SYNE1-ataxia: Novel genotypic and phenotypic findings

Unraveling the nexus of nesprin in dilated cardiomyopathy: From molecular insights to therapeutic prospects

Dilated cardiomyopathy is a complex and debilitating heart disorder characterized by the enlargement and weakening of the cardiac chambers, leading to impaired contractility and heart failure. Nesprins, a family of nuclear envelope spectrin repeat proteins that include isoforms Nesprin-1/-2, are integral components of the LInker of Nucleoskeleton and Cytoskeleton complex. They facilitate the connection between the nuclear envelope and the cytoskeleton, crucial for maintaining nuclear architecture, migration and positioning, and mechanical transduction and signaling. Nesprin-1/-2 are abundantly expressed in cardiac and skeletal muscles.They have emerged as key players in the pathogenesis of dilated cardiomyopathy. Mutations in synaptic nuclear envelope-1/-2 genes encoding Nesprin-1/-2 are associated with dilated cardiomyopathy, underscoring their significance in cardiac health. This review highlights the all known cases of Nesprin-1/-2 related dilated cardiomyopathy, focusing on their interactions with the nuclear envelope, their role in mechanical transduction, and their influence on gene expression. Moreover, it delves into the underlying mechanisms through which Nesprin dysfunction disrupts nuclear-cytoskeletal coupling, leading to abnormal nuclear morphology, impaired mechanotransduction, and altered gene regulation. The exploration of Nesprin's impact on dilated cardiomyopathy offers a promising avenue for therapeutic interventions aimed at ameliorating the disease. This review provides a comprehensive overview of recent advancements in understanding the pivotal role of Nesprins in dilated cardiomyopathy research.

Diverse Roles of the LINC Complex in Cellular Function and Disease in the Nervous System

The linker of nucleoskeleton and cytoskeleton (LINC) complex, which spans the nuclear envelope, physically connects nuclear components to the cytoskeleton and plays a pivotal role in various cellular processes, including nuclear positioning, cell migration, and chromosomal configuration. Studies have revealed that the LINC complex is essential for different aspects of the nervous system, particularly during development. The significance of the LINC complex in neural lineage cells is further corroborated by the fact that mutations in genes associated with the LINC complex have been implicated in several neurological diseases, including neurodegenerative and psychiatric disorders. In this review, we aimed to summarize the expanding knowledge of LINC complex-related neuronal functions and associated neurological diseases.

Challenging Diagnosis of a Patient with Two Novel Variants in the SYNE1 Gene

We report a case of SYNE1-associated autosomal recessive spinocerebellar ataxia (SCAR8) presenting with a complex multisystemic phenotype, including highly elevated creatine kinase levels and lower-leg muscle atrophy. In addition to identifying two novel pathogenic variants in the SYNE1 gene, whole-exome sequencing revealed three variants of uncertain significance in the DYSF gene. Electromyography and muscle magnetic resonance imaging indicated a neurogenic pattern of muscle involvement. These findings, along with the segregation analysis of the variants, allowed us to exclude DYSF-associated muscular dystrophy; however, we cannot entirely rule out the possibility that the DYSF gene variants may act as modifiers of the patient's phenotype.

Dissecting the shared genetic architecture between endometriosis and polycystic ovary syndrome

Background

Previous study suggested evidence for coexistence and similarities between endometriosis and polycystic ovary syndrome (PCOS), but it is unclear regarding the shared genetic architecture and causality underlying the phenotypic similarities observed for endometriosis and PCOS.

Methods

By leveraging summary statistics from public genome-wide association studies regarding endometriosis (European-based: N=470,866) and PCOS (European-based: N=210,870), we explored the genetic correlation that shared between endometriosis and PCOS using linkage disequilibrium score regression. Shared risk SNPs were derived using PLACO (Pleiotropic analysis under composite null hypothesis) and FUMA (Functional Mapping and Annotation of Genetic Associations). The potential causal association between endometriosis and PCOS was investigated using two-sample Mendelian randomization (MR). Linkage disequilibrium score for the specific expression of genes analysis (LDSC-SEG) were performed for tissue enrichment analysis. The expression profiles of the risk gene in tissues were further examined.

Results

A positive genetic association was observed between endometriosis and PCOS. 12 significant pleiotropic loci shared between endometriosis and PCOS were identified. Genetic associations between endometriosis and PCOS were particularly enriched in uterus, endometrium and fallopian tube. Two-sample MR analysis further indicated a potential causative effect of endometriosis on PCOS, and vice versa. Microarray and RNA-seq verified the expressions of SYNE1 and DNM3 were significantly altered in the endometrium of patients with endometriosis or PCOS compared to those of control subjects.

