCP2, an axial elements (AE)/lateral elements (LEs) component [19]
Summary
Precise segregation of homologous chromosomes poses a major logistical challenge for the germ cell This difficult problem is elegantly solved by bringing homologs in physical proximity and cementing their associations by means of the synaptonemal complex (SC) [1,2,3,4,5]. We focused on mouse spermatocytes and, on the physical length of the SC, a proteinaceous structure prominently featuring between homologous chromosomes in pachynema of meiotic prophase I. It has been shown previously in several species that the length of the SC positively correlates with the number of COs [7,8]. COs are more evenly spaced throughout the genome [10,11]
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