Björn Nilsson

Human genetic studies have identified key regulators of fetal haemoglobin (HbF) expression, including BCL11A, resulting in therapeutic advances ^1–8 . Yet the mechanisms by which HbF expression is activated remain incompletely understood ⁹ . Here we conduct a large multi-ancestry genome-wide association study of HbF levels in 28,279 individuals that identifies 91 conditionally independent associations across 12 genomic regions. In one previously uncharacterized associated region, the high-HbF-linked causal variant rs1010474-C reduces BACH2 expression and elevates HbF levels. Direct perturbation or inhibition of BACH2 likewise increases HbF expression. Mechanistically, BACH2 restrains activation of the HbF-encoding γ-globin genes, while loss of BACH2 enhances NRF2 chromatin occupancy and promotes the formation of activation foci at the γ-globin genes. Although BACH2 and NRF2 binding motifs in the γ-globin promoters overlap, they can be selectively edited to activate or repress γ-globin, respectively, and do so independently of BCL11A. These findings illustrate how human genetic variation continues to advance our understanding of therapeutically relevant regulatory mechanisms underlying HbF expression.

Genome-wide association studies have linked thousands of sequence variants to immune-mediated diseases, yet their cellular mechanisms remain largely unresolved. Here we present BloodVariome, a high-resolution atlas of genetic effects across the human immune cell hierarchy. Combining deep immunophenotyping with automated pattern-recognition, we quantified 1,533 traits across 127 immune cell populations in 11,983 individuals. We identified 259 significant associations, the vast majority of which are not captured by conventional bulk blood trait studies. Most associations were restricted to single immune lineages or cell populations, revealing a fine-grained genetic compartmentalization of the immune system. By linking known disease risk alleles to specific immune cell phenotypes, BloodVariome illuminates cellular mechanisms underlying autoimmunity, immunodeficiency, and hematologic malignancy. Moreover, we implicate novel regulators of human immune cell development and function. By bridging the gap between cohort size and phenotypic depth, BloodVariome establishes a high-resolution framework for interpreting how genetic variation shapes cellular immunity at population-scale.

Understanding the genetic regulation of blood CD34 ⁺ cell levels could lead to better methods for stem cell mobilization and transplantation. Recently, in a genome-wide association study (GWAS), we identified 11 genetic associations with blood CD34 ⁺ cell levels. One of the most significant maps to an intergenic region between the ENO1 and RERE genes at chromosome 1p36.23. However, the underlying mechanism remains unknown. Here, using functional fine-mapping, we identify rs10864368:C > T as a causal non-coding variant. Specifically, the rs10864368-T allele abrogates a binding site for the GATA2 transcription factor, leading to downregulation of ENO1 and RERE and lower CD34 ⁺ cell levels. Our data link a specific GATA2 target to the regulation of CD34 ⁺ cell levels, expanding on the role of GATA2 in human hematopoieisis.

Multiple myeloma (MM) is the second most common blood malignancy, with several lines of evidence supporting an inherited genetic component. Here, we sequenced 177 affected individuals from 128 families, and 170 early-onset MM cases diagnosed before 55 years of age. Samples were identified and collected through nationwide efforts in France, Sweden, and Greece. We focused on rare germline protein truncating and likely deleterious missense variants in genes harboring variants in at least two families showing variant-disease segregation, and in additional index (≥2) and/or early-onset (≥2) cases. We identified likely pathogenic variants in ATM (N = 12), ANGPTL6 (N = 5), and FBXW9 (N = 6). Additionally, we detected variants in previously reported MM predisposition genes, including DIS3, EP300, and KDM1A. Our results represent the largest sequencing study on familial and early-onset MM to date, and further illuminate the constitutional genetic basis of MM.

Immunoglobulin G (IgG) is the main isotype of antibody in human blood. IgG consists of four subclasses (IgG1 to IgG4), encoded by separate constant region genes within the Ig heavy chain locus (IGH). Here, we report a genome-wide association study on blood IgG subclass levels. Across 4334 adults and 4571 individuals under 18 years, we discover ten new and identify four known variants at five loci influencing IgG subclass levels. These variants also affect the risk of asthma, autoimmune diseases, and blood traits. Seven variants map to the IGH locus, three to the Fcγ receptor (FCGR) locus, and two to the human leukocyte antigen (HLA) region, affecting the levels of all IgG subclasses. The most significant associations are observed between the G1m (f), G2m(n) and G3m(b*) allotypes, and IgG1, IgG2 and IgG3, respectively. Additionally, we describe selective associations with IgG4 at 16p11.2 (ITGAX) and 17q21.1 (IKZF3, ZPBP2, GSDMB, ORMDL3). Interestingly, the latter coincides with a highly pleiotropic signal where the allele associated with lower IgG4 levels protects against childhood asthma but predisposes to inflammatory bowel disease. Our results provide insight into the regulation of antibody-mediated immunity that can potentially be useful in the development of antibody based therapeutics.

Multiple myeloma (MM) is an incurable malignancy of plasma cells. Epidemiological studies indicate a substantial heritable component, but the underlying mechanisms remain unclear. Here, in a genome-wide association study totaling 10,906 cases and 366,221 controls, we identify 35 MM risk loci, 12 of which are novel. Through functional fine-mapping and Mendelian randomization, we uncover two causal mechanisms for inherited MM risk: longer telomeres; and elevated levels of B-cell maturation antigen (BCMA) and interleukin-5 receptor alpha (IL5RA) in plasma. The largest increase in BCMA and IL5RA levels is mediated by the risk variant rs34562254-A at TNFRSF13B. While individuals with loss-of-function variants in TNFRSF13B develop B-cell immunodeficiency, rs34562254-A exerts a gain-of-function effect, increasing MM risk through amplified B-cell responses. Our results represent an analysis of genetic MM predisposition, highlighting causal mechanisms contributing to MM development.