Systemic lupus erythematosus (SLE) is an autoimmune disease with marked gender and ethnic disparities. We report a large transancestral association study of SLE using Immunochip genotype data from 27,574 individuals of European (EA), African (AA) and Hispanic Amerindian (HA) ancestry. We identify 58 distinct non-HLA regions in EA, 9 in AA and 16 in HA (∼50% of these regions have multiple independent associations); these include 24 novel SLE regions (P<5 × 10−8), refined association signals in established regions, extended associations to additional ancestries, and a disentangled complex HLA multigenic effect. The risk allele count (genetic load) exhibits an accelerating pattern of SLE risk, leading us to posit a cumulative hit hypothesis for autoimmune disease. Comparing results across the three ancestries identifies both ancestry-dependent and ancestry-independent contributions to SLE risk. Our results are consistent with the unique and complex histories of the populations sampled, and collectively help clarify the genetic architecture and ethnic disparities in SLE.

Despite the availability of thousands of transit peptide (TP) primary sequences, the structural and/or physicochemical properties that determine TP recognition by components of the chloroplast translocon are not well understood. By combining a series of in vitro and in vivo experiments, we reveal that TP recognition is determined by sequence-independent interactions and vectorial-specific recognition domains. Using both native and reversed TPs for two well-studied precursors, small subunit of ribulose-1,5-bis-phosphate carboxylase/oxygenase, and ferredoxin, we exposed these two modes of recognition. Toc34 receptor (34-kD subunit of the translocon of the outer envelope) recognition in vitro, preprotein binding in organellar, precursor binding in vivo, and the recognition of TPs by the major stromal molecular motor Hsp70 are specific for the physicochemical properties of the TP. However, translocation in organellar and in vivo demonstrates strong specificity to recognition domain organization. This organization specificity correlates with the N-terminal placement of a strong Hsp70 recognition element. These results are discussed in light of how individual translocon components sequentially interact with the precursor during binding and translocation and helps explain the apparent lack of sequence conservation in chloroplast TPs.

Integrative multiomics analyses of adipose and muscle tissue transcripts, S, and genotypes revealed novel genetic regulatory mechanisms of insulin resistance in African Americans.

Relative to European Americans, type 2 diabetes (T2D) is more prevalent in African Americans (AAs). Genetic variation may modulate transcript abundance in insulin-responsive tissues and contribute to risk; yet published studies identifying expression quantitative trait loci (eQTLs) in African ancestry populations are restricted to blood cells. This study aims to develop a map of genetically regulated transcripts expressed in tissues important for glucose homeostasis in AAs, critical for identifying the genetic etiology of T2D and related traits. Quantitative measures of adipose and muscle gene expression, and genotypic data were integrated in 260 non-diabetic AAs to identify expression regulatory variants. Their roles in genetic susceptibility to T2D, and related metabolic phenotypes were evaluated by mining GWAS datasets. eQTL analysis identified 1,971 and 2,078 cis-eGenes in adipose and muscle, respectively. Cis-eQTLs for 885 transcripts including top cis-eGenes CHURC1, USMG5, and ERAP2, were identified in both tissues. 62.1% of top cis-eSNPs were within ±50kb of transcription start sites and cis-eGenes were enriched for mitochondrial transcripts. Mining GWAS databases revealed association of cis-eSNPs for more than 50 genes with T2D (e.g. PIK3C2A, RBMS1, UFSP1), gluco-metabolic phenotypes, (e.g. INPP5E, SNX17, ERAP2, FN3KRP), and obesity (e.g. POMC, CPEB4). Integration of GWAS meta-analysis data from AA cohorts revealed the most significant association for cis-eSNPs of ATP5SL and MCCC1 genes, with T2D and BMI, respectively. This study developed the first comprehensive map of adipose and muscle tissue eQTLs in AAs (publically accessible at https://mdsetaa.phs.wakehealth.edu) and identified genetically-regulated transcripts for delineating genetic causes of T2D, and related metabolic phenotypes.

