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Global DNA Methylation patterns on marsupial and devil facial tumour chromosomes.

Ingles ED, Deakin JE - Mol Cytogenet (2015)

Bottom Line: In males, the X chromosome was hypermethylated as was one X in females.Similarly, telomeric regions on DFTD chromosomes and regions corresponding to material from one of the two X chromosomes were hypermethylated.No difference in global methylation in samples of the same strain taken in different years was observed.

View Article: PubMed Central - PubMed

Affiliation: Institute for Applied Ecology, University of Canberra, Canberra, ACT 2601 Australia.

ABSTRACT

Background: Despite DNA methylation being one of the most widely studied epigenetic modifications in eukaryotes, only a few studies have examined the global methylation status of marsupial chromosomes. The emergence of devil facial tumour disease (DFTD), a clonally transmissible cancer spreading through the Tasmanian devil population, makes it a particularly pertinent time to determine the methylation status of marsupial and devil facial tumour chromosomes. DNA methylation perturbations are known to play a role in genome instability in human tumours. One of the interesting features of the devil facial tumour is its remarkable karyotypic stability over time as only four strains with minor karyotypic differences having been reported. The cytogenetic monitoring of devil facial tumour (DFT) samples collected over an eight year period and detailed molecular cytogenetic analysis performed on the different DFT strains enables chromosome rearrangements to be correlated with methylation status as the tumour evolves.

Results: We used immunofluorescent staining with an antibody to 5-methylcytosine on metaphase chromosomes prepared from fibroblast cells of three distantly related marsupials, including the Tasmanian devil, as well as DFTD chromosomes prepared from samples collected from different years and representing different karyotypic strains. Staining of chromosomes from male and female marsupial cell lines indicate species-specific differences in global methylation patterns but with the most intense staining regions corresponding to telomeric and/or centromeric regions of autosomes. In males, the X chromosome was hypermethylated as was one X in females. Similarly, telomeric regions on DFTD chromosomes and regions corresponding to material from one of the two X chromosomes were hypermethylated. No difference in global methylation in samples of the same strain taken in different years was observed.

Conclusions: The methylation patterns on DFTD chromosomes suggests that the hypermethylated active X was shattered in the formation of the tumour chromosomes, with atypical areas of methylation on DFTD chromosomes corresponding to locations of X chromosome material from the shattered X. The incredibly stable broad methylation patterns observed between strains and over time may reflect the overall genomic stability of the devil facial tumour.

No MeSH data available.


Related in: MedlinePlus

Methylation status of marsupial sex chromosomes. Xa and Xi denote the active and inactive X chromosomes in females respectively. Line scans indicate the distribution of DNA methylation (green) and DAPI staining (blue) along the X chromosomes
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Fig5: Methylation status of marsupial sex chromosomes. Xa and Xi denote the active and inactive X chromosomes in females respectively. Line scans indicate the distribution of DNA methylation (green) and DAPI staining (blue) along the X chromosomes

Mentions: In female tammar wallaby fibroblast cells, the long arm of one X chromosome was hypermethylated compared to the other (Fig. 5). The short arm was hypomethylated on both X chromosomes. In males, both the short and long arms of the X chromosome were hypermethylated. Similar to the tammar wallaby, one devil X in female fibroblasts was hypermethylated compared to the other one, which only had a small amount of staining on the long arm (Fig. 5). In male fibroblasts, the X chromosome was likewise hypermethylated. In contrast, both X chromosomes in female M. domestica were methylated, although one more so than the other (Fig. 5) and the male cells possessed a hypermethylated X chromosome. Importantly, the methylation patterns observed for male wallaby and opossum chromosomes were consistent with those observed in the previous studies [2, 3]. Evidence suggests that the hypomethylated X in these species corresponds to the inactive X as this has been demonstrated previously using sequential staining with the repressive mark H3K9me3 associated with the inactive X followed by staining for 5-methylcytosine in the brushtail possum [2]. This means that the active X is hypermethylated in line with the hypermethylation of the single active X chromosome in males.Fig. 5


Global DNA Methylation patterns on marsupial and devil facial tumour chromosomes.

