Recent Genome-wide Association Studies Research Articles

Three Decades of Rust Surveys in the United States Reveal Drastic Virulence Changes in Oat Crown Rust.

To better understand how the pathogenicity of the oat crown rust pathogen Puccinia coronata f. sp. avenae (Pca) has changed in the United States, 30 years of United States Department of Agriculture (USDA) survey isolates (n = 5,456) tested on 30 to 40 differential lines were analyzed for overall and Pc-resistance-gene-specific virulence trends and correlations. Pca is incredibly pathologically diverse, with 88% of races represented by a single isolate. There are a slightly higher proportion of unique races from the Northern region of the United States, and for one fourth of the years, Northern region isolates were significantly more virulent than Southern isolates, which supports the idea that sexual recombination in this region is mediated by the alternate host as a major factor in creating new races. However, there is also support for regular isolate movement between North and South regions as isolates in the United States are steadily accumulating virulences at a rate of 0.35 virulences per year. Virulence significantly increased for 23 and decreased for four of the 40 differential lines. In the past few years, virulence has reached 90% or greater for 16 differential lines. There were also strong correlations in virulence for certain Pc genes that are likely identical, allelic, or target the same or closely linked pathogen effectors (e.g., Pc39, Pc55, and Pc71), and the results were largely in concordance with recent genome-wide association study (GWAS) effector studies using USDA isolate subsets. Understanding changes in Pca pathogenicity is essential for the responsible deployment and management of Pc resistance genes for sustainable and profitable oat production.

Biochemical and functional characterization of the p.A165T missense variant of mitochondrial amidoxime-reducing component 1

Recent genome-wide association studies have identified a missense variant p.A165T in mitochondrial amidoxime-reducing component 1 (mARC1) that is strongly associated with protection from all-cause cirrhosis and improved prognosis in nonalcoholic steatohepatitis (NASH). The precise mechanism of this protective effect is unknown. Substitution of alanine 165 with threonine is predicted to affect mARC1 protein stability and to have deleterious effects on its function. To investigate the mechanism, we have generated a knock-in mutant mARC1 A165T and a catalytically dead mutant C273A (as a control) in human hepatoma HepG2 cells, enabling characterization of protein subcellular distribution, stability, and biochemical functions of the mARC1 mutant protein expressed from its endogenous locus. Compared to wild-type (WT) mARC1, we found that the A165T mutant exhibits significant mislocalization outside of its traditional location anchored in the mitochondrial outer membrane and reduces protein stability, resulting in lower basal levels. We evaluated the involvement of the ubiquitin proteasome system in mARC1 A165T degradation and observed increased ubiquitination and faster degradation of the A165T variant. In addition, we have shown that HepG2 cells carrying the MTARC1 p.A165T variant exhibit lower N-reductive activity on exogenously-added amidoxime substrates in vitro. The data from these biochemical and functional assays suggest a mechanism by which the MTARC1 p.A165T variant abrogates enzyme function which may contribute to its protective effect in liver disease.

A functional schizophrenia-associated genetic variant near the TSNARE1 and ADGRB1 genes

Recent collaborative genome wide association studies (GWAS) have identified >200 independent loci contributing to risk for schizophrenia (SCZ). The genes closest to these loci have diverse functions, supporting the potential involvement of multiple relevant biological processes; yet there is no direct evidence that individual variants are functional or directly linked to specific genes. Nevertheless, overlap with certain epigenetic marks suggest that most GWAS-implicated variants are regulatory. Based on the strength of association with SCZ and the presence of regulatory epigenetic marks, we chose one such variant near TSNARE1 and ADGRB1, rs4129585, to test for functional potential and assay differences that may drive the pathogenicity of the risk allele. We observed that the variant-containing sequence drives reporter expression in relevant neuronal populations in zebrafish. Next, we introduced each allele into human induced pluripotent cells and differentiated 4 isogenic clones homozygous for the risk allele and 5 clones homozygous for the non-risk allele into neural precursor cells. Employing RNA-seq, we found that the two alleles yield significant transcriptional differences in the expression of 109 genes at FDR <0.05 and 259 genes at FDR <0.1. We demonstrate that these genes are highly interconnected in pathways enriched for synaptic proteins, axon guidance, and regulation of synapse assembly. Exploration of genes near rs4129585 suggests that this variant does not regulate TSNARE1 transcripts, as previously thought, but may regulate the neighboring ADGRB1, a regulator of synaptogenesis. Our results suggest that rs4129585 is a functional common variant that functions in specific pathways likely involved in SCZ risk.

