Rapid emergence of independent “chromosomal lineages” in silvered-leaf monkey triggered by Y/autosome translocation

Abstract

Sex/autosome translocations are rare events. The only known example in catarrhines is in the silvered-leaf monkey. Here the Y chromosome was reciprocally translocated with chromosome 1. The rearrangement produced an X1X2Y1Y2 sex chromosome system. At least three chromosomal variants of the intact chromosome 1 are known to exist. We characterized in high resolution the translocation products (Y1 and Y2) and the polymorphic forms of the intact chromosome 1 with a panel of more than 150 human BAC clones. We showed that the translocation products were extremely rearranged, in contrast to the high level of marker order conservation of the other silvered-leaf monkey chromosomes. Surprisingly, each translocation product appeared to form independent “chromosome lineages”; each having a myriad of distinct rearrangements. We reconstructed the evolutionary history of the translocation products by comparing the homologous chromosomes of two other colobine species: the African mantled guereza and the Indian langur. The results showed a massive reuse of breakpoints: only 12, out of the 40 breaks occurred in domains never reused in other rearrangements, while, strikingly, some domains were used up to four times. Such frequent breakpoint reuse if proved to be a general phenomenon has profound implications for mechanisms of chromosome evolution.

Sex chromosome systems in Neotropical Primates: What have we learnt so far from cytogenetics and genomics?

“…The presence of these multiple sex chromosome systems in several genera seems to constitute a unifying feature in the structural organization of Platyrrhini genome. In contrast, multiple sexual systems were only described in the silvered leaf monkey ( Trachypithecus cristatus ) within Catarrhini (Bigoni et al, 1997; Xiaobo et al, 2013; Capozzi et al, 2018).…”

Chromosomes in the DNA era: Perspectives in diagnostics and research

“…The common bases for acquired or constitutional chromosomal rearrangements and for chromosomal changes between species are DNA double-strand breaks. One specific class of cytogenetically visible breaks of decondensed chromatin are fragile sites (FSs) that are considered as regions of chromosomal instability with overlapping signatures for breakpoints repeatedly observed in tumors [49][50][51], in constitutional rearrangements [4,52,53], and also as evolutionarily conserved breakpoints [54][55][56][57][58]. In addition, those breakage-prone regions are conserved beyond the mammalian linage [59] and seem to be a general and conserved feature of chromosome biology.…”