Conclusion

Our study indicates the genetic correlation and shared risk genes between PCOS and endometriosis. These findings provide insights into the potential mechanisms behind their comorbidity and the future development of therapeutics.

No-observed-adverse-effect-level (NOAEL) clothianidin, a neonicotinoid pesticide, impairs hippocampal memory and motor learning associated with alteration of gene expression in cerebellum

Neonicotinoid pesticides (NNs) have been associated with numerous neurobehavioral effects in rodents, raising concerns about their impact on cognitive function. Clothianidin (CLO), a type of NN, was orally administered to male mice (10 weeks old, C57BL/6N) at the no-observed-adverse-effect level (NOAEL) of 50 mg/kg/day as indicated in the pesticide risk assessment report. Behavioral tests (novel location recognition and rotarod tests) evaluated hippocampal memory and cerebellar motor learning. After each test, plasma monoamines (3-methoxytyramine, histamine, serotonin, tryptamine) were measured by LC-ESI/MS/MS (Liquid chromatography-electrospray ionization/tandem mass spectrometry), and cerebellar mRNA expression was quantified by microarray and qRT-PCR analyses. The NOAEL of CLO was found to impair hippocampal memory, leading to decreased spontaneous locomotor activity and motor function. We reported, for the first time, multiple alterations of gene expression in the cerebellum associated with motor dysfunction.

[Rare forms of autosomal recessive spinocerebellar ataxia associated with mutations in the ANO10 (ATX-ANO10) and SYNE1 (ATX-SYNE1) genes]

OBJECTIVE

To analyze clinical and genetic characteristics of patients with the verified rare forms of autosomal recessive spinocerebellar ataxias, ATX-ANO10 and ATX-SYNE1.

MATERIAL AND METHODS

Six unrelated patients with established diagnoses were examined: 4 patients with ATX-ANO10 and 2 patients with ATX-SYNE1. Brain MRI and nerve conduction study were performed. To screen for cognitive impairment, the scale for the Assessment and Rating of Ataxia (SARA), and the Montreal Cognitive Assessment Scale (MoCA) were used. Mutation screening included panel sequencing on the Illumina MiSeq platform.

RESULTS

Six variants were found in the ANO10 gene: the previously described pathogenic nonsense mutations c.G1025A (p.W342X) and c.C1244G (p.S415X), as well as novel probably pathogenic variants c.1477-2A>G and c.G101T (p.W34L) and missense mutations c.A110C (p.N37T) and c.T104C (p.L35P) of undetermined significance. A novel nonsense mutation c.C8911T (p.Q2971X) and a previously described pathogenic variant c.C4939T (p.Q1647X) were found in the SYNE1 gene. The clinical presentation of the ATX-ANO10 and ATX-SYNE1 was typical presenting with slowly progressive cerebellar ataxia with pyramidal signs, with young onset and cerebellar atrophy according to brain MRI study.

CONCLUSION

We provided first-ever data on clinical features and mutation spectrum In Russian patients with ATX-ANO10 and ATX-SYNE1. The phenotype of these ataxias is nonspecific, so the method of choice for molecular diagnostics is massive parallel sequencing.

A Case Report of SYNE1 Deficiency-Mimicking Mitochondrial Disease and the Value of Pangenomic Investigations

Mitochondrial disorders are characterized by a huge clinical, biochemical, and genetic heterogeneity, which poses significant diagnostic challenges. Several studies report that more than 50% of patients with suspected mitochondrial disease could have a non-mitochondrial disorder. Thus, only the identification of the causative pathogenic variant can confirm the diagnosis. Herein, we describe the diagnostic journey of a family suspected of having a mitochondrial disorder who were referred to our Genetics Department. The proband presented with the association of cerebellar ataxia, COX-negative fibers on muscle histology, and mtDNA deletions. Whole exome sequencing (WES), supplemented by a high-resolution array, comparative genomic hybridization (array-CGH), allowed us to identify two pathogenic variants in the non-mitochondrial SYNE1 gene. The proband and her affected sister were found to be compound heterozygous for a known nonsense variant (c.13258C>T, p.(Arg4420Ter)), and a large intragenic deletion that was predicted to result in a loss of function. To our knowledge, this is the first report of a large intragenic deletion of SYNE1 in patients with cerebellar ataxia (ARCA1). This report highlights the interest in a pangenomic approach to identify the genetic basis in heterogeneous neuromuscular patients with the possible cause of mitochondrial disease. Moreover, even rare copy number variations should be considered in patients with a phenotype suggestive of SYNE1 deficiency.

