What is Huntington’s disease?

Hi, my name is Lauren Byrne and I am a research
fellow at the UCL Huntington’s Disease centre. My research career in Huntington’s disease
began in 2014… but in reality I’ve been researching Huntington’s
disease for the most part of my life. I grew up in a family affected by Huntington’s
disease, back in Northern Ireland, and experienced it first hand with my Aunt
and Uncle, who had it when I was a child. I’ve only memories of them being in wheelchairs. I started to notice the subtle signs in my
dad when I was a teenager and every year I have watched him deteriorate mentally and
physically ever since. I was naturally drawn to studying Huntington’s. But what really fascinated me about the disease
was that, despite researchers knowing the exact cause of Huntington’s disease since
1993… there still remains so much unknown about
this extremely complex brain disease. Huntington’s disease is a genetic, neurodegenerative
and ultimately fatal disease with devastating impact on individuals and entire families. Huntington’s causes problems with a person’s
ability to think, behave and move. Over time, the disease causes progressive
functional decline, leading to a loss of independence and the ability to perform daily activities. Huntington’s typically strikes a person
in the prime of their life, between the ages of 30 and 50, although symptoms may appear
earlier or later. Today, clinical diagnosis is made when movement
problems are obvious. However, subtle changes known as “prodromal”
or “pre-motor onset” symptoms often appear years earlier. Each child of a parent with Huntington’s
has a 50% chance of inheriting the disease, which affects men and women equally. We call this pattern of inheritance autosomal
dominant. About 1 in 10,000 people live with Huntington’s
today, with many more at risk, including over 30 individuals within my own
family. Everyone has two copies of the huntingtin
gene… which contains a section of repeated genetic
letters known as CAG repeats. The huntingtin protein is produced throughout
the body. And although the normal function is not yet
fully understood, it is thought to be involved in many biological functions, …
… including the development of the nervous system. Huntington’s disease occurs when one copy
of the Huntingtin gene has a CAG repeat expansion over a certain threshold. People with 40 or more CAG repeats will develop
Huntington’s in their lifetime. People with 36 to 39 repeats may or may not
develop the disease within an average lifespan. And, those with 27 to 35 CAGs will not develop
Huntington’s themselves, but risk passing on the disease to the next generation. The Huntingtin gene carries instructions to
make the huntingtin protein. The DNA is used to create a messenger RNA
that carries the code to the cellular factory that makes the protein. Too many CAG repeats result in a toxic form
of the protein being produced, known as mutant huntingtin protein. Mutant huntingtin protein damages the normal
functioning of neurons in many ways, including interfering with their transport networks
and gene regulation. This causes them to malfunction and die prematurely,
resulting in the symptoms of Huntington’s. Huntington’s is increasingly recognized
as a disease of the whole brain and body. Areas of the brain responsible for cognition,
personality and movement are particularly affected, leading to the classic triad of
symptoms in Huntington’s disease. While research is ongoing, there is currently
no treatment that can slow, stop or reverse disease progression in Huntington’s. The goals of current disease management focus
on providing symptom relief, maximizing function, and optimizing quality of life. It is because of my family and Huntington’s
families around the world, that I and other scientists continue to work to progress Huntington’s
disease research. It is a huge collaborative effort between
researchers, and family members, that will bring about a new chapter in this fight against
Huntington’s disease.

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