Department of Biology, The Pennsylvania State University, University Park, PA 16802, USA.
Philos Trans R Soc Lond B Biol Sci. 2022 Aug;377(1856):20210206. doi: 10.1098/rstb.2021.0206. Epub 2022 Jun 13.
DNA within chromosomes in the nucleus is non-randomly organized into chromosome territories, compartments and topologically associated domains (TADs). Chromosomal rearrangements have the potential to alter chromatin organization and modify gene expression leading to selection against these structural variants. has a wealth of naturally occurring gene arrangements that were generated by overlapping inversion mutations caused by two chromosomal breaks that rejoin the central region in reverse order. Unlike humans, inversion heterozygotes do not have negative effects associated with crossing over during meiosis because males use achiasmate mechanisms for proper segregation, and aberrant recombinant meiotic products generated in females are lost in polar bodies. As a result, populations are found to harbour extensive inversion polymorphisms. It is not clear, however, whether chromatin architecture constrains which inversions breakpoints persist in populations. We mapped the breakpoints of seven inversions in to the TAD map to determine if persisting inversion breakpoints are more likely to occur at boundaries between TADs. Our results show that breakpoints occur at TAD boundaries more than expected by chance. Some breakpoints may alter gene expression within TADs supporting the hypothesis that position effects contribute to inversion establishment. This article is part of the theme issue 'Genomic architecture of supergenes: causes and evolutionary consequences'.
细胞核中染色体上的 DNA 是非随机组织成染色体区域、隔室和拓扑关联域（TAD）的。染色体重排有可能改变染色质组织并改变基因表达，从而导致对这些结构变体的选择。果蝇拥有丰富的自然发生的基因排列，这些排列是由两个染色体断裂引起的重叠倒位突变产生的，两个断裂重新连接中央区域的顺序相反。与人类不同，果蝇倒位杂合体在减数分裂期间没有与交叉相关的负面影响，因为雄性使用非联会机制进行正确的分离，而在雌性中产生的异常重组减数分裂产物在极体中丢失。因此，果蝇种群中发现存在广泛的倒位多态性。然而，目前尚不清楚染色质结构是否限制了哪些倒位断点在群体中持续存在。我们将七个倒位的断点映射到果蝇的 TAD 图谱上，以确定持续存在的倒位断点是否更有可能发生在 TAD 之间的边界上。我们的结果表明，断点发生在 TAD 边界上的频率高于预期的随机频率。一些断点可能会改变 TAD 内的基因表达，支持位置效应有助于倒位建立的假说。本文是主题为“超级基因的基因组结构：原因和进化后果”的一部分。
