Genome-Wide Association Study Meta-Analysis of Stroke in 22 000 Individuals of African Descent Identifies Novel Associations With Stroke.

BACKGROUND AND PURPOSE: Stroke is a complex disease with multiple genetic and environmental risk factors. Blacks endure a nearly 2-fold greater risk of stroke and are 2× to 3× more likely to die from stroke than European Americans. METHODS: The COMPASS (Consortium of Minority Population Genome-Wide Association Studies of Stroke) has conducted a genome-wide association meta-analysis of stroke in >22 000 individuals of African ancestry (3734 cases, 18 317 controls) from 13 cohorts. RESULTS: In meta-analyses, we identified one single nucleotide polymorphism (rs55931441) near the HNF1A gene that reached genome-wide significance (P=4.62×10-8) and an additional 29 variants with suggestive evidence of association (P<1×10-6), representing 24 unique loci. For validation, a look-up analysis for a 100 kb region flanking the COMPASS single nucleotide polymorphism was performed in SiGN (Stroke Genetics Network) Europeans, SiGN Hispanics, and METASTROKE (Europeans). Using a stringent Bonferroni correction P value of 2.08×10-3 (0.05/24 unique loci), we were able to validate associations at the HNF1A locus in both SiGN (P=8.18×10-4) and METASTROKE (P=1.72×10-3) European populations. Overall, 16 of 24 loci showed evidence for validation across multiple populations. Previous studies have reported associations between variants in the HNF1A gene and lipids, C-reactive protein, and risk of coronary artery disease and stroke. Suggestive associations with variants in the SFXN4 and TMEM108 genes represent potential novel ischemic stroke loci. CONCLUSIONS: These findings represent the most thorough investigation of genetic determinants of stroke in individuals of African descent, to date.

Genetic Analysis of a Large Family with Migraine, Vertigo, and Motion Sickness.

BACKGROUND: Migraine is a common disorder most typically presenting as headache and often associated with vertigo and motion sickness. It is a genetically complex condition with multiple genes ultimately contributing to the predisposition and development of this episodic neurological disorder. We identified a large American family of 29 individuals of which 17 members suffered from at least one of these disorders, migraine, vertigo, or motion sickness. Many of these individuals suffered from several simultaneously. We hypothesized that vertigo and motion sickness may involve genes that are independent to those directly contributing to migraine susceptibility. METHODS: Genome-wide linkage analysis performed using 400 microsatellite repeat markers spaced at 10 cM throughout the genome. The members of this family were phenotyped for each condition, migraine, vertigo, and motion sickness and analyzed separately. Statistical analysis was performed using two-point and multipoint linkage analysis employing a number of models including autosomal recessive or dominant patterns of inheritance with high and low genetic penetrance. RESULTS: We identified a novel locus for migraine, 9q13-q22 (maximum two-point logarithm of odds [LOD] score-2.51). In addition, there are suggestive LOD scores that localize to different chromosomes for each phenotype; vertigo (chromosome 18, LOD score of 1.82) and motion sickness (chromosome 4, LOD score of 2.09). CONCLUSIONS: Our analysis supports our hypothesis that the migraine-associated vertigo and motion sickness may involve distinct susceptibility genes.

