Mendelian Model Research Articles

Multi-omics combined to investigate potential druggable therapeutic targets for stroke: A systematic Mendelian randomization study and transcriptome verification

ObjectiveStroke is a highly prevalent and disabling disease whose disease mechanisms are not fully understood. The discovery of disease-associated proteins with genetic evidence of pathogenicity provides an opportunity to identify new therapeutic targets. MethodWe examined the observed and causal associations of thousands of plasma and inflammatory proteins that were measured using affinity-based proteomic assays. First, we pooled >3000 relevant proteins using a fixed-effects meta-analysis of 2 population-based studies involving 48,383 participants, then investigated the causal effects of stroke and its subtype-associated proteins by forward Mendelian randomization using cis-protein quantitative locus genetic tools identified from genome-wide association studies of these >48,000 individuals. To improve the accuracy of causal estimation, we implemented a systematic Mendelian randomization model that accounts for cascading imbalances between instruments and tested the robustness of causal estimation through multi-method analyses. To further validate the hypothesis that ginsenoside Rg1 monomer acts on the five protein targets screened for drug-targeted regulation, we conducted a comparative analysis of the mRNA (gene) expression levels of a limited number of genes in the brain tissues of different groups of SD rats. The druggability of the candidate proteins was investigated and the mechanism of action and potential targeting side effects were explored by Phenome-wide MR. ResultsSix circulating proteins were identified to have a significant genetic association with stroke (PFDR < 0.05). For example, in patients with cardioembolic stroke, higher genetically predicted APRT was associated with a lower risk of cardioembolic stroke (ORivw [95 % CI] = 0.641 [0.517, 0.795]; P = 5.25 × 10−5, ORSMR [95 % CI] = 0.572, [0.397, 0.825], PSMR = 0.003). Mediation analyses suggested that atrial fibrillation, angina pectoris, and heart failure may mediate the association of CD40L, LIFR, and UPA with stroke. Molecular docking revealed promising interactions between the identified proteins and glycosides. Transcriptomic sequencing in animal models indicated that ginsenoside Rg1 may act through APRT, IL15RA, and VSIR pathways, with APRT showing significant variability in mRNA sequencing expression. Phenome-wide MR of the six target proteins showed an overwhelming predominance of PFDR > 0.05, indicating less toxicity. ConclusionsThe present study provides genetic evidence to support the potential efficacy of targeting the three druggable protein targets for the treatment of stroke. This is achieved by triangulating population genomic and proteomic data. Furthermore, the study validates the pathway mechanisms by which APRT, IL15RA, and VSIR dock ginsenoside Rg1 in animal models. This will help to prioritize stroke drug development.

Exploring the Genotype-Phenotype Correlations in a Child with Inherited Seizure and Thrombocytopenia by Digenic Network Analysis.

Understanding the correlation between genotype and phenotype remains challenging for modern genetics. Digenic network analysis may provide useful models for understanding complex phenotypes that traditional Mendelian monogenic models cannot explain. Clinical data, whole exome sequencing data, in silico, and machine learning analysis were combined to construct a digenic network that may help unveil the complex genotype-phenotype correlations in a child presenting with inherited seizures and thrombocytopenia. The proband inherited a maternal heterozygous missense variant in SCN1A (NM_001165963.4:c.2722G>A) and a paternal heterozygous missense variant in MYH9 (NM_002473.6:c.3323A>C). In silico analysis showed that these two variants may be pathogenic for inherited seizures and thrombocytopenia in the proband. Moreover, focusing on 230 epilepsy-associated genes and 35 thrombopoiesis genes, variant call format data of the proband were analyzed using machine learning tools (VarCoPP 2.0) and Digenic Effect predictor. A digenic network was constructed, and SCN1A and MYH9 were found to be core genes in the network. Further analysis showed that MYH9 might be a modifier of SCN1A, and the variant in MYH9 might not only influence the severity of SCN1A-related seizure but also lead to thrombocytopenia in the bone marrow. In addition, another eight variants might also be co-factors that account for the proband's complex phenotypes. Our data show that as a supplement to the traditional Mendelian monogenic model, digenic network analysis may provide reasonable models for the explanation of complex genotype-phenotype correlations.

