Question

7) Canavan disease is a gene-linked neurological disorder, in which the brain degenerates into spongy tissues riddled with microscopic fluid-filled spaces. Canavan disease has been classified as a group of genetic disorders termed leukodystrophies. In the normal population, oligodendrocytes carry out an essential developmental task by producing myelin sheets, which constitute the fatty coverings that act as insulators around nerve fibers in the brain and provide nutritional support for nerve cells. In patients with Canavan disease, many oligodendrocytes do not mature and instead die, leaving nerve cell projections known as axons vulnerable and unable to properly function.

According to a group of investigators, Canavan disease is caused by a mutation in the gene that encodes for an enzyme called aspartoacylase, which breaks down the amino acid N-acetyl-aspartate. However, a competing laboratory published an article claiming that aspartoacylase mutation is not relevant for the pathogenesis and progression of Canavan disease.

Design an experimental plan to determine who is right. Include all the controls for full credit. Animal models cannot be used

Answer 1

Well, I am not sure which techniques you are studying in your subject, which would make it easier to think of any experiment. However, this is my idea for an experiment to solve the problem.

1) Design animal cell-expression vectors with the sequence of wild type aspartoacylase and mutated aspartoacylase. You will have to sequence the plasmids to check the aspartoacylase WT and mutant sequences.

2) Generate oligodendrocytes cultures and transfect them with one of the two vectors each.

3) Measure the viability and proliferation rate of the cells transfected with the WT enzyme, compared with the mutated enzyme.

4) Myelinization is based on the "wrapping" of axons by oligodendrocytes. Leukodystrophies arise because of demyelinization, and in the case of Canavan disease, this is caused by the death of oligodendrocytes. So, if your cultures show significant differences of viability or proliferation rates, you can associate a mutation in the enzyme with myelinization processes.