Analyse génétique d'une famille étendue dont les membres souffrent de migraines, de vertiges et du mal des transports. Contexte : La migraine est un trouble courant qui entraîne habituellement des maux de tête et qui est souvent associé à des vertiges et au mal des transports. Il s'agit aussi d'une condition génétique complexe en vertu de laquelle de nombreux gènes contribuent à terme à cette prédisposition et au développement de ce trouble neurologique périodique. À cet égard, nous avons identifié une famille étendue américaine comptant 29 membres. De ce nombre, 17 d'entre eux avaient souffert d'au moins un de ces troubles : des migraines, des vertiges ou le mal des transports. À noter que plusieurs d'entre eux avaient souffert de ces troubles en même temps. Nous avons émis l'hypothèse que les vertiges et le mal des transports pourraient impliquer des gènes qui sont indépendants de ceux contribuant directement à la propension aux migraines. Méthodes : Nous avons effectué une analyse de liaison au moyen de 400 marqueurs microsatellites répétés et espacés à tous les 10 cm au sein de l'ensemble du génome des membres de cette famille. Les membres de cette famille ont été « phénotypés ¼ pour chaque type de trouble (les migraines, les vertiges et le mal des transports) et ont été ensuite analysés de façon séparée. Nous avons effectué une analyse statistique au moyen de l'analyse de liaison multipoint et à deux points, utilisant pour ce faire un certain nombre de modèles, par exemple le modèle autosomique récessif ou des patterns dominants de transmission avec une pénétrance génétique élevée ou faible. Résultats : Nous avons été en mesure d'identifier un nouveau locus dans le cas de la migraine : 9q13-q22 (maximum 2-points ; score au logarithme des probabilités ou LOD : - 2,51). De plus, il est des scores révélateurs au logarithme des probabilités qui permettent de localiser divers chromosomes pour chaque phénotype : vertiges (chromosome 18 ; score au logarithme des probabilités ou LOD : 1,82) et mal des transports (chromosome 4 ; score au logarithme des probabilités ou LOD : 2,09). Conclusions : Notre analyse confirme ainsi notre hypothèse initiale, à savoir que les cas de migraine auxquels sont associés des vertiges et le mal des transports pourraient très bien impliquer différents gènes de susceptibilité.

Genetic variation at 16q24.2 is associated with small vessel stroke.

OBJECTIVE: Genome-wide association studies (GWAS) have been successful at identifying associations with stroke and stroke subtypes, but have not yet identified any associations solely with small vessel stroke (SVS). SVS comprises one quarter of all ischemic stroke and is a major manifestation of cerebral small vessel disease, the primary cause of vascular cognitive impairment. Studies across neurological traits have shown that younger-onset cases have an increased genetic burden. We leveraged this increased genetic burden by performing an age-at-onset informed GWAS meta-analysis, including a large younger-onset SVS population, to identify novel associations with stroke. METHODS: We used a three-stage age-at-onset informed GWAS to identify novel genetic variants associated with stroke. On identifying a novel locus associated with SVS, we assessed its influence on other small vessel disease phenotypes, as well as on messenger RNA (mRNA) expression of nearby genes, and on DNA methylation of nearby CpG sites in whole blood and in the fetal brain. RESULTS: We identified an association with SVS in 4,203 cases and 50,728 controls on chromosome 16q24.2 (odds ratio [OR; 95% confidence interval {CI}] = 1.16 [1.10-1.22]; p = 3.2 × 10-9 ). The lead single-nucleotide polymorphism (rs12445022) was also associated with cerebral white matter hyperintensities (OR [95% CI] = 1.10 [1.05-1.16]; p = 5.3 × 10-5 ; N = 3,670), but not intracerebral hemorrhage (OR [95% CI] = 0.97 [0.84-1.12]; p = 0.71; 1,545 cases, 1,481 controls). rs12445022 is associated with mRNA expression of ZCCHC14 in arterial tissues (p = 9.4 × 10-7 ) and DNA methylation at probe cg16596957 in whole blood (p = 5.3 × 10-6 ). INTERPRETATION: 16q24.2 is associated with SVS. Associations of the locus with expression of ZCCHC14 and DNA methylation suggest the locus acts through changes to regulatory elements. Ann Neurol 2017;81:383-394.

Autosomal dominant hereditary spastic paraplegia with axonal sensory motor polyneuropathy maps to chromosome 21q 22.3.

