Epigenetics of Heart Failure Flashcards
do cardiac myocytes grow?
no they are post mitotic
what are diseases that causes cardiac myocytes to hypertrophy?
1) HTN
2) heart attack
3) genetic mutation
PRE-CLINICAL MODEL OF CARDIAC HYPERTROPHY
1) suture around aorta incr P overload on LV for 3-4 weeks
2) add drugs to test in vivo
possible drug used for HF in mouse models
Artesunate (anti-malarial)
how do you measure systolic fxn in mouse model
use ultrasound
and measure hypertrophy (stain myocytes and quantify cell surface area)
what is E/A ratio
E = early phase = passive movement of blood from LA –> LV
A = active movement and requires atria to contract for leftover blood
how does E/A ratio change in diastolic HF?
decrease E/A ratio (LV stiff and less compliant)
how to study cardiac hypertrophy in petri dish
1) take heart of neonatal mice
2) mince/digest and purify cardiac myocytes
to remove fibroblast/endo cells
3) can stain with antibodies (ex: BNP)
4) culture cells on plate and quantify cell area and amount of BNP
hallmarks for cardiac hypertrophy
1) new protein synthesis
2) sarcomere assembly
3) gene expression
define gene transcription
template strand of DNA used by RNA polymerase to make RNA copy
–> indiv nucleotides link
define enhancers
specific DNA sequence control whether gene on/off
at gene level how are different structures (cardiac vs. skeletal muscle formed)
diff core promotor/enhancers on whether gene expressed
define chromatin
DNA wrapped on histone (compact)
can RNAP reach enhancer sequence on chromatin
NO because RNAP 2 is too big to target enhancer sequence
define epigenetics
Mechanisms for Altering
Gene Transcription Without Changing the Underlying DNA Nucleotide Sequence
ARE epigenetics based on mutations?
NO
CHEMICAL MODIFICATIONS TO NUCLEOTIDES/HISTONES
DETERMINE WHETHER GENE TRANSCRIBED OR NOT
DEFINE epigenetic marks
modifications of histole tails (mainly Lys) with acetyl and methyl
what are sites of reversible post translational modification
histone tails
most common histone tail modified?
lysine
define chromatin immunoprecepitation
1) take cells, fix chromatin with fixing agent
2) isolate chromatin (DNA + protein together)
3) fragment chromatin into small pieces
4) immunoprecipitate specific amino acid using
antibody that recognizes epitope
5) attach antibody to bead
6) mix with chromatin and precipitate
7) PCR recog specific locus for p53 promotor
define histone code
each modification creates code (docking site) read by proteins
how does histone code determine whether gene transcribed?
ex: bromo protein recog modification of amino acid
bromo interacts with other proteins to determine whether RNAP 2 interacts
acetylation activating or deactivating
activating
unwinds DNA
deacetylation activating or deactivating
deactivating
makes DNA more tight wound around DNA
Ways to study protein function (2 ways)
1) Gain of fxn = transgenic overexpression
2) Loss of fxn = genetic knockout or chemical inhibition
ex of transgenic overexpression
overexpress proteins in heart and see if affect disease
which hdac important in decreasing heart failure
HDAC9 overexpression blocks cardiomyocyte hypertrophy
HDAC9 knockdown stim cardiomyocyte hypertrophy (using siRNA to knockout)
HDAC9 overexpression ___
blocks cardiomyocyte hypertrophy
HDAC9 knockdown ____
stim cardiomyocyte hypertrophy (using siRNA to knockout)