Membrane-bound O-acyltransferase 7 (MBOAT7) shapes lysosomal lipid homeostasis and function to control alcohol-associated liver injury

Recent genome-wide association studies (GWAS) have identified a link between single-nucleotide polymorphisms (SNPs) near the MBOAT7 gene and advanced liver diseases. Specifically, the common MBOAT7 variant (rs641738) associated with reduced MBOAT7 expression is implicated in non-alcoholic fatty liver disease (NAFLD), alcohol-associated liver disease (ALD), and liver fibrosis. However, the precise mechanism underlying MBOAT7-driven liver disease progression remains elusive. Previously, we identified MBOAT7-driven acylation of lysophosphatidylinositol lipids as key mechanism suppressing the progression of NAFLD (Gwag et al., 2019). Here, we show that MBOAT7 loss of function promotes ALD via reorganization of lysosomal lipid homeostasis. Circulating levels of MBOAT7 metabolic products are significantly reduced in heavy drinkers compared to healthy controls. Hepatocyte- (Mboat7-HSKO), but not myeloid-specific (Mboat7-MSKO), deletion of Mboat7 exacerbates ethanol-induced liver injury. Lipidomic profiling reveals a reorganization of the hepatic lipidome in Mboat7-HSKO mice, characterized by increased endosomal/lysosomal lipids. Ethanol-exposed Mboat7-HSKO mice exhibit dysregulated autophagic flux and lysosomal biogenesis, associated with impaired transcription factor EB-mediated lysosomal biogenesis and autophagosome accumulation. This study provides mechanistic insights into how MBOAT7 influences ALD progression through dysregulation of lysosomal biogenesis and autophagic flux, highlighting hepatocyte-specific MBOAT7 loss as a key driver of ethanol-induced liver injury.

Membrane-bound O-acyltransferase 7 (MBOAT7) shapes lysosomal lipid homeostasis and function to control alcohol-associated liver injury.

Recent genome-wide association studies (GWAS) have identified a link between single-nucleotide polymorphisms (SNPs) near the MBOAT7 gene and advanced liver diseases. Specifically, the common MBOAT7 variant (rs641738) associated with reduced MBOAT7 expression is implicated in non-alcoholic fatty liver disease (NAFLD), alcohol-associated liver disease (ALD), and liver fibrosis. However, the precise mechanism underlying MBOAT7-driven liver disease progression remains elusive. Previously, we identified MBOAT7-driven acylation of lysophosphatidylinositol lipids as key mechanism suppressing the progression of NAFLD (Gwag et al., 2019). Here, we show that MBOAT7 loss of function promotes ALD via reorganization of lysosomal lipid homeostasis. Circulating levels of MBOAT7 metabolic products are significantly reduced in heavy drinkers compared to healthy controls. Hepatocyte- (Mboat7-HSKO), but not myeloid-specific (Mboat7-MSKO), deletion of Mboat7 exacerbates ethanol-induced liver injury. Lipidomic profiling reveals a reorganization of the hepatic lipidome in Mboat7-HSKO mice, characterized by increased endosomal/lysosomal lipids. Ethanol-exposed Mboat7-HSKO mice exhibit dysregulated autophagic flux and lysosomal biogenesis, associated with impaired transcription factor EB-mediated lysosomal biogenesis and autophagosome accumulation. This study provides mechanistic insights into how MBOAT7 influences ALD progression through dysregulation of lysosomal biogenesis and autophagic flux, highlighting hepatocyte-specific MBOAT7 loss as a key driver of ethanol-induced liver injury.

