Fragile Sites | ScienceGate

A cytogenetic assay based on fragile sites (FS) enables the identification of breaks, chromatid gaps, and deletions. In healthy individuals, the number of these instabilities remains low. Genome stability in these species is affected by Robertsonian translocations in the karyotype of the blue fox and by B chromosomes in the silver fox. The aims of the study were to characterise the karyotype of blue foxes, silver foxes, and their hybrids and to identify chromosomal fragile sites used to evaluate genome stability. The diploid number of A chromosomes in blue foxes ranged from 48 to 50, while the number of B chromosomes in silver foxes varied from one to four, with a constant number of A chromosomes (2n = 34). In interspecific hybrids, both types of karyotypic variation were identified, with the diploid number of A chromosomes ranging from 40 to 44 and the number of B chromosomes varying from 0 to 3. The mean frequency of FS in foxes was 4.06 ± 0.19: 4.61 ± 0.37 in blue foxes, 3.46 ± 0.28 in silver foxes, and 4.12 ± 0.22 in hybrids. A relationship was identified between an increased number of A chromosomes in the karyotype of the hybrids and the frequency of chromosomal breaks. The FS assay was used as a biomarker for the evaluation of genomic stability in the animals in the study.

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Fragile sites and nucleosome formation

Molecular Medicine Today ◽

10.1016/s1357-4310(97)83484-3 ◽

1997 ◽

Vol 3 (1) ◽

pp. 4

Author(s):

Robert A. Brooksbank

Keyword(s):

Fragile Sites ◽

Nucleosome Formation

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Replication Stress and Telomere Dysfunction Are Present in Cultured Human Embryonic Stem Cells

Cytogenetic and Genome Research ◽

10.1159/000441245 ◽

2015 ◽

Vol 146 (4) ◽

pp. 251-260 ◽

Cited By ~ 3

Author(s):

Christine Janson ◽

Kristine Nyhan ◽

John P. Murnane

Keyword(s):

Stem Cells ◽

Dna Damage ◽

Embryonic Stem Cells ◽

Human Embryonic Stem Cells ◽

Chromosome Instability ◽

Embryonic Stem ◽

Replication Stress ◽

Activin A ◽

Fragile Sites ◽

Telomere Dysfunction

Replication stress causes DNA damage at fragile sites in the genome. DNA damage at telomeres can initiate breakage-fusion-bridge cycles and chromosome instability, which can result in replicative senescence or tumor formation. Little is known about the extent of replication stress or telomere dysfunction in human embryonic stem cells (hESCs). hESCs are grown in culture with the expectation of being used therapeutically in humans, making it important to minimize the levels of replication stress and telomere dysfunction. Here, the hESC line UCSF4 was cultured in a defined medium with growth factor Activin A, exogenous nucleosides, or DNA polymerase inhibitor aphidicolin. We used quantitative fluorescence in situ hybridization to analyze individual telomeres for dysfunction and observed that it can be increased by aphidicolin or Activin A. In contrast, adding exogenous nucleosides relieved dysfunction, suggesting that telomere dysfunction results from replication stress. Whether these findings can be applied to other hESC lines remains to be determined. However, because the loss of telomeres can lead to chromosome instability and cancer, we conclude that hESCs grown in culture for future therapeutic purposes should be routinely checked for replication stress and telomere dysfunction.

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