How Do Autism Risk Genes Affect Brain Function?
Two well-established autism risk genes, NRXN1 and NLGN1, are best known as cell adhesion molecules which help form brain connections called synapses. However, new evidence suggests that they also control synapse communication. When expression of NRXN1 or NLGN1 is blocked, synapses communicate slowly and for longer periods of time. Read more about neurobiological roles of autism risk genes with our “How Do Autism Risk Genes Affect Brain Function?” section.
Brain development is an extremely complicated process. Thousands of genes are involved, and problems with any one of them can alter brain function. Several of the known autism risk genes affect the connections (also called synapses) between brain cells called neurons.
To understand what roles genes play in the brain, let's take a closer look at neuronal development and structure.
Neurons Develop Tree-Like Architecture
Neurons develop in a manner similar to a tree. The cell body acts as the ‘seed’, containing all the information needed to instruct the neuron how to grow. In the right environment, neurons will extend ‘stems’ known as dendrites which will then branch in complex patterns to form a tree-like arbor. In fact, the word dendrite actually originates from the Greek word dendron, meaning tree. Neurons also extend another projection called an axon, which can be thought of as the ‘root’ in our tree metaphor. Whereas dendrites receive information from other neurons, axons send information to other neurons.
Synapses Form Between Axons and Dendrites
Neurons communicate by forming synapses between axons and dendrites. After neurons appear, they can extend axons for long distances in order to reach their appropriate targets. Once there, they branch into axon terminals which form synapses with other neurons via special parts of dendrites called dendritic spines. In the tree metaphor described above, dendritic spines can be thought of as the ‘leaves’ of the dendritic branches.