Introduction to CpG island power point presentation

CpG IslandBy Muhammad Sohail

2011-ag-3378Agri.biotechnology

5th semester

OutlinesCpG islandCpG sitesRelation between CpG island and geneWhere they occurMethylation

CpG IslandsCpG islands (CGI) are genomic regions that contain a high concentration of CpG sites.

CpG sitesCpG sites are regions of DNA where a

cytosine nucleotide occurs next to a guanine nucleotide in the linear sequence of bases along its length.

"CpG" is shorthand for "—C—phosphate—G—", that is, cytosine and guanine separated by only one phosphate; phosphate links any two nucleosides together in DNA

CpG sitesThe "CpG" notation is used to distinguish this linear sequence from the CG base-pairing of cytosine and guanine. The CpG notation can also be interpreted as the cytosine being 5 prime to the guanine base.

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CpG islands & GenesCpG islands located in the promoter regions of

genes can play important roles in gene silencing

Housekeeping genesAlmost all housekeeping genes are associated with at

least one CpG island

Tissue specific genesAbout 40 % tissue specific genes are associated with

islands

Where they occurs?In mammalian genomes, CpG islands are

typically 300-3,000 base pairs in length, and have been found in or near approximately 40% of promoters of mammalian genes. About 70% of human promoters have a high CpG content.

Based on an extensive search on the complete sequences of human chromosomes 21 and 22, DNA regions greater than 500 bp were found more likely to be the "true" CpG islands associated with the 5' regions of genes.

Where they occurs?CpG islands typically occur at or near the

transcription start site of genes, particularly housekeeping genes, in vertebrates.

Normally a C (cytosine) base followed immediately by a G (guanine) base (a CpG) is rare in vertebrate DNA because the cytosines in such an arrangement tend to be methylated. This methylation helps distinguish the newly synthesized DNA strand from the parent strand, which aids in the final stages of DNA proofreading after duplication

Epigenetic

Epigenetic is the study of heritable changes in gene activity which are not caused by changes in the DNA sequence.

e.g. DNA methylation

DNA methylationDNA Methylation is a biochemical process involving the addition of a methyl group to the cytosine or adenine DNA nucleotides. DNA Methylation stably alters the expression of genes in cells.

DNA methylationA DNA molecule that is methylated at the two center cytosine. DNA Methylation plays an important role for epigenetic gene regulation in development and disease.

Methylation & Silencing Mechanism

One way cells differentiate is Methylation

Addition of CH3 in C-nucleotidesSilences genes in region

Methylation is inherited during cell division…….

Epigenetic Mechanism

Disease Categories Associated with Methylation Loss Aging Cardiovascular

MI Hypertension Stroke Hypercholesterolemia

Metabolic Lipid

Fatty acid cholesterol

Diabetes (type 1 and 2) Adiposity

• Neurologic Chemical dependency Bipolar disorder Cognitive function Asperger syndrome Schizophrenia Major depressive disorder Alzheimer’s disease

Immune Arthritis Asthma Antiphospholipid syndrome Grave’s disease Hashimoto thyroiditis Lupus erythematosus Multiple sclerosis

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