Context: A research paper published in Scientific Reports Journal, has provided important information on Huntington disease, using fruit flies. 

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Fly Models of Huntington Disease

• Methodology: Researchers genetically engineered fruit flies (Drosophila melanogaster) to express the polyglutamine tract of a mutated human HTT gene (which causes the disease) in the nervous system of fruit flies. 
• Solution: Through overexpression of a specific gene called Yod1, the signs of neurodegeneration by the disease were ameliorated.  
• Usefulness: Model systems such as fruit flies and yeasts offer scientists unparalleled versatility to investigate the molecular mechanisms triggered by disease genes in humans. 

What is Huntington Disease?

• About: Huntington disease is a neurological genetic disorder which damages nerve cells in the brain causing them to stop working properly. It’s passed on from a person’s parents. 
• Genetic Mutation: The reason for the disease is that they carry a mutated version of a gene called HTT. The HTT gene provides a blueprint for a protein called huntingtin, or Htt.
  • Htt protein: Nerve cells in the human body require the Htt protein for their normal functioning and survival. 
  • The mutated gene encodes an abnormal Htt protein that instead destroys the neurons that regulate movement, thinking, and memory.
• Mechanism of Mutation: The normal HTT gene contains a stretch of DNA that specifies the number of times the amino acid glutamine is repeated in the Htt protein about 11 to 31 times. 
  • The mutant version contains 35 or more repeats up to 150 repeats. 
  • As the number of repetitions increase, the severity of Huntington disease increases and its debilitation begins at an earlier age.

• Glutamines: Their fragments are toxic because they interfere adversely with several cellular processes. 
  • Glutamine is an important amino acid and is used for removing excess ammonia. 
  • Challenge: We neither know why some of these genes are expanded nor how exactly the short fragments cause neuronal degeneration.
• Dominant Gene: Of the two copies of the HTT gene, one from the father and one from the mother, The disease is triggered even if only one copy of the gene is mutated. 
• Symptoms: Mood swings, difficulty in reasoning, abnormal and uncontrollable jerky movements, and difficulty in speaking, swallowing, and walking.
  • Symptoms begin in the ages 30-50, and the patient eventually dies. 

Must Read: Parliamentary Committee Report On Mental Health Care

Source: The Hindu