Developmental Epigenetics Flashcards
Genetic control of developmet
transcription factorstr
transcription factors
a protein that regulates other genes;
Oct4
Activates a network of genes that are critical for self renewal of pluripotent stem cells
Pluripotent cells
stem cells in the inner embryo are pluripotent and can become any cell type in the body
Epigenetic
A heritable phenotypic change that does not result from DNA sequence change (mitotic or generational)
gene expression
Determine cell identity and cell function
Waddington’s epigenetic landscape (EL)
Contains a set of development choices that is faced by a differentiating cell in the embryo, ball rolling down a landscape with multiple valleys, cell goes from pluripotent to unipotent as it faces a number of branching points
Cell fate during development
regulated epigenetically, by genes being turned off and on at the right place and time
DNA methylation
carried out by DNA Methyltransferase, inhibits DNA transcription by blocking transcription factors to binding to promoters, recruit methyl-CpG-binding proteins
CpG Islands (Binding proteins)
a region rich in C and G Nucleotides recruit more proteins and block transcription result of full methylation
Histone methylation
can convert heterochromatin to euchromatin (open up DNA for transcription)
Euchromatin
is open and available for transcriptin factors and DNA polymerase to enter and transcribe genes, more gene rich than heterochromatin
Heterochromatin
closed and inaccessible
Nucleosome acetylation
DNA wrapped around a histone, addition of an acetyl group (to a lysine residue) to the core histone proteins releases DNA from the nucleosome
Sperm
pack DNA tighter to make it less accessible to enzymes/transcriptase
Tortoiseshell cats
two X chromosomes, which are randomly inactivated during development, each X encodes different allele for a coat pigment
1. Orange fur allele
2. Black fur allele
if the orange allele is silenced the fur is black and vice versa, maintained for a lifetime
epigenetics allows these genetically identical cats to have different phenotypes
Timing of X chromosomes inactivation
In pluripotent XX cells, both X chromosomes are active (Xa), after implantation, one X in each cell is randomly inactivated (Xi), when Xa/Xi cells divide, the XCl status is inherited in the daughter cells by an epigenetic mechanism
How does Xist (Inactive Specific Transfer) silence the X
In XX cells, one X randomly expresses Xist after implantations
Xist
is a noncoding RNA that coats the X that expresses it, recruits chromatin-modifying enzymes that compact the chromatin, epigenetically silencing expression of the genes
Transcription factors target specific genes for epigenetic regulation
Myogenic Differentiation gene, confers muscle cell identity by regulating other genes, initially expressed from a trans gene, after multiple cell divisions the MyoD transgene is gone, but the cells have stably converted to myoblast and myotubes
Epigenetic change evoked by MyoD
Transcription factor, binds thousands of genetics regulatory elements while converting fibroblasts to muscle cells, activates hundreds of genes including its own