AIM: Hereditary spastic paraplegia (HSP) are a genetically and clinically heterogeneous group of disorders. At present, 19 autosomal dominant loci for HSP have been mapped. We ascertained an American family of European descent segregating an autosomal dominant HSP associated with peripheral neuropathy. METHODS: A genome wide scan was performed with 410 microsatellite repeat marker (Weber lab screening set 16) and following linkage and haplotype analysis, fine mapping was performed. Established genes or loci for HSP were excluded by direct sequencing or haplotype analysis. RESULTS: All established loci for HSP were excluded. Fine mapping suggested a locus on chromosome 21q22.3 flanked by markers D21S1411 and D21S1446 with a maximum logarithm of odds score of 2.05 and was supported by haplotype analysis. A number of candidate genes in this region were analyzed and no disease-producing mutations were detected. CONCLUSION: We present the clinical and genetic analysis of an American family with autosomal dominant HSP with axonal sensory motor polyneuropathy mapping to a novel locus on chromosome 21q22.3 designated SPG56.

A familial form of benign paroxysmal positional vertigo maps to chromosome 15.

AIM: Benign positional paroxysmal vertigo (BPPV) is characterized by short-lived episodes of vertigo in association with rapid changes in head position, most commonly extension and rotation of the neck while supine. It has been clinically observed that there is a subgroup of patients in whom the BPPV disease is inherited in an autosomal dominant fashion. However, little is known about the familial/genetic factors that may contribute to a predisposition to develop the disease. MATERIALS AND METHODS: We ascertained and performed a genome-wide scan on a three-generation family in which multiple family members developed BPPV. We performed whole genome mapping with 400 microsatellite repeat markers and analyzed this trait using both autosomal dominant and recessive models of inheritance. RESULTS: Two point linkage analysis showed LOD scores of one or greater than one on chromosomes 7, 15, 16 and 20. Independent of the model of inheritance, the highest two-point LOD scores localized to same marker on chromosome 15. Multipoint linkage analysis showed the highest LOD score of 2.84 to markers on chromosome 15 with the autosomal dominant model. Haplotype reconstruction indicates that the BPPV gene in this family maps to a critical chromosomal 15 interval between markers GATA151F03N and GATA85D02. CONCLUSIONS: Discovery of a BPPV gene (or genes) will facilitate a better understanding of not only BPPV, but also the vestibular system. In addition, with improved understanding of the pathophysiology the potential development of alternative therapies for BPPV may be possible.

Pathogenic ischemic stroke phenotypes in the NINDS-stroke genetics network.

BACKGROUND AND PURPOSE: NINDS (National Institute of Neurological Disorders and Stroke)-SiGN (Stroke Genetics Network) is an international consortium of ischemic stroke studies that aims to generate high-quality phenotype data to identify the genetic basis of pathogenic stroke subtypes. This analysis characterizes the etiopathogenetic basis of ischemic stroke and reliability of stroke classification in the consortium. METHODS: Fifty-two trained and certified adjudicators determined both phenotypic (abnormal test findings categorized in major pathogenic groups without weighting toward the most likely cause) and causative ischemic stroke subtypes in 16 954 subjects with imaging-confirmed ischemic stroke from 12 US studies and 11 studies from 8 European countries using the web-based Causative Classification of Stroke System. Classification reliability was assessed with blinded readjudication of 1509 randomly selected cases. RESULTS: The distribution of pathogenic categories varied by study, age, sex, and race (P<0.001 for each). Overall, only 40% to 54% of cases with a given major ischemic stroke pathogenesis (phenotypic subtype) were classified into the same final causative category with high confidence. There was good agreement for both causative (κ 0.72; 95% confidence interval, 0.69-0.75) and phenotypic classifications (κ 0.73; 95% confidence interval, 0.70-0.75). CONCLUSIONS: This study demonstrates that pathogenic subtypes can be determined with good reliability in studies that include investigators with different expertise and background, institutions with different stroke evaluation protocols and geographic location, and patient populations with different epidemiological characteristics. The discordance between phenotypic and causative stroke subtypes highlights the fact that the presence of an abnormality in a patient with stroke does not necessarily mean that it is the cause of stroke.

Analysis of the interleukin-1 receptor antagonist gene variable number tandem repeats in ischemic stroke.

