Two marsupial families exemplify divergent rates of karyotypic change. The Dasyurid family has an extremely conserved karyotype. In contrast, there is significant chromosomal variation within the Macropodidae family, best exemplified by members of the genus Petrogale (rock-wallabies). Both families are also distinguished by their telomere landscape (length and epigenetics), with the dasyurids having a unique telomere length dimorphism not observed in other marsupials and hypothesised to be regulated in a parent-of-origin fashion. Previous work has shown that proximal ends of chromosomes are enriched in cytosine methylation in dasyurids, but that the chromosomes of a macropod, the tammar wallaby, have DNA methylation enrichment of pericentric regions. Using a combination of telomere and 5-methylcytosine immunofluorescence staining, we investigated the telomere landscape of four dasyurid and three Petrogale species. As part of this study, we also further examined the parent-of-origin hypothesis for the regulation of telomere length dimorphism in dasyurids, using epigenetic modifications known to differentiate the active maternal X chromosome, including 5-methylcytosine methylation and histone modifications H3K4me2, H3K9ac and H4Kac. Our results give further support to the parent-of-origin hypothesis for the regulation of telomere length dimorphism in dasyurids, where the paternally derived X chromosome in females was associated with long telomeres and the maternally derived with short telomeres. In contrast to the tammar wallaby, rock-wallabies demonstrated a similar 5-methylcytosine staining pattern across all chromosomes to that of dasyurids, suggesting that DNA methylation of telomeric regions is not responsible for differences in the rates of chromosome evolution between these two families.

中文翻译：

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两个有袋动物家族的甲基化和端粒景观具有不同的染色体进化速率。

两个有袋动物家族证明了核型变化的差异率。Dasyurid家族具有极为保守的核型。相比之下，Macropodidae家族中存在明显的染色体变异，最好的例证是Petrogale属（岩袋鼠）。这两个家族的特征还在于它们的端粒分布（长度和表观遗传学），dasyurids具有独特的端粒长度二态性，这在其他有袋动物中没有观察到，并被认为是由母本来调控的。先前的研究表明，扁豆中的染色体近端富含胞嘧啶甲基化，但是巨脚（tammar）袋鼠的染色体具有围绕中心区域的DNA甲基化富集。结合使用端粒和5-甲基胞嘧啶免疫荧光染色，我们调查了4个dasyurid和3个Petrogale物种的端粒景观。作为这项研究的一部分，我们还使用已知的区别活跃母体X染色体的表观遗传修饰，包括5-甲基胞嘧啶甲基化和组蛋白修饰H3K4me2，H3K9ac，进一步研究了父本假说对dasyurids端粒长度二态性的调控。和H4Kac。我们的结果进一步支持了起源于父母的假说，以调节dasyurids中端粒长度二态性，其中雌性的父系X染色体与长端粒有关，而母体的X染色体与短端粒有关。与淡水袋鼠相反，岩袋鼠在所有染色体上的5甲基胞嘧啶染色模式与dasyurids相似，