Exome sequencing identifies novel genes underlying primary congenital glaucoma in the National Birth Defects Prevention Study.

Primary congenital glaucoma (PCG) affects approximately 1 in 10,000 live born infants in the United States (U.S.). PCG has a autosomal recessive inheritance pattern, and variable expressivity and reduced penetrance have been reported. Likely causal variants in the most commonly mutated gene, CYP1B1, are less prevalent in the U.S., suggesting that alternative genes may contribute to the condition. This study utilized exome sequencing to investigate the genetic architecture of PCG in the U.S. and to identify novel genes and variants. We studied 37 family trios where infants had PCG and were part of the National Birth Defects Prevention Study (births 1997-2011), a U.S. multicenter study of birth defects. Samples underwent exome sequencing and sequence reads were aligned to the human reference sample (NCBI build 37/hg19). Variant filtration was conducted under de novo and Mendelian inheritance models using GEMINI. Among candidate variants, CYP1B1 was most represented (five trios, 13.5%). Twelve probands (32%) had potentially pathogenic variants in other genes not previously linked to PCG but important in eye development and/or to underlie Mendelian conditions with potential phenotypic overlap (e.g., CRYBB2, RXRA, GLI2). Variation in the genes identified in this population-based study may help to further explain the genetics of PCG.

Exploring Putative Causal Associations between Diet and Periodontal Disease Susceptibility.

Dietary factors may play an important role in periodontal health. However, current evidence from observational studies remains inconclusive. This study aimed to investigate the causal relationships between dietary exposures and periodontal disease risks using Mendelian randomization analysis. Large-scale genome-wide association study summary statistics for 20 dietary factors were obtained from the MRC-IEU consortium. Multivariable and univariable 2-sample Mendelian randomization analyses were performed to assess the causal effects of each dietary exposure on 6 periodontal outcomes, including gingivitis and periodontitis. Genetically predicted higher dried fruit intake was significantly associated with reduced risks of acute gingivitis (odds ratio [OR]: 0.02; 95% confidence interval [CI]: 0.00-0.42; P = 0.01) and bleeding gums (OR: 0.96; 95% CI: 0.93-0.99; P = 0.01). Higher fresh fruit and water intake showed protective effects against chronic gingivitis (OR: 0.18; 95% CI: 0.04-0.91; P = 0.04 and OR: 0.15; 95% CI: 0.04-0.53; P = 0.00) and bleeding gums (OR: 0.95; 95% CI: 0.92-0.981; P = 0.00 and OR: 0.98; 95% CI: 0.96-0.99; P = 0.02). Alcohol intake frequency and processed meat intake were risk factors for bleeding gums (OR: 1.01; 95% CI: 1.00-1.02; P = 0.01 and OR: 1.05; 95% CI: 1.01-1.08; P = 0.00) and painful gums (OR: 1.01; 95% CI: 1.00-1.01; P = 0.00 and OR: 1.02; 95% CI: 1.01-1.03; P = 0.00). Most of the causal relationships between genetic predisposition to the specified dietary factors and periodontal diseases remained statistically significant (P < 0.05) after adjusting for genetic risks associated with dentures, smoking, and type 2 diabetes in multivariable Mendelian randomization models. The findings suggest potential protective effects of higher fruit and water intake against gingivitis and other periodontal problems, while alcohol and processed meat intake may increase the risks of periodontal disease. Our study provides preliminary causal evidence on the effects of diet on periodontal health and could inform prevention strategies targeting dietary habits to improve oral health. This study suggests that fruit and water intake may protect against periodontal disease, while alcohol and processed meats increase risk, informing dietary guidelines to improve oral health.