BACKGROUND: There is an increasing interest in the role of inflammatory mechanisms contributing to the development of stroke. Recent studies have reported an association between allele 2 of a variable number tandem repeat of the interleukin-1 receptor antagonist (IL1RN) gene in Caucasian patients with ischemic stroke. The purpose of this investigation is to independently confirm these results in our study population. METHODS: We recruited and genotyped 516 Caucasian patients with ischemic stroke and 380 matched controls. Tests of association were performed to estimate odds ratio (OR) for the IL1RN gene variable number tandem repeat polymorphism with case-control status. Genotype frequencies of IL1RN gene were compared by case-control and symptom status using χ2 contingency tables and logistic regression models. RESULTS: No significant association was observed between any of the IL1RN gene genotypes and ischemic stroke. The unadjusted association model a, and the fully saturated model e, adjusted for age, gender, and stroke risk factors demonstrated no significant increase in risk associated with the IL1RN gene 2/2 genotype (a: OR, 1.11; 95% confidence interval [CI], .67-1.89; P=.615; and e: OR, .95; 95% CI, .46-1.94; P=.574). Analyses of genotypic and allelic frequencies of each Trial of Org 10172 in Acute Stroke Treatment subtype with control and pairwise comparison between stroke subtypes did not show any significant differences in their distributions, and all P values were greater than the significance level of .05. CONCLUSION: Our results do not confirm an association between the gene and ischemic stroke in Caucasian patients.

A Patient With Charcot-Marie-Tooth Disease Type 4C (CMT4C) Presenting With Muscle Fasciculations and Motor Neuropathy.

We report an unusual patient who, at age 47 years, had presented with complaints of muscle fasciculations. After neurological examination and electromyogram testing, he was diagnosed with motor neuropathy. Over the next 10 years, in addition to fasciculations, he developed numbness in his feet without any other symptoms. His current neurological examination at age 57 years was normal, except for mildly decreased light touch in the anterior portion of both feet. The nerve conduction studies performed repeatedly showed sensorimotor polyneuropathy with demyelination features. Blood tests, including anti-ganglioside antibodies, were normal. Genetic testing revealed two rare variants in trans in the SH3 domain and tetratricopeptide repeats 2gene, c.3413 G>A p.(S1138N) and c.3269 C>G p.(A1090G). Protein modeling suggests that these are disease-producing mutations and likely the cause of the neuropathy of our patient. Our study expands the clinical and genetic spectrum of patients with Charcot-Marie-Tooth disease type 4C.

Stroke Genetics Network (SiGN) study: design and rationale for a genome-wide association study of ischemic stroke subtypes.

BACKGROUND AND PURPOSE: Meta-analyses of extant genome-wide data illustrate the need to focus on subtypes of ischemic stroke for gene discovery. The National Institute of Neurological Disorders and Stroke SiGN (Stroke Genetics Network) contributes substantially to meta-analyses that focus on specific subtypes of stroke. METHODS: The National Institute of Neurological Disorders and Stroke SiGN includes ischemic stroke cases from 24 genetic research centers: 13 from the United States and 11 from Europe. Investigators harmonize ischemic stroke phenotyping using the Web-based causative classification of stroke system, with data entered by trained and certified adjudicators at participating genetic research centers. Through the Center for Inherited Diseases Research, the Network plans to genotype 10,296 carefully phenotyped stroke cases using genome-wide single nucleotide polymorphism arrays and adds to these another 4253 previously genotyped cases, for a total of 14,549 cases. To maximize power for subtype analyses, the study allocates genotyping resources almost exclusively to cases. Publicly available studies provide most of the control genotypes. Center for Inherited Diseases Research-generated genotypes and corresponding phenotypes will be shared with the scientific community through the US National Center for Biotechnology Information database of Genotypes and Phenotypes, and brain MRI studies will be centrally archived. CONCLUSIONS: The Stroke Genetics Network, with its emphasis on careful and standardized phenotyping of ischemic stroke and stroke subtypes, provides an unprecedented opportunity to uncover genetic determinants of ischemic stroke.

