Spondylocarpotarsal synostosis syndrome (SCTS) is characterized by intervertebral fusions and fusion of the carpal and tarsal bones. Biallelic mutations in FLNB cause this condition in some families, whereas monoallelic variants in MYH3, encoding embryonic heavy chain myosin 3, have been implicated in dominantly inherited forms of the disorder. Here, five individuals without FLNB mutations from three families were hypothesized to be affected by recessive SCTS on account of sibling recurrence of the phenotype. Initial whole-exome sequencing (WES) showed that all five were heterozygous for one of two independent splice-site variants in MYH3. Despite evidence indicating that three of the five individuals shared two allelic haplotypes encompassing MYH3, no second variant could be located in the WES datasets. Subsequent genome sequencing of these three individuals demonstrated a variant altering a 5' UTR splice donor site (rs557849165 in MYH3) not represented by exome-capture platforms. When the cohort was expanded to 16 SCTS-affected individuals without FLNB mutations, nine had truncating mutations transmitted by unaffected parents, and six inherited the rs557849165 variant in trans, an observation at odds with the population allele frequency for this variant. The rs557849165 variant disrupts splicing in the 5' UTR but is still permissive of MYH3 translational initiation, albeit with reduced efficiency. Although some MYH3 variants cause dominant SCTS, these data indicate that others (notably truncating variants) do not, except in the context of compound heterozygosity for a second hypomorphic allele. These observations make genetic diagnosis challenging in the context of simplex presentations of the disorder.

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Gout is of particularly high prevalence in the Māori and Pacific (Polynesian) populations of Aotearoa New Zealand (NZ). Here, we investigated the contribution of common population-specific CNV to gout in the Aotearoa NZ Polynesian population. Microarray-generated genome-wide genotype data from Aotearoa NZ Polynesian individuals with (n = 1196) and without (n = 1249) gout were analyzed. Comparator population groups were 552 individuals of European ancestry and 1962 of Han Chinese ancestry. Levels of circulating MHC Class I Polypeptide-related sequence A (MICA) were measured by ELISA. Fifty-four CNV regions (CNVRs) appearing in at least 10 individuals were detected, of which seven common CNVRs were specific to or amplified in Polynesian people. A burden test of these seven revealed associations of insertion/deletion with gout (OR = 1.80 [1.01; 3.22], P = 0.046). Individually testing of the seven CNVRs for association with gout revealed nominal association of CNVR1 with gout in Western Polynesian (Chr6: 31.36–31.45 Mb, OR = 1.72 [1.03; 2.92], P = 0.04), CNVR6 in the meta-analyzed Polynesian sample sets (Chr1: 196.75–196.92 Mb, OR = 1.86 [1.16; 3.00], P = 0.01) and CNVR9 in Western Polynesian (Chr1: 189.35–189.54 Mb, OR = 2.75 [1.15; 7.13], P = 0.03). Analysis of European gout genetic association data demonstrated a signal of association at the CNVR1 locus that was an expression QTL for MICA. The most common CNVR (CNVR1) includes deletion of the MICA gene, encoding an immunomodulatory protein. Expression of MICA was reduced in the serum of individuals with the deletion. In summary, we provide evidence for the association of CNVR1 containing MICA with gout in Polynesian peoples, implicating class I MHC-mediated antigen presentation in gout.

Background Historically, geneticists have relied on genotyping arrays and imputation to study human genetic variation. However, an underrepresentation of diverse populations has resulted in arrays that poorly capture global genetic variation, and a lack of reference panels. This has contributed to deepening global health disparities. Whole genome sequencing (WGS) better captures genetic variation but remains prohibitively expensive. Thus, we explored WGS at “mid-pass” 1-7x coverage. Results Here, we developed and benchmarked methods for mid-pass sequencing. When applied to a population without an existing genomic reference panel, 4x mid-pass performed consistently well across ethnicities, with high recall (98%) and precision (97.5%). Conclusion Compared to array data imputed into 1000 Genomes, mid-pass performed better across all metrics and identified novel population-specific variants with potential disease relevance. We hope our work will reduce financial barriers for geneticists from underrepresented populations to characterize their genomes prior to biomedical genetic applications.

Objective The Māori and Pacific (Polynesian) population of Aotearoa New Zealand (NZ) has a high prevalence of gout. Our aim was to identify potentially functional missense genetic variants in candidate inflammatory genes amplified in frequency that may underlie the increased prevalence of gout in Polynesian populations. Methods A list of 712 inflammatory disease-related genes was generated. An in silico targeted exome set was extracted from whole genome sequencing data in people with gout of various ancestral groups (Polynesian, European, East Asian; n = 55, 780, 135, respectively) to identify Polynesian-amplified common missense variants (AF > 0.05). Candidate functional variants were tested for association with gout by multivariable-adjusted regression analysis in 2,528 individuals of Polynesian ancestry. Results We identified 26 variants common in the Polynesian population and uncommon in the European and East Asian populations. Three of the 26 population-specific variants were nominally associated with the risk of gout (rs1635712, KIAA0319, ORmeta = 1.28, Pmeta = 0.028; rs16869924, CLNK, ORmeta = 1.37, Pmeta = 0.0017; rs2070025, FGA, ORmeta = 1.34, Pmeta = 0.017). The CLNK variant, within the established SLC2A9 gout locus, was genetically-independent of the association signal at SLC2A9. Conclusion We provide nominal evidence for the existence of population-amplified genetic variants conferring risk of gout in Polynesian populations. Polymorphisms in CLNK have previously been associated with gout in other populations, supporting our evidence for association of this gene with gout.

Gout is a chronic disease of monosodium urate crystal deposition in the setting of hyperuricemia that typically presents with recurrent flares of acute inflammatory arthritis that occur due to innate immune response to deposited crystals. The molecular mechanism of the progression from hyperuricemia to clinical gout is poorly understood. Here we provide insights into this progression from a genetic study of 2.6 million people, including 120,282 people with gout. We detected 376 loci and 410 genetically independent signals (148 new loci in urate and gout). We identified 1,768 candidate genes with subsequent pathway analysis revealing urate metabolism, type 2 diabetes, and chromatin modification and structure as top pathways in gout. Genes located within or statistically linked to significant GWAS loci were prioitized for their potential to control the progression from hyperuricemia to gout. This identified strong candidate immune genes involved in epigenetic remodelling, cell osmolarity, and regulation of NLRP3-inflammasome activity. The genetic association signal at XDH, encoding the urate-producing enzyme xanthine oxidoreductase (XOR), co-localizes with genetic control of XDH expression, but only in the prostate. We demonstrate XOR activity and urate production in the mouse prostate, and use single-cell RNA sequence data to propose a model of urate reuptake, synthesis, and secretion by the prostate. The gout-associated loci were over-represented for genes implicated in clonal hematopoeiesis of indeterminate potential (CHIP) and Mendelian randomization analysis provided evidence for a causal role of CHIP in gout. In concert with implication of epigenomic regulators, this provides support for epigenomic remodelling as causal in gout. We provide new insights into the molecular pathogenesis of gout and identify an array of candidate genes for a role in the inflammatory process of gout.

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