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- Algady, Walid, et al.
(författare)
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The Malaria-Protective Human Glycophorin Structural Variant DUP4 Shows Somatic Mosaicism and Association with Hemoglobin Levels
- 2018
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Ingår i: American Journal of Human Genetics. - : Elsevier BV. - 0002-9297 .- 1537-6605. ; 103:5, s. 769-776
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Tidskriftsartikel (refereegranskat)abstract
- Glycophorin A and glycophorin B are red blood cell surface proteins and are both receptors for the parasite Plasmodium falciparum, which is the principal cause of malaria in sub-Saharan Africa. DUP4 is a complex structural genomic variant that carries extra copies of a glycophorin A-glycophorin B fusion gene and has a dramatic effect on malaria risk by reducing the risk of severe malaria by up to 40%. Using fiber-FISH and Illumina sequencing, we validate the structural arrangement of the glycophorin locus in the DUP4 variant and reveal somatic variation in copy number of the glycophorin B-glycophorin A fusion gene. By developing a simple, specific, PCR-based assay for DUP4, we show that the DUP4 variant reaches a frequency of 13% in the population of a malaria-endemic village in southeastern Tanzania. We genotype a substantial proportion of that village and demonstrate an association of DUP4 genotype with hemoglobin levels, a phenotype related to malaria, using a family-based association test. Taken together, we show that DUP4 is a complex structural variant that may be susceptible to somatic variation and show that DUP4 is associated with a malarial-related phenotype in a longitudinally followed population.
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- Almqvist, E, et al.
(författare)
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Risk reversals in predictive testing for Huntington disease.
- 1997
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Ingår i: American Journal of Human Genetics. - : Elsevier BV. - 0002-9297 .- 1537-6605. ; 61:4, s. 945-52
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Tidskriftsartikel (refereegranskat)abstract
- The first predictive testing for Huntington disease (HD) was based on analysis of linked polymorphic DNA markers to estimate the likelihood of inheriting the mutation for HD. Limits to accuracy included recombination between the DNA markers and the mutation, pedigree structure, and whether DNA samples were available from family members. With direct tests for the HD mutation, we have assessed the accuracy of results obtained by linkage approaches when requested to do so by the test individuals. For six such individuals, there was significant disparity between the tests. Three went from a decreased risk to an increased risk, while in another three the risk was decreased. Knowledge of the potential reasons for these changes in results and impact of these risk reversals on both patients and the counseling team can assist in the development of strategies for the prevention and, where necessary, management of a risk reversal in any predictive testing program.
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- Almqvist, E W, et al.
(författare)
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A worldwide assessment of the frequency of suicide, suicide attempts, or psychiatric hospitalization after predictive testing for Huntington disease.
- 1999
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Ingår i: American Journal of Human Genetics. - 0002-9297 .- 1537-6605. ; 64:5, s. 1293-304
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Tidskriftsartikel (refereegranskat)abstract
- Prior to the implementation of predictive-testing programs for Huntington disease (HD), significant concern was raised concerning the likelihood of catastrophic events (CEs), particularly in those persons receiving an increased-risk result. We have investigated the frequency of CEs-that is, suicide, suicide attempt, and psychiatric hospitalization-after an HD predictive-testing result, through questionnaires sent to predictive-testing centers worldwide. A total of 44 persons (0.97%) in a cohort of 4,527 test participants had a CE: 5 successful suicides, 21 suicide attempts, and 18 hospitalizations for psychiatric reasons. All persons committing suicide had signs of HD, whereas 11 (52.4%) of 21 persons attempting suicide and 8 (44.4%) of 18 who had a psychiatric hospitalization were symptomatic. A total of 11 (84.6%) of 13 asymptomatic persons who experienced a CE during the first year after HD predictive testing received an increased-risk result. Factors associated with an increased risk of a CE included (a) a psychiatric history
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- Ameur, Adam, et al.
(författare)
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Genetic Adaptation of Fatty-Acid Metabolism : A Human-Specific Haplotype Increasing the Biosynthesis of Long-Chain Omega-3 and Omega-6 Fatty Acids
- 2012
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Ingår i: American Journal of Human Genetics. - : Elsevier BV. - 0002-9297 .- 1537-6605. ; 90:5, s. 809-820
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Tidskriftsartikel (refereegranskat)abstract
- Omega-3 and omega-6 long-chain polyunsaturated fatty acids (LC-PUFAs) are essential for the development and function of the human brain. They can be obtained directly from food, e.g., fish, or synthesized from precursor molecules found in vegetable oils. To determine the importance of genetic variability to fatty-acid biosynthesis, we studied FADS1 and FADS2, which encode rate-limiting enzymes for fatty-acid conversion. We performed genome-wide genotyping (n = 5,652 individuals) and targeted resequencing (n = 960 individuals) of the FADS region in five European population cohorts. We also analyzed available genomic data from human populations, archaic hominins, and more distant primates. Our results show that present-day humans have two common FADS haplotypes-defined by 28 closely linked SNPs across 38.9 kb-that differ dramatically in their ability to generate LC-PUFAs. No independent effects on FADS activity were seen for rare SNPs detected by targeted resequencing. The more efficient, evolutionarily derived haplotype appeared after the lineage split leading to modern humans and Neanderthals and shows evidence of positive selection. This human-specific haplotype increases the efficiency of synthesizing essential long-chain fatty acids from precursors and thereby might have provided an advantage in environments with limited access to dietary LC-PUFAs. In the modern world, this haplotype has been associated with lifestyle-related diseases, such as coronary artery disease.
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- Andrew, S E, et al.
(författare)
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Huntington disease without CAG expansion : phenocopies or errors in assignment?
- 1994
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Ingår i: American Journal of Human Genetics. - 0002-9297 .- 1537-6605. ; 54:5, s. 852-63
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Tidskriftsartikel (refereegranskat)abstract
- Huntington disease (HD) has been shown to be associated with an expanded CAG repeat within a novel gene on 4p16.3 (IT15). A total of 30 of 1,022 affected persons (2.9% of our cohort) did not have an expanded CAG in the disease range. The reasons for not observing expansion in affected individuals are important for determining the sensitivity of using repeat length both for diagnosis of affected patients and for predictive testing programs and may have biological relevance for the understanding of the molecular mechanism underlying HD. Here we show that the majority (18) of the individuals with normal sized alleles represent misdiagnosis, sample mix-up, or clerical error. The remaining 12 patients represent possible phenocopies for HD. In at least four cases, family studies of these phenocopies excluded 4p16.3 as the region responsible for the phenotype. Mutations in the HD gene that are other than CAG expansion have not been excluded for the remaining eight cases; however, in as many as seven of these persons, retrospective review of these patients' clinical features identified characteristics not typical for HD. This study shows that on rare occasions mutations in other, as-yet-undefined genes can present with a clinical phenotype very similar to that of HD.
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