Sandford, Richard

ABSTRACT Background Primary Biliary Cholangitis (PBC) is an autoimmune cholangiopathy with polygenic architecture and unknown aetiology. Evidence links Neanderthal‐derived genetic variants to autoimmune conditions; however, their contribution to PBC susceptibility remains unexplored. Objective We investigate whether archaic alleles influence PBC risk. Design Genotype data from four PBC cohorts were analysed: CANUK (4615 cases, 9233 controls), OLD IT (444 cases, 901 controls), NEW IT (255 cases, 579 controls) and MAYO (891 cases, 621 controls). Association testing with 235 592 Neanderthal Informative Markers (NIMs) was performed, adjusting for population stratification. Heritability was estimated using RHE‐mc and temporal haplotype dynamics were assessed using ancient DNA data from Europe and Asia. Results A Neanderthal‐derived variant in TNPO3 (rs12531711), previously reported by Cordell et al. showed strong association in CANUK ( p = 2.04 × 10 −26 ) and replicated across all validation cohorts. This variant functions as an eQTL, upregulating IRF5 and downregulating TNPO3 in blood. It is rare in African populations but common both in Europeans and Asians. Temporal analysis of the haplotype carrying rs12531711 revealed frequency increased substantially during the Bronze Age (5000–3000 BP), rising from 2.0% to 7.7% in Europe and 3.4% to 17.4% in Asia, before stabilizing. Despite this strong single‐variant association, the heritability explained by NIMs was not significantly different from that of non‐NIM variants. Conclusion A Neanderthal‐derived variant contributes to PBC risk and its frequency increased in the Bronze Age, possibly due to pathogen‐driven selection. Archaic introgression overall has limited influence on PBC heritability. Functional studies are needed to elucidate the role of rs12531711.

Background For many patients with kidney failure, the cause and underlying defect remain unknown. Here, we describe a novel mechanism of a genetic order characterized by renal Fanconi syndrome and kidney failure. Methods We clinically and genetically characterized members of five families with autosomal dominant renal Fanconi syndrome and kidney failure. We performed genome-wide linkage analysis, sequencing, and expression studies in kidney biopsy specimens and renal cells along with knockout mouse studies and evaluations of mitochondrial morphology and function. Structural studies examined the effects of recognized mutations. Results The renal disease in these patients resulted from monoallelic mutations in the gene encoding glycine amidinotransferase (GATM), a renal proximal tubular enzyme in the creatine biosynthetic pathway that is otherwise associated with a recessive disorder of creatine deficiency. In silico analysis showed that the particular GATM mutations, identified in 28 members of the five families, create an additional interaction interface within the GATM protein and likely cause the linear aggregation of GATM observed in patient biopsy specimens and cultured proximal tubule cells. GATM aggregates-containing mitochondria were elongated and associated with increased ROS production, activation of the NLRP3 inflammasome, enhanced expression of the profibrotic cytokine IL-18, and increased cell death. Conclusions In this novel genetic disorder, fully penetrant heterozygous missense mutations in GATM trigger intramitochondrial fibrillary deposition of GATM and lead to elongated and abnormal mitochondria. We speculate that this renal proximal tubular mitochondrial pathology initiates a response from the inflammasome, with subsequent development of kidney fibrosis.

Objective Primary sclerosing cholangitis (PSC) is a genetically complex, inflammatory bile duct disease of largely unknown aetiology often leading to liver transplantation or death. Little is known about the genetic contribution to the severity and progression of PSC. The aim of this study is to identify genetic variants associated with PSC disease progression and development of complications. Design We collected standardised PSC subphenotypes in a large cohort of 3402 patients with PSC. After quality control, we combined 130 422 single nucleotide polymorphisms of all patients—obtained using the Illumina immunochip—with their disease subphenotypes. Using logistic regression and Cox proportional hazards models, we identified genetic variants associated with binary and time-to-event PSC subphenotypes. Results We identified genetic variant rs853974 to be associated with liver transplant-free survival (p=6.07×10–9). Kaplan-Meier survival analysis showed a 50.9% (95% CI 41.5% to 59.5%) transplant-free survival for homozygous AA allele carriers of rs853974 compared with 72.8% (95% CI 69.6% to 75.7%) for GG carriers at 10 years after PSC diagnosis. For the candidate gene in the region, RSPO3, we demonstrated expression in key liver-resident effector cells, such as human and murine cholangiocytes and human hepatic stellate cells. Conclusion We present a large international PSC cohort, and report genetic loci associated with PSC disease progression. For liver transplant-free survival, we identified a genome-wide significant signal and demonstrated expression of the candidate gene RSPO3 in key liver-resident effector cells. This warrants further assessments of the role of this potential key PSC modifier gene.