The potential, analysis and prospect of ctDNA sequencing in hepatocellular carcinoma

Background

The genome map of hepatocellular carcinoma (HCC) is complex. In order to explore whether circulating tumor cell DNA (ctDNA) can be used as the basis for sequencing and use ctDNA to find tumor related biomarkers, we analyzed the mutant genes of ctDNA in patients with liver cancer by sequencing.

Methods

We used next-generation targeted sequencing technology to identify mutations in patients with liver cancer. The ctDNA from 10 patients with hepatocellular carcinoma (including eight cases of primary hepatocellular carcinoma and two cases of secondary hepatocellular carcinoma) was sequenced. We used SAMtools to detect and screen single nucleotide polymorphisms (SNPs) and insertion deletion mutations (INDELs) and ANNOVAR to annotate the structure and function of the detected mutations. Screening of pathogenic and possible pathogenic genes was performed using American College of Medical Genetics and Genomics (ACMG) guidelines. GO analysis and KEGG analysis of pathogenic and possible pathogenic genes were performed using the DAVID database, and protein-protein interaction network analysis of pathogenic and possible pathogenic genes was performed using the STRING database. Then, the Kaplan-Meier plotter database, GEPIA database and HPA database were used to analyse the relationship between pathogenic and possible pathogenic genes and patients with liver cancer.

Results

Targeted capture and deep sequencing of 560 cancer-related genes in 10 liver cancer ctDNA samples revealed 8,950 single nucleotide variation (SNV) mutations and 70 INDELS. The most commonly mutated gene was PDE4DIP, followed by SYNE1, KMT2C, PKHD1 and FN1. We compared these results to the COSMIC database and determined that ctDNA could be used for sequencing. According to the ACMG guidelines, we identified 54 pathogenic and possible pathogenic mutations in 39 genes in exons and splice regions of 10 HCC patients and performed GO analysis, KEGG analysis, and PPI network analysis. Through further analysis, four genes significantly related to the prognosis of liver cancer were identified.

Conclusion

In this study, our findings indicate that ctDNA can be used for sequencing. Our results provide some molecular data for the mapping of genetic variation in Chinese patients with liver cancer, which enriches the understanding of HCC pathogenesis and provides new ideas for the diagnosis and prognosis of HCC patients.

Case Report: Late-Onset Autosomal Recessive Cerebellar Ataxia Associated With SYNE1 Mutation in a Chinese Family

Autosomal recessive cerebellar ataxia type 1 (ARCA-1), also known as autosomal recessive spinocerebellar ataxia type 8 (SCAR8), is caused by spectrin repeat containing nuclear envelope protein 1 (SYNE1) gene mutation. Nesprin-1, encoded by SYNE1, is widely expressed in various tissues, especially in the striated muscle and cerebellum. The destruction of Nesprin-1 is related to neuronal and neuromuscular lesions. It has been reported that SYNE1 gene variation is associated with Emery-Dreifuss muscular dystrophy type 4, arthrogryposis multiplex congenita, SCAR8, and dilated cardiomyopathy. The clinical manifestations of SCAR8 are mainly characterized by relatively pure cerebellar ataxia and may be accompanied by upper and/or lower motor neuron dysfunction. Some affected people may also display cerebellar cognitive affective syndrome. It is conventionally held that the age at the onset of SCAR8 is between 6 and 42 years (the median age is 17 years). Here, we report a pedigree with SCAR8 where the onset age in the proband is 48 years. This case report extends the genetic profile and clinical features of SCAR8. A new pathogenic site (c.7578del; p.S2526Sfs*8) located in SYNE1, which is the genetic cause of the patient, was identified via whole exome sequencing (WES).

Understanding the molecular basis of cardiomyopathy

Inherited cardiomyopathies are a major cause of mortality and morbidity worldwide and can be caused by mutations in a wide range of proteins located in different cellular compartments. The present review is based on Dr. Ju Chen's 2021 Robert M. Berne Distinguished Lectureship of the American Physiological Society Cardiovascular Section, in which he provided an overview of the current knowledge on the cardiomyopathy-associated proteins that have been studied in his laboratory. The review provides a general summary of the proteins in different compartments of cardiomyocytes associated with cardiomyopathies, with specific focus on the proteins that have been studied in Dr. Chen's laboratory.