Causal effect of gut microbiota and diabetic nephropathy: a Mendelian randomization study

BackgroundThe interaction of dysbiosis of gut microbiota (GM) with diabetic nephropathy (DN) drew our attention and a better understanding of GM on DN might provide potential therapeutic approaches. However, the exact causal effect of GM on DN remains unknown.MethodsWe applied two-sample Mendelian Randomization (MR) analysis, including inverse variance weighted (IVW), MR-Egger methods, etc., to screen the significant bacterial taxa based on the GWAS data. Sensitivity analysis was conducted to assess the robustness of MR results. To identify the most critical factor on DN, Mendelian randomization-Bayesian model averaging (MR-BMA) method was utilized. Then, whether the reverse causality existed was verified by reverse MR analysis. Finally, transcriptome MR analysis was performed to investigate the possible mechanism of GM on DN.ResultsAt locus-wide significance levels, the results of IVW suggested that order Bacteroidales (odds ratio (OR) = 1.412, 95% confidence interval (CI): 1.025–1.945, P = 0.035), genus Akkermansia (OR = 1.449, 95% CI: 1.120–1.875, P = 0.005), genus Coprococcus 1 (OR = 1.328, 95% CI: 1.066–1.793, P = 0.015), genus Marvinbryantia (OR = 1.353, 95% CI: 1.037–1.777, P = 0.030) and genus Parasutterella (OR = 1.276, 95% CI: 1.022–1.593, P = 0.032) were risk factors for DN. Reversely, genus Eubacterium ventriosum (OR = 0.756, 95% CI: 0.594–0.963, P = 0.023), genus Ruminococcus gauvreauii (OR = 0.663, 95% CI: 0.506–0.870, P = 0.003) and genus Erysipelotrichaceae (UCG003) (OR = 0.801, 95% CI: 0.644–0.997, P = 0.047) were negatively associated with the risk of DN. Among these taxa, genus Ruminococcus gauvreauii played a crucial role in DN. No significant heterogeneity or pleiotropy in the MR result was found. Mapped genes (FDR < 0.05) related to GM had causal effects on DN, while FCGR2B and VNN2 might be potential therapeutic targets.ConclusionsThis work provided new evidence for the causal effect of GM on DN occurrence and potential biomarkers for DN. The significant bacterial taxa in our study provided new insights for the ‘gut-kidney’ axis, as well as unconventional prevention and treatment strategies for DN.

‘Almost nothing is firmly established’: A History of Heredity and Genetics in Mental Health Science

Background For more than a century, scientists have tried to find the key to causation of mental ill health in heredity and genetics. The difficulty of finding clear and actionable answers in our genes has not stopped them looking. This history offers important context to understanding mental health science today. Methods This article explores the main themes in research on genetics and inheritance in psychiatry from the second half of the nineteenth century to the present day, to address the question: what is the history of genetics as a causative explanation in mental health science? We take a critical historical approach to the literature, interrogating primary and secondary material for the light it brings to the research question, while considering the social and historical context. Results We begin with the statistics gathered in asylums and used to ‘prove’ the importance of heredity in mental ill health. We then move through early twentieth century Mendelian models of mental inheritance, the eugenics movement, the influence of social psychiatry, new classifications and techniques of the postwar era, the Human Genome Project and Genome Wide Association Studies (GWAS) and epigenetics. Setting these themes in historical context shows that this research was often popular because of wider social, political and cultural issues, which impacted the views of scientists just as they did those of policymakers, journalists and the general public. Conclusions We argue that attempting to unpick this complex history is essential to the modern ethics of mental health and genetics, as well as helping to focus our efforts to better understand causation in mental ill-health.

Mendelian Randomization Analysis of the Causal Effect of Cigarette Smoking on Hospital Costs.