Racial-ethnic differences in stroke risk factors and subtypes: results of a prospective hospital-based registry.

A majority of stroke research in the United States focuses on Caucasian and African-American populations, limiting the amount of comparative stroke data available on other racial and ethnic groups. The purpose of this research was to examine differences in stroke risk factors/subtypes between minority stroke patient groups in the United States (Asian-Indian, African-American, and Hispanic), using a Caucasian reference group. All patients had a comprehensive stroke work-up to ascertain their stroke risk factors and their stroke etiology applying TOAST criteria. Minority groups were younger compared with the white stroke patients, with the mean age significantly lower in the Asian-Indian and the Hispanic groups. The male:female ratio favored males in the Asian-Indian and Hispanic subgroups and females in the Caucasian and African-American groups. Diabetes was more prevalent in the minority subgroups, with a highest prevalence (55%) noted in the Asian-Indian group. The minority groups had lower prevalence of atrial fibrillation, carotid stenosis (≥70%), CAD, PVD, smoking, and alcohol use. The Asian-Indian stroke group had a higher median fasting plasma homocysteine level compared with the reference white group (12.1 vs. 10.4, p = 0.002). Compared to the reference white stroke group, the Asian-Indian stroke group had fewer strokes related to cardioembolism (7% vs. 25%) and a higher number of strokes related to small vessel occlusive disease (25% vs. 11%). There are some similarities in the stroke risk factors between the minority stroke groups, but the data indicate that there are different trends in stroke risk factors and subtypes.

Demyelinating Peripheral Neuropathy Caused by the p.R160H Mutation in the LITAF Gene.

We report a 62-year-old woman who presented with complaints of numbness and tingling in her feet without a family history suggestive of neuropathy. Neurological examination and electromyogram testing confirmed the presence of a demyelinating neuropathy with a mild phenotype. Extensive testing revealed no etiology and she was diagnosed and treated unsuccessfully for chronic inflammatory demyelinating polyneuropathy. Ultimately, with the availability of next-generation sequencing, genetic testing revealed a heterozygous variant, chr16:11643500C > T, c.479 G > A, p.R160H, in the lipopolysaccharide-induced tumor necrosis factor (LITAF ) gene. Further analysis of this variant employing protein modeling suggests that this is a disease producing mutation causing Charcot Marie Tooth disease type 1C (CMT1C). Our study demonstrates the power of next-generation sequencing to diagnose patients with idiopathic neuropathy. This is important as it avoids unnecessary and expensive treatments for the patient and furthermore, allows genetic counseling for family members.

Clinical and Genetic Analysis of a Patient with CMT4J.

We report the clinical and genetic analysis of a patient with a rare form of an autosomal recessive genetic neuropathy, Charcot Marie Tooth (CMT) disease type 4J. She presented at age 62 years with signs and symptoms consistent with a mild neuropathy. The onset of symptoms began approximately ten years earlier. Electrophysiological testing confirmed a demyelinating neuropathy and a comprehensive neuropathy screening for common causes of neuropathy was unrevealing. She underwent commercial whole exome sequencing, analyzing more than eighty genes known to cause neuropathy. Two mutations were detected, c.122T > C, p.Ile41Thr and c.2247dupC, p.Ser750GlnX10 in the FIG4 gene. The p.Ile41Thr mutation, which is paternally inherited, is a recurrent mutation reported in a number of unrelated families of European descent. The patient's father, also of European descent, provides further evidence supporting a founder effect for this mutation. In most patients carrying the p.Ile41Thr mutation, the neuropathy, unlike our patient, is often severe with early onset. The second mutation, c.2247dupC, p.Ser750GlnX10 is maternally inherited and not previously reported. Furthermore, based upon our protein modeling analysis, c.2247dupC is disease producing, representing a novel pathogenic mutation. Our study of this patient expands the clinical and genetic spectrum of patients with CMT 4J.

