For Huntington’s disease clues, scientists are looking in fruit flies

For Huntington’s disease clues, scientists are looking in fruit flies

Subject: Science and Tech

Section: Health

Context: Researchers from Hungary, genetically engineered fruit flies (Drosophila melanogaster) to express the polyglutamine tract of a mutated human HTTgene in their nervous system by using a gene called Gal4 from baker’s yeast (Saccharomyces cerevisiae).

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The medical genetics clinic at the Nizam’s Institute of Medical Sciences, Hyderabad sees three to four patients with Huntington’s disease every month.

About Huntington’s disease:

• Genetic / Inherited: Huntington’s disease (HD) is an inherited disorder that causes nerve cells (neurons) in parts of the brain to gradually break down and die.
• Affects neural system: The disease attacks areas of the brain that help to control voluntary (intentional) movement, as well as other areas.
• Causes: A gene called HTT are involved in the production of a protein called huntingtin.
• Mutation: When these genes mutate, they provide faulty instructions leading to production of abnormal huntingtin proteins and these form into clumps.
• The clumps disrupt the normal functioning of the brain cells, which eventually leads to death of neurons in the brain, resulting in Huntington disease.
• Treatment: Treatment consists of supportive therapy to manage symptoms
• Cure: No cure exists, but drugs, physiotherapy and speech therapy can help manage some symptoms.

About Glutamine repeats:

• Mutated version of Htt:The patient’s misfortune is that they carry a mutated version of a gene called HTT. The HTT gene codes for a protein called huntingtin, or Htt.
• Destroys Neural systems: Nerve cells requires the Htt protein for their normal functioning and survival. The mutated gene which encodes an abnormal Htt protein that instead destroys the neurons that regulate movement, thinking, and memory.
• Inheritance: Each one of us has two copies of the HTT gene of which one is inherited from the father and one from the mother. The disease is triggered even if only one copy of the gene is mutated while the other is normal.

Clues from fruit flies

Recent study: In the new study from Hungary, the researchers genetically engineered fruit flies (Drosophila melanogaster) to express the polyglutamine tract of a mutated human HTTgene in their nervous system.

About GaIp and UAS:They used a gene called Gal4 from baker’s yeast (Saccharomyces cerevisiae), containing information with which cells manufacture a protein called Gal4p. This protein binds specifically to a short DNA sequence called the upstream activating sequence (UAS)

Gene expression: DNA sequence for the Gal4p protein when  is placed downstream of a fly gene called elav, leading to expression of  the Gal4p protein in all of the fly’s neurons Expressing the longer tract produced symptoms in the fruit flies resembling those of Huntington’s disease in humans while on the other hand expressing the shorter tract did not.

The Science of Yod1 gene:On investigating 32 genes it was found that excessive expression – or overexpression – of gene called Yod1, removed all of the disease-like effects in the flies including the neurodegeneration, impediments to motor activity, and lower viability and longevity.