Epigenetic&ms pcr inna

EPIGENETICS & MSP

Kursus Teknik Biologi Molekuler, October 2015

Inna ArmandariDepartment of Histology and Cell Biology Faculty of Medicine, Universitas Gadjah Mada

Epigenetic phenomena

Identical twins

Calico cat

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Kursus Teknik Biologi Molekuler 2015

Epigenetic, Environment, and Disease

Constant interaction between external and internal environments occur via epigenetic process. These will lead to normal development and health maintenance as well as for influencing disease load and resistance.

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Kursus Teknik Biologi Molekuler 2015Kanherkar et al., 2014

Epigenetics vs Genetics

Epigenetic was first coined by Conrad Waddington in 1942

Every cell has identical genome, but the terminal phenotype is not fixed

Therefore, epigenetic serves as a bridge between genotype and phenotype

Various unspecified non-genetic mechanisms influencing phenotype

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Epigenetic


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• Epigenetic comes from Greek :Epi (επί- over, above, outside of ) –genetics

• Epigenetic is heritable changes in gene activity and expression that occur without alteration in DNA sequence

• Epigenome reflects the overall epigenetic state of a cell and refers to global analyses of epigenetic markers across the entire genome.

Epigenetic modifications Epigenetic modifications are crucial for

packaging and interpreting the genome under the influence

They can be considered as the punctuation marks in the genome

They demarcate the start and end of genes; provide structure to the chromosome; lead to genes being expressed (active) or repressed (silent, inactive)

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Epigenetic mechanism


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DNA methylation The covalent addition of a

methyl group at position 5 of cytosine 5-methyl C or CMe

In human & other mammals : occur at cytosine next to guanine, linked by phosphate CpG site

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CpG islands

Kursus Teknik Biologi

Molekuler 2015

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Short stretches of CpG-dense DNA promoter regions transcription start site

In human, 60-80% of 28 million CpG dinucleotides are methylated

Cme in a CpG island denotes inactive promoter owing to the condensation of chromatin

Detecting methylated DNA


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Specific technique to detect methylation at CpG island methylation specific (MS)-PCR

MSP principle

DNA methylation and cancer


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Esteller M Hum. Mol. Genet. 2007;16:R50-R59

Histone code Histones are the core protein that

provide structural backbone where DNA is packed into chromatin

Octamer histone consist of two of each of histones H2A, H2B, H3, and H4

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Histone modifications


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Post-translational changes on the histone tails, that are flexible stretches of N or C terminal residues extending from the globular histone octamer

Type of Modifications : •Acetylation•Methylation•Phosphorylation•Ubiquitination

Histone modifications


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Epigenetic state of histone15


Histone acetylation and gene transcription

RNAs-based mechanism


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Type of post-transcriptional gene modification during which the gene expression is down-regulated or suppressed by Non-coding RNA (ncRNA)

Non-coding RNA (ncRNA) : RNA molecule that is not translated into protein microRNA (miRNA) and small interfering RNAs (siRNA)

microRNA


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Small non-coding RNA molecule (±22 nucleotides) functions in RNA silencing and post-transcriptional regulation of gene expression

bind to complementary sequences on target messenger RNA transcripts (mRNAs) translational repression and gene silencing

miRNA function


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Small interfering (siRNA)


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a class of double stranded RNA molecules (±25 bp) that plays role in RNAi pathway

siRNA functions by causing mRNA to be broken down after transcription no translation


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Inna ArmandariDepartment of Histology and Cell Biology

[email protected]

Health & Medicine

Epigenetic&ms pcr inna