Ethnic differences and disease phenotypes

Direct-to-Consumer Genetic Testing's Red Herring: "Genetic Ancestry" and Personalized Medicine

The growth in the direct-to-consumer genetic testing industry poses a number of challenges for healthcare practice, among a number of other areas of concern. Several companies providing this service send their customers reports including information variously referred to as genetic ethnicity, genetic heritage, biogeographic ancestry, and genetic ancestry. In this article, we argue that such information should not be used in healthcare consultations or to assess health risks. Far from representing a move toward personalized medicine, use of this information poses risks both to patients as individuals and to racialized ethnic groups because of the way it misrepresents human genetic diversity.

Preventing biological weapon development through the governance of life science research

The dual-use dilemma in the life sciences-that illicit applications draw on the same science and technology base as legitimate applications-makes it inherently difficult to control one without inhibiting the other. Since before the September 11 attacks, the science and security communities in the United States have struggled to develop governance processes that can simultaneously minimize the risk of misuse of the life sciences, promote their beneficial applications, and protect the public trust. What has become clear over that time is that while procedural steps can be specified for assessing and managing dual-use risks in the review of research proposals, oversight of ongoing research, and communication of research results, the actions or decisions to be taken at each of these steps to mitigate dual-use risk defy codification. Yet the stakes are too high to do nothing, or to be seen as doing nothing. The U.S. government should therefore adopt an oversight framework largely along the lines recommended by the National Science Advisory Board for Biosecurity almost 5 years ago-one that builds on existing processes, can gain buy-in from the scientific community, and can be implemented at modest cost (both direct and opportunity), while providing assurance that a considered and independent examination of dual-use risks is being applied. Without extraordinary visibility into the actions of those who would misuse biology, it may be impossible to know how well such an oversight system will actually succeed at mitigating misuse. But maintaining the public trust will require a system to be established in which reasonably foreseeable dual-use consequences of life science research are anticipated, evaluated, and addressed.

Racial differences in the diagnosis of Parkinson's disease

The objective of this cohort study was to determine the incidence of Parkinson's disease (PD) and the effects of race/ethnicity, other demographic characteristics, geography, and healthcare utilization on probability of diagnosis. The authors used the Pennsylvania state Medicaid claims dataset from 1999 to 2003 to identify newly diagnosed cases of PD among the 182,271 Medicaid enrolled adults age 40-65; 319 incident cases of PD were identified. The 4-year cumulative incidence of PD was 45 per 100,000; 54 per 100,000 among whites, 23 per 100,000 among African-Americans and 40 per 100,000 among Latinos (P < 0.0001), corresponding to a relative risk (RR) of PD of 0.43 for African-Americans (P < 0.0001) compared with whites. After adjusting for age, sex, geography, reason for Medicaid eligibility, and average number of visits, African-Americans were still half as likely to be diagnosed with PD as whites (RR 0.45, P < 0.0001). Older age, more healthcare visits and Medicaid eligibility because of income alone also were significantly associated with PD diagnosis, while male sex was not. Observed racial differences in incidence of PD are not explained by differences in age, sex, income, insurance or healthcare utilization but still may be explained by biological differences or other factors such as education or aging beliefs. Better understanding of the complex biological and social determinants of these disparities is critical to improve PD care.

Race, genetics and medicine: does the color of a leopard's spots matter?

PURPOSE OF REVIEW

Accurate inference of genetic ancestry is critical because common diseases and drug responses can be influenced by genetic factors that vary in frequency or differ altogether among populations. Frequently, clinicians and researchers use popular notions of race to make inferences about a child's genetic ancestry and predict whether he or she carries specific risk factors that influence health. The extent to which race is useful for making such predictions depends on how well race corresponds with genetic inferences of ancestry and whether ancestry is predictive of genotypes associated with risk.

RECENT FINDINGS

Recent studies of human population genetic variation show that while race captures some information about genetic ancestry, particularly in US populations, it often fails to account for admixture and population structure. Ancestry is more accurately inferred by geographical origin or, better yet, explicit genetic data. This is an important result because the genetic variants predicted to underlie common disease are often not common across populations with different ancestry or differ significantly in frequency among such populations.

SUMMARY

Geographical origin and explicit genetic data are more accurate predictors of ancestry than race. Using such alternatives is an important step toward identifying genetic risk variants for common pediatric diseases and personalizing disease prevention and intervention strategies.

Psychiatric disorder criteria and their application to research in different racial groups

BACKGROUND

The advent of standardized classification and assessment of psychiatric disorders, and considerable joint efforts among many countries has led to the reporting of international rates of psychiatric disorders, and inevitably, their comparison between different racial groups.

