Meiotic recombination, synapsis, meiotic inactivation and sperm aneuploidy in a chromosome 1 inversion carrier

Abstract

Disrupted meiotic behaviour of inversion carriers may be responsible for suboptimal sperm parameters in these carriers. This study investigated meiotic recombination, synapsis, transcriptional silencing and chromosome segregation effects in a pericentric inv(1) carrier. Recombination (MLH1), synapsis (SYCP1, SYCP3) and transcriptional inactivation (γH2AX, BRCA1) were examined by fluorescence immunostaining. Chromosome specific rates of recombination were determined by fluorescence in-situ hybridization. Furthermore, testicular sperm was examined for aneuploidy and segregation of the inv(1). Our findings showed that global recombination rates were similar to controls. Recombination on the inv(1) and the sex chromosomes were reduced. The inv(1) associated with the XY body in 43.4% of cells, in which XY recombination was disproportionately absent, and 94.3% of cells displayed asynapsed regions which displayed meiotic silencing regardless of their association with the XY body. Furthermore, a low frequency of chromosomal imbalance was observed in spermatozoa (3.4%). Our results suggest that certain inversion carriers may display unimpaired global recombination and impaired recombination on the involved and the sex chromosomes during meiosis. Asynapsis or inversion-loop formation in the inverted region may be responsible for impaired spermatogenesis and may prevent sperm-chromosome imbalance.

Heterologous Synapsis and Crossover Suppression in Heterozygotes for a Pericentric Inversion in the Zebra Finch

“…A possible way to test if a chromosome segment was affected by an inversion is to analyze the pattern of synapsis and crossing over in SC spreads in heterozygotes. Extensive analyses of SC spreads in plants, mice and humans carrying inversions have shown that these rearrangements can lead to synaptic irregularities, loop formation and disruption of the normal crossover pattern [Ashley et al, 1981;Moses et al, 1982;Gabriel-Robez et al, 1986;Anderson et al, 1988;Koehler et al, 2004;Massip et al, 2010;Kirkpatrick et al, 2012].…”

Recombination suppression in heterozygotes for a pericentric inversion induces interchromosomal effect on crossovers inArabidopsis

“…The reduction/suppression of COs within inversions is well documented across several organisms [12, 13]. Different mechanisms are invoked to explain this CO suppression such as non-homologous synapsis (hetero-synapsis) [32] and asynapsis [16] between the normal and inverted regions. However, in this work recombination events such as double COs are detected in chromosome 3 suggesting that homo-synapsis occurs in the rearranged region.…”

“…One of these mechanisms operates through inversions, which are strong suppressors of recombination across the rearranged chromosomal regions [12]. Reduction/suppression of COs in inverted regions is reported in various organisms including yeast [13], C. elegans [14], mammals [15, 16] and plants [17–19]. Inversions have been studied extensively in multiple Drosophila species [20].…”

Different segregation patterns in five carriers due to a pericentric inversion of chromosome 1

“…The detection of particular breakpoint sites can be correlated with a degree of spermatogenic failure in male carriers. The inv(1) carrier displayed synapsis impairment for all unsynapsed bivalents exhibiting markers of transcriptional silencing, which may cause impaired spermatogenesis [Kirkpatrick et al 2012]. A meiotic failure could be due to a reduction in recombination events with an absence of a full loop formation and the rare occurrence of a partial loop leading [Chandley et al 1987].…”