Assembling pieces of the centromere epigenetics puzzle

The centromere is a key region for cell division where the kinetochore assembles, recognizes and attaches to microtubules so that each sister chromatid can segregate to each daughter cell. The centromeric chromatin is a unique rigid chromatin state promoted by the presence of the histone H3 variant CENP-A, in which epigenetic histone modifications of both heterochromatin or euchromatin states and associated protein elements are present. Although DNA sequence is not regarded as important for the establishment of centromere chromatin, it has become clear that this structure is formed as a result of a highly regulated epigenetic event that leads to the recruitment and stability of kinetochore proteins. We describe an integrative model for epigenetic processes that conform regional chromatin interactions indispensable for the recruitment and stability of kinetochore proteins. If alterations of these chromatin regions occur, chromosomal instability is promoted, although segregation may still take place.     

Cytogenetic and phylogenetic studies of diploid and polyploid members of tribe Anemoninae (Ranunculaceae)

The ancestry, phylogenetic differentiation and systematic classification of the worldwide-distributed genus Anemone have been debated for many years. In this paper 11 Anemone, three Pulsatilla species and Hepatica nobilis were subjected to detailed karyotype analysis with the aim of obtaining new cytogenetic data that will contribute to karyotype evolutionary studies of the tribe Anemoninae. The results are interpreted in a phylogenetic context, established from the intergenic nontranscribed spacer (NTS) of 5S rDNA and internal transcribed spacer (ITS) of 35S rDNA. One to three 35S and one to three 5S rDNA loci are present in diploid and polyploid taxa. The 35S rDNA loci are located terminally on the short arm of acrocentric chromosomes, while for 5S rDNA there is no preferential chromosomal position as it exhibits terminal, subterminal, interstitial or pericentromeric positions, and is located either on acrocentric or metacentric chromosomes. The karyotype of hexaploid A. baldensis (2n = 6x = 48) is presented for the first time, and A. sylvestris is proposed as one of its putative parental species. Chromosome fusion/translocation is proposed as the key mechanism involved in reduction of the basic chromosome number from 8 in the Anemone subgenus to 7 in the Anemonidium subgenus. The cytogenetic data obtained are mainly supported by ITS and NTS phylogeny. Diversification of the genus Anemone was accompanied by a large reduction of heterochromatin, from the Mediterranean anemones that have large amounts of heterochromatin to the New World anemones without any detectable heterochromatic blocks.     

A re-assigned American mink (Neovison vison) map optimal for genome-wide studies

Our previously published second generation genetic map for the American mink (Neovison vison) has been used and redesigned in its best for genome-wide studies with maximum of efficiency. A number of 114 selected markers, including 33 newly developed microsatellite markers from the CHORI-231 mink Bacterial Artificial Chromosome (BAC) library, have been genotyped in a two generation population composed of 1200 individuals. The outcome reassigns the position of some markers on the chromosomes and it produces a more reliable map with a convenient distance between markers. A total of 104 markers mapped to 14 linkage groups corresponding to the mink autosomes. Six markers are unlinked and four markers are allocated to the X chromosome by homology but no linkage was detected. The sex-average linkage map spans 1192 centiMorgans (cM) with an average intermarker distance of 11.4 cM and 1648 cM when the ends of the linkage groups and the autosomal unlinked markers are added. Sex-specific genetic linkage maps were also generated. The male sex-specific map had a total length of 1014.6 cM between the linked markers and an average inter-marker interval of 9.7 cM. The female map has a corresponding length of 1378.6 cM and an average inter-marker interval of 13.3 cM. The study is complemented with additional anchorage for most of the chromosomes of the map by BAC in situ hybridization with clones containing microsatellites strategically selected from the various parts of the genome. This map provides an improved tool for genetic mapping and comparative genomics in mink, also useful for the future assembly of the mink genome sequence when this will be taken forward.     

Monosomy 9pter and trisomy 9q34.11qter in two sisters due to a maternal pericentric inversion

Pericentric inversions of chromosome 9 leading to unbalanced live-born offspring are relatively rare and so far only four cases have been reported. Here we present two sisters with an unbalanced recombinant chromosome 9 which resulted from a large maternal pericentric inversion inv(9)(p24.3q34.1). Further molecular characterisation of the aberrant chromosome 9 by 250k SNP array analysis showed a terminal 460 kb loss of 9p24.3 and a terminal 8.9 Mb gain of 9q34.11. We compared the clinical features of these two patients with the previous reported four cases as well as with patients with similar sized 9pter deletions or 9qter duplications. Based upon this study, we suggest that the recombinant chromosome 9 phenotype is mainly the result of duplication of a 3.4 Mb region of chromosome 9q34.11q34.13.     

