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Viability of X-autosome translocations in mammals: an epigenomic hypothesis from a rodent case-study

机译:X-常染色体易位在哺乳动物中的生存能力:来自啮齿动物病例研究的表观基因组假设

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X-autosome translocations are highly deleterious chromosomal rearrangements due to meiotic disruption, the effects of X-inactivation on the autosome, and the necessity of maintaining different replication timing patterns between the two segments. In spite of this, X-autosome translocations are not uncommon. We here focus on the genus Taterillus (Rodentia, Gerbillinae) which provides two sister lineages differing by two autosome–gonosome translocations. Despite the recent and dramatic chromosomal repatterning characterising these lineages, the X-autosome translocated species all display intercalary heterochromatic blocks (IHBs) between the autosomal and the ancestral sexual segments. These blocks, composed of highly amplified telomeric repeats and rDNA clusters, are not observed on the chromosomes of the non-translocated species, nor the Y1 and Y2 of the translocated species. Such IHBs are found in all mammals documented for X-autosome translocation. We propose an epigenomic hypothesis which explains the viability of X-autosome translocations in mammals. This posits that constitutive heterochromatin is probably selected for in X-autosome translocations since it may (1) prevent facultative heterochromatinization of the inactivated X from spreading to the autosomal part, and (2) allow for the independent regulation of replication timing of the sex and autosomal segments.
机译:X-常染色体易位是高度有害的染色体重排,其原因是减数分裂中断,X-灭活对常染色体的影响以及必须在两个片段之间维持不同的复制时机。尽管如此,X常染色体易位并不少见。在这里,我们重点介绍Taterillus属(Rodentia,Gerbillinae),它提供了两个姊妹谱系,它们之间存在两个常染色体-基因体易位。尽管最近和戏剧性的染色体谱系表征这些谱系,但X常染色体易位物种在常染色体和祖先性节之间都显示出inter间异色块(IHBs)。这些块由高度扩增的端粒重复序列和rDNA簇组成,未在非易位物种的染色体上也未观察到,也未在易位物种的Y1和Y2上观察到。在所有记录有X常染色体易位的哺乳动物中都发现了这种IHBs。我们提出了表观基因学假说,该假说解释了X常染色体易位在哺乳动物中的生存能力。这表明在X常染色体易位中可能选择组成型异染色质,因为它可能(1)防止灭活X的兼性异染色质扩散到常染色体部分,并且(2)允许独立调节性和常染色体区段。

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  • 来源
    《Chromosoma》 |2004年第1期|34-41|共8页
  • 作者单位

    Laboratoire Origine Structure et Evolution de la Biodiversité Muséum National d’Histoire NaturelleService de Systématique Moléculaire MNHNEvolutionary Genomics Group Department of Zoology University of Stellenbosch;

    Service de Systématique Moléculaire MNHN;

    Service de Systématique Moléculaire MNHN;

    Laboratoire Origine Structure et Evolution de la Biodiversité Muséum National d’Histoire Naturelle;

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