Hierarchical joint analysis of marginal summary statistics-Part I: Multipopulation fine mapping and credible set construction.

Recent advancement in genome-wide association studies (GWAS) comes from not only increasingly larger sample sizes but also the shift in focus towards underrepresented populations. Multipopulation GWAS increase power to detect novel risk variants and improve fine-mapping resolution by leveraging evidence and differences in linkage disequilibrium (LD) from diverse populations. Here, we expand upon our previous approach for single-population fine-mapping through Joint Analysis of Marginal SNP Effects (JAM) to a multipopulation analysis (mJAM). Under the assumption that true causal variants are common across studies, we implement a hierarchical model framework that conditions on multiple SNPs while explicitly incorporating the different LD structures across populations. The mJAM framework can be used to first select index variants using the mJAM likelihood with different feature selection approaches. In addition, we present a novel approach leveraging the ideas of mediation to construct credible sets for these index variants. Construction of such credible sets can be performed given any existing index variants. We illustrate the implementation of the mJAM likelihood through two implementations: mJAM-SuSiE (a Bayesian approach) and mJAM-Forward selection. Through simulation studies based on realistic effect sizes and levels of LD, we demonstrated that mJAM performs well for constructing concise credible sets that include the underlying causal variants. In real data examples taken from the most recent multipopulation prostate cancer GWAS, we showed several practical advantages of mJAM over other existing multipopulation methods.

Genetic variant of the sheep E2F8 gene and its associations with litter size

The economic efficiency of sheep breeding, aiming to enhance productivity, is a focal point for improvement of sheep breeding. Recent studies highlight the involvement of the Early Region 2 Binding Factor transcription factor 8 (E2F8) gene in female reproduction. Our group’s recent genome-wide association study (GWAS) emphasizes the potential impact of the E2F8 gene on prolificacy traits in Australian White sheep (AUW). Herein, the purpose of this study was to assess the correlation of the E2F8 gene with litter size in AUW sheep breed. This work encompassed 659 AUW sheep, subject to genotyping through PCR-based genotyping technology. Furthermore, the results of PCR-based genotyping showed significant associations between the P1-del-32bp bp InDel and the fourth and fifth parities litter size in AUW sheep; the litter size of those with genotype ID were superior compared to those with DD and II genotypes. Thus, these results indicate that the P1-del-32bp InDel within the E2F8 gene can be useful in marker-assisted selection (MAS) in sheep.

Causal associations of antioxidants with Alzheimer’s disease and cognitive function: a Mendelian randomisation study

BackgroundCirculating antioxidants are associated with a lower risk of Alzheimer’s disease (AD) in observational studies, suggesting potential target areas for intervention. However, whether the associations are causal remains unclear. Here,...

Genetic risk score based on obesity-related genes and progression in weight loss after bariatric surgery: a 60-month follow-up study

BackgroundObesity is a polygenic multifactorial disease. Recent genome-wide association studies have identified several common loci associated with obesity-related phenotypes. Bariatric surgery (BS) is the most effective long-term treatment for patients with severe obesity. The huge variability in BS outcomes between patients suggests a moderating effect of several factors, including the genetic architecture of the patients. ObjectiveTo examine the role of a genetic risk score (GRS) based on 7 polymorphisms in 5 obesity-candidate genes (FTO, MC4R, SIRT1, LEP, and LEPR) on weight loss after BS. SettingUniversity hospital in Spain. MethodsWe evaluated a cohort of 104 patients with severe obesity submitted to BS (Roux-en-Y gastric bypass or sleeve gastrectomy) followed up for >60 months (lost to follow-up, 19.23%). A GRS was calculated for each patient, considering the number of carried risk alleles for the analyzed genes. During the postoperative period, the percentage of excess weight loss total weight loss and changes in body mass index were evaluated. Generalized estimating equation models were used for the prospective analysis of the variation of these variables in relation to the GRS. ResultsThe longitudinal model showed a significant effect of the GRS on the percentage of excess weight loss (P = 1.5 × 10–5), percentage of total weight loss (P = 3.1 × 10–8), and change in body mass index (P = 7.8 × 10–16) over time. Individuals with a low GRS seemed to experience better outcomes at 24 and 60 months after surgery than those with a higher GRS. ConclusionThe use of the GRS in considering the polygenic nature of obesity seems to be a useful tool to better understand the outcome of patients with obesity after BS.