Background: In African Americans (AAs), APOL1 G1 and G2 nephropathy risk variants are associated with non-diabetic end-stage kidney disease (ESKD) in an autosomal recessive pattern. Additional risk and protective genetic variants may be present near the APOL1 loci, since earlier age ESKD is observed in some AAs with one APOL1 renal-risk variant, and because the adjacent gene MYH9 is associated with nephropathy in populations lacking G1 and G2 variants. Methods: Re-sequencing was performed across a ∼275 kb region encompassing the APOL1-APOL4 and MYH9 genes in 154 AA cases with non-diabetic ESKD and 38 controls without nephropathy who were heterozygous for a single APOL1 G1 or G2 risk variant. Results: Sequencing identified 3,246 non-coding single nucleotide polymorphisms (SNPs), 55 coding SNPs, and 246 insertion/deletions. No new coding variations were identified. Eleven variants, including a rare APOL3 Gln⁵⁸Ter null variant (rs11089781), were genotyped in a replication panel of 1,571 AA ESKD cases and 1,334 controls. After adjusting for APOL1 G1 and G2 risk effects, these variations were not significantly associated with ESKD. In subjects with <2 APOL1 G1 and/or G2 alleles (849 cases; 1,139 controls), the APOL3 null variant was nominally associated with ESKD (recessive model, OR 1.81; p = 0.026); however, analysis in 807 AA cases and 634 controls from the Family Investigation of Nephropathy and Diabetes did not replicate this association. Conclusion: Additional common variants in the APOL1-APOL4-MYH9 region do not contribute significantly to ESKD risk beyond the APOL1 G1 and G2 alleles.

Background and Purpose Intracerebral hemorrhage (ICH) has a substantial genetic component. We performed a preliminary search for rare coding variants associated with ICH. Methods 757 cases and 795 controls were genotyped using the Illumina HumanExome Beadchip (Illumina, Inc. San Diego, CA, USA). Meta-analyses of single-variant and gene-based association were computed. Results No rare coding variants were associated with ICH. Three common variants on chromosome 19q13 at an established susceptibility locus, encompassing TOMM40, APOE, and APOC1 met genome-wide significance (p<5e-08). After adjusting for the APOE epsilon alleles, this locus was no longer convincingly associated with ICH. No gene reached genome-wide significance level in gene-based association testing. Conclusions While no coding variants of large effect were detected, this study further underscores a major challenge for the study of genetic susceptibility loci – large sample sizes are required for sufficient power except for loci with large effects.

This study investigated the association of copy number variants (CNVs) in type 2 diabetes (T2D) and T2D-associated end-stage renal disease (ESRD) in African Americans. Using the Affymetrix 6.0 array, >900,000 CNV probes spanning the genome were interrogated in 965 African Americans with T2D-ESRD and 1029 non-diabetic African American controls. Previously identified and novel CNVs were separately analyzed and were evaluated for insertion/deletion status and then used as predictors in a logistic regression model to test for association. One common CNV insertion on chromosome 1 was significantly associated with T2D-ESRD (p=6.17×10−5, OR=1.63) after multiple comparison correction. This CNV region encompasses the genes AMY2A and AMY2B, which encode amylase isoenzymes produced by the pancreas. Additional common and novel CNVs approaching significance with disease were also detected. These exploratory results require further replication but suggest the involvement of the AMY2A/AMY2B CNV in T2D and/or T2D-ESRD, and indicate that CNVs may contribute to susceptibility for these diseases.

Summary Family-based methods are a potentially powerful tool to identify trait-defining genetic variants in extended families, particularly when used to complement conventional association analysis. We utilized two-point linkage analysis and single variant association analysis to evaluate whole exome sequencing (WES) data from 1,205 Hispanic Americans (78 families) from the Insulin Resistance Atherosclerosis Family Study. WES identified 211,612 variants above the minor allele frequency threshold of ≥0.005. These variants were tested for linkage and/or association with 50 cardiometabolic traits after quality control checks. Two-point linkage analysis yielded 10,580,600 LOD scores with 1,148 LOD scores ≥3, 183 LOD scores ≥4, and 29 LOD scores ≥5. The maximal novel LOD score was 5.50 for rs2289043:T>C, in UNC5C with subcutaneous adipose tissue volume. Association analysis identified 13 variants attaining genome-wide significance (p<5×10-08), with the strongest association between rs651821:C>T in APOA5, and triglyceride levels (p=3.67×10-10). Overall, there was a 5.2-fold increase in the number of informative variants detected by WES compared to exome chip analysis in this population, nearly 30% of which were novel variants relative to dbSNP build 138. Thus, integration of results from two-point linkage and single-variant association analysis from WES data enabled identification of novel signals potentially contributing to cardiometabolic traits.