Cytogenetics, morphology and evolution of four subspecies of the Giant Sheep argali (Ovis ammon) of Asia

Dalai-lamae (Ovis ammon dalai-lamae), Gobi (O. a. darwini), Kara Tau (O. a. nigrimontana) and Tibetan (O. a. hodgsoni) argali share a 2n = 56 diploid chromosome number and a karyotype consisting of 2 pairs of biarmed and 25 pairs of acrocentric autosomes, a large acrocentric X and a minute Y chromosome. The Giemsa-banding patterns of the largest pair of biarmed chromosomes were identical to those of the largest biarmed chromosomes in all wild sheep and domestic sheep of the genus Ovis. The banding patterns of the second pair of biarmed chromosomes (metacentric) were identical to the third pair of biarmed chromosomes in Ovis with 2n = 54 and to the third largest pair of chromosomes in the 2n = 52 karyotype of Siberian snow sheep (O. nivicola). The G-banded karyotypes of dalai-lamae, darwini, hodgsoni and nigrimontana are consistent with all subspecies of argali (O. ammon), except that the Y chromosome is acrocentric instead of metacentric as typical of the argaliform wild sheep and Ovis. The Dalai-lamae and Tibetan argali specimens exhibit the light-colored, long-haired ruffs and body coloration typical of argalis from the Tibetan Plateau. The Gobi argali, from the extreme western Gobi, is similar to the dark phase argali.

Comparative cytogenetics of bats (Chiroptera): The prevalence of Robertsonian translocations limits the power of chromosomal characters in resolving interfamily phylogenetic relationships

Although the monophyly of Chiroptera is well supported by many independent studies, higher-level systematics, e.g. the monophyly of microbats, remains disputed by morphological and molecular studies. Chromosomal rearrangements, as one type of rare genomic changes, have become increasingly popular in phylogenetic studies as alternatives to molecular and other morphological characters. Here, the representatives of families Megadermatidae and Emballonuridae are studied by comparative chromosome painting for the first time. The results have been integrated into published comparative maps, providing an opportunity to assess genome-wide chromosomal homologies between the representatives of eight bat families. Our results further substantiate the wide occurrence of Robertsonian translocations in bats, with the possible involvement of whole-arm reciprocal translocations (WARTs). In order to search for valid cytogenetic signature(s) for each family and superfamily, evolutionary chromosomal rearrangements identified by chromosomal painting and/or banding comparison are subjected to two independent analyses: (1) a cladistic analysis using parsimony and (2) the mapping of these chromosomal changes onto the molecularly defined phylogenetic tree available fromthe literature. Both analyses clearly indicate the prevalence of homoplasic events that reduce the reliability of chromosomal characters for resolving interfamily relationships in bats.

Chromosomal rearrangements underlying karyotype differences between Chinese pangolin (Manis pentadactyla) and Malayan pangolin (Manis javanica) revealed by chromosome painting

The Chinese pangolin (Manis pentadactyla), a representative species of the order Pholidota, has been enlisted in the mammalian whole-genome sequencing project mainly because of its phylogenetic importance. Previous studies showed that the diploid number o

Induction of cytogenetic adaptive response in spermatogonia and spermatocytes by pre-exposure of mouse testis to low-dose C-12(6+) ions

To investigate the effects of pre-exposure of mouse testis to low-dose C-12(6+) ions on cytogenetics of spermatogonia and spermatocytes induced by subsequent high-dose irradiation. the testes of outbred Kun-Ming strain mice were irradiated with 0.05 Gy of C-12(6+) ions as the pre-exposure dose, and then irradiated with 2 Gy as challenging dose at 4 h after per-exposure. Poly(ADP-ribose) polymerase (PARPs) activity and PARP-1 protein expression were respectively measured by using the enzymatic and Western blot assays at 4 h after irradiation; chromosomal aberrations in spermatogonia and spermatocytes were analyzed by the air-drying method at 8 h after irradiation. The results showed that there was a significant increase in the frequency of chromosomal aberrations and significant reductions of PARP activity and PARP-1 expression level in the mouse testes irradiated with 2 Gy of C-12(6+) ions. However, pre-exposure of mouse testes to a low dose of C-12(6+) ions significantly increased PARPs activity and PARP-1 expression and alleviated the harmful effects induced by a subsequent high-dose irradiation. PARP activity inhibitor 3-aminobenzamide (3-AB) treatment blocked the effects of PARP-1 on cytogenetic adaptive response induced by low-dose C-12(6+) ion irradiation. The data suggest that pre-exposure of testes to a low dose of heavy ions can induce cytogenetic adaptive response to subsequent high-dose irradiation. The increase of PARP-1 protein induced by the low-dose ionizing irradiation may be involved in the mechanism of these observations. (C) 2008 Elsevier B.V. All rights reserved.

