Limits...
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

Colocalisation of X-borne genes and hypermethylated regions. a The region containing X-borne genes (PLP – green; SRPX2 – red) overlaps with the extended hypermethylated region on the longer homologue of chromosome 2 (2L). The hypermethyated region and X-borne genes are absent from the shorter chromosome 2 homologue (2s). bHEPH (red) and methylation staining (green) on marker chromosome 2. cARHGEF6 and methylation staining (green) on marker chromosome 3
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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

Fig7: Colocalisation of X-borne genes and hypermethylated regions. a The region containing X-borne genes (PLP – green; SRPX2 – red) overlaps with the extended hypermethylated region on the longer homologue of chromosome 2 (2L). The hypermethyated region and X-borne genes are absent from the shorter chromosome 2 homologue (2s). bHEPH (red) and methylation staining (green) on marker chromosome 2. cARHGEF6 and methylation staining (green) on marker chromosome 3

Mentions: One chromosome 2 homologue had an extended methylation range on one of its arms, which was observed across all strains and time periods. Based on chromosome measurements, this increased methylation was always present on the longer chromosome 2 homologue, which has been shown to have an added region consisting of DNA material from chromosomes 1 and X [8]. We performed fluorescence in situ hybridisation on the same metaphase spreads that had been stained for 5-methylcytosine, with two X chromosome genes (PLP and SRPX) mapping to this region on DFTD chromosomes, demonstrating that the extended region of methylation overlaps with the translocated genes (Fig. 7a). Similarly, an additional region of methylation was observed on M2 in the region where X-borne gene HEPH is located (Fig. 7b). The hypermethylated M4 and M5 chromosomes have also been previously shown to harbour material from the X chromosome [8]. Interestingly, the short arm of M3, which also shares homology with the X chromosome, was not hypermethylated beyond the telomeric region (Fig. 7c). The proposed chromothripsis event is thought to have resulted in the shattering of one homologue each of chromosomes 1 and X, distributing X material across chromosomes 2, 6, M1, M2 and M4. The short arm of chromosome M4 appears to have been duplicated to form the long arm of M5. The X chromosome material on M3 corresponds to almost an entire, yet rearranged, X chromosome [8]. We posit, based on the hypermethylation of regions corresponding to X chromosome fragments on chromosomes 2, 6, M1, M2 and M4, that the active X was shattered in the chromothripsis event and the hypomethylated X chromosome material on M3 corresponds to the inactive X.Fig. 7


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

Ingles ED, Deakin JE - Mol Cytogenet (2015)

Colocalisation of X-borne genes and hypermethylated regions. a The region containing X-borne genes (PLP – green; SRPX2 – red) overlaps with the extended hypermethylated region on the longer homologue of chromosome 2 (2L). The hypermethyated region and X-borne genes are absent from the shorter chromosome 2 homologue (2s). bHEPH (red) and methylation staining (green) on marker chromosome 2. cARHGEF6 and methylation staining (green) on marker chromosome 3
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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

Fig7: Colocalisation of X-borne genes and hypermethylated regions. a The region containing X-borne genes (PLP – green; SRPX2 – red) overlaps with the extended hypermethylated region on the longer homologue of chromosome 2 (2L). The hypermethyated region and X-borne genes are absent from the shorter chromosome 2 homologue (2s). bHEPH (red) and methylation staining (green) on marker chromosome 2. cARHGEF6 and methylation staining (green) on marker chromosome 3
Mentions: One chromosome 2 homologue had an extended methylation range on one of its arms, which was observed across all strains and time periods. Based on chromosome measurements, this increased methylation was always present on the longer chromosome 2 homologue, which has been shown to have an added region consisting of DNA material from chromosomes 1 and X [8]. We performed fluorescence in situ hybridisation on the same metaphase spreads that had been stained for 5-methylcytosine, with two X chromosome genes (PLP and SRPX) mapping to this region on DFTD chromosomes, demonstrating that the extended region of methylation overlaps with the translocated genes (Fig. 7a). Similarly, an additional region of methylation was observed on M2 in the region where X-borne gene HEPH is located (Fig. 7b). The hypermethylated M4 and M5 chromosomes have also been previously shown to harbour material from the X chromosome [8]. Interestingly, the short arm of M3, which also shares homology with the X chromosome, was not hypermethylated beyond the telomeric region (Fig. 7c). The proposed chromothripsis event is thought to have resulted in the shattering of one homologue each of chromosomes 1 and X, distributing X material across chromosomes 2, 6, M1, M2 and M4. The short arm of chromosome M4 appears to have been duplicated to form the long arm of M5. The X chromosome material on M3 corresponds to almost an entire, yet rearranged, X chromosome [8]. We posit, based on the hypermethylation of regions corresponding to X chromosome fragments on chromosomes 2, 6, M1, M2 and M4, that the active X was shattered in the chromothripsis event and the hypomethylated X chromosome material on M3 corresponds to the inactive X.Fig. 7

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