Epigenetic Mechanisms That Regulate Puberty And Sexual Maturation
Epigenetics is the study of heritable changes that do not involve alterations to DNA sequence but instead affect gene expression through modifying nucleic acids or chromatin structure. During puberty and sexual maturation, these epigenetic mechanisms play an important role in regulating the timing and progression of developmental events. One such mechanism is histone modification, which involves the addition or removal of chemical groups to histones - protein subunits around which DNA is packaged in chromatin. Histone modifications can influence accessibility of specific genes for transcription, leading to their activation or repression.
The addition of trimethylated lysine residues on histone H3 at lysine 4 (H3K4me3) promotes transcription, while the presence of trimethylated lysine residues on histone H3 at lysine 27 (H3K27me3) can repress it. Another epigenetic mechanism is DNA methylation, where methyl groups are added to cytosine bases within DNA sequences. DNA methylation can silence certain genes by blocking their transcription, or even induce silencing via formation of heterochromatin structures. Further, microRNAs (miRNAs), small non-coding RNA molecules, have been shown to modulate gene expression during sexual maturation by binding to complementary regions of target messenger RNA (mRNA). This process leads to either degradation or translational repression of the target mRNA.
During puberty, a number of hormones contribute to the initiation and progression of changes, including gonadotropins, estrogen, testosterone, prolactin, growth hormone, insulin-like growth factor-1 (IGF-1), thyroid hormone, and cortisol. These hormones act through specific receptors located in various tissues such as the hypothalamus, pituitary, ovaries, testes, adrenal glands, bones, muscles, and fat cells.
The release of gonadotropins from the pituitary stimulates the production of sex steroids - estradiol and testosterone - which are responsible for secondary sexual characteristics like breast development and facial hair growth in females and males, respectively. The sex steroids also promote growth spurts and skeletal maturation, while IGF-1 promotes linear growth and bone mineralization. In addition to hormonal regulation, genetic factors can play a role in the timing and tempo of puberty onset. Genome-wide association studies have identified several loci associated with age at menarche and puberty onset, providing insight into potential candidate genes that may be involved.
Epigenetic mechanisms also modulate sexual behavior in adults.
DNA methylation patterns at specific regions within the brain, such as the ventromedial nucleus, can influence sexual motivation in female rats. Further, miRNAs expressed in different brain regions have been shown to regulate sexual behavior by targeting specific proteins involved in neurotransmission.
Epigenetic mechanisms provide an intricate regulatory network that contributes to the complex process of puberty and sexual maturation, shaping the timing and progression of physical changes as well as influencing subsequent behaviors throughout life.
Which epigenetic mechanisms regulate the onset, tempo, and progression of puberty and sexual maturation?
Sexual maturity is controlled by both hormones and environmental factors. Epigenetic modifications such as DNA methylation, histone acetylation/deacetylation, and microRNA expression can influence how genes are turned on or off during this process.