Novel Titin Gene Mutation Causing Autosomal Dominant Limb-Girdle Muscular Dystrophy.

We report a genotype-phenotype analysis of a family in which a titinopathy is transmitted in an autosomal dominant pattern. In this family, following neurological history and examination, electromyogram, and muscle biopsy, the diagnosis of limb-girdle muscular dystrophy with contractures was made in an affected mother and son. Genetic testing employing the whole exome was performed and revealed two variants in the TTN gene, c.712G>C, p. Glu238Gln and c.1397A>C, p.Gln466Arg, which segregated with the disease in the affected mother-son duo but not in an unaffected sibling. Although protein modeling suggests that the c.712G>C, p. Glu238Gln polymorphism is damaging, it has been reported in the Genome Aggregation Database which includes exome and genome sequence data of unrelated individuals sequenced as part of various disease-specific and population genetic studies. In contrast, the c.1397A>C, p.Gln466Arg variant is novel and has not been reported in any public genetic databases or our internal laboratory database. Protein modeling analysis indicates that p.Gln466Arg is damaging and we hypothesize that it is the disease-producing mutation resulting in muscular dystrophy. Our research report expands the spectrum of mutations causing titinopathy.

Contribution of Common Genetic Variants to Risk of Early Onset Ischemic Stroke.

BACKGROUND AND OBJECTIVES: Current genome-wide association studies of ischemic stroke have focused primarily on late onset disease. As a complement to these studies, we sought to identifythe contribution of common genetic variants to risk of early onset ischemic stroke. METHODS: We performed a meta-analysis of genome-wide association studies of early onset stroke (EOS), ages 18-59, using individual level data or summary statistics in 16,730 cases and 599,237 non-stroke controls obtained across 48 different studies. We further compared effect sizes at associated loci between EOS and late onset stroke (LOS) and compared polygenic risk scores for venous thromboembolism between EOS and LOS. RESULTS: We observed genome-wide significant associations of EOS with two variants in ABO, a known stroke locus. These variants tag blood subgroups O1 and A1, and the effect sizes of both variants were significantly larger in EOS compared to LOS. The odds ratio (OR) for rs529565, tagging O1, 0.88 (95% CI: 0.85-0.91) in EOS vs 0.96 (95% CI: 0.92-1.00) in LOS, and the OR for rs635634, tagging A1, was 1.16 (1.11-1.21) for EOS vs 1.05 (0.99-1.11) in LOS; p-values for interaction = 0.001 and 0.005, respectively. Using polygenic risk scores, we observed that greater genetic risk for venous thromboembolism, another prothrombotic condition, was more strongly associated with EOS compared to LOS (p=0.008). DISCUSSION: The ABO locus, genetically predicted blood group A, and higher genetic propensity for venous thrombosis are more strongly associated with EOS than with LOS, supporting a stronger role of prothrombotic factors in EOS.

X-linked dominant scapuloperoneal myopathy is due to a mutation in the gene encoding four-and-a-half-LIM protein 1.

Scapuloperoneal (SP) syndrome encompasses heterogeneous neuromuscular disorders characterized by weakness in the shoulder-girdle and peroneal muscles. In a large Italian-American pedigree with dominant SP myopathy (SPM) previously linked to chromosome 12q, we have mapped the disease to Xq26, and, in all of the affected individuals, we identified a missense change (c.365G-->C) in the FHL1 gene encoding four-and-a-half-LIM protein 1 (FHL1). The mutation substitutes a serine for a conserved trypophan at amino acid 122 in the second LIM domain of the protein. Western blot analyses of muscle extracts revealed FHL1 loss that paralleled disease severity. FHL1 and an isoform, FHL1C, are highly expressed in skeletal muscle and may contribute to stability of sarcomeres and sarcolemma, myofibrillary assembly, and transcriptional regulation. This is the first report, to our knowledge, of X-linked dominant SP myopathy and the first human mutation in FHL1.

