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Snapshot: What is FGF14?

FGF14 or fibroblast growth factor 14 is an essential protein found predominantly in the brain, specifically in Purkinje cells. These brain cells are responsible for maintaining everyday functions such as learning and coordinating movement. FGF14 is critical for both allowing the brain to undergo healthy development and maintaining its function once developed. It does this by helping facilitate two main functions: neuronal plasticity and neuronal excitability.

Neuronal plasticity refers to how the brain adapts and changes overtime by making new connections between nerve cells and reinforcing old ones.

When the brain cannot effectively make and sustain these connections, we cannot properly respond to new experiences causing reduced memory and learning. Furthermore, a decline in plasticity is also liked to various brain diseases where we see impairments in cognition, such as Alzheimer’s disease.

Neuronal excitability refers to how easily brain cells can communicate with each other by sending/receiving electrical signals.

Maintaining the correct excitability levels is vital to ensure our brain cells are not over or under active as these can result in symptoms such as seizures (from overactivity) or movement delays/impairments in reactions (from underactivity).

FGF14 specifically helps to maintain neuronal plasticity and excitability by participating in the mechanism that lets the brain send electrical signals, called an action potential. An action potential involves the brain sending information as electrical signals. Like electrical circuits, brain cells need to generate a particular voltage to send the signal. This process is facilitated by proteins in the brain called sodium-ion channels. Sodium-ion channels are known to physically contact FGF14 in specific locations. Disruptions to this physical interaction with FGF14 can impair how well electrical signals are sent.

Two Ataxia Types Caused by FGF14 Mutations: SCA27A and SCA27B

In rare instances, genetic abnormalities can result in an individual having a dysfunctional form of FGF14, which can cause ataxia. Depending on the type of mutation someone has in FGF14, they will develop spinocerebellar ataxia 27 type A (SCA27A) or spinocerebellar ataxia 27 type B (SCA27B). Both SCA27A and SCA27B are types of ataxia but have different symptoms.

SCA27A is a very rare form of ataxia. It is caused by point mutations or deletions of the FGF14 gene. Symptoms can begin anywhere from infancy to adulthood. Symptoms are also quite variable. Difficulty with balance, coordination, tremors, speech, and vision is common. People with SCA27A may also have mild intellectual impairments or psychiatric symptoms.

SCA27B is a common form of ataxia. It is caused by a GAA repeat mutation in the FGF14 gene. Symptoms usually begin in mid to late adulthood. Symptoms are quite variable between people. Common symptoms include difficulty with balance, coordination, dizziness, speech, and vision.

Many people with SCA27B have episodic symptoms, meaning that their condition fluctuates over time. They will have periods of wellness with few or no symptoms, followed by episodes where their ataxia symptoms are challenging. Different types of medications are being studied to help treat SCA27B symptoms.

If you would like to learn more about FGF14, take a look at these resources by the SCA27b Ataxia Foundation and SCA27B for Me.

Written by Paige Chandran Blair and edited by Asmer Aliyeva.