Brain

How it works, what we know and what is important for us as human!

Thinking about our brain, we realise we know very few facts about it! A complex structure that controls and influence every single act of our body, while it is controlled by our acts and our body! what we eat, what we see, what we breath, what we do.... Interesting, yes? Simply say, we are our genetic and epigenetic! There are few things that can be done to our genes, but our epigenetic?! More to some extend.

To better understand, let's first dive into the epigenetic definition.

Epigenetic

When we are born, we have a set of fix (not exactly!) genes that we inherited from our parents, of course with some changes that we call mutation.

These genes are all important, but depends on where and when, they are on or off. Imagine in your eyes, you don't want the genes related to digestion be on, so they will remain off, which means they will not produce any protein that affect that tissue. This process is happening in every single cell in our body. Depends on their duties, they will have a set of specific genes that are on and they control the activities of the cells...and subsequently the tissue and our body.
But how some of these genes stay on and the rest will be off? Well, this is exactly epigenetic!

Epigenetic is changes of gene expression (being on, active, and producing something) without any change at DNA level. The process of modification of genes, in the way that facilitate or stop access of expression machines to some genes. To be more scientifc, we can also think of how this can happen. Below, you can see how the access is guaranteed or denied, but the mechanisms influencing what we call epigenetic is complex and rely under many differnt factors like our genes (yes, it is such a loop!), environment, food. It is where we can say we are our genes plus what we eat and our environment.

Epigenetic Mechanisms of Action:

1. DNA Methylation

Addition of a methyl group to cytosine (usually at CpG sites).
Typically silences gene expression by blocking transcription factor binding or recruiting repressive proteins.

Crucial for:

X‑chromosome inactivation
Genomic imprinting
Suppression of transposable elements

2. Histone Modifications

Histones are proteins around which DNA is wrapped. Their chemical modification changes how tightly DNA is packaged.

Common modifications include:

Acetylation → generally activates transcription
Methylation → can activate or repress depending on the site
Phosphorylation
Ubiquitination
Sumoylation

These marks form a complex “histone code” that influences chromatin structure.

3. Chromatin Remodeling

ATP‑dependent chromatin‑remodeling complexes (e.g., SWI/SNF) reposition or eject nucleosomes to make DNA more or less accessible.

Effects:

Open chromatin (euchromatin) → active genes
Closed chromatin (heterochromatin) → repressed genes

4. Non‑coding RNAs (ncRNAs)

These regulate gene expression at transcriptional and post‑transcriptional levels.

Types:

microRNAs (miRNAs) – degrade mRNA or block translation
long non‑coding RNAs (lncRNAs) – recruit chromatin modifiers, scaffold complexes
piRNAs – silence transposons in germ cells

5. 3D Genome Architecture

The genome folds into loops and domains that bring enhancers, promoters, and regulatory elements into contact.

Key structures:

Topologically associating domains (TADs)
Enhancer–promoter loops
Insulator elements (CTCF)

Changes in 3D structure can activate or silence gene networks.

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