Knowledge of the impact of smoking on health care costs is important for establishing the external effects of smoking and for evaluating policies intended to modify this behavior. Conventional analysis of this association is difficult because of omitted variable bias, reverse causality, and measurement error. We approached these challenges using a Mendelian Randomization study design; genetic variants associated with smoking behaviors were used in instrumental variables models with inpatient hospital costs (calculated from electronic health records) as the outcome. We undertook genome-wide association studies to identify genetic variants associated with smoking initiation and a composite smoking index (reflecting cumulative health impacts of smoking) on up to 300 045 individuals (mean age: 57 years at baseline, range 39-72 years) in the UK Biobank. We followed individuals up for a mean of 6 years. Genetic liability to initiate smoking (ever vs. never smoking) was estimated to increase mean per-patient annual inpatient hospital costs by £477 (95% confidence interval (CI): £187 to £766). A one-unit change in genetic liability to the composite smoking index (range: 0-4.0) increased inpatient hospital costs by £204 (95% CI: £105 to £303) per unit increase in this index. There was some evidence that the composite smoking index causal models violated the instrumental variable assumptions, and all Mendelian Randomization models were estimated with considerable uncertainty. Models conditioning on risk tolerance were not robust to weak instrument bias. Our findings have implications for the potential cost-effectiveness of smoking interventions. We report the first Mendelian Randomization analysis of the causal effect of smoking on health care costs. Using two smoking phenotypes, we identified substantial impacts of smoking on inpatient hospital costs, although the causal models were associated with considerable uncertainty. These results could be used alongside other evidence on the impact of smoking to evaluate the cost-effectiveness of antismoking interventions and to understand the scale of externalities associated with this behavior.

Luxenburger's 1939 Essay on "Schizophrenia and its Hereditary Circle".

In 1939, Hans Luxenburger published a detailed overview of the current status of schizophrenia genetics research, reaching six major conclusions. First, schizophrenia is clearly a hereditary disease. Second, however, schizophrenia is not the hereditary trait itself but rather the consequences of a slowly developing biological progress, the nature of which remains entirely unknown. Third, the full manifestation of the disorder requires certain environmental influences that must come into play. In around 30% of cases, the environment can inhibit hereditary factors so that the predisposition does not manifest in schizophrenia. Fourth, the mode of inheritance of schizophrenia remains unknown, although recessivity is more likely than dominance and monomerism is more likely than polymerism. Fifth, current evidence suggests that schizophrenia is likely etiologically homogenous. Sixth, schizophrenia is part of a hereditary circle that includes "normal" variants of the human personality (schizothymia), a pathological version of this dimension (schizoidia), and other schizophrenia-like delusional syndromes. Luxenburger is skeptical of efforts to clarify further Mendelian transmission models in the absence of pathophysiological markers because schizophrenia cannot serve as a typical phenotype for genetic analysis. By contrast, he strongly supports empirical work on hereditary prognosis, which does not depend on assumptions about any particular phenotype-genotype relationship.

Diverse genetic basis of Vip3Aa resistance in five independent field-derived strains of Helicoverpa zea in the US.

Practical resistance of Helicoverpa zea to Cry proteins has become widespread in the US, making Vip3Aa the only effective Bacillus thuringiensis (Bt) protein for controlling this pest. Understanding the genetic basis of Vip3Aa resistance in H. zea is essential in sustaining the long-term efficacy of Vip3Aa. The objectives of this study were to characterize the inheritance of Vip3Aa resistance in four distinct field-derived H. zea strains (M1-RR, AC4-RR, R2-RR and R15-RR), and to test for shared genetic basis among these strains and a previously characterized Texas resistant strain (LT#70-RR). Maternal effects and sex linkage were absent, and the effective dominance level (DML) was 0.0 across Vip3Aa39 concentrations ranging from 1.0 to 31.6 μg cm-2, in all H. zea resistant strains. Mendelian monogenic model tests indicated that Vip3Aa resistance in each of the four strains was controlled by a single gene. However, interstrain complementation tests indicated that three distinct genetic loci are involved in Vip3Aa resistance in the five resistant H. zea strains: one shared by M1-RR and LT#70-RR; another shared by R2-RR and R15-RR; and a distinct one for AC4-RR. Results of this study indicate that Vip3Aa resistance in all H. zea strains was controlled by a single, recessive and autosomal gene. However, there were three distinct genetic loci associated with Vip3Aa resistance in the five resistant H. zea strains. The information generated from this study is valuable for exploring mechanisms of Vip3Aa resistance, monitoring the evolution of Vip3Aa resistance, and devising effective strategies for managing Vip3Aa resistance in H. zea. © 2024 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Causal Effects of Blood Metabolites and Obstructive Sleep Apnea: A Mendelian Randomization Study.

