Evolutionary usage and developmental roles of vertebrate non-methylated DNA
<p>Vertebrate genomes exhibit global methylation of cytosine residues where they occur in a cytosine-guanine dinucleotide (CpG) context and this epigenetic mark is generally thought to be repressive to transcription. Punctuating this pervasive DNA methylation landscape are short, contiguous r...
| Main Author: | |
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| Other Authors: | |
| Format: | Thesis |
| Language: | English |
| Published: |
2014
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| Subjects: |
| _version_ | 1811139722800529408 |
|---|---|
| author | Long, HK |
| author2 | Klose, R |
| author_facet | Klose, R Long, HK |
| author_sort | Long, HK |
| collection | OXFORD |
| description |
<p>Vertebrate genomes exhibit global methylation of cytosine residues where they occur in a cytosine-guanine
dinucleotide (CpG) context and this epigenetic mark is generally thought to be repressive to transcription.
Punctuating this pervasive DNA methylation landscape are short, contiguous regions of non-methylated DNA
which are found at two thirds of mammalian gene promoters. These non-methylated regions exhibit CpG
content close to expected levels as they escape the depletion of CpGs observed across the methylated fraction
of the genome. The unique nucleotide properties of these CpG island (CGI) regions enable their identification
by computational prediction in mammalian genomes. Owing to a lack of high-resolution genome-wide DNA
methylation profiles in non-mammalian species, these CGI predictions have often been used as a proxy for
non-methylated DNA in these organisms. In contrast to mammals, CGI predictions in cold-blooded vertebrates
rarely coincide with gene promoters, leading to the belief that CGIs are significantly divergent between
vertebrate species, and that unique promoter-associated features may have been acquired during warmblooded vertebrate evolution.</p>
<p>This thesis is primarily concerned with the location, establishment and biological function of non-methylated
islands of DNA in vertebrate genomes. To experimentally determine genome-wide profiles of non-methylated
DNA, a novel biochemical technique was established called biotinylated ZF-CxxC affinity purification (Bio-CAP),
and development of this method is discussed in Chapter 3. Experimental analysis of non-methylated DNA
profiles in this thesis initially addresses two main questions: (1) ‘How does the non-methylated DNA landscape
compare genome-wide for seven vertebrates considering distinct tissue types and developmental stages?’ (2)
‘How are vertebrate non-methylated regions of DNA defined and interpreted in the nuclear environment?’
To address the first question, non-methylated DNA was profiled by Bio-CAP sequencing across the genomes of
seven diverse vertebrate species, representing all major branch points of vertebrate evolution, and the results
are discussed in Chapters 4 and 5. Contrary to previously held dogma, experimentally determined nonmethylated islands of DNA (NMIs) constitute an ancient epigenetic feature of vertebrate gene regulatory
elements. However, despite having numerous high-resolution maps of vertebrate non-methylated DNA, the
means by which NMIs are identified and maintained in the nuclear environment remains poorly understood.</p>
<p>To address the second question and identify features which determine the methylation state of DNA,
exogenous DNA sequences were introduced into mouse embryonic stem (ES) cells. Non-methylated DNA was
profiled by Bio-CAP sequencing to investigate how different features, such as sequence-specific binding motifs,
chromatin architecture and nucleotide composition of a given DNA sequence impact local DNA methylation
patterns. Interestingly, the majority of exogenous promoters were appropriately non-methylated in mouse ES
cells, germline and somatic cells suggesting that gene promoters have retained strong signals for the nonmethylated state across millions of years of evolution (discussed in Chapter 6).</p>
<p>During mouse embryogenesis, genome-scale DNA demethylation and remethylation events occur to remodel
the epigenetic landscape and loss of DNA methylation during this time leads to embryonic lethality. To
investigate the biological function of non-methylated DNA, the third question addressed in this thesis is (3)
‘What is the developmental importance of non-methylated islands of DNA during vertebrate embryogenesis?’