食虫目核心类群的比较分子细胞遗传学研究

食虫目（Order Insectivora）是理解哺乳动物系统进化关系的一个关键类群。然 而, 对于其分类以及系统发育的关系，300 多年的研究都没有得出一致的结论。染色 体在进化过程中所发生的重组可以作为生物分类和系统发育关系的一个指标。通过 比较染色体涂色技术（Chromosome Painting）可以从全基因组水平揭示染色体同源 关系，并且可以鉴定物种进化过程中所发生的染色体重组。 本论文旨在对分布在我国的猬科、鼹科与鼩鼱科的代表物种的基因组结构进行 研究。通过比较染色体涂色的方法，建立了它们与人的基因组同源性。通过人与食 虫目主要代表类群的比较染色体涂色研究，我们从全基因组水平揭示了食虫目几个 代表类群之间的核型系统发育关系。研究结果表明： 猬科动物具有高度重组的基因组结构。人染色体片段联合HAS 4/8/5 和11/15 可 能是猬科动物的细胞遗传学鉴定特征。 与猬科动物具有高度重组的核型相比，鼹科动物的基因组结构相对保守。染色 体臂间的倒位是鼹科核型进化的主要方式。 鼩鼱科中的麝鼩亚科动物具有保守的核型。 以染色体重排作为系统发育指标，鼩鼱科与鼹科相对于猬科，具有比较近的亲 缘关系。 食虫目核心类群（猬科，鼹科与鼩鼱科）的基因组结构与现划入Afrotheria 超目 的象鼩科、无尾猬科和金鼹科的基因组结构有很大的差异。 此外，本研究所构建的比较染色体图谱，有助于已经测序的人的基因组序列信 息向其他没有基因定位数据的食虫目动物转移

食肉动物的比较分子细胞遗传学研究

猫和狗是人类重要的伴侣动物，也是生物医学研究的重要模式动物。猫是哺乳动物中核型最为保守的物种之一，而狗的基因组则经历了迄今为止最为广泛的重组。猫和狗基因组计划的长足进步，使猫和狗的基因组成为食肉动物比较基因组研究理想的参照物。种间染色体涂色，以其准确、高效和适合于全基因组比较等优点，已成为比较细胞遗传学，特别是远缘物种或核型高度重排物种间比较的首选方法。利用染色体涂色技术建立的比较染色体图谱，记录了物种形成过程中所发生的基因组改变的历史。通过比较分析保守的染色体片段在不同系统发生分支物种上的分布和排列方式，可以推测在被比较物种之间，染色体重排的速率、类型和方向以及系统发生关系，重建哺乳动物的基因组进化历程。本研究利用人、狗、猫和石貂的染色体特异探针，通过染色体涂色，建立了人与石貂以及食肉动物各主要类群物种间的比较染色体图谱。研究结果表明，现生的食肉动物可以被分成三组，每一组具有其独特的祖先核型组成、染色体改变的速率和进化途径等特征。，第一组由具有高度保守核型的猫超科、融科、洗熊科和小熊猫等组成。第二组是大熊猫和熊科，具有中等程度的核型重排。第三组是犬科，具有高度重排的核型。猫和石貂等核型保守物种的探针有利于检测染色体间的重排，而基因组高度重排的狗染色体探针则有利于追踪核型保守的物种在基因组进化过程中发生的染色体内重排，为探讨食肉动物的核型进化提供了进一步的信息。另外，我们的结果还表明小熊猫与融科动物之间有很近的系统发生关系。根据这些比较染色体图谱，重建了食肉动物各主要系统发生分支的祖先核型和核型系统发生关系。这些比较染色体图谱的建立有助于理解食肉动物基因组进化和系统发生关系，促进人、猫和狗的基因序列数据和定位资料向其他没有基因定位数据的食肉动物转移。