Tay-sachs disease thesis statements


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In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript. Genetic testing for Tay-Sachs and Canavan disease is particularly important for Ashkenazi Jews, because both conditions are more frequent in that population. This comparative case study was possible because of different patenting and licensing practices. The first-line screening test for Tay-Sachs remains an enzyme activity test rather than genotyping. Genotyping is used for preimplantation diagnosis and confirmatory testing.

In contrast, DNA-based testing is the basis for Canavan screening and diagnosis. Miami Children's Hospital did not inform family members and patient groups that had contributed to the gene discovery that it was applying for a patent, and pursued restrictive licensing practices when a patent issued in This led to intense controversy, litigation, and a sealed, nonpublic settlement that apparently allowed for nonexclusive licensing.

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A survey of laboratories revealed a possible price premium for ASPA testing, with per-unit costs higher than for other genetic tests in the Secretary's Advisory Committee on Genetics, Health, and Society case studies. The main conclusion from comparing genetic testing for Tay-Sachs and Canavan diseases, however, is that patenting and licensing conducted without communication with patients and advocates cause mistrust and can lead to controversy and litigation, a negative model to contrast with the positive model of patenting and licensing for genetic testing of cystic fibrosis.

Tay-Sachs and Canavan disease are both neurological conditions that predominantly but not exclusively affect the Ashkenazi Jewish population. Carrier screening and genetic diagnosis for Tay-Sachs are mainly through enzyme assay, with DNA-based testing for ambiguous cases or for diagnostic confirmation. DNA-based analysis is the mainstay for both screening and diagnostic confirmation of Canavan disease.

Nonprofit research institutions obtained patents on both relevant genes, first the gene that when mutated causes Tay-Sachs the HEXA gene encoding the enzyme hexosaminidase A and later for Canavan disease the ASPA gene encoding aspartoacylase. That discovery is, therefore, effectively in the public domain. The patents relevant to Canavan disease, in contrast, were licensed by Miami Children's Hospital.

The patents were eventually nonexclusively licensed at least 20 times. Patenting and licensing were initially highly controversial and led to litigation. Because the two diseases are pathologically similar and affect the same population, this difference in licensing history created a natural experiment to assess the impact of licensing practices on patients' and physicians' clinical access to genetic tests.

Tay-Sachs disease TSD is a progressive disease that destroys brain function. TSD is caused by inheriting two mutated copies of the HEXA gene one from each parent , which produces the hexosaminidase A subunit of an enzyme-protein complex. In an unaffected individual, the enzyme is part of a pathway that degrades Gm2 gangliosides, complex protein-carbohydrate molecules.

In an individual affected by TSD, the absence or reduced activity of the enzyme causes the Gm2 gangliosides to build up in the brain—the metabolic pathway is blocked. This causes progressive destruction of the central nervous system. There are three types of TSD, differentiated by age of onset: acute infantile, juvenile, and late-onset.

Infantile onset is the most common. In the classic progression of acute infantile TSD, the infant gets progressively weaker and loses motor skills between the ages of 6 months and 3 years.

The infant has progressively diminished attentiveness and an exaggerated startle response. As TSD continues to destroy the brain, the infant suffers seizures, blindness, and eventually death, which usually occurs before 4 years of age. Disease progression is painful for its victim and agonizing for parents and family.


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  5. There is no cure for TSD, and treatment is limited to supportive care. Canavan disease also causes progressive deterioration of the brain. It is caused by inheriting two mutated copies of the ASPA gene, which encodes the aspartoacylase enzyme. In a normal individual, aspartoacylase breaks down N -acetylaspartic acid. In Canavan disease, the lack of aspartoacylase leads to a buildup of N -acetylaspartic acid in the brain, which causes demyelination and degeneration. As the brain continues to deteriorate, the affected child suffers from muscle spasms and seizures.

    Individuals with Canavan disease are expected to live into their teens. Clinical details are summarized in Table 1. Because there is no official disease registry for either TSD or Canavan disease, it is difficult to estimate how many children in the United States are affected per year by each disease. Crawford's estimates also include cases of Sandhoff disease, a clinically similar disorder.

    NTSAD is the primary support community for families affected by Tay-Sachs, so their estimates are likely as accurate as can be found. However, Drs. Lois Neufeld, past president of the Canavan Foundation, estimated in a phone interview that there are at least children in the United States living with Canavan disease L. Neufeld, former President of Canavan Foundation, personal communication, For a summary, see the timeline in the appendix at the end of the article.