Does Thrombosis Play a Causal Role in Lacunar Stroke and Cerebral Small Vessel Disease?

The importance of thromboembolism in the pathogenesis of lacunar stroke (LS), resulting from cerebral small vessel disease (cSVD), is debated, and although antiplatelets are widely used in secondary prevention after LS, there is limited trial evidence from well-subtyped patients to support this approach. We sought to evaluate whether altered anticoagulation plays a causal role in LS and cSVD using 2-sample Mendelian randomization. From a recent genome-wide association study (n=81 190), we used 119 genetic variants associated with venous thrombosis at genome-wide significance (P<5*10-8) and with a linkage disequilibrium r2<0.001 as instrumental variables. We also used genetic associations with stroke from the GIGASTROKE consortium (62 100 ischemic stroke cases: 10 804 cardioembolic stroke, 6399 large-artery stroke, and 6811 LS). In view of the lower specificity for LS with the CT-based phenotyping mainly used in GIGASTROKE, we also used data from patients with magnetic resonance imaging-confirmed LS (n=3199). We also investigated associations with more chronic magnetic resonance imaging features of cSVD, namely, white matter hyperintensities (n=37 355) and diffusion tensor imaging metrics (n=36 533). Mendelian randomization analyses showed that genetic predisposition to venous thrombosis was associated with an increased odds of any ischemic stroke (odds ratio [OR], 1.19 [95% CI, 1.13-1.26]), cardioembolic stroke (OR, 1.32 [95% CI, 1.21-1.45]), and large-artery stroke (OR, 1.41 [95% CI, 1.26-1.57]) but not with LS (OR, 1.07 [95% CI, 0.99-1.17]) in GIGASTROKE. Similar results were found for magnetic resonance imaging-confirmed LS (OR, 0.94 [95% CI, 0.81-1.09]). Genetically predicted risk of venous thrombosis was not associated with imaging markers of cSVD. These findings suggest that altered thrombosis plays a role in the risk of cardioembolic and large-artery stroke but is not a causal risk factor for LS or imaging markers of cSVD. This raises the possibility that antithrombotic medication may be less effective in cSVD and underscores the necessity for further trials in well-subtyped cohorts with LS to evaluate the efficacy of different antithrombotic regimens in LS.

The Immunometabolic Gene N-Acetylglucosamine Kinase Is Uniquely Involved in the Heritability of Multiple Sclerosis Severity.

The clinical severity of multiple sclerosis (MS), an autoimmune disorder of the central nervous system, is thought to be determined by environmental and genetic factors that have not yet been identified. In a recent genome-wide association study (GWAS), a single nucleotide polymorphism (SNP), rs10191329, has been associated with MS severity in two large independent cohorts of patients. Different approaches were followed by the authors to prioritize the genes that are transcriptionally regulated by such an SNP. It was concluded that the identified SNP regulates a group of proximal genes involved in brain resilience and cognitive abilities rather than immunity. Here, by conducting an alternative strategy for gene prioritization, we reached the opposite conclusion. According to our re-analysis, the main target of rs10191329 is N-Acetylglucosamine Kinase (NAGK), a metabolic gene recently shown to exert major immune functions via the regulation of the nucleotide-binding oligomerization domain-containing protein 2 (NOD2) pathway. To gain more insights into the immunometabolic functions of NAGK, we analyzed the currently known list of NAGK protein partners. We observed that NAGK integrates a dense network of human proteins that are involved in glucose metabolism and are highly expressed by classical monocytes. Our findings hold potentially major implications for the understanding of MS pathophysiology.