To investigate this, members of the ZF-CxxC domain-containing family of chromatin modifiers were ablated in
zebrafish embryos to perturb the chromatin landscape at NMIs, and therefore interfere with their function
during early development (Chapter 7). Early embryonic development and patterning was disrupted in knockdown embryos, suggesting that interpretation of non-methylated DNA and placement of chromatin
modifications at NMIs is essential for normal zebrafish embryogenesis. Together this work sheds light on the
evolutionary origins of NMIs, the mechanisms involved in the recognition and establishment of nonmethylated loci and provides an insight into the function of non-methylated DNA during early embryonic
development.</p>
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| first_indexed | 2024-03-07T00:09:25Z |
| format | Thesis |
| id | oxford-uuid:78b14c1d-1fa3-46f1-815f-a8ba55579c43 |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-09-25T04:10:37Z |
| publishDate | 2014 |
| record_format | dspace |
| spelling | oxford-uuid:78b14c1d-1fa3-46f1-815f-a8ba55579c432024-06-24T10:41:44ZEvolutionary usage and developmental roles of vertebrate non-methylated DNAThesishttp://purl.org/coar/resource_type/c_db06uuid:78b14c1d-1fa3-46f1-815f-a8ba55579c43Medical SciencesBiologyEvolution (zoology)Bioinformatics (biochemistry)Genetics (life sciences)Cell Biology (see also Plant sciences)Development (zoology)BiochemistryBioinformatics (life sciences)EnglishOxford University Research Archive - Valet2014Long, HKKlose, RPatient, R <p>Vertebrate genomes exhibit global methylation of cytosine residues where they occur in a cytosine-guanine dinucleotide (CpG) context and this epigenetic mark is generally thought to be repressive to transcription. Punctuating this pervasive DNA methylation landscape are short, contiguous regions of non-methylated DNA which are found at two thirds of mammalian gene promoters. These non-methylated regions exhibit CpG content close to expected levels as they escape the depletion of CpGs observed across the methylated fraction of the genome. The unique nucleotide properties of these CpG island (CGI) regions enable their identification by computational prediction in mammalian genomes. Owing to a lack of high-resolution genome-wide DNA methylation profiles in non-mammalian species, these CGI predictions have often been used as a proxy for non-methylated DNA in these organisms. In contrast to mammals, CGI predictions in cold-blooded vertebrates rarely coincide with gene promoters, leading to the belief that CGIs are significantly divergent between vertebrate species, and that unique promoter-associated features may have been acquired during warmblooded vertebrate evolution.</p> <p>This thesis is primarily concerned with the location, establishment and biological function of non-methylated islands of DNA in vertebrate genomes. To experimentally determine genome-wide profiles of non-methylated DNA, a novel biochemical technique was established called biotinylated ZF-CxxC affinity purification (Bio-CAP), and development of this method is discussed in Chapter 3. Experimental analysis of non-methylated DNA profiles in this thesis initially addresses two main questions: (1) ‘How does the non-methylated DNA landscape compare genome-wide for seven vertebrates considering distinct tissue types and developmental stages?’ (2) ‘How are vertebrate non-methylated regions of DNA defined and interpreted in the nuclear environment?’ To address the first question, non-methylated DNA was profiled by Bio-CAP sequencing across the genomes of seven diverse vertebrate species, representing all major branch points of vertebrate evolution, and the results are discussed in Chapters 4 and 5. Contrary to previously held dogma, experimentally determined nonmethylated islands of DNA (NMIs) constitute an ancient epigenetic feature of vertebrate gene regulatory elements. However, despite having numerous high-resolution maps of vertebrate non-methylated DNA, the means by which NMIs are identified and maintained in the nuclear environment remains poorly understood.</p> <p>To address the second question and identify features which determine the methylation state of DNA, exogenous DNA sequences were introduced into mouse embryonic stem (ES) cells. Non-methylated DNA was profiled by Bio-CAP sequencing to investigate how different features, such as sequence-specific binding motifs, chromatin architecture and nucleotide composition of a given DNA sequence impact local DNA methylation patterns. Interestingly, the majority of exogenous promoters were appropriately non-methylated in mouse ES cells, germline and somatic cells suggesting that gene promoters have retained strong signals for the nonmethylated state across millions of years of evolution (discussed in Chapter 6).</p> <p>During mouse embryogenesis, genome-scale DNA demethylation and remethylation events occur to remodel the epigenetic landscape and loss of DNA methylation during this time leads to embryonic lethality. To investigate the biological function of non-methylated DNA, the third question addressed in this thesis is (3) ‘What is the developmental importance of non-methylated islands of DNA during vertebrate embryogenesis?’ To investigate this, members of the ZF-CxxC domain-containing family of chromatin modifiers were ablated in zebrafish embryos to perturb the chromatin landscape at NMIs, and therefore interfere with their function during early development (Chapter 7). Early embryonic development and patterning was disrupted in knockdown embryos, suggesting that interpretation of non-methylated DNA and placement of chromatin modifications at NMIs is essential for normal zebrafish embryogenesis. Together this work sheds light on the evolutionary origins of NMIs, the mechanisms involved in the recognition and establishment of nonmethylated loci and provides an insight into the function of non-methylated DNA during early embryonic development.</p> |
| spellingShingle | Medical Sciences Biology Evolution (zoology) Bioinformatics (biochemistry) Genetics (life sciences) Cell Biology (see also Plant sciences) Development (zoology) Biochemistry Bioinformatics (life sciences) Long, HK Evolutionary usage and developmental roles of vertebrate non-methylated DNA |
| title | Evolutionary usage and developmental roles of vertebrate non-methylated DNA |
| title_full | Evolutionary usage and developmental roles of vertebrate non-methylated DNA |
| title_fullStr | Evolutionary usage and developmental roles of vertebrate non-methylated DNA |
| title_full_unstemmed | Evolutionary usage and developmental roles of vertebrate non-methylated DNA |
| title_short | Evolutionary usage and developmental roles of vertebrate non-methylated DNA |
| title_sort | evolutionary usage and developmental roles of vertebrate non methylated dna |
| topic | Medical Sciences Biology Evolution (zoology) Bioinformatics (biochemistry) Genetics (life sciences) Cell Biology (see also Plant sciences) Development (zoology) Biochemistry Bioinformatics (life sciences) |
| work_keys_str_mv | AT longhk evolutionaryusageanddevelopmentalrolesofvertebratenonmethylateddna |