Obstructive sleep apnea (OSA) is one of the most common forms of sleep-disordered breathing. Studies have shown that certain changes in metabolism play an important role in the pathophysiology of OSA. However, the causal relationship between these metabolites and OSA remains unclear. We use a mendelian randomization (MR) approach to investigate the causal associations between the genetic liability to metabolites and OSA. We performed a 2-sample inverse-variance weighted mendelian randomization analysis to evaluate the causal effects of genetically determined 486 metabolites on OSA. Multiple sensitivity analyses were performed to assess pleiotropy. We used multivariate mendelian randomization analyses to assess confounding factors and mendelian randomization Bayesian model averaging to rank the significant biomarkers by their genetic evidence. We also conducted a metabolic pathway analysis to identify potential metabolic pathways. We identified 14 known serum metabolites (8 risk factors and 6 protective factors) and 12 unknown serum metabolites associated with OSA. These 14 known metabolites included 8 lipids( 1-arachidonoylglycerophosphoethanolamine, Tetradecanedioate, Epiandrosteronesulfate, Acetylca Glycerol3-phosphate, 3-dehydrocarnitine, Margarate17:0, Docosapentaenoaten3;22:5n3), 3 Aminoacids (Isovalerylcarnitine,3-methyl-2-oxobutyrate,Methionine), 2 Cofactors and vitamins [Bilirubin(E,ZorZ,E),X-11593--O-methylascorbate], 1Carbohydrate(1,6-anhydroglucose). We also identified several metabolic pathways that involved in the pathogenesis of OSA. MR (mendelian randomization) approach was performed to identify 6 protective factors and 12 risk factors for OSA in the present study. 3-Dehydrocarnitine was the most significant risk factors for OSA. Our study also confirmed several significant metabolic pathways that were involved in the pathogenesis of OSA. Valine, leucine and isoleucine biosynthesis metabolic pathways were the most significant metabolic pathways that were involved in the pathogenesis of OSA.

Human Genetics of Hypoplastic Left Heart Syndrome.

Hypoplastic left heart syndrome (HLHS) is a severe congenital cardiovascular malformation characterized by hypoplasia of the left ventricle, aorta, and other structures on the left side of the heart. The pathologic definition includes atresia or stenosis of both the aortic and mitral valves. Despite considerable progress in clinical and surgical management of HLHS, mortality and morbidity remain concerns. One barrier to progress in HLHS management is poor understanding of its cause. Several lines of evidence point to genetic origins of HLHS. First, some HLHS cases have been associated with cytogenetic abnormalities (e.g., Turner syndrome). Second, studies of family clustering of HLHS and related cardiovascular malformations have determined HLHS is heritable. Third, genomic regions that encode genes influencing the inheritance of HLHS have been identified. Taken together, these diverse studies provide strong evidence for genetic origins of HLHS and related cardiac phenotypes. However, using simple Mendelian inheritance models, identification of single genetic variants that "cause" HLHS has remained elusive, and in most cases, the genetic cause remains unknown. These results suggest that HLHS inheritance is complex rather than simple. The implication of this conclusion is that researchers must move beyond the expectation that a single disease-causing variant can be found. Utilization of complex models to analyze high-throughput genetic data requires careful consideration of study design.

'Almost nothing is firmly established': A History of Heredity and Genetics in Mental Health Science.

For more than a century, scientists have tried to find the key to causation of mental ill health in heredity and genetics. The difficulty of finding clear and actionable answers in our genes has not stopped them looking. This history offers important context to understanding mental health science today. This article explores the main themes in research on genetics and inheritance in psychiatry from the second half of the nineteenth century to the present day, to address the question: what is the history of genetics as a causative explanation in mental health science? We take a critical historical approach to the literature, interrogating primary and secondary material for the light it brings to the research question, while considering the social and historical context. We begin with the statistics gathered in asylums and used to 'prove' the importance of heredity in mental ill health. We then move through early twentieth century Mendelian models of mental inheritance, the eugenics movement, the influence of social psychiatry, new classifications and techniques of the postwar era, the Human Genome Project and Genome Wide Association Studies (GWAS) and epigenetics. Setting these themes in historical context shows that this research was often popular because of wider social, political and cultural issues, which impacted the views of scientists just as they did those of policymakers, journalists and the general public. We argue that attempting to unpick this complex history is essential to the modern ethics of mental health and genetics, as well as helping to focus our efforts to better understand causation in mental ill-health.For a succinct timeline of the history of psychiatric genetics, alongside the history of other proposed causes for mental ill-health, visit: https://historyofcauses.co.uk/.