Abstract 3020: The tumor suppressive role of methylthioadenosine phosphorylase in melanoma

Abstract Methylthioadenosine phosphorylase (MTAP) is an enzyme that is expressed in virtually all tissues but lost in many cancers. MTAP deficiency can be due to either deletion of the MTAP gene or methylation of the MTAP promoter. In normal cells, MTAP catalyzes the conversion of methylthioadenosine (MTA), produced during polyamine biosynthesis, to adenine and 5-methylthioribose-1-phosphate, which is subsequently converted to methionine. MTAP deficiency results in intracellular accumulation of MTA. Although recent genome wide association studies (GWAS) have associated the MTAP locus with melanoma risk, the molecular mechanisms linking MTAP loss to increased tumorigenesis are not yet fully understood. In this study, we hypothesized that loss of MTAP and the resulting accumulation of MTA would dysregulate microphthalmia transcription factor (MITF), a master transcriptional regulator of melanocytes that is also an amplified or mutated oncogene in melanoma. We identify a novel signaling mechanism in which MTA accumulation from MTAP deficiency aberrantly induces MITF expression via inhibition of the cAMP phosphodiesterase PDE4D3 in melanocytes. Inhibition of PKA abolishes this MITF induction, suggesting that the PKA pathway is hyperactivated upon MTAP deficiency. Downregulation of MTAP leads to increased proliferation of melanoma cells in vitro and increased melanoma tumor growth in vivo. We also show that MTAP deficient melanoma cells are more resistant to the BRAF inhibitor vemurafenib and observe MTAP downregulation in BRAF inhibitor resistant melanoma clinical specimens. Furthermore, MTAP downregulation via decreased expression and/or genomic loss corresponds to significantly worse outcomes in early-stage cutaneous melanomas from multiple datasets, thereby identifying a clinically important sub-category of “thin-lethal” tumors. Citation Format: Jennifer J. Hsiao, Pedro Andreu-Perez, Lajos V. Kemény, Miroslav Hejna, Jérémie Nsengimana, Jennifer Allouche, Abdullah Al Emran, D. Timothy Bishop, Göran B. Jönsson, Julia Newton-Bishop, Jun Song, David E. Fisher. The tumor suppressive role of methylthioadenosine phosphorylase in melanoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3020.

Abstract 7327: Investigating the cell-type specific regulation of IRF4 and its role in lung cancer via a lung cancer risk-associated pleiotropic variant

Abstract Although smoking is a main risk factor for lung cancer, genetic factors also contribute to the risk, as shown by over 50 genomic loci identified by genome-wide association studies (GWAS). A recent cross-ancestry lung cancer GWAS identified a common germline variant, rs12203592 (C/T), in chr6p25.3 as a new signal, and quantitative trait loci (eQTL) colocalization analysis using lung and blood tissues (GTEx v8) identified IRF4 as a likely target of rs12203592. rs12203592 has previously been linked with diverse traits, including pigmentation phenotypes, smoking cessation, lymphoblastic leukemia, melanoma, and other skin cancers. rs12203592 also appears to have varied allelic effects in different cell types. Namely, the lung cancer risk-associated T allele is correlated with higher IRF4 expression in lung tissue and blood cells (GTEx v8) but lower expression in primary melanocytes (n = 106; Zhang et al). Since previous studies established the melanocyte-specific allelic function of this SNP through lineage-specific transcription factors (TFs), we hypothesized that cell-type-specific TFs mediate the observed allelic effect in different tissue/cell types and further contribute to the unique role of IRF4 in lung tumorigenesis. To identify these potential cell-type-specific regulators, we performed mass spectrometry using the nuclear extracts from three cell lines representing lung, blood, and melanocyte lineage. The results nominated the NF-kB and ZEB protein families as the most prominent T-specific binders in the A549 lung cancer cell line, which was validated by electromobility shift assays. Consistent with these findings, tissue-based SNP-gene interaction analysis demonstrated that the mRNA levels of NF-kB and ZEB family members (4 of 7 genes) were correlated with IRF4 expression with a significant interaction with rs12203592 in GTEx lung tissue (P &amp;lt; 0.017), where the correlation is mainly observed with the T allele. Notably, the SNP interaction was less pronounced in whole blood or melanocytes, and the correlation of these TFs and IRF4 expression was mainly observed with the C allele in melanocytes. To begin to establish the roles of these TFs and IRF4 in lung tumorigenesis and given that IRF4 was shown to promote endogenous DNA damage and proliferation of lung-lineage cell lines, we will investigate the roles of NF-kB and ZEB in IRF4 regulation in these contexts using knockdown and overexpression of these TFs. To further investigate lung cancer-specific IRF4 function, we will identify potential targets of IRF4 among lung cancer-associated functional variants established through our previous studies. This data will help elucidate the context-specific roles of IRF4 in lung cancer development and provide clues to gene regulation in a pleiotropic GWAS locus. Citation Format: Alexander Kane, Jinhu Yin, Erping Long, James Feng, Cathrin Gräwe, Harsh Patel, Jinyoung Byun, Christopher Amos, Kevin Brown, Jun Xia, Michiel Vermeulen, Jiyeon Choi. Investigating the cell-type specific regulation of IRF4 and its role in lung cancer via a lung cancer risk-associated pleiotropic variant [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 7327.