Autosomal recessive adult onset ataxia

Autosomal recessive ataxias (ARCA) represent a complex group of diseases ranging from primary ataxias to rare and complex metabolic disorders in which ataxia is a part of the clinical picture. Small number of ARCA manifest exclusively in adulthood, while majority of typical childhood onset ARCA may also start later with atypical clinical presentation. We have systematically searched the literature for ARCA with adult onset, both in the group of primary ataxias including those that are less frequently described in isolated or in a small number of families, and also in the group of complex and metabolic diseases in which ataxia is only part of the clinical picture. We propose an algorithm that could be used when encountering a patient with adult onset sporadic or recessive ataxia in whom the acquired causes are excluded. ARCA are frequently neglected in the differential diagnosis of adult-onset ataxias. Rising awareness of their clinical significance is important, not only because some of these disorders may be potentially treatable, but also for prognostic implications and inclusion of patients to future clinical trials with disease modifying agents.

Novel Homozygous Truncating Variant Widens the Spectrum of Early-Onset Multisystemic SYNE1 Ataxia

Pathogenic variants in the SYNE1 gene are associated with a phenotypic spectrum spanning from late-onset, slowly progressive, relatively pure ataxia to early-onset, fast progressive multisystemic disease. Since its first description in 2007 as an adult-onset ataxia in French Canadian families, subsequent identification of patients worldwide has widened the clinical spectrum and increased the number of identified pathogenic variants. We report a 20-year-old Faroese female with early-onset progressive gait problems, weakness, dysphagia, slurred speech, orthostatic dizziness, and urge incontinence. Neurological examination revealed mild cognitive deficits, dysarthria, broken slow pursuit, hypometric saccades, weakness with spasticity, hyperreflexia, absent ankle reflexes, ataxia, and wide-based, spastic gait. Magnetic resonance imaging displayed atrophy of the cerebellum, brainstem, and spinal cord. Severely prolonged central motor conduction time and lower motor neuron involvement was demonstrated electrophysiologically. Fluorodeoxyglucose-positron emission tomography (FDG-PET) scan showed hypometabolism of the cerebellum and right frontal lobe. Muscle biopsy revealed chronic neurogenic changes and near-absent immunostaining for Nesprin-1. Next-generation sequencing revealed a previously undescribed homozygous truncating, likely pathogenic variant in the SYNE1 gene. The patient's mother and paternal grandfather were heterozygous carriers of the variant. Her father's genotype was unobtainable. We expand the list of likely pathogenic variants in SYNE1 ataxia with a novel homozygous truncating variant with proximity to the C-terminus and relate it to a phenotype comprising early-onset cerebellar deficits, upper and lower motor neuron involvement and cognitive deficits. Also, we report novel findings of focally reduced frontal lobe FDG-PET uptake and motor evoked potential abnormalities suggestive of central demyelination.

Autosomal Recessive Cerebellar Ataxia Type 1: Phenotypic and Genetic Correlation in a Cohort of Chinese Patients with SYNE1 Variants

Mutations in the synaptic nuclear envelope protein 1 (SYNE1) gene have been reported to cause autosomal recessive cerebellar ataxia (ARCA) type 1 with highly variable clinical phenotypes. The aim of this study was to describe the phenotypic-genetic spectrum of SYNE1-related ARCA1 patients in the Chinese population. We screened 158 unrelated patients with autosomal recessive or sporadic ataxia for variants in SYNE1 using next-generation sequencing. Pathogenicity assessment of SYNE1 variants was interpreted according to the American College of Medical Genetics standards and guidelines. We identified eight truncating variants and two missense variants spreading throughout the SYNE1 gene from six unrelated families, including nine novel variants and one reported variant. Of the six index patients, two patients showed the classical pure cerebellar ataxia, while four patients exhibited non-cerebellar phenotypes, including motor neuron symptoms, cognitive impairment, or mental retardation. The variants associated with motor neuron or cognition involvement tend to be located in the C-terminal region of SYNE1 protein, compared with the variants related to pure cerebellar ataxia. Our data indicating SYNE1 mutation is one of the more common causes of recessive ataxia in the Chinese population. The use of next-generation sequencing has enabled the rapid analysis of recessive ataxia and further expanded our understanding of genotype-phenotype correlation.