    There are two basic types of tests used to screen people for TSD: one is an enzyme assay, and the other is a DNA-based test. The enzyme test, which was the basis of many carrier screening campaigns in the United States, is still widely used for carrier screening and diagnosis. The DNA-based test can be used to confirm an inconclusive enzyme test, to identify the specific mutation in an individual, to evaluate an individual for a pseudodeficiency allele a sequence variant, in this case one or two copies of the R or R W alleles, that does not alter protein function sufficiently to cause disease and thus means that a person is not a carrier for TSD , 4 for carrier testing, and for prenatal testing, including preimplantation genetic diagnosis PGD.

    Monaghan et al. John O'Brien and Shintaro Okada developed the first enzyme test in the early s. Michael Kaback modified the O'Brien enzyme test and used it to spearhead a Tay-Sachs carrier screening campaign in Washington and Baltimore in the s. According to Dr. Kaback, there was never any effort to patent the original Tay-Sachs enzyme test M. Elizabeth F.

    Neufeld when she decided to clone the defective Tay-Sachs gene. She had previously done her biochemistry thesis at the University of Michigan on GM1 gangliosidosis, another rare lysosomal disorder. When she began in Dr.

    Sphingolipids: Sphingolipidoses - Tay Sachs Disease (a Lysosomal Storage Disease) [free sample]

    Neufeld's laboratory, she worked on Hurler syndrome, another lysosomal disorder caused by defective iduronidase enzyme, 9 and decided that she wanted to clone the iduronidase gene. However, material from Tay-Sachs patients was easier to obtain, so she switched to cloning the genes for hexosaminidase R.

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    Myerowitz, Department of Biology, St. Mary's College of Maryland, personal communication, Myerowitz, personal communication, Myerowitz was approached by a lawyer from NIH who advised her to file a patent application. US patent 5,, has a filing date of October 31, , and US 5,, has a filing date of December 7, ; however, both stemmed from one original application ,, filed July 5, During the patent prosecution process, the original application's claims were split into two separate patents.

    Myerowitz left the NIH in for a position at St. Mary's College of Maryland. In , she contacted the NIH legal department to ask about developments with the patents. Thus, although the Tay-Sachs gene was patented, the patents were never licensed and never enforced. Reuben Matalon and coinventors. Matalon had been recruited in May to search for the cause of Canavan disease, while he was a professor at the University of Illinois at Chicago, by Daniel and Deborah Greenberg, a Chicago-based family that had two children, Jonathan and Amy, born with Canavan disease.

    Tay Sachs Disease Essay

    In , Matalon published an article in the Journal of Inherited Metabolic Diseases detailing a prenatal enzymatic screening test that could diagnose Canavan disease using amniocytes cells taken from the amniotic fluid of a gestating pregnancy or chorionic villus sampling CVS; cells taken from the placenta. In , Bennett et al. However, complications with the amniotic fluid assay were reported: it was only reliable at the extremes, and mid-range levels of enzyme activity were inconclusive.

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    Unlike TSD, then, the only way to provide carrier screening for Canavan disease was through DNA-based testing, and DNA-based prenatal diagnosis would be an easier and more reliable method than amniotic fluid analysis. On October 1, , Matalon and his researchers published exciting results in Nature Genetics : they had isolated and sequenced the aspartoacylase gene and found a common mutation that causes Canavan disease. The patent granted in covered the DNA sequence of the gene, mutated sequences associated with Canavan disease, use of the sequence in DNA testing, and test kits for Canavan disease.

    The patent granted in claimed mutated versions of the aspartoacylase protein. After the first patent was granted, MCH's chief financial officer, David Carroll, sent letters to laboratories and hospitals, advising them that MCH had received the patent, and that those doing Canavan tests would have to take out a license or risk an infringement lawsuit. The letter also set volume limitations of individual tests per academic laboratory per year M.

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    Tay sachs disease thesis statements

    In response, the Canavan Disease Screening Consortium was formed. They wanted the Canavan patent to be dedicated to the public good, as the University of Michigan's patent for the Cystic Fibrosis gene had been. If the patent could not be dedicated to the public good, they requested four actions from MCH:. Set up a fund to assist people unable to pay for screening or prenatal diagnosis M. Watson, personal communication, Michael Watson, Executive Director of the ACMG, who was present at the meetings, the representatives of MCH offered an undisclosed sum of money to be used for the proposed educational outreach program but did not agree to the Consortium's other requests M.

    The MCH marketing plan had two phases: first, MCH would offer nonexclusive licenses to a limited number of academic laboratories, allowing them to perform a limited number of tests per year.