Titin Mutations Research Articles

Construction and validation of a TTN mutation associated immune prognostic model for evaluating immune microenvironment and outcomes of gastric cancer: An observational study.

Gastric cancer (GC) is a prevalent form of cancer worldwide, and TTN (titin) mutations are frequently observed in GC. However, the association between TTN mutations and immunotherapy for GC remains unclear, necessitating the development of novel prognostic models. The prognostic value and potential mechanisms of TTN in stomach adenocarcinoma were evaluated by TCGA (The Cancer Genome Atlas)-stomach adenocarcinoma cohort analysis, and an immune prognostic model was constructed based on TTN status. We validated it using the GSE84433 dataset. We performed Gene Set Enrichment Analysis and screened for differentially expressed genes, and used lasso (least absolute shrinkage and selection operator) regression analysis to screen for survival genes to construct a multifactorial survival model. In addition, we evaluated the relative proportions of 22 immune cells using the CIBERSORT algorithm for immunogenicity analysis. Finally, we constructed the nomogram integrating immune prognostic model and other clinical factors. GESA showed enrichment of immune-related phenotypes in patients with TTN mutations. We constructed an immune prognostic model based on 16 genes could identify gastric cancer patients with higher risk of poor prognosis. Immuno-microenvironmental analysis showed increased infiltration of naive B cells, plasma cells, and monocyte in high-risk patients. In addition, Nomo plots predicted the probability of 1-year, 3-year, and 5-year OS (overall survival) in GC patients, showing good predictive performance. In this study, we identified that TTN gene may be a potential clinical biomarker for GC and TTN mutations may be a predictor of immunotherapy in patients. We constructed and validated a new model for prognosis of GC patients based on immune characteristics associated with TTN mutations. This study may provide potential therapeutic strategies for gastric cancer.

Prognostic value of GARS in bladder cancer and its role in the tumor microenvironment.

Bladder cancer (BC), as a common type of cancer, has a poor prognosis, also some common invasive prognostic or therapeutic markers are difficult to obtain, which makes further treatment of BC difficult. Glycyl-tRNA synthetase (GARS), as one of the aminoacyl-tRNA synthetases that charge tRNAs with their cognate amino acids, has been identified as a target in many diseases, including tumors. Bioassay analysis revealed that GARS was in high expression in most cancer tissues. The expression of GARS gene in BC tissues could assess the prognosis of BC patients, and the expression in urinary extracellular vesicles (uEVs) of patients was positively correlated with the expression in tissues. In addition to this, we analyzed GARS-related differential gene expression, copy number variation (CNV) and mutation profiles, potential biological functions, immune cell infiltration and drug sensitivity. In vivo and vitro tumorigenic experiments were performed to validate the function of GARS. Single-cell data were used to further analyze its role in the microenvironment. In our study, we found that GARS was highly expressed in 30 cancer tissues including BC, and high GARS expression was negatively correlated with the prognosis of BC patients. To address this phenomenon, we analyzed the differential genes between high and low GARS groups by enrichment analysis, and identified the biological signaling pathways that were mainly enriched for their functions, and found that the enrichment was found in immune-related signaling pathways and regulation of cell-cell adhesion. Then we found that GARS was positively associated with immune cell infiltration in BC, and some common immune