Integrative regulation of hLMR1 by dietary and genetic factors in nonalcoholic fatty liver disease and hyperlipidemia.

Long non-coding RNA (lncRNA) genes represent a large class of transcripts that are widely expressed across species. As most human lncRNAs are non-conserved, we recently employed a unique humanized liver mouse model to study lncRNAs expressed in human livers. We identified a human hepatocyte-specific lncRNA, hLMR1 (human lncRNA metabolic regulator 1), which is induced by feeding and promotes hepatic cholesterol synthesis. Recent genome-wide association studies (GWAS) found that several single-nucleotide polymorphisms (SNPs) from the hLMR1 gene locus are associated with blood lipids and markers of liver damage. These results suggest that dietary and genetic factors may regulate hLMR1 to affect disease progression. In this study, we first screened for nutritional/hormonal factors and found that hLMR1 was robustly induced by insulin/glucose in cultured human hepatocytes, and this induction is dependent on the transcription factor SREBP1. We then tested if GWAS SNPs genetically linked to hLMR1 could regulate hLMR1 expression. We found that DNA sequences flanking rs9653945, a SNP from the last exon of the hLMR1 gene, functions as an enhancer that can be robustly activated by SREBP1c depending on the presence of rs9653945 major allele (G). We further performed CRISPR base editing in human HepG2 cells and found that rs9653945 major (G) to minor (A) allele modification resulted in blunted insulin/glucose-induced expression of hLMR1. Finally, we performed genotyping and gene expression analyses using a published human NAFLD RNA-seq dataset and found that individuals homozygous for rs9653945-G have a higher expression of hLMR1 and risk of NAFLD. Taken together, our data support a model that rs9653945-G predisposes individuals to insulin/glucose-induced hLMR1, contributing to the development of hyperlipidemia and NAFLD.

Epilepsy and childhood psychiatric disorders: a two-sample bidirectional Mendelian randomization study.