Intrafamilial Phenotypic Variability Associated with the I1739V Mutation in the SCN9A Gene.

The SCN9A gene encodes a voltage gated sodium channel Nav1.7 in which mutations can result in a wide variety of phenotypes ranging from congenital insensitivity to pain to small fiber neuropathy. We report the genotype phenotype analysis in a family carrying a specific mutation, I1739V, in the SCN9A gene. Neurophysiological studies have documented the gain of function impact of this mutation on this sodium channel. Interestingly, there is significant interfamilial phenotypic variability in individuals carrying this mutation. In our family, a father daughter combination had identical genotypes analyzing the SCN9A gene and multiple other genes known to cause neuropathy. Both of them carry the I1739V mutation but exhibit significant phenotypic variability with complaints of decreased sensitivity to discomfort in the father while the daughter has the clinical and laboratory features consistent with a small fiber neuropathy. We hypothesize that there are modifiers of the I1739V mutation that could involve intronic or exonic gene variants which contribute to this intrafamilial phenotypic variability. Our study has implications for genetic counseling, personalized medicine and the development of drugs to treat neuropathic pain.

Genotype phenotype analysis in a family carrying truncating mutations in the titin gene.

We report a family carrying a previously described truncating mutation, NM_001267550.2(TTN):c.107889del p.(Lys35963Asnfs*9) in exon 364, and a novel truncating mutation, NM_001267550.1:c.100704C > A p.(Tyr33568*) in exon 358 in the titin gene. The c.107889del mutation, which was maternally transmitted, has been previously described in patients from the Iberian Peninsula. The mother was of Peruvian descent suggesting a potential European ancestral origin of this mutation. In this family, a daughter, who is a compound heterozygote carrying both these mutations, developed a peripartum cardiomyopathy during her second pregnancy. Subsequently, she was diagnosed with a myopathy following electromyography testing and a muscle biopsy which showed fiber type disproportion. Her brother, who carries only the paternally inherited c.100704C > A mutation, developed a cardiomyopathy following a suspected viral illness. Their father, who transmitted this mutation, has no evidence of a cardiomyopathy. We hypothesize that the c.100704C > A mutation confers susceptibility to the development of cardiomyopathy which may be brought on by cardiovascular stress. Our study of this family expands the genotype and phenotype spectrum of disorders that can be associated with mutations in the titin gene.

Genetic basis of lacunar stroke: a pooled analysis of individual patient data and genome-wide association studies.