Genetic analyses identify brain imaging-derived phenotypes associated with the risk of amyotrophic lateral sclerosis.

Brain imaging-derived phenotypes have been suggested to be associated with amyotrophic lateral sclerosis in observational studies, but whether these associations are causal remains unclear. We aimed to assess the potential bidirectional causal associations between imaging-derived phenotypes and amyotrophic lateral sclerosis using bidirectional 2-sample Mendelian randomization analyses. Summary statistics for 469 imaging-derived phenotypes (33,224 individuals) and amyotrophic lateral sclerosis (20,806 cases and 59,804 controls) were obtained from 2 large-scale genome-wide association studies of European ancestry. We used the inverse-variance weighted Mendelian randomization method in the main analysis to assess the bidirectional associations between imaging-derived phenotypes and amyotrophic lateral sclerosis, followed by several sensitivity analyses for robustness validation. In the forward Mendelian randomization analyses, we found that genetically determined high orientation dispersion index in the right cerebral peduncle was associated with the increased risk of amyotrophic lateral sclerosis (odds ratio = 1.30, 95% confidence interval = 1.16-1.45, P = 2.26 × 10-6). In addition, the reverse Mendelian randomization analysis indicated that amyotrophic lateral sclerosis had no effect on 469 imaging-derived phenotypes. Mendelian randomization-Egger regression analysis showed no directional pleiotropy for the association between high orientation dispersion index in the right cerebral peduncle and amyotrophic lateral sclerosis, and sensitivity analyses with different Mendelian randomization models further confirmed these findings. The present systematic bidirectional Mendelian randomization analysis showed that high orientation dispersion index in the right cerebral peduncle might be the potential causal mediator of amyotrophic lateral sclerosis, which may provide predictive guidance for the prevention of amyotrophic lateral sclerosis. Further studies are warranted to replicate our findings and clarify the underlying mechanisms.

Bruno Schulz's 1936 book "Methodology of medical genetic research particularly with regard to psychiatry".

In 1936, Bruno Schulz published the first detailed, book-length review of the methodology of psychiatric genetic research, based on his experiences at the German Research Institute of Psychiatry. Emphasis is placed on proper selection of relatives and the ascertainment corrections required for Mendelian transmission models. Twin studies are considered as is the impact of reduced fertility on patterns of risk. For the field work, Schulz emphasizes the importance of trust-building, confidentiality, collateral informants, and the use of medical and other administrative records, all ideally stored in personal files. Several methods of age-correction are reviewed. Schulz provides detailed algebraic treatments of these and other problems, including tests for etiologic homogeneity, with worked examples. He emphasizes two fundamental concerns in psychiatric genetics research: (i) its inter-dependency with the optimal diagnostic boundaries, which are rarely known and (ii) the genetic homogeneity of clinical samples. Given these problems, he is pessimistic about finding Mendelian transmission patterns. He assesses the predominant 19th-century method of psychiatric genetic investigation-"hereditary burden"-to be crude and biased by family size. Although written at a time of consolidation of Nazi power in Germany, this book nowhere endorses their racial/eugenic policies and can be seen as subtly questioning them.

Identifying the Relationship between PM2.5 and Hyperlipidemia Using Mendelian Randomization, RNA-seq Data and Model Mice Subjected to Air Pollution.