Chromosomal variability of human mesenchymal stem cells cultured under hypoxic conditions

Bone marrow derived human mesenchymal stem cells (hMSCs) have attracted great interest from both bench and clinical researchers because of their pluripotency and ease of expansion ex vivo. However, these cells do finally reach a senescent stage and lose their multipotent potential. Proliferation of these cells is limited up to the time of their senescence, which limits their supply, and they may accumulate chromosomal changes through ex vivo culturing. The safe, rapid expansion of hMSCs is critical for their clinical application. Chromosomal aberration is known as one of the hallmarks of human cancer, and therefore it is important to understand the chromosomal stability and variability of ex vivo expanded hMSCs before they are used widely in clinical applications. In this study, we examined the effects of culturing under ambient (20%) or physiologic (5%) O(2) concentrations on the rate of cell proliferation and on the spontaneous transformation of hMSCs in primary culture and after expansion, because it has been reported that culturing under hypoxic conditions accelerates the propagation of hMSCs. Bone marrow samples were collected from 40 patients involved in clinical research. We found that hypoxic conditions promote cell proliferation more favourably than normoxic conditions. Chromosomal aberrations, including structural instability or aneuploidy, were detected in significantly earlier passages under hypoxic conditions than under normoxic culture conditions, suggesting that amplification of hMSCs in a low-oxygen environment facilitated chromosomal instability. Furthermore, smoothed hazard-function modelling of chromosomal aberrations showed increased hazard after the fourth passage under both sets of culture conditions, and showed a tendency to increase the detection rate of primary karyotypic abnormalities among donors aged 60 years and over. In conclusion, we propose that the continuous monitoring of hMSCs will be required before they are used in therapeutic applications in the clinic, especially when cells are cultured under hypoxic conditions.     

陆地棉染色体片段代换系（BC5F3和BC5F3︰4）产量和纤维品质性状表现的初步评价

本研究以海岛棉海1为供体亲本,陆地棉中棉所36为轮回亲本构建了一套棉花染色体片段代换系,通过对BC5F3和BC5F3∶4这两个世代材料表型数据的分析,结果显示,同年份中与轮回亲本比较,群体各性状的极差和遗传变异系数都比较大;1942个BC5F3单株群体中衣分最高达49.57%,超轮回亲本比例为71.78%,纤维断裂比强度最高为36.5cN/tex;658个BC5F3∶4株行群体中纤维上半部平均长度最大值32.25mm,超轮回亲本比例为47.57%,断裂比强度最高达到32.2cN/tex,超轮回亲本比例为40.27%;通过相关性分析,主要产量性状和纤维品质性状在两个世代间呈极显著正相关,衣分与纤维长度及强度在群体内呈极显著负相关。这些结果表明,通过高代回交后连续自交得到的染色体片段代换系群体中存在丰富的遗传变异,含有大量具有丰产、纤维品质优异的单株,两个世代材料具有较好的一致性与稳定性;产量和品质同步改良还存在一定难度。本研究为进一步的近等基因系分析、基因克隆、基因聚合效应分析等储备了大量的研究材料。     

GLPp16/CSP17 探针在膀胱尿路上皮癌诊断中的应用

目的:探讨荧光原位杂交技术辅助诊断膀胱尿路上皮癌的可行性。方法:标记为17号染色体着丝粒及9号染色体p16位点9p21区带探针,采用荧光原位杂交技术(Fluorescence in Situ Hybridization FISH)对80例膀胱肿瘤患者尿液间期细胞核进行荧光原位杂交,以20例健康志愿者作为正常对照组,建立阈值。以术后病理结果作为诊断"金标准",对80例膀胱肿瘤患者同时行尿脱落细胞学检查,与FISH进行比较。结果:17号染色体和9p21的畸变率分别为57.5%和63.8%。17号染色体畸变率主要表现为多倍体,与膀胱癌的分级有显著相关性(P<0.01);9号染色体畸变率主要变现为染色体缺失,与膀胱癌分期分级均无相关性(P>0.05)。尿脱落细胞学灵敏度为12.2%,FTSH技术灵敏度为86.5%;两者差异有统计学意义(P<0.01)。结论:荧光原位杂交技术可以作为膀胱尿路上皮癌诊断的一项重要方法,并可能在预后判断中具有重要临床意义。     

Shape and size variation on the wing of <Emphasis Type="Italic">Drosophila mediopunctata</Emphasis>: influence of chromosome inversions and genotype-environment interaction

The second chromosome of Drosophila mediopunctata is highly polymorphic for inversions. Previous work reported a significant interaction between these inversions and collecting date on wing size, suggesting the presence of genotype-environment interaction. We performed experiments in the laboratory to test for the joint effects of temperature and chromosome inversions on size and shape of the wing in D. mediopunctata. Size was measured as the centroid size, and shape was analyzed using the generalized least squares Procrustes superimposition followed by discriminant analysis and canonical variates analysis of partial warps and uniform components scores. Our findings show that wing size and shape are influenced by temperature, sex, and karyotype. We also found evidence suggestive of an interaction between the effects of karyotype and temperature on wing shape, indicating the existence of genotype-environment interaction for this trait in D. mediopunctata. In addition, the association between wing size and chromosome inversions is in agreement with previous results indicating that these inversions might be accumulating alleles adapted to different temperatures. However, no significant interaction between temperature and karyotype for size was found--in spite of the significant presence of temperature-genotype (cross) interaction. We suggest that other ecological factors--such as larval crowding--or seasonal variation of genetic content within inversions may explain the previous results.