Observational studies have indicated that psychiatric disorders are the most common comorbidities in pediatric epilepsy. However, the existence and direction of a causal relationship between the two remains controversial. This study aims to investigate the association between common childhood psychiatric disorders and epilepsy using a two-sample, bidirectional Mendelian randomization (MR) approach. Genetic instruments were obtained from the most recent and largest genome-wide association studies (GWAS), including datasets for epilepsy (N_case = 29,994, N_control = 52,538), attention deficit hyperactivity disorder (ADHD) (N_case = 38,691, N_control = 186,843), autism spectrum disorder (ASD) (N_case = 18,381, N_control = 27,969), and Tourette syndrome (TS) (N_case = 4,819, N_control = 9488). MR analyses were conducted using the inverse variance weighted (IVW) method, weighted median method, and MR-Egger regression. No reliable evidence was found to suggest a causal effect of ADHD, ASD, or TS on epilepsy, nor was there any reliable evidence indicating that epilepsy increases the risk of these three psychiatric disorders. These findings remained consistent across various sensitivity analyses. Although observational studies have highlighted a high comorbidity rate between pediatric epilepsy and psychiatric disorders like ADHD and ASD, the MR analysis did not confirm a causal relationship between them. This suggests that previous studies might have been influenced by confounding biases or other biases, potentially overestimating the true relationship. A deeper understanding of the mechanisms underlying these comorbidities is crucial for refining the treatment of pediatric epilepsy.

Testing SIPA1L2 as a modifier of CMT1A using mouse models.

Charcot-Marie-Tooth disease type 1A (CMT1A) is a demyelinating peripheral neuropathy caused by the duplication of peripheral myelin protein 22 (PMP22), leading to muscle weakness and loss of sensation in the hands and feet. A recent case-only genome-wide association study of CMT1A patients conducted by the Inherited Neuropathy Consortium identified a strong association between strength of foot dorsiflexion and variants in signal induced proliferation associated 1 like 2 (SIPA1L2), indicating that it may be a genetic modifier of disease. To validate SIPA1L2 as a candidate modifier and to assess its potential as a therapeutic target, we engineered mice with deletion of exon 1 (including the start codon) of the Sipa1l2 gene and crossed them to the C3-PMP22 mouse model of CMT1A. Neuromuscular phenotyping showed that Sipa1l2 deletion in C3-PMP22 mice preserved muscular endurance assayed by inverted wire hang duration and changed femoral nerve axon morphometrics such as myelin thickness. Gene expression changes suggest involvement of Sipa1l2 in cholesterol biosynthesis, a pathway that is also implicated in C3-PMP22 mice. Although Sipa1l2 deletion did impact CMT1A-associated phenotypes, thereby validating a genetic interaction, the overall effect on neuropathy was mild.

Mendelian randomization study of the relationship between blood and urine biomarkers and schizophrenia in the UK Biobank cohort

BackgroundThe identification of suitable biomarkers is of crucial clinical importance for the early diagnosis of treatment-resistant schizophrenia (TRS). This study aims to comprehensively analyze the association between TRS and blood and urine biomarkers.MethodsCandidate TRS-related single nucleotide polymorphisms (SNPs) were obtained from a recent genome-wide association study. The UK Biobank cohort, comprising 376,807 subjects with blood and urine biomarker testing data, was used to calculate the polygenic risk score (PRS) for TRS. Pearson correlation analyses were performed to evaluate the correlation between TRS PRS and each of the biomarkers, using calculated TRS PRS as the instrumental variables. Bidirectional two-sample Mendelian randomization (MR) was used to assess potential causal associations between candidate biomarkers with TRS.ResultsHere we identify a significant association between TRS PRS and phosphate (r = 0.007, P = 1.96 × 10−4). Sex subgroup analyses identify seven and three candidate biomarkers associated with TRS PRS in male and female participants, respectively. For example, total protein and phosphate for males, creatinine and phosphate for females. Bidirectional two-sample MR analyses indicate that TRS is negatively associated with cholesterol (estimate = −0.363, P = 0.008). Conversely, TRS is positively associated with total protein (estimate = 0.137, P = 0.027), mean corpuscular volume (estimate = 0.032, P = 2.25 × 10−5), and mean corpuscular hemoglobin (estimate = 0.018, P = 0.007).ConclusionsOur findings provide insights into the roles of blood and urine biomarkers in the early detection and treatment of TRS.

Divergent role of Mitochondrial Amidoxime Reducing Component 1 (MARC1) in human and mouse.