Air pollution is an important public health problem that endangers human health. However, the casual association and pathogenesis between particles < 2.5 μm (PM2.5) and hyperlipidemia remains incompletely unknown. Mendelian randomization (MR) and transcriptomic data analysis were performed, and an air pollution model using mice was constructed to investigate the association between PM2.5 and hyperlipidemia. MR analysis demonstrated that PM2.5 is associated with hyperlipidemia and the triglyceride (TG) level in the European population (IVW method of hyperlipidemia: OR: 1.0063, 95%CI: 1.0010-1.0118, p = 0.0210; IVW method of TG level: OR: 1.1004, 95%CI: 1.0067-1.2028, p = 0.0350). Mest, Adipoq, Ccl2, and Pcsk9 emerged in the differentially expressed genes of the liver and plasma of PM2.5 model mice, which might mediate atherosclerosis accelerated by PM2.5. The studied animal model shows that the Paigen Diet (PD)-fed male LDLR-/- mice had higher total cholesterol (TC), TG, and CM/VLDL cholesterol levels than the control group did after 10 times 5 mg/kg PM2.5 intranasal instillation once every three days. Our study revealed that PM2.5 had causality with hyperlipidemia, and PM2.5 might affect liver secretion, which could further regulate atherosclerosis. The lipid profile of PD-fed Familial Hypercholesterolemia (FH) model mice is more likely to be jeopardized by PM2.5 exposure.

The examination of Kraepelin's diagnoses of dementia praecox and manic-depressive insanity in pedigrees: Studies of Schuppius in 1912 and Wittermann in 1913.

In the first two decades of the 20th century, a new approach to psychiatric genetics research emerged in Germany from three roots: (i) the wide-spread acceptance of Kraepelin's diagnostic system, (ii) increasing interest in pedigree research, and (iii) excitement about Mendelian models. We review two relevant papers, reporting analyses of, respectively, 62 and 81 pedigrees: S. Schuppius in 1912 and E. Wittermann in 1913. While most prior asylum based studies only reported a patient's "hereditary burden," they examined diagnoses of individual relatives at a particular place in a pedigree. Both authors focused on the segregation of dementia praecox (DP) and manic-depressive insanity (MDI). Schuppius reported that the two disorders frequently co-occurred in his pedigrees while Wittermann found them to be largely independent. Schuppius was skeptical of the feasibility of evaluating Mendelian models in humans. Wittermann, by contrast, with advice from Wilhelm Weinberg, applied algebraic models with proband correction to DP in his sibships with results consistent with autosomal recessive transmission. While he had less data, Wittermann suggested that MDI was likely an autosomal dominant disorder. Both authors were interested in other disorders or traits appearing in pedigrees dense with DP (e.g., idiocy) or MDI (e.g., highly excitable individuals).

Classic Text No. 135: 'On inheritance of the insanities', by Jens Chr. Smith (1924).

Serious and realistic research into the inheritance of the psychoses started in earnest at the beginning of the twentieth century. This was encouraged by both the acceptance of the Kraepelinian classification and the rediscovery of the Mendelian model of inheritance. The application of Mendelian rules to the very complex genetics of the psychoses led to agonizing debate. The Classic Text is a translation of the introduction of the doctoral thesis of Jens Chr. Smith, a little-known Danish psychiatrist who was able to summarize, with the enthusiasm typical to his youth and with surprising accuracy, the early stages of the debate mentioned above.

