Mutation Makes Mirror Movements

Alright heroes/cool kids, this article talks about a specific mutation and the effect it has on the body. There is a mutation that messes with your immune system causing you to always do mirror movements. Meaning if you raise your right hand, the left one is going up with it. In more formal terms, one side of the body always involuntarily mirrors movements done voluntarily on the other side of the body.
Now you may be thinking that this must be such an annoying disease to live with but people like Andree Marion live with it every hour of every day. Marion is a 47-year-old accountant from St. Sauveur, Quebec and it turns out her 19-year-old son also has mirror movements. In fact if you trace Marion's family back four generations, of her 23 blood relatives, about half of them have mirror movements. These rare mirror movements are caused by a gene defect.

A neurologist and geneticist at the University of Montreal named Guy Roleau was the senior author of a study that uncovered the mutation found in Marion and her relatives. The wires of the nervous system cross. Axons from motor neurons in the brain sweep over the middle of the body before connecting to other motor neurons in the spinal cord. These motor neurons then connect to the muscles. Roleau comments on how scientists still don't know why or how this happens in humans.

Mirror movements are quite rare and are normally found only in people with disorders of nervous system crossings. No one in Marion's family had any such disorder so Roleau and colleagues were given a great opportunity to see just how wiring went wrong. What they found was the in Marion and relatives, the right side of the brain controlled the right hand... but also the left hand. Some axons crossed over, but some did not. The axons that didn't cross over would just go on the exact same spinal motor neuron, just on the opposite side of the spinal cord.
Since Marion and many relatives had mirror movements, Roleau and his team knew it was hereditary. While it took them one and half year to collect the DNA from all of the relatives it only took them 3 months to find the faulty gene. the faulty gene was deleted in colorectal cancer (DCC). This mutation interferes with DCC's interaction with netrin, which is a diffusible extracellular protein that helps guide axons across the body's midline while the body is developing. DCC is expressed in the midline of the nervous system. Once axons sense the protein they begin to move towards it. However, this mutation cuts the level of functionality of the protein in Marion and relatives. In essence, they don't have enough of the protein to get all of the nerves to cross over.
Marion explained that she always noticed the mirror movements since she was a child, but they were never a big concern because she was able to do what she wanted. Marion can type and drive without any difficulty. She joked the only thing she has a problem with is playing pool. What a jokester Ms. Marion is... She also said she has to be careful when cutting and cooking food. Marion also noted that her mirror movements are more pronounced than her sons. For her son, the mirror movements are more in his hands, while hers are also in the biceps and toes.