What causes mirror movement syndrome?

The team of ^Dr Frédéric Charron, researcher at the Montreal Clinical Research Institute (IRCM) and professor at the Faculty of Medicine of the University of Montreal, has made a promising breakthrough in understanding the origins of the mysterious mirror movement syndrome.


Mirror movement syndrome is a hereditary neurological disorder that manifests from an early age, primarily affecting the arms and hands. In individuals with this condition, the right hand involuntarily mimics the movements of the left hand, and vice versa, hence the term "mirror movements." This syndrome can cause arm pain during prolonged activities and make it difficult to perform tasks that require coordinated use of both hands.

"Mirror movement syndrome disrupts the daily lives of those affected. Simple actions like opening a water bottle can become challenging, as well as playing a musical instrument," notes ^Dr Charron, head of the Neuronal Development Molecular Biology Research Unit at IRCM.

Conducted in collaboration with the team of ^Dr Greg Bashaw from the University of Pennsylvania, this study, co-authored by Kaiyue Zhang, a PhD student at IRCM, and ^Dr Karina Chaudhari from the University of Pennsylvania, was published in the journal Science Signaling.

Axonal guidance of neurons and the cytoskeleton implicated

The cellular mechanism behind mirror movements involves a defect in a process known as "axonal guidance."

During embryonic development, neurons extend their axon, a long cellular cable that allows them to connect specific regions of the body, thereby establishing neural connections. Axonal guidance is the collection of processes that control the elongation of the axon and guide its navigation. Among other things, it enables each neuron to connect to its target. It is therefore crucial for the proper development of the nervous system.

Various molecules known as guidance cues direct axons to their targets, acting like signposts guiding axons toward their destination. To achieve this, when these guidance molecules are detected by the axons, they must trigger axonal movement. This movement requires a complex and still poorly understood molecular machinery.

In this study, the research team demonstrates that the machinery required for guidance is actually the cytoskeleton. The cytoskeleton, as its name suggests, is the skeleton of the cell, providing it with structural rigidity, much like bones in the body enable movement by providing firmness.

Understanding the mechanisms underlying mirror movements is essential for developing innovative treatments. The work of ^Dr Charron's laboratory potentially paves the way for new promising targets to treat mirror movement syndrome as well as other disorders stemming from nervous system developmental defects.