PNB 3260 Stem Cell Week 3 Notes
PNB 3260 Stem Cell Week 3 Notes 3260
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This 2 page Class Notes was uploaded by AnnaCiara on Thursday February 4, 2016. The Class Notes belongs to 3260 at University of Connecticut taught by Dr. Conover in Spring 2016. Since its upload, it has received 24 views. For similar materials see Stem Cell Biology in Physiology at University of Connecticut.
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Date Created: 02/04/16
PNB 3260 Week 3 Notes Lec 6: Epigenetics and Pluripotency Epigenetics: changes in gene expression or phenotype that does not include changes in actual DNA sequencing Genetic reprograming: converting differentiated somatic cells to stem cells Flaws with iPSCs: memory of somatic cell may still exist iPSCs compared to Embryonic stem cells: variations in: transcribed genes, epigenetic landscape(can be very complex), differentiation potential(check for pluripotency in culture by ability to form teratoma), and mutational load (caused by reprogramming method) somatic cell may retain traits if o silencing is incomplete o ESC-specific pluripotency genes aren't strong enough o existence of marks that resemble neither cell (parental and ESC) Developmental potential, each with different epigenetic status Totipotent Pluripotent Multipotent Unipotent iPSC Model goes backwards in the list can result in o 1) complete return to totipotency o 2) Semi-reprogrammed state: returns to pluripotency but may differentiate again o 3) Trans-differentiation to another cell type o 4) Cell death - apoptosis Addition of certain transcriptional factors can increase efficiency Oct4/Sox2/Nanog Triad don't have to be used together but are all 3 known to be master regulators require additional factors to have full effects Chromatin structure - condensed state allows large amount of DNA to fit in nucleus Heterochromatin: typically silent (no transcription occurring), tight packaging results in closed form Euchromatin: expressed, loosely packed and open form Epigenetic modification: typically suppress gene modification (area will not be transcribed DNA methylation: directly onto DNA at promoter regions o on CpG islands (5C position on cytosines) o heritable regulation of gene regulation o embryogenesis is composed of various waves of methylation and demethylation o **** o ~60% of all human genes are transcribed from a CG-rich promoter sequences - most are unmethylated**** o Passive demethylation: means transcription factors already bound to promoter region of gene and methyl transferase are blocked - cant methylate so transcription occurs o active demethylation: requires a demethylase to remove the methyl groups, results in hypomethylation and transcription occurs histone methylation histone deacetylation Histone modifications o tails are likely to get modified o 147 base pairs Nucleosome o core histones: H2A o K4-HMT - histone methyl transferase o K9-HDM - histone demethylase differentiation means repressing many pluripotency genes Histone code hypothesis modification implications are based on amino acid sequence Chromatin remodelers ATP-dependent if you don't have CHD7 you can get CHARGE syndrome Poised state is neither silenced nor expressed Polycomb group (PcG) of proteins found in pluripotent cells repress differentiation catalyze post-translational modifications of histones to control developmental gene expression patterns PRC1/2 bind loci or key regulators of development (control di- and tri- methylation at H3K27 resulting in inactivation of gene expression) Their absence results in inappropriate MEFs are the fibroblasts that are going to be reprogrammed Acetylation is usually associated with pluripotent cells Aspects effecting epigenome (paper on this won't be tested on) 1. Mechanical forces 2. Biological stimuli 3. Physical material properties
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