title: Immunofluorescent staining reveals hypermethylation of microchromosomes in the central bearded dragon, Pogona vitticeps.
abstract: BACKGROUND
  Studies of model organisms have demonstrated that DNA cytosine methylation and histone modifications are key regulators of gene expression in biological processes. Comparatively little is known about the presence and distribution of epigenetic marks in non-model amniotes such as non-avian reptiles whose genomes are typically packaged into chromosomes of distinct size classes. Studies of chicken karyotypes have associated the gene-richness and high GC content of microchromosomes with a distinct epigenetic landscape. To determine whether this is likely to be a common feature of amniote microchromosomes, we have analysed the distribution of epigenetic marks using immunofluorescence on metaphase chromosomes of the central bearded dragon (Pogona vitticeps). This study is the first to study the distribution of epigenetic marks on non-avian reptile chromosomes.
  
  
  RESULTS
  We observed an enrichment of DNA cytosine methylation, active modifications H3K4me2 and H3K4me3, as well as the repressive mark H3K27me3 in telomeric regions on macro and microchromosomes. Microchromosomes were hypermethylated compared to macrochromosomes, as they are in chicken. However, differences between macro- and microchromosomes for histone modifications associated with actively transcribed or repressed DNA were either less distinct or not detectable.
  
  
  CONCLUSIONS
  Hypermethylation of microchromosomes compared to macrochromosomes is a shared feature between P. vitticeps and avian species. The lack of the clear distinction between macro- and microchromosome staining patterns for active and repressive histone modifications makes it difficult to determine at this stage whether microchrosome hypermethylation is correlated with greater gene density as it is in aves, or associated with the greater GC content of P. vitticeps microchromosomes compared to macrochromosomes.
authors.affiliation: Institute for Applied Ecology, University of Canberra, Canberra, ACT 2601 Australia.|Present address: John Curtin School of Medical Research, The Australian National University, Canberra, ACT Australia.
authors.forename: Renae
authors.initials: R
authors.lastname: Domaschenz
authors.affiliation: Institute for Applied Ecology, University of Canberra, Canberra, ACT 2601 Australia.
authors.forename: Alexandra M
authors.initials: AM
authors.lastname: Livernois
authors.affiliation: Discipline of Biomedical Sciences, Faculty of Education, Science, Technology and Mathematics, University of Canberra, Canberra, ACT 2601 Australia.
authors.forename: Sudha
authors.initials: S
authors.lastname: Rao
authors.affiliation: Institute for Applied Ecology, University of Canberra, Canberra, ACT 2601 Australia.
authors.forename: Tariq
authors.initials: T
authors.lastname: Ezaz
authors.affiliation: Institute for Applied Ecology, University of Canberra, Canberra, ACT 2601 Australia.
authors.forename: Janine E
authors.initials: JE
authors.lastname: Deakin
keywords: Epigenetics; Histone modifications; Methylation; Reptiles