Huntingtons Disease :: essays research papers

Huntingtons DiseaseBackgroundHuntingtons disease is inherited as an autosomal dominant disease that givesrise to progressive, elective (localized) neural cell decease associated withcholeric movements (uncontrollable movements of the arms, legs, and face) anddementia. It is one of the more common inherited brain disorders. About 25,000Americans have it and another 60,000 or so will carry the defective element andwill develop the disorder as they age. Physical deterioration occurs over aperiod of 10 to 20 years, usually beginning in a persons 30s or 40s. The geneis dominant and thus does not skip generations. Having the gene means a 92percent chance of getting the disease. The disease is associated with increasesin the length of a CAG triplet repeat present in a gene called huntingtonlocated on chromosome 4. The classic signs of Huntington disease are progressivechorea, rigidity, and dementia, ofttimes associated with seizures. Studies &Research Studies were done to determine if som atic mtDNA (mitochondria DNA)mutations might contribute to the neurodegeneration observed in Huntingtonsdisease. Part of the research was to analyze cerebral excision levels in the laic and anterior lobes. Research hypothesis HD patients have significantlyhigher mtDNA deletionlevels than agematched controls in the frontal and temporallobes of the cortex. To test the hypothesis, the amount of mtDNA deletion in 22HD patients brains was examined by serial dilution-polymerase chain reaction(PCR) and compared the results with mtDNA deletion levels in 25 aged matchedcontrols. Brain tissues from three cortical regions were taken during an autopsy(from the 22 HD symptomatic HD patients) frontal lobe, temporal lobe andoccipital lobe, and putamen. Molecular analyses were performed on genetic DNAisolated from 200 mg of frozen brain regions as described above. The HDdiagnosis was sustain in patients by PCR amplification of the trinucleotiderepeat in the IT 15 gene. One group was screened wit h primers that includedpolymorphism and the other was screened without the polymorphism. After heatingthe reaction to 94 degrees C for 4 minutes, 27 cycles of 1 minute at 94 degreesCand 2 minutes at 67 degrees C, tests were performed. The PCR products weresettled on 8% polyacrylamide gels. The mtDNA deletion levels were quantitatedrelative to the total mtDNA levels by the dilution-PCR method. When thepercentage of the mtDNA deletion relative to total mtDNA was used as a marker ofmtDNA damage, most regions of the brain accrued a very small amount of mtDNAdamage before age 75. Cortical regions accrued 1 to 2% deletion levels betweenages 80-90, and the putamen accrued up to 12% of this deletion after age 80.