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Reprogramming

 

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Reprogramming



 
 
Reprogramming refers to erasure and remodeling of epigenetic marks, such as DNA methylation
DNA methylation

DNA methylation is a type of chemical modification of DNA that can be inherited and subsequently removed without changing the original DNA sequence....
, during mammalian development. After fertilization some cells of the newly formed embryo migrate to the germinal ridge and will eventually become the germ cells (sperm and oocytes). Due to the phenomenon of genomic imprinting, maternal and paternal genomes are differentially marked and must be properly reprogrammed every time they pass through the germline.






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Reprogramming refers to erasure and remodeling of epigenetic marks, such as DNA methylation
DNA methylation

DNA methylation is a type of chemical modification of DNA that can be inherited and subsequently removed without changing the original DNA sequence....
, during mammalian development. After fertilization some cells of the newly formed embryo migrate to the germinal ridge and will eventually become the germ cells (sperm and oocytes). Due to the phenomenon of genomic imprinting, maternal and paternal genomes are differentially marked and must be properly reprogrammed every time they pass through the germline. Therefore, during the process of gametogenesis
Gametogenesis

Gametogenesis is a process by which diploid or haploid precursor cells undergo cell division and differentiation to form mature haploid gametes....
 the primordial germ cells must have their original biparental DNA methylation
DNA methylation

DNA methylation is a type of chemical modification of DNA that can be inherited and subsequently removed without changing the original DNA sequence....
 patterns erased and re-established based on the sex of the transmitting parent.

After fertilization the paternal and maternal genomes are once again demethylated and remethylated (except for differentially methylated regions associated with imprinted genes). This reprogramming is likely required for totipotency of the newly formed embryo and erasure of acquired epigenetic changes. In vitro manipulation of pre-implantation embryos has been shown to disrupt methylation patterns at imprinted loci and plays a crucial role in cloned animals.

Somatic cell nuclear transfer


Oocyte
Oocyte

An oocyte, ovocyte, or rarely ocyte, is a female gametocyte or germ cell involved in biological reproduction. In other words, it is an immature ovum, or ovum cell....
 can reprogramme an adult nucleus into an embryonic state after somatic cell nuclear transfer
Somatic cell nuclear transfer

In genetics and developmental biology, somatic cell nuclear transfer is a laboratory technique for creating a clonal embryo, using an ovum with a donor nucleus ....
, so that a new organism can be developed from such cell (see also: cloning
Cloning

Cloning in biology is the process of producing populations of genetically-identical individuals that occurs in nature when organisms such as bacteria, insects or plants reproduce Asexual Reproduction....
)

Reprogramming is distinct from development of a somatic epitype
Somatic epitype

A somatic epitype is a non-heritable epigenetic alteration in a gene. It is similar to conventional epigenetics in that it does not involve changes in the DNA primary sequence....
, as somatic epitypes can potentially be altered after an organism has left the developmental stage of life.