Elongating expansions in HD and SCA1

Written by Dr. Marija Cvetanovic  Edited by Dr. Larissa Nitschke

Expanded CAG repeats are the cause of Huntington’s disease (HD) and several spinocerebellar ataxias (SCAs). Longer inherited CAG expansions correlate with the earlier disease onset and worse symptoms. We know from past research that these expansions are unstable and become longer from one generation to the next.

This study by Mouro Pinto and colleagues shows that repeat expansions also keep getting longer throughout life in patients affected with HD and SCA1 in many cells, including brain, muscle, and liver cells.

Expansion of CAG repeats in different human genes cause several neurodegenerative diseases. This includes Huntington’s disease (HD) and several spinocerebellar ataxias (SCAs). These long CAG repeats in disease genes tend to be unstable in the sperm and egg cells. This instability in sperm and egg cells can result in either longer repeat tracts (expansions) or shorter ones (contractions) in the children of affected patients. Unfortunately, CAG repeats more often expand than shrink. This results in a worse disease in the affected children, with earlier onset and more severe symptoms than their parents.

However, repeat instability and expansion of repeats are not confined to the sperm and egg cells. It can occur in many cells in a patient’s body. This ongoing expansion that occurs in other body cells is called somatic expansion.

Abstract background of DNA sequence
Long CAG repeats in disease genes can be unstable and expand. Photo used under license by Enzozo/Shutterstock.com.

As affected patients age, the ongoing somatic expansion, especially in the brain, may accelerate the onset of neuronal dysfunction and loss of neurons and. This may worsen the disease progression. This has been previously shown in mouse models and patients with HD. However, those studies examined expansion in only a few brain regions and tissues outside the brain (called peripheral tissues).

In this study lead by Dr. Vanessa C. Wheeler, the authors systematically examined repeat instability in 26 different regions of the brain, post-mortem cerebrospinal fluid (CSF) and nine peripheral tissues, including testis and ovaries from seven patients with HD and one patient with SCA1.

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Spotlight: The Movement Analysis and Robotics Laboratory (MARlab)

MAR lab logo

Principal Investigator: Dr. Maurizio Petrarca

Location: Bambino Gesù Children Hospital, Rome, Italy

Year Founded: 2000

What models and techniques do you use?

  • Wearable Technologies
  • Movement analysis
  • Robotics
  • Clinical standardized assessment tools
Seven researchers stand infrom of a presentation screen
This is group picture taken during a conference. From left to right: Silvia Minosse, Alberto Romano, Martina Favetta, Maurizio Petrarca (PI), Gessica Vasco, Susanna Summa and Riccardo Carbonetti. Image courtesy of Susanna Summa.

Research Focus

What is your research about?

MARlab has a lot of experience in the rehabilitation of children with motor disorders including cerebellar diseases. We specialize in the use of motion analysis systems and robotics. Using advanced tools, we customize assessments and rehabilitative settings matching children needs in an ecological context.

We are involved in research to define specific digital biomarker and we are exploring different technological solutions, including wearable technology, to monitor the patient at home.

Rehabilitative competencies assure clinical opportunity in developing technological tools for training and assessment of the postural control, upper-limb coordination, gait, speech and cognition in pathological conditions.

Why do you do this research?

Ataxias are rare and chronic diseases usually without cure. The progression of the disease needs to be monitored periodically, so patients visit the hospital to control their condition by performing several clinical protocols. Developing more accurate and precise technology, to measure symptoms remotely, will help us better measure the impact of different treatments and rehabilitation in ecological contexts, decreasing the patient’s stress. This will help researchers and doctors knowing what works best for the patient. 

Bambino Gesù Children Hospital Logo

The Movement Analysis and Robotics Laboratory (MARlab) is located in the Bambino Gesù Children Hospital in Rome, Italy.

Fun Fact

We are a pediatric hospital very close to sea and our walls are painted with underwater landscapes.

A hospital walkway with the walls painted with sea creatures and submarines

For More Information, check out the Bambino Gesù Children Hospital website!


Written by Dr. Susanna Summa, Edited by Celeste Suart