Ingles ED, Deakin JE - Mol Cytogenet (2015)

Methylation status of marsupial sex chromosomes. Xa and Xi denote the active and inactive X chromosomes in females respectively. Line scans indicate the distribution of DNA methylation (green) and DAPI staining (blue) along the X chromosomes
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4591559&req=5

Fig5: Methylation status of marsupial sex chromosomes. Xa and Xi denote the active and inactive X chromosomes in females respectively. Line scans indicate the distribution of DNA methylation (green) and DAPI staining (blue) along the X chromosomes
Mentions: In female tammar wallaby fibroblast cells, the long arm of one X chromosome was hypermethylated compared to the other (Fig. 5). The short arm was hypomethylated on both X chromosomes. In males, both the short and long arms of the X chromosome were hypermethylated. Similar to the tammar wallaby, one devil X in female fibroblasts was hypermethylated compared to the other one, which only had a small amount of staining on the long arm (Fig. 5). In male fibroblasts, the X chromosome was likewise hypermethylated. In contrast, both X chromosomes in female M. domestica were methylated, although one more so than the other (Fig. 5) and the male cells possessed a hypermethylated X chromosome. Importantly, the methylation patterns observed for male wallaby and opossum chromosomes were consistent with those observed in the previous studies [2, 3]. Evidence suggests that the hypomethylated X in these species corresponds to the inactive X as this has been demonstrated previously using sequential staining with the repressive mark H3K9me3 associated with the inactive X followed by staining for 5-methylcytosine in the brushtail possum [2]. This means that the active X is hypermethylated in line with the hypermethylation of the single active X chromosome in males.Fig. 5

Bottom Line: In males, the X chromosome was hypermethylated as was one X in females.Similarly, telomeric regions on DFTD chromosomes and regions corresponding to material from one of the two X chromosomes were hypermethylated.No difference in global methylation in samples of the same strain taken in different years was observed.

View Article: PubMed Central - PubMed

Affiliation: Institute for Applied Ecology, University of Canberra, Canberra, ACT 2601 Australia.

ABSTRACT

Background: Despite DNA methylation being one of the most widely studied epigenetic modifications in eukaryotes, only a few studies have examined the global methylation status of marsupial chromosomes. The emergence of devil facial tumour disease (DFTD), a clonally transmissible cancer spreading through the Tasmanian devil population, makes it a particularly pertinent time to determine the methylation status of marsupial and devil facial tumour chromosomes. DNA methylation perturbations are known to play a role in genome instability in human tumours. One of the interesting features of the devil facial tumour is its remarkable karyotypic stability over time as only four strains with minor karyotypic differences having been reported. The cytogenetic monitoring of devil facial tumour (DFT) samples collected over an eight year period and detailed molecular cytogenetic analysis performed on the different DFT strains enables chromosome rearrangements to be correlated with methylation status as the tumour evolves.

Results: We used immunofluorescent staining with an antibody to 5-methylcytosine on metaphase chromosomes prepared from fibroblast cells of three distantly related marsupials, including the Tasmanian devil, as well as DFTD chromosomes prepared from samples collected from different years and representing different karyotypic strains. Staining of chromosomes from male and female marsupial cell lines indicate species-specific differences in global methylation patterns but with the most intense staining regions corresponding to telomeric and/or centromeric regions of autosomes. In males, the X chromosome was hypermethylated as was one X in females. Similarly, telomeric regions on DFTD chromosomes and regions corresponding to material from one of the two X chromosomes were hypermethylated. No difference in global methylation in samples of the same strain taken in different years was observed.

Conclusions: The methylation patterns on DFTD chromosomes suggests that the hypermethylated active X was shattered in the formation of the tumour chromosomes, with atypical areas of methylation on DFTD chromosomes corresponding to locations of X chromosome material from the shattered X. The incredibly stable broad methylation patterns observed between strains and over time may reflect the overall genomic stability of the devil facial tumour.

No MeSH data available.


Related in: MedlinePlus