Brain Primer

Neurons, Genes, and Gene Expression

  • Published29 Nov 2022
  • Author Diane A. Kelly
  • Source BrainFacts/SfN
Close up image of a neuron via PublicDomainPictures

Neurons inside the brain can differ in appearance and function. They can produce different types of neurotransmitters, determining whether their signals have excitatory or inhibitory effects in their circuits. They can have different assortments of neurotransmitter receptors, determining the cells’ sensitivity to the effects of specific neurotransmitters. And, in their cell membranes, neurons possess different combinations of receptors capable of detecting neuromodulators that influence neuronal behavior — for example, hormones such as vasopressin, estradiol, or cortisol.

All cells in your body, including neurons, contain the same DNA housing the same genes. Differences among your neurons result from differences in which genes direct cellular activities, a process called gene expression. Each cell (or cell type) builds proteins from a slightly different subset of genes in its genetic code, the same way different children will build different structures from the same starting set of Lego blocks. 

The mechanisms that cause neurons to express some genes and not others are currently an area of intense research. Many of these mechanisms depend on chemical changes to chromatin, the complex of protein and DNA that compactly packages the long DNA molecule inside the nucleus. Genes that a cell is using to build proteins need to be accessible and are associated with open, unfolded chromatin, while unexpressed genes are typically in tightly packed regions. Chemical changes that tighten or spread out chromatin complexes can, respectively, shut down or activate the genes on that segment of DNA. These changes are reversible, giving neurons flexibility to alter the genes they express in response to hormonal cues and environmental changes. 

The genes that affect neuron structure and function can also differ between individuals. Gene variants, or alleles, reflect differences in the nucleotide sequences that make up a gene. While different alleles code for forms of the same protein, the variants can produce structural differences that affect their function. An allele might code for a version of an enzyme that is less effective than the usual version, and specific alleles of some genes can even cause neurological diseases. For example, Tay-Sachs disease, a fatal degenerative neurological condition, is caused by mutations in a gene that codes for part of a fat-metabolizing enzyme called beta-hexosaminidase A. Because the variant enzyme is poor at breaking down specific fats, these build up in neurons and become toxic. There are many cases where small changes in genetic sequence affects how our brain can function, and in the next 10 years — with our capacity to sequence a person’s entire genome now possible — we will be able to move much closer to understanding the genetic basis of brain disorders.

Adapted from the 8th edition of Brain Facts by Diane A. Kelly.



Albuixech-Crespo, B., López-Blanch, L., Burguera, D., Maeso, I., Sánchez-Arrones, L., et al. (2017). Molecular regionalization of the developing amphioxus neural tube challenges major partitions of the vertebrate brain. PLOS Biology, 15(4): e2001573.

Barton, R. A., & Venditti, C. (2014). Rapid Evolution of the Cerebellum in Humans and Other Great Apes. Current Biology, 24(20), 2440–2444. 

Bekkers, J. M. (2011). Pyramidal neurons. Current Biology, 21(24), PR975. 

Belkhiria, C., Driss, T., Habas, C., Jaafar, H., Guillevin, R., & de Marco, G. (2017). Exploration and Identification of Cortico-Cerebellar-Brainstem Closed Loop During a Motivational-Motor Task: an fMRI Study. The Cerebellum, 16, 326–339. 

Bromfield, E. B., Cavazos, J. E., Sirven, J. I. (2006). An Introduction to Epilepsy,  

Carpenter, R., & Reddi, B. (2012). Neurophysiology: A Conceptual Approach, 5th edition. Hodder Arnold: London.

Castro, A., Becerra, M., Manso, M. J., & Anadón, R. (2015). Neuronal organization of the brain in the adult amphioxus (Branchiostoma lanceolatum): A study with acetylated tubulin immunohistochemistry. The Journal of Comparative Neurology, 523(15), 2211–2232. 

Clarke, L. E., & Barres, B. A. (2013). Emerging roles of astrocytes in neural circuit development. Nature Reviews Neuroscience, 14, 311–321.

Fain, G. L., & O’Dell T. J. (2014). Molecular and Cellular Physiology of Neurons, 2nd edition. Harvard University Press: Cambridge.

Forger, N. G. (2016). Epigenetic mechanisms in sexual differentiation of the brain and behaviour. Philosophical Transactions of the Royal Society B: Biological Sciences, 371(1688), 20150114. 

Frohlich, F. (2016). Network Neuroscience, 1st edition. Academic Press: London.

Guo, J. U., Ma, D. K., Mo, H., Ball, M. P., Jang, M. H., Bonaguidi, M. A., Balazer, J. A., Eaves, H. L., Xie, B., Ford, E., Zhang, K., Ming, G. L., Gao, Y., & Song, H. (2011). Neuronal activity modifies the DNA methylation landscape in the adult brain. Nature Neuroscience, 14, 1345–1351. 

Hammond, C. (2014). Cellular and Molecular Neurophysiology, 4th edition. Academic Press.

Human Brain. (2017). Allen Brain Atlas. Allen Institute for Brain Science. 

Lee, A., Fakler, B., Kaczmarek, L. K., & Isom, L. L. (2014). More Than a Pore: Ion Channel Signaling Complexes. The Journal of Neuroscience, 34(46), 15159–15169. 

Noback, C. R. et al (eds.). (2005). The Human Nervous System: Structure and Function, 6th edition. Humana Press: Totowa NJ.

O'Muircheartaigh, J., Keller, S. S., Barker, G. J., & Richardson, M. P. (2015). White Matter Connectivity of the Thalamus Delineates the Functional Architecture of Competing Thalamocortical Systems. Cerebral Cortex, 25(11), 4477–4489. 

Peer, M., Nitzan, M., Bick, A. S., Levin, N., & Arzy, S. (2017). Evidence for Functional Networks within the Human Brain's White Matter. The Journal of Neuroscience, 37(27), 6394–6407.

Pyka, M., & Cheng, S. (2014). Pattern Association and Consolidation Emerges from Connectivity Properties between Cortex and Hippocampus. PLOS ONE, 9(1), e85016. 

Saladin, K. (2015). Anatomy & Physiology: The Unity of Form and Function, 7th edition. McGraw Hill: New York.

Schneider, G. E. (2014). Brain Structure and its Origins: in Development and in Evolution of Behavior and the Mind. MIT Press: Cambridge.

Sheng, M., Kim, E. (2011). The postsynaptic organization of synapses. Cold Spring Harbor Perspectives in Biology, 3(12), a005678. 

Sporns, O. (2013). Structure and function of complex brain networks. Dialogues in Clinical Neuroscience, 15(3), 247–262.

Verberne, A. J., Sabetghadam, A., & Korim, W. S. (2014). Neural pathways that control the glucose counterregulatory response. Frontiers in Neuroscience, 8(38). 

Wells, R. B. (2005). Cortical Neurons and Circuits: A Tutorial Introduction.

BrainFacts Book

Download a copy of the newest edition of the book, Brain Facts: A Primer on the Brain and Nervous System.


Core Concepts

A beginner's guide to the brain and nervous system.


Educator Resources

Explain the brain to your students with a variety of teaching tools and resources.