Modifiable pathways for longevity: A Mendelian randomization analysis

A variety of factors, including diet and lifestyle, obesity, physiology, metabolism, hormone levels, psychology, and inflammation, have been associated with longevity. The specific influences of these factors, however, are poorly understood. Here, possible causal relationships between putative modifiable risk factors and longevity are investigated. A random effects model was used to investigate the association between 25 putative risk factors and longevity. The study population comprised 11,262 long-lived subjects (≥90 years old, including 3484 individuals ≥99 years old) and 25,483 controls (≤60 years old), all of European ancestry. The data were obtained from the UK Biobank database. Genetic variations were used as instruments in two-sample Mendelian randomization to reduce bias. The odds ratios for genetically predicted SD unit increases were calculated for each putative risk factor. Egger regression was used to determine possible violations of the Mendelian randomization model. Thirteen potential risk factors showed significant associations with longevity (≥90th) after correction for multiple testing. These included smoking initiation (OR:1.606; CI: 1.112-2.319) and educational attainment (OR:2.538, CI: 1.685-3.823) in the diet and lifestyle category, systolic and diastolic blood pressure (OR per SD increase: 0.518; CI: 0.438-0.614 for SBP and 0.620; CI 0.514-0.748 for DBP) and venous thromboembolism (OR:0.002; CI: 0.000-0.047) in the physiology category, obesity (OR: 0.874; CI: 0.796-0.960), BMI (OR per 1-SD increase: 0.691; CI: 0.628-0.760), and body size at age 10 (OR per 1-SD increase:0.728; CI: 0.595-0.890) in the obesity category, type 2 diabetes (T2D) (OR:0.854; CI: 0.816-0.894), LDL cholesterol (OR per 1-SD increase: 0.743; CI: 0.668-0.826), HDL cholesterol (OR per 1-SD increase: 1.243; CI: 1.112-1.390), total cholesterol (TC) (OR per 1-SD increase: 0.786; CI: 0.702-0.881), and triglycerides (TG) (OR per 1-SD increase: 0.865; CI: 0.749-0.998) in the metabolism category. Both longevity (≥90th) and super-longevity (≥99th), smoking initiation, body size at age 10, BMI, obesity, DBP, SBP, T2D, HDL, LDL, and TC were consistently associated with outcomes. The examination of underlying pathways found that BMI indirectly affected longevity through three pathways, namely, SBP, plasma lipids (HDL/TC/LDL), and T2D (p<0.05). BMI was found to significantly affect longevity through SBP, plasma lipid (HDL/TC/LDL), and T2D. Future strategies should focus on modifying BMI to improve health and longevity.

Celiac Disease Is a Risk Factor for Mature T and NK Cell Lymphoma: A Mendelian Randomization Study.

Celiac disease (CeD) is an immune-mediated disorder triggered by gluten ingestion that damages the small intestine. Although CeD has been associated with a higher risk for cancer, the role of CeD as a risk factor for specific malignancies, such as enteropathy-associated T-cell lymphoma (EATL), remains controversial. Using two-sample Mendelian randomization (2SMR) methods and the summarized results of large genome-wide association studies from public repositories, we addressed the causal relationship between CeD and eight different malignancies. Eleven non-HLA SNPs were selected as instrumental variables (IVs), and causality estimates were obtained using four 2SMR methods: random-effects inverse variance-weighted, weighted median estimation, MR-Egger regression, and MR pleiotropy residual sum and outlier (MR-PRESSO). We identified a significant causal relationship between CeD and mature T/NK cell lymphomas. Under a multivariate Mendelian randomization model, we observed that the causal effect of CeD was not dependent on other known lymphoma risk factors. We found that the most instrumental IV was located in the TAGAP locus, suggesting that aberrant T cell activation might be relevant in the T/NK cell malignization process. Our findings provide new insights into the connection between immune imbalance and the development of severe comorbidities, such as EATL, in patients with CeD.

Getting it right: Teaching undergraduate biology to undermine racial essentialism.

How we teach human genetics matters for social equity. The biology curriculum appears to be a crucial locus of intervention for either reinforcing or undermining students' racial essentialist views. The Mendelian genetic models dominating textbooks, particularly in combination with racially inflected language sometimes used when teaching about monogenic disorders, can increase middle and high school students' racial essentialism and opposition to policies to increase equity. These findings are of particular concern given the increasing spread of racist misinformation online and the misappropriation of human genomics research by white supremacists, who take advantage of low levels of genetics literacy in the general public. Encouragingly, however, teaching updated information about the geographical distribution of human genetic variation and the complex, multifactorial basis of most human traits, reduces students' endorsement of racial essentialism. The genetics curriculum is therefore a key tool in combating misinformation and scientific racism. Here, we describe a framework and example teaching materials for teaching students key concepts in genetics, human evolutionary history, and human phenotypic variation at the undergraduate level. This framework can be flexibly applied in biology and anthropology classes and adjusted based on time availability. Our goal is to provide undergraduate-level instructors with varying levels of expertise with a set of evidence-informed tools for teaching human genetics to combat scientific racism, including an evolving set of instructional resources, as well as learning goals and pedagogical approaches. Resources can be found at https://noto.li/YIlhZ5. Additionally, we hope to generate conversation about integrating modern genetics into the undergraduate curriculum, in light of recent findings about the risks and opportunities associated with teaching genetics.