RESULTS

In neurologic diseases with defined genetic etiologies, the same genetic cause has different phenotypes in different racial groups.

CONCLUSION

We suggest that genetic differences between races mean that diagnostic criteria refined in one racial group, may not be directly and simply applicable to other racial groups and thus more effort needs to be expended on defining diseases in other groups. Cross-racial confounds (in addition to cultural confounds) make the interpretation of rates in different groups even more hazardous than seems to have been appreciated.

A novel approach to characterise pathogen candidate genetic polymorphisms involved in clinical outcome

Understanding the key factors influencing the clinical outcome of an infection is crucial for early diagnosis and optimised treatment. Despite widespread recognition of the importance of the genetics composition of pathogens, most efforts so far have focused on characterising disease and susceptibility genes in humans. Here, we propose a new flexible and powerful methodological framework to detect candidate genetic polymorphisms influencing clinical outcome from pathogen genomes. The rationale is to use well-supported clades in a phylogeny as statistical predictors for clinical outcomes rather than the individual polymorphisms themselves. This greatly increases the statistical power to detect candidate polymorphisms when analysing a large number of variable sites. In a second step, the candidate polymorphisms are recovered by characterising the polymorphisms that most strongly support the clades predicting the clinical outcome. The modelling approach further allows including host factors and testing for possible interactions between factors. We illustrate the approach by an application on a dataset of hepatitis B polymerase genes. The statistical model retains age at infection as well as six candidate polymorphisms as predictors for clinical outcome (acute, chronic and fulminant). The method is straightforward to apply and computationally effective. While the approach is focused on detecting candidate polymorphisms from pathogen genomes, the method might be more broadly applied for characterising the link between genotype and phenotype while statistically controlling for environmental factors.

Spectrum and prevalence of cardiac sodium channel variants among black, white, Asian, and Hispanic individuals: implications for arrhythmogenic susceptibility and Brugada/long QT syndrome genetic testing

OBJECTIVES

The purpose of this study was to determine the prevalence and spectrum of nonsynonymous polymorphisms (amino acid variants) in the cardiac sodium channel among healthy subjects.

BACKGROUND

Pathogenic mutations in the cardiac sodium channel gene, SCN5A, cause approximately 15 to 20% of Brugada syndrome (BrS1), 5 to 10% of long QT syndrome (LQT3), and 2 to 5% of sudden infant death syndrome.

METHODS

Using single-stranded conformation polymorphism, denaturing high-performance liquid chromatography, and/or direct DNA sequencing, mutational analysis of the protein-encoding exons of SCN5A was performed on 829 unrelated, anonymous healthy subjects: 319 black, 295 white, 112 Asian, and 103 Hispanic.

RESULTS

In addition to the four known common polymorphisms (R34C, H558R, S1103Y, and R1193Q), four relatively ethnic-specific polymorphisms were identified: R481W, S524Y, P1090L, and V1951L. Overall, 39 distinct missense variants (28 novel) were elucidated. Nineteen variants (49%) were found only in the black cohort. Only seven variants (18%) localized to transmembrane-spanning domains. Four variants (F1293S, R1512W, and V1951L cited previously as BrS1-causing mutations and S1787N previously published as a possible LQT3-causing mutation) were identified in this healthy cohort.

CONCLUSIONS

This study provides the first comprehensive determination of the prevalence and spectrum of cardiac sodium channel variants in healthy subjects from four distinct ethnic groups. This compendium of SCN5A variants is critical for proper interpretation of SCN5A genetic testing and provides an essential hit list of targets for future functional studies to determine whether or not any of these variants mediate genetic susceptibility for arrhythmias in the setting of either drugs or disease.

Age-specific changes in epistatic effects on mortality rate in Drosophila melanogaster

Models for the evolution of senescence assume that genes with age-specific effects act independently of one another. Although recent empirical data show that longevity is influenced in part by interactions between genes, there are currently few data on whether epistasis influences age-specific components of mortality. To gauge if and how interactions affect age-specific traits, we incorporated the Drosophila visible marker mutations ebony, forked, and purple into seven wild-caught strains of D. melanogaster to examine gene x genetic background interactions. We found significant natural genetic variation for longevity and baseline mortality rates. Gene x genetic background interactions were prevalent not only for longevity but also for baseline mortality rates and age-specific mortality rates. We conclude that gene x genetic background epistasis is prevalent for aging-related traits and could play a significant role in the evolution of aging. These results suggest that future genetic models for the evolution of aging should incorporate the effects of epistasis.