Synapsis and Meiotic Recombination in Male Chinese Muntjac (Muntiacus reevesi)

Abstract

The muntjacs (Muntiacus, Cervidae) have been extensively studied in terms of chromosomal and karyotypic evolution. However, little is known about their meiotic chromosomes particularly the recombination patterns of homologous chromosomes. We used immunostained surface spreads to visualise synaptonemal complexes (SCs), recombination foci and kinetochores with antibodies against marker proteins. As in other mammals pachytene was the longest stage of meiotic prophase. 39.4% of XY bivalents lacked MLH1 foci compared to less than 0.5% of autosomes. The average number of MLH1 foci per pachytene cell in M. reevesi was 29.8. The distribution of MLH1 foci differed from other mammals. On SCs with one focus, the distribution was more even in M. reevesi than in other mammals; for SCs that have two or more MLH1 foci, usually there was a larger peak in the sub-centromere region than other regions on SC in M. reevesi. Additionally, there was a lower level of interference between foci in M. reevesi than in mouse or human. These observations may suggest that the regulation of homologous recombination in M. reevesi is slightly different from other mammals and will improve our understanding of the regulation of meiotic recombination, with respect to recombination frequency and position.

A Comparative Study of Meiotic Recombination in Cattle <b><i>(Bos taurus)</i></b> and Three Wildebeest Species <b><i>(Connochaetes gnou, C. taurinus taurinus</i></b> and <b><i>C. t. albojubatus)</i></b>

“…A similar covariance was observed in humans [Lynn et al, 2002] and rhesus monkeys [Hassold et al, 2009]. The distribution of recombination events along individual bivalents was influenced by interference, as reported previously for other mammalian species [Froenicke et al, 2002;Sun et al, 2004;Basheva et al, 2008;Borodin et al, 2008;Yang et al, 2011].…”

“…In species in which individual chromosomes cannot be determined by multicolor FISH, the MLH1 foci distribution on chromosomes can be assessed by ranking SCs according to their length, as it was published for mice [Anderson et al, 1999], dogs [Basheva et al, 2008] and Chinese muntjac [Yang et al, 2011]. We report mean numbers of recombination events in individual SCs classified according to their length in the 4 studied species.…”

“…In the species reported in this study, the sex chromosomes showed MLH1 foci in 40.3-61.7% of the analyzed pachytene spermatocytes. Concerning other mammals, an MLH1 focus was observed in about 60-70% of the XY pairs in Chinese muntjac [Yang et al, 2011] and humans [Codina-Pascual et al, 2005;Sun et al, 2006b]. The absence of the MLH1 focus on the sex chromosomes might be caused by its asynchronous appearance with a maximum of autosomal MLH1 foci [Anderson et al, 1999].…”

Evolution of recombination in eutherian mammals: insights into mechanisms that affect recombination rates and crossover interference

“…We observed that cell-tocell differences in numbers of recombination sites (reflected by the standard deviation of the mean; electronic supplementary material, table S2) were especially low in species with karyotypes comprising a high number of acrocentric chromosomes (dog-all acrocentric chromosomes; lemur-85% acrocentric chromosomes). The same pattern is found in mouse and Chinese muntjac, both of which have strictly acrocentric karyotypes, where standard deviations were similarly low (+ 2.0-2.7) [15,39]. On the other hand, species with karyotypes comprising metacentric and submetacentric chromosomes show high cell-to-cell variability in the mean number of MLH1 foci (see electronic supplementary material, table S1), and this was particularly pronounced in the rat (+6.2) and tiger (+5.9).…”

Variation of Meiotic Recombination Rates and MLH1 Foci Distribution in Spermatocytes of Cattle, Sheep and Goats

“…The vast majority of papers which focus on mammalian meiosis and the process of recombination deal with humans or mice [Lynn et al, 2002;Jensen-Seaman et al, 2004], but in recent years many other mammalian species have been studied [Borodin et al, 2007Basheva et al, 2008;Dumont and Payseur, 2011;Garcia-Cruz et al, 2011;Yang et al, 2011;Segura et al, 2013;Vozdova et al, 2013;Al-Jaru et al, 2014;Mary et al, 2014].…”