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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

DFT chromosomes and their homology to normal devil chromosomes. a Chromosomes present in all strains. b M5 is present in strains 2 – 4. c Chromosome 6 in strain 4 has had an addition to the long arm, the origin of which is currently unknown. Variable numbers of double minutes are also present in strain 4. * denotes chromosomes with variations within and between strains [8]
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Fig2: DFT chromosomes and their homology to normal devil chromosomes. a Chromosomes present in all strains. b M5 is present in strains 2 – 4. c Chromosome 6 in strain 4 has had an addition to the long arm, the origin of which is currently unknown. Variable numbers of double minutes are also present in strain 4. * denotes chromosomes with variations within and between strains [8]

Mentions: Evidence from cytogenetic and sequencing analyses indicate that the original DFTD tumour was derived from a Schwann cell of a female devil and this tumour has since spread through the population [7, 8, 10, 11]. Transmission of the tumour appears to occur by healthy devils biting into the tumours of infected devils, with biting being a part of normal social interaction [12]. A notable feature of this unusual tumour includes its remarkable karyotypic stability over time. After an initial major genome restructuring, presumed to have resulted from a chromothripsis event, DFT chromosomes have undergone very few changes given the number of cell divisions the tumour would have experienced since its formation [8, 9]. The first reported DFTD karyotypes consisted of 13 chromosomes with both homologues of chromosomes 2, 3, 4 and 6 as well as one homologue of chromosome 5 recognisable [7]. Material from chromosomes 1, 4, 5 and X was rearranged to form four marker chromosomes (M1 – M4) [8] (Fig. 2a). There are now four reported karyotypic strains of the disease [9]. Strains 2, 3 and 4 have an additional small marker chromosome (M5) (Fig. 2b), rearrangements and/or deletions on the short arm of chromosome 3 (strains 2 and 3), a presumed addition to one homologue of chromosome 6 (strain 4) and the presence of double minutes (strain 4) (Fig. 2c). It has been suggested that either strain 1 or 2 appear closest to the original DFTD cell line, with strains 3 and 4 most likely being offshoots of strain 2 [9]. Tetraploid versions have been observed for each of the strains [9].Fig. 2


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

Ingles ED, Deakin JE - Mol Cytogenet (2015)

DFT chromosomes and their homology to normal devil chromosomes. a Chromosomes present in all strains. b M5 is present in strains 2 – 4. c Chromosome 6 in strain 4 has had an addition to the long arm, the origin of which is currently unknown. Variable numbers of double minutes are also present in strain 4. * denotes chromosomes with variations within and between strains [8]
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4591559&req=5

Fig2: DFT chromosomes and their homology to normal devil chromosomes. a Chromosomes present in all strains. b M5 is present in strains 2 – 4. c Chromosome 6 in strain 4 has had an addition to the long arm, the origin of which is currently unknown. Variable numbers of double minutes are also present in strain 4. * denotes chromosomes with variations within and between strains [8]
Mentions: Evidence from cytogenetic and sequencing analyses indicate that the original DFTD tumour was derived from a Schwann cell of a female devil and this tumour has since spread through the population [7, 8, 10, 11]. Transmission of the tumour appears to occur by healthy devils biting into the tumours of infected devils, with biting being a part of normal social interaction [12]. A notable feature of this unusual tumour includes its remarkable karyotypic stability over time. After an initial major genome restructuring, presumed to have resulted from a chromothripsis event, DFT chromosomes have undergone very few changes given the number of cell divisions the tumour would have experienced since its formation [8, 9]. The first reported DFTD karyotypes consisted of 13 chromosomes with both homologues of chromosomes 2, 3, 4 and 6 as well as one homologue of chromosome 5 recognisable [7]. Material from chromosomes 1, 4, 5 and X was rearranged to form four marker chromosomes (M1 – M4) [8] (Fig. 2a). There are now four reported karyotypic strains of the disease [9]. Strains 2, 3 and 4 have an additional small marker chromosome (M5) (Fig. 2b), rearrangements and/or deletions on the short arm of chromosome 3 (strains 2 and 3), a presumed addition to one homologue of chromosome 6 (strain 4) and the presence of double minutes (strain 4) (Fig. 2c). It has been suggested that either strain 1 or 2 appear closest to the original DFTD cell line, with strains 3 and 4 most likely being offshoots of strain 2 [9]. Tetraploid versions have been observed for each of the strains [9].Fig. 2

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