BACKGROUND: The genetic basis of lacunar stroke is poorly understood, with a single locus on 16q24 identified to date. We sought to identify novel associations and provide mechanistic insights into the disease. METHODS: We did a pooled analysis of data from newly recruited patients with an MRI-confirmed diagnosis of lacunar stroke and existing genome-wide association studies (GWAS). Patients were recruited from hospitals in the UK as part of the UK DNA Lacunar Stroke studies 1 and 2 and from collaborators within the International Stroke Genetics Consortium. Cases and controls were stratified by ancestry and two meta-analyses were done: a European ancestry analysis, and a transethnic analysis that included all ancestry groups. We also did a multi-trait analysis of GWAS, in a joint analysis with a study of cerebral white matter hyperintensities (an aetiologically related radiological trait), to find additional genetic associations. We did a transcriptome-wide association study (TWAS) to detect genes for which expression is associated with lacunar stroke; identified significantly enriched pathways using multi-marker analysis of genomic annotation; and evaluated cardiovascular risk factors causally associated with the disease using mendelian randomisation. FINDINGS: Our meta-analysis comprised studies from Europe, the USA, and Australia, including 7338 cases and 254 798 controls, of which 2987 cases (matched with 29 540 controls) were confirmed using MRI. Five loci (ICA1L-WDR12-CARF-NBEAL1, ULK4, SPI1-SLC39A13-PSMC3-RAPSN, ZCCHC14, ZBTB14-EPB41L3) were found to be associated with lacunar stroke in the European or transethnic meta-analyses. A further seven loci (SLC25A44-PMF1-BGLAP, LOX-ZNF474-LOC100505841, FOXF2-FOXQ1, VTA1-GPR126, SH3PXD2A, HTRA1-ARMS2, COL4A2) were found to be associated in the multi-trait analysis with cerebral white matter hyperintensities (n=42 310). Two of the identified loci contain genes (COL4A2 and HTRA1) that are involved in monogenic lacunar stroke. The TWAS identified associations between the expression of six genes (SCL25A44, ULK4, CARF, FAM117B, ICA1L, NBEAL1) and lacunar stroke. Pathway analyses implicated disruption of the extracellular matrix, phosphatidylinositol 5 phosphate binding, and roundabout binding (false discovery rate <0·05). Mendelian randomisation analyses identified positive associations of elevated blood pressure, history of smoking, and type 2 diabetes with lacunar stroke. INTERPRETATION: Lacunar stroke has a substantial heritable component, with 12 loci now identified that could represent future treatment targets. These loci provide insights into lacunar stroke pathogenesis, highlighting disruption of the vascular extracellular matrix (COL4A2, LOX, SH3PXD2A, GPR126, HTRA1), pericyte differentiation (FOXF2, GPR126), TGF-ß signalling (HTRA1), and myelination (ULK4, GPR126) in disease risk. FUNDING: British Heart Foundation.

An analysis of methylenetetrahydrofolate reductase and glutathione S-transferase omega-1 genes as modifiers of the cerebral response to ischemia.

BACKGROUND: Cerebral ischemia involves a series of reactions which ultimately influence the final volume of a brain infarction. We hypothesize that polymorphisms in genes encoding proteins involved in these reactions could act as modifiers of the cerebral response to ischemia and impact the resultant stroke volume. The final volume of a cerebral infarct is important as it correlates with the morbidity and mortality associated with non-lacunar ischemic strokes. METHODS: The proteins encoded by the methylenetetrahydrofolate reductase (MTHFR) and glutathione S-transferase omega-1 (GSTO-1) genes are, through oxidative mechanisms, key participants in the cerebral response to ischemia. On the basis of these biological activities, they were selected as candidate genes for further investigation. We analyzed the C677T polymorphism in the MTHFR gene and the C419A polymorphism in the GSTO-1 gene in 128 patients with non-lacunar ischemic strokes. RESULTS: We found no significant association of either the MTHFR (p = 0.72) or GSTO-1 (p = 0.58) polymorphisms with cerebral infarct volume. CONCLUSION: Our study shows no major gene effect of either the MTHFR or GSTO-1 genes as a modifier of ischemic stroke volume. However, given the relatively small sample size, a minor gene effect is not excluded by this investigation.

Adult Diagnosis of Type 1 Fiber Predominance Myopathy Caused by Novel Mutations in the RYR1 Gene.

We describe a 57-year-old patient with mild diffuse weakness that was incidentally detected when he was evaluated for restless leg syndrome. An electromyography confirmed the presence of a myopathy without suggestion of inflammatory myopathy. A muscle biopsy demonstrated type 1 fiber predominance with minimal inflammatory features suggesting a genetic myopathy. Exome sequencing revealed c.10648C > T variant (p.R3550W), and a novel variant, c.10749_10753delGGAGG (E3584Rfs*3), in the ryanodine receptor 1 (RYR1) gene transmitted through his asymptomatic father indicating these mutations are in trans. Prompted by these results, a 47-year-old sister presented for evaluation. Her examination showed mild proximal muscle weakness, and an electromyography confirmed a noninflammatory myopathy. Her genotype was identical to her affected brother confirming that in these siblings, the RYR1 mutations, transmitted in an autosomal recessive pattern, are the cause of their myopathy. The adult age at diagnosis of these affected siblings likely reflects the mild and minimally progressive nature of the myopathy.