Genetic and Epigenetic Mechanisms of Brain Development

Genetics of brain development:

How genes work in the body and brain:

All of the cells in our body contain exactly the same genes, although in individual cells, while some genes are active, others are inactive. Active genes can produce proteins, which is a process called gene expression. Inactive genes cannot participate in gene expression.

Approximately one third of the genes that make up the human genome are expressed mainly in the brain, which is the highest proportion of genes expressed in any part of the body. This is how the functionality of the brain is created. The things that are influenced by this are our movement, thought process, emotions, and behavior.

DNA (deoxyribonucleic acid) is where the genes in the brain make protein. DNA is packaged into chromosomes, humans having 23 pairs. Within the DNA are genes. This is where the instructions can be found for making/regulating specific proteins, also called protein-coding genes. RNA (ribonucleic acid) copies the DNA code and sends it to the part of the cell involved in protein synthesis.

Protein forms the connective tissue between brain cells. The communication between brain cells is also a result of protein. Genes that make protein are especially important for an infant when their brain is developing. The ASMP gene makes a specific protein that is crucial in the production of new neurons in a newly developing brain.

There are also genes in the brain that create proteins that make neurotransmitters. Neurotransmitters are chemicals that can send information between different neurons. Another example of a protein that is created in the brain is called the SOD1 gene. This makes a type of protein that go against neurons that are no longer healthy.

Gene Expression:

There are numerous cell types in the body that serve different functions. Some of these functions are so specific that the body only needs them during a certain time of it’s life. For example, some genes are specific to the development of early life. Once these cells have done their job, they are silences and no longer will be expressed, because they are not needed anymore. The body decides which cells are to be expressed and which cells are to be silenced based off of cues from the cell’s history and also from it’s environment. Below are some of the factors that influence the cell.

• DNA Binding Proteins – Roughly 10% of our genes are responsible for making proteins that stick to DNA. Some of these proteins are like switches, and they find specific spots on the DNA and turn certain genes on. Others, like histones, work more like spools, wrapping up the DNA tightly to keep those genes turned off.
• sRNA – This is placed all through the genome. These are small RNA that regulate gene expression. Being small comes in handy when they need to target certain parts of the genetic code in order to deactivate it.
• Epigenetic Factors – This refers to long-lasting changes in gene expression while not influencing the genetic code. Epigentic factors are chemical bookmarks on DNA or histones that control gene expression.

Single Gene Mutations:

DNA-based tests can be prescribed by doctors when looking for a mutation disorder such as muscular dystrophy, neurofibromatosis type 1, and Huntington’s disease. Patients normally have symptoms that are occurring that indicate one of these diseases before the tests are done. It can also be done on patients who are at risk for one of these types of diseases but haven’t experienced any symptoms yet.

There is a relationship between genes and complex diseases. Understanding this relationship makes it possible to administer personalized medications to patients. These genes are studied in labs, which is where discoveries of new disease prevention mechanisms and diagnosis and treatment can be discovered.

Epigenetic mechanisms of brain development:

Epigenetic markers: These can influence gene activity.

Examples:

• Methylation can occur. Methyl groups attach to DNA in specific locations. This keeps transcription from occurring. Transcription is very crucial because it is involved in protein synthesis. This is relevant when the DNA uses transcription to connect to the mRNA. Translation is also a large part of protein synthesis. This is when the mRNA is used as a template allowing the correct amino acids to be brought in and eventually will create a protein.
• Can impact the histones. Histones are proteins that DNA will wind up around. Histone methylation can occur, which tends to prevent transcription.

References

U.S. Department of Health and Human Services. (2010, July). Brain basics: Genes at work in the brain. National Institute of Neurological Disorders and Stroke. https://www.ninds.nih.gov/health-information/patient-caregiver-education/brain-basics-genes-work-brain