Previous studies have established that the gene responsible for Huntington’s disease (HD) is located in chromosome 4 – labeled as 4p16.3. Early symptoms of the disease include chorea or involuntary movements, loss of balance, as well as cerebral atrophy1. Although the disease has a late onset, juvenile form of the disease is also probable. The disease is manifested in children and teenagers and is characterized by transmission from an affected father (paternal transmission effect), unusually large repeat size of nucleotides, and rigidity and seizure disorder2. The neuropathology of the disease shows selective loss of neurons that is most severe in caudate and putamen. Despite heavy research, the treatment to effectively delay or prevent the
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Two libraries were then used to isolate these cosmids. The first library was a somatic mouse/human cell hybrid with the sole human chromosome 4. The second library was an arrayed flow-sorted chromosome 4 cosmid library. They isolated 64 overlapping cosmids which were ~480 kb from D4S180 to a location between D4S95 and D4S182 using YAC and cosmid probe hybridization. Sixteen (16) of these cosmids were identified. Exon trapping was then applied to cosmids from the region proximal to D4S127. This procedure provided probes for screening the cDNA libraries. After processing, nine exon clones in the region from cosmids L134B9 and L181B10 were produced. Two non-overlapping cDNA sequences, IT15A and IT16A, were isolated using exon probes. These cDNAs both detected an approximately 10-11 kb transcript as determined by Northern blot analysis suggesting that they came from the same mRNA. The full-length transcript was obtained from the “walking” of IT15A and IT16A to the cDNA libraries. The transcript consisted 10,366 bases including 18 A’s. The open reading frame which is 9.4 kb long predicted the protein product. The protein is predicted to be 348 kd containing 3,144 amino …show more content…
They examined two pedigrees from families with sporadic cases of HD. PCR analysis of the HD chromosomes of these families revealed that some of the offspring produced PCR product containing approximately 36 copies which was at the extreme high end of the normal range. The trinucleotide repeat had also undergone sequential expansions to approximately 44 to 46 copies. Similar results were obtained in the second family where the new HD mutant had chromosomes containing expanded repeat. The results suggested that the ultimate HD chromosome displayed the marker haplotype of 1/3 of all HD chromosome which may be predisposed to undergoing repeat
Two libraries were then used to isolate these cosmids. The first library was a somatic mouse/human cell hybrid with the sole human chromosome 4. The second library was an arrayed flow-sorted chromosome 4 cosmid library. They isolated 64 overlapping cosmids which were ~480 kb from D4S180 to a location between D4S95 and D4S182 using YAC and cosmid probe hybridization. Sixteen (16) of these cosmids were identified. Exon trapping was then applied to cosmids from the region proximal to D4S127. This procedure provided probes for screening the cDNA libraries. After processing, nine exon clones in the region from cosmids L134B9 and L181B10 were produced. Two non-overlapping cDNA sequences, IT15A and IT16A, were isolated using exon probes. These cDNAs both detected an approximately 10-11 kb transcript as determined by Northern blot analysis suggesting that they came from the same mRNA. The full-length transcript was obtained from the “walking” of IT15A and IT16A to the cDNA libraries. The transcript consisted 10,366 bases including 18 A’s. The open reading frame which is 9.4 kb long predicted the protein product. The protein is predicted to be 348 kd containing 3,144 amino …show more content…
They examined two pedigrees from families with sporadic cases of HD. PCR analysis of the HD chromosomes of these families revealed that some of the offspring produced PCR product containing approximately 36 copies which was at the extreme high end of the normal range. The trinucleotide repeat had also undergone sequential expansions to approximately 44 to 46 copies. Similar results were obtained in the second family where the new HD mutant had chromosomes containing expanded repeat. The results suggested that the ultimate HD chromosome displayed the marker haplotype of 1/3 of all HD chromosome which may be predisposed to undergoing repeat