epigenetic programing of female pronucleus

Definition

Target type: biologicalprocess

The global programming of epigenetic modifications in the female pronucleus of the newly fertilized zygote. The maternal genome is protected from global DNA demethylation before the first division of the zygote, and instead undergoes passive, replication-dependent demethylation during early embryogenesis, arising from inhibition of the DNA maintenance methyltransferase Dnmt1. [GOC:sp, PMID:22868271]

Epigenetic programming of the female pronucleus is a complex and crucial process that establishes the initial epigenetic landscape of the developing embryo. This process involves the erasure and re-establishment of epigenetic marks, primarily DNA methylation and histone modifications, which play a vital role in regulating gene expression.

The female pronucleus, derived from the oocyte, carries the maternal genome. Upon fertilization, the female pronucleus undergoes a series of epigenetic changes to ensure proper development.

1. **Global Demethylation:** The oocyte possesses a specific methylation pattern, characterized by high levels of DNA methylation. Upon fertilization, the female pronucleus undergoes active demethylation, removing these pre-existing methylation marks. This process is mediated by ten-eleven translocation (TET) enzymes, which convert 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC), a key intermediate in the demethylation pathway.

2. **Re-Establishment of De Novo Methylation:** As demethylation proceeds, new methylation patterns are established, reflecting the developmental stage and the specific cell lineage. This de novo methylation is carried out by DNA methyltransferases (DNMTs), primarily DNMT3A and DNMT3B. These enzymes establish methylation patterns that are crucial for silencing repetitive elements and ensuring appropriate gene expression.

3. **Histone Modifications:** Along with DNA methylation, histone modifications, such as acetylation, methylation, and phosphorylation, play a crucial role in regulating gene expression. These modifications are influenced by various enzymes, including histone acetyltransferases (HATs), histone deacetylases (HDACs), histone methyltransferases (HMTs), and histone demethylases (HDMs). They orchestrate changes in chromatin structure, impacting accessibility to DNA and influencing gene transcription.

4. **Imprinting:** A unique aspect of epigenetic programming is the establishment of genomic imprinting. This process involves differential methylation of specific genomic regions based on parental origin. Imprinted genes are expressed exclusively from either the maternal or paternal allele, contributing to proper embryonic development.

5. **X-Chromosome Inactivation:** In female embryos, one of the two X chromosomes is inactivated to equalize gene expression between males and females. This process, known as X-chromosome inactivation (XCI), involves the silencing of one X chromosome through epigenetic modifications, including methylation and histone modifications.

The epigenetic programming of the female pronucleus is a tightly regulated and complex process that establishes the initial epigenetic landscape of the embryo. Any disruptions in this process can lead to developmental defects and diseases. This intricate interplay of epigenetic modifications is essential for proper embryonic development, ensuring the correct temporal and spatial expression of genes needed for the formation of a healthy organism.'
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Compounds (9)