According to a new Duke University study the protein that is mutated in Huntington’s disease is critical for wiring the brain in early life.Symptoms like uncontrolled movements, inability to focus or remember, depression and aggression are characteristic of Huntington’s disease, a progressive neurodegenerative disorder. These symptoms become apparent in middle age by which time the disease has already ravaged the brain.
The new findings add to the growing evidence that neurodegenerative disorders like Huntington’s may take root during development, said lead author Cagla Eroglu, in the Duke University Medical School.
“If the study helps us these developmental errors, we may be able to interfere with the first stage of the disease, before it becomes evident,” Eroglu said.
In their previous studies Eroglu and her team searched for the molecular players that help in forming new connections, or synapses in early brain development. In the course of their work they stumbled upon the Huntington (Htt) protein, which forms clumps in the brain cells of people with Huntington’s disease.
“Though implicated in certain cellular functions and synaptic dysfunction in Huntington’s, the direct role of Htt in synapse formation had not been explored,” Eroglu said. To understand this, the scientists removed Htt only from the cortex area of mice. This part of the brain is associated with the disease and controls perception, memory and thought. The researchers observed faulty circuits in the mice without the cortical Htt. In addition, there were signs of cellular stress in the exact spots within the cortex that project to the striatum, another brain area targeted by Huntington’s.
On examining early brain development in a mouse model the researchers noticed that these animals have one normal copy of the Htt gene and one mutated copy, exactly as in human patients. The synapses initially mature much faster in the cortex of these animals as compared to normal and then die off. The results suggest that the absence of Htt over an extended period of time not only affects the development but also the maintenance of healthy synapses.
This is particularly relevant to the current strategy against the disease, which is focused on dialling down Htt levels in the brain by employing gene therapy or small-molecule inhibitors. However, it has been extremely difficult to pick out the mutated copy of the gene from the normal ones for the therapy. The group plans to delete Htt in the mouse brain later in life and measure the number of its synapses.