DNA-based carrier screening in the Ashkenazi Jewish population

Cellular and molecular mechanisms of aspartoacylase and its role in Canavan disease

Canavan disease is an autosomal recessive and lethal neurological disorder, characterized by the spongy degeneration of the white matter in the brain. The disease is caused by a deficiency of the cytosolic aspartoacylase (ASPA) enzyme, which catalyzes the hydrolysis of N-acetyl-aspartate (NAA), an abundant brain metabolite, into aspartate and acetate. On the physiological level, the mechanism of pathogenicity remains somewhat obscure, with multiple, not mutually exclusive, suggested hypotheses. At the molecular level, recent studies have shown that most disease linked ASPA gene variants lead to a structural destabilization and subsequent proteasomal degradation of the ASPA protein variants, and accordingly Canavan disease should in general be considered a protein misfolding disorder. Here, we comprehensively summarize the molecular and cell biology of ASPA, with a particular focus on disease-linked gene variants and the pathophysiology of Canavan disease. We highlight the importance of high-throughput technologies and computational prediction tools for making genotype-phenotype predictions as we await the results of ongoing trials with gene therapy for Canavan disease.

Evolving health care through personal genomics

With the rapid evolution of next-generation DNA sequencing technologies, the cost of sequencing a human genome has plummeted, and genomics has started to pervade health care across all stages of life - from preconception to adult medicine. Challenges to fully embracing genomics in a clinical setting remain, but some approaches are starting to overcome these barriers, such as community-driven data sharing to improve the accuracy and efficiency of applying genomics to patient care.

Development of genomic DNA reference materials for genetic testing of disorders common in people of ashkenazi jewish descent

Many recessive genetic disorders are found at a higher incidence in people of Ashkenazi Jewish (AJ) descent than in the general population. The American College of Medical Genetics and the American College of Obstetricians and Gynecologists have recommended that individuals of AJ descent undergo carrier screening for Tay Sachs disease, Canavan disease, familial dysautonomia, mucolipidosis IV, Niemann-Pick disease type A, Fanconi anemia type C, Bloom syndrome, and Gaucher disease. Although these recommendations have led to increased test volumes and number of laboratories offering AJ screening, well-characterized genomic reference materials are not publicly available. The Centers for Disease Control and Prevention-based Genetic Testing Reference Materials Coordination Program, in collaboration with members of the genetic testing community and Coriell Cell Repositories, have developed a panel of characterized genomic reference materials for AJ genetic testing. DNA from 31 cell lines, representing many of the common alleles for Tay Sachs disease, Canavan disease, familial dysautonomia, mucolipidosis IV, Niemann-Pick disease type A, Fanconi anemia type C, Bloom syndrome, Gaucher disease, and glycogen storage disease, was prepared by the Repository and tested in six clinical laboratories using three different PCR-based assay platforms. A total of 33 disease alleles was assayed and 25 different alleles were identified. These characterized materials are publicly available from Coriell and may be used for quality control, proficiency testing, test development, and research.

Heterozygote carrier testing in high schools abroad: what are the lessons for the U.S.?

The main value of carrier detection in the general population is to determine reproductive risks. In this manuscript I examine the practice of providing carrier screening programs in the school setting. While the data show that high school screening programs can achieve high uptake, I argue that this may reflect a lack of full understanding about risks, benefits, and alternatives, and the right not to know. It may also reflect the inherent coercion in group testing, particularly for adolescents who are prone to peer pressure. The problem of carrier screening in the schools is compounded when the condition has a predilection for certain groups based on race, ethnicity or religion. I examine programs around the world that seek to test high school students for Tay Sachs and Cystic Fibrosis carrier status. I argue that carrier programs should be designed so as to minimize stigma and to allow individuals to refuse. The mandatory school environment cannot achieve this. Rather, I conclude that screening programs should be designed to attract young adults and not adolescents to participate in a more voluntary venue.