Meiotic Crossover Patterning

Abstract

Proper number and placement of meiotic crossovers is vital to chromosome segregation, with failures in normal crossover distribution often resulting in aneuploidy and infertility. Meiotic crossovers are formed via homologous repair of programmed double-strand breaks (DSBs). Although DSBs occur throughout the genome, crossover placement is intricately patterned, as observed first in early genetic studies by Muller and Sturtevant. Three types of patterning events have been identified. Interference, first described by Sturtevant in 1915, is a phenomenon in which crossovers on the same chromosome do not occur near one another. Assurance, initially identified by Owen in 1949, describes the phenomenon in which a minimum of one crossover is formed per chromosome pair. Suppression, first observed by Beadle in 1932, dictates that crossovers do not occur in regions surrounding the centromere and telomeres. The mechanisms behind crossover patterning remain largely unknown, and key players appear to act at all scales, from the DNA level to inter-chromosome interactions. There is also considerable overlap between the known players that drive each patterning phenomenon. In this review we discuss the history of studies of crossover patterning, developments in methods used in the field, and our current understanding of the interplay between patterning phenomena.

Diversity and determinants of recombination landscapes in flowering plants

“…We showed that, for most species, the smallest chromosome had roughly one or two COs, independently of chromosome size. This is in agreement with the idea that CO assurance is a ubiquitous regulation process among angiosperms (Pazhayam et al, 2021). Moreover, it seems that this constraint imposes a kind of basal recombination rate for each species, on the order of 50/ Sc cM/Mb, where Sc is the size of the lowest chromosome in Mb.…”

“…Recombination also plays an evolutionary role by breaking the linkage between neighbouring sites and creating new genetic combinations transmitted to the next generation upon which selection can act (Barton, 1995; Charlesworth and Jensen, 2021; Otto, 2009). However, the number and location of crossovers (COs) along the chromosome are finely regulated through mechanisms of crossover assurance, interference and homeostasis (Otto and Payseur, 2019; Pazhayam et al, 2021). In most species, at least one CO per chromosome is mandatory to achieve proper segregation and to avoid deleterious consequences of nondisjunction.…”

“…In most species, at least one CO per chromosome is mandatory to achieve proper segregation and to avoid deleterious consequences of nondisjunction. Additional COs are also usually regulated through interference, ensuring that they are not too numerous and not too close to each other (Pazhayam et al, 2021; Wang et al, 2015). In addition to regulation on a large scale (Cooper et al, 2016; Zelkowski et al, 2019), recombination is also finely tuned on a small scale.…”

Crossover patterning through kinase-regulated condensation and coarsening of recombination nodules

“…The role of the SC in crossover interference A variety of physical and mathematical models have been proposed to explain crossover interference (reviewed by Otto and Payseur, 2019;Pazhayam et al, 2021). An early model suggested that the SC might behave as a "compartment" within which recombination proteins might diffuse and accumulate cooperatively at a limited number of recombination sites (Holliday, Robin, 1977).…”

Loss, Gain, and Retention: Mechanisms Driving Late Prophase I Chromosome Remodeling for Accurate Meiotic Chromosome Segregation

“…Although there are exceptions (reviewed in [ 6 ]), COs are essential for accurate chromosome segregation in most organisms. Specifically, COs in conjunction with sister chromatid cohesion (SCC) result in structures referred to as “chiasmata”, which tether homolog pairs, thereby facilitating their correct orientation on the MI spindle [ 7 , 8 , 9 ].…”