Skin color variation in Africa

Population designations in biomedical research: Limitations and perspectives

In biomedical research, population differences are of central interest. Variations in the frequency and severity of diseases and in treatment effects among human subpopulation groups are common in many medical conditions. Unfortunately, the practices in terms of subpopulation labeling do not exhibit the level of rigor one would expect in biomedical research, especially when studying multifactorial diseases such as cancer or atherosclerosis. The reporting of population differences in clinical research is characterized by large disparities in practices, and fraught with methodological issues and inconsistencies. The actual designations such as "Black" or "Asian" refer to broad and heterogeneous groups, with a great discrepancy among countries. Moreover, the use of obsolete concepts such as "Caucasian" is unfortunate and imprecise. The use of adequate labeling to reflect the scientific hypothesis needs to be promoted. Furthermore, the use of "race/ethnicity" as a unique cause of human heterogeneity may distract from investigating other factors related to a medical condition, particularly if this label is employed as a proxy for cultural habits, diet, or environmental exposure. In addition, the wide range of opinions among researchers does not facilitate the attempts made for resolving this heterogeneity in labeling. "Race," "ethnicity," "ancestry," "geographical origin," and other similar concepts are saturated with meanings. Even if the feasibility of a global consensus on labeling seems difficult, geneticists, sociologists, anthropologists, and ethicists should help develop policies and practices for the biomedical field.

Racial Disparity in Oxygen Saturation Measurements by Pulse Oximetry: Evidence and Implications

The pulse oximeter is a ubiquitous clinical tool used to estimate blood oxygen concentrations. However, decreased accuracy of pulse oximetry in patients with dark skin tones has been demonstrated since as early as 1985. Most commonly, pulse oximeters may overestimate the true oxygen saturation in individuals with dark skin tones, leading to higher rates of occult hypoxemia (i.e., clinically unrecognized low blood oxygen saturation). Overestimation of oxygen saturation in patients with dark skin tones has serious clinical implications, as these patients may receive insufficiently rigorous medical care when pulse oximeter measurements suggest that their oxygen saturation is higher than the true value. Recent studies have linked pulse oximeter inaccuracy to worse clinical outcomes, suggesting that pulse oximeter inaccuracy contributes to known racial health disparities. The magnitude of device inaccuracy varies by pulse oximeter manufacturer, sensor type, and arterial oxygen saturation. The underlying reasons for decreased pulse oximeter accuracy for individuals with dark skin tones may be related to failure to control for increased absorption of red light by melanin during device development and insufficient inclusion of individuals with dark skin tones during device calibration. Inadequate regulatory standards for device approval may also play a role in decreased accuracy. Awareness of potential pulse oximeter limitations is an important step for providers and may encourage the consideration of additional clinical information for management decisions. Ultimately, stricter regulatory requirements for oximeter approval and increased manufacturer transparency regarding device performance are required to mitigate this racial bias.

Transposable element insertions shape gene regulation and melanin production in a fungal pathogen of wheat

BACKGROUND

Fungal plant pathogens pose major threats to crop yield and sustainable food production if they are highly adapted to their host and the local environment. Variation in gene expression contributes to phenotypic diversity within fungal species and affects adaptation. However, very few cases of adaptive regulatory changes have been reported in fungi and the underlying mechanisms remain largely unexplored. Fungal pathogen genomes are highly plastic and harbor numerous insertions of transposable elements, which can potentially contribute to gene expression regulation. In this work, we elucidated how transposable elements contribute to variation in melanin accumulation, a quantitative trait in fungi that affects survival under stressful conditions.

RESULTS

We demonstrated that differential transcriptional regulation of the gene encoding the transcription factor Zmr1, which controls expression of the genes in the melanin biosynthetic gene cluster, is responsible for variation in melanin accumulation in the fungal plant pathogen Zymoseptoria tritici. We show that differences in melanin levels between two strains of Z. tritici are due to two levels of transcriptional regulation: (1) variation in the promoter sequence of Zmr1 and (2) an insertion of transposable elements upstream of the Zmr1 promoter. Remarkably, independent insertions of transposable elements upstream of Zmr1 occurred in 9% of Z. tritici strains from around the world and negatively regulated Zmr1 expression, contributing to variation in melanin accumulation.

CONCLUSIONS

Our studies identified two levels of transcriptional control that regulate the synthesis of melanin. We propose that these regulatory mechanisms evolved to balance the fitness costs associated with melanin production against its positive contribution to survival in stressful environments.