Recent human genome-wide association studies have identified common missense variants in MARC1, p.Ala165Thr and p.Met187Lys, associated with lower hepatic fat, reduction in liver enzymes and protection from most causes of cirrhosis. Using an exome-wide association study we recapitulated earlier MARC1 p.Ala165Thr and p.Met187Lys findings in 540,000 individuals from five ancestry groups. We also discovered novel rare putative loss of function variants in MARC1 with a phenotype similar to MARC1 p.Ala165Thr/p.Met187Lys variants. In vitro studies of recombinant human MARC1 protein revealed Ala165Thr substitution causes protein instability and aberrant localization in hepatic cells, suggesting MARC1 inhibition or deletion may lead to hepatoprotection. Following this hypothesis, we generated Marc1 knockout mice and evaluated the effect of Marc1 deletion on liver phenotype. Unexpectedly, our study found that whole-body Marc1 deficiency in mouse is not protective against hepatic triglyceride accumulation, liver inflammation or fibrosis. In attempts to explain the lack of the observed phenotype, we discovered that Marc1 plays only a minor role in mouse liver while its paralogue Marc2 is the main Marc family enzyme in mice. Our findings highlight the major difference in MARC1 physiological function between human and mouse.

White blood cells and type 2 diabetes: A Mendelian randomization study.

Observational studies have demonstrated an association between white blood cells (WBC) subtypes and type 2 diabetes (T2D) risk. However, it is unknown whether this relationship is causal. We used Mendelian randomization (MR) to investigate the causal effect of WBC subtypes on T2D and glycemic traits. The summary data for neutrophil, lymphocyte, monocyte, eosinophil, and basophil counts were extracted from a recent genome-wide association study (n = 173,480). The DIAGRAM and MAGIC consortia offered summary data pertaining to T2D and glycemic characteristics, including fasting glucose (FG) (n = 133,010), glycosylated hemoglobin (HbA1c) (n = 46,368), and homeostatic model assessment-estimated insulin resistance (HOMA-IR) (n = 37,037). A series of MR analyses (univariable MR, multivariable MR, and reverse MR) were used to investigate the causal association of different WBC subtypes with T2D and glycemic traits. Using the inverse-variance weighted method, we found one standard deviation increases in genetically determined neutrophil [odd ratio (OR): 1.086, 95% confidence interval (CI): 0.877-1.345], lymphocyte [0.878 (0.766-1.006)], monocyte [1.010 (0.906-1.127)], eosinophil [0.995 (0.867-1.142)], and basophil [0.960 (0.763-1.207)] were not causally associated with T2D risk. These findings were consistent with the results of three pleiotropy robust methods (MR-Egger, weighted median, and mode-based estimator) and multivariable MR analyses. Reverse MR analysis provided no evidence for the reverse causation of T2D on WBC subtypes. The null causal effects of WBC subtypes on FG, HbA1c, and HOMA-IR were also identified. WBCs play no causal role in the development of insulin resistance and T2D. The observed association between these factors may be explained by residual confounding.

Unsupervised ensemble-based phenotyping enhances discoverability of genes related to left-ventricular morphology

Recent genome-wide association studies have successfully identified associations between genetic variants and simple cardiac morphological parameters derived from cardiac magnetic resonance images. However, the emergence of large databases, including genetic data linked to cardiac magnetic resonance facilitates the investigation of more nuanced patterns of cardiac shape variability than those studied so far. Here we propose a framework for gene discovery coined unsupervised phenotype ensembles. The unsupervised phenotype ensemble builds a redundant yet highly expressive representation by pooling a set of phenotypes learnt in an unsupervised manner, using deep learning models trained with different hyperparameters. These phenotypes are then analysed via genome-wide association studies, retaining only highly confident and stable associations across the ensemble. We applied our approach to the UK Biobank database to extract geometric features of the left ventricle from image-derived three-dimensional meshes. We demonstrate that our approach greatly improves the discoverability of genes that influence left ventricle shape, identifying 49 loci with study-wide significance and 25 with suggestive significance. We argue that our approach would enable more extensive discovery of gene associations with image-derived phenotypes for other organs or image modalities.