The Recombination Landscape of the Khoe-San - the Upper Limits of Recombination Divergence in Humans

Recombination maps are important resources for epidemiological and evolutionary analyses, however, there are currently no recombination maps representing any African population outside of those with West African ancestry. We inferred the demographic history for the Nama, an indigenous Khoe-San population of southern Africa, and derived a novel, population-specific recombination map from the whole genome sequencing of 54 Nama individuals. We hypothesized that there are no publicly available recombination maps representative of the Nama, considering the deep population divergence and subsequent isolation of the Khoe-San from other African groups. We showed that the recombination landscape of the Nama does not cluster with any continental groups with publicly available representative recombination maps. Finally, we used selection scans as an example of how fine-scale differences between the Nama recombination map and the combined Phase II HapMap recombination map can impact the outcome of selection scans.

Serum proteomics links suppression of tumor immunity to ancestry and lethal prostate cancer

There is evidence that tumor immunobiology and immunotherapy response may differ between African American and European American prostate cancer patients. Here, we determined if men of African descent harbor a unique systemic immune-oncological signature and measured 82 circulating proteins in almost 3000 Ghanaian, African American, and European American men. Protein signatures for suppression of tumor immunity and chemotaxis were significantly elevated in men of West African ancestry. Importantly, the suppression of tumor immunity protein signature associated with metastatic and lethal prostate cancer, pointing to clinical significance. Moreover, two markers, pleiotrophin and TNFRSF9, predicted poor disease survival specifically among African American men. These findings indicate that immune-oncology marker profiles differ between men of African and European descent. These differences may contribute to the disproportionate burden of lethal prostate cancer in men of African ancestry. The elevated peripheral suppression of tumor immunity may have important implication for guidance of cancer therapy which could particularly benefit African American patients.

Enrichment for Cases of African-American Patients with Pathogenic TTR V142I Variant in the TOPCAT Trial

Transthyretin cardiac amyloidosis (ATTR-CA) is a treatable cause of heart failure with a hereditary form that disproportionally affects patients of West African ancestry. The clinical management of ATTR-CA has dramatically changed in the past five years, with rapidly evolving diagnostic approaches and life-prolonging therapies. The TTR variant c.424G>A, p.V142I (aka V122I) is pathogenic and occurs in 3-4% of individuals of West African ancestry. Despite its high frequency, V142I ATTR-CA is often unrecognized due to variable clinical penetrance, limited knowledge, and lack of inexpensive non-invasive diagnostic tests. Currently unknown is which TTR V142I carriers will progress to heart failure and at what age. Here we studied the prevalence of TTR V142I among a random cohort of African-American patients enrolled in the Treatment of Preserved Cardiac Function Heart Failure With an Aldosterone Antagonist Trial (TOPCAT). Three of the 26 HFpEF patients (11.5%) studied carried the pathogenic TTR V142I variant. While we cannot conclude at this point that TTR V142I was the underlying cause of the clinical phenotype in these patients, our results suggest that rapid TTR V142I genotyping, in combination with heart imaging, could have immediate clinical utility for identifying under-/mis-diagnosed HFpEF patients.

Variation of ApoL1 Testing Practices for Living Kidney Donors

Introduction: Tests exist for ApoL1 genetic variants to determine whether a potential donor’s kidneys are at increased risk of kidney failure. Variants of the ApoL1 gene associated with increased risk are primarily found in people with West African ancestry. Given uncertainty about clinical implications of ApoL1 test results for living kidney donors and recipients and the lack of uniform guidelines for ApoL1 testing, transplant centers across the United States vary in ApoL1 testing practices. Research Questions: (1) What approach do transplant centers take to determine whether prospective donors are of West African ancestry? (2)How do transplant centers engage potential donors during the ApoL1 testing process? (3) What do transplant centers identify as concerns and barriers to ApoL1 testing? and (4) What actions do transplant centers take when a potential donor has 2 ApoL1 risk variants? Design: We explored the current practices of transplant centers by surveying nephrologists and transplant surgeons at transplant centers evaluating the majority of black living donors in the United States. Results: About half of these transplant centers offered ApoL1 testing. Of those who offered ApoL1 testing, only half involved the donor in decision-making about donation when the donor has 2 risk variants. Discussion: Unaddressed differences in the priorities of transplant centers and black living donors may stigmatize black donors and undermine trust in the health-care and organ donation systems. Variation in transplant center testing practices points to the critical need for further research and community engagement to inform the development of guidelines for ApoL1 testing.