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Epigenetic regulation of neurogenesis
Epigenetics is the study of heritable changes in gene expression which do not result from modifications to the sequence of DNA. Neurogenesis is the mechanism for neuron proliferation and differentiation. It entails many different complex processes which are all time and order dependent. Processes such as neuron proliferation, fate specification, differentiation, maturation, and functional integration of newborn cells into existing neuronal networks are all interconnected. In the past decade many epigenetic regulatory mechanisms have been shown to play a large role in the timing and determination of neural stem cell lineages.〔
==Relevant Mechanisms & Definitions==
Three important methods of epigenetic regulation include histone modification, DNA methylation and demethylation, and MicroRNA (miRNA) expression. Histones keep the DNA of the eukaryotic cell tightly packaged through charge interactions between the positive charge on the histone tail and the negative charge of the DNA, as well as between histone tails of nearby nucleosomes.While there are many different types of Histone modifications, in neural epigenetics there are two primary mechanisms which have been explored: histone methylation and histone acetylation.〔
In the former, methyl groups are either added or removed to the histone altering its structure and exposing chromatin and leading to gene activation or deactivation. In the latter, histone acetylation causes the histone to hold the DNA more loosely, allowing for more gene activation. DNA Methylation, in which methyl groups are added to cytosine or adenosine redisdues on the DNA, is a more lasting method of gene inactivation than histone modification, though is still reversible in some cases.〔〔 MicroRNAs are a small form of non-coding RNA (ncRNA) which often act as "fine-tuning" mechanisms for gene expression by repressing or inducing messenger RNA (mRNA) in neural cells but can also act directly with transcription factors to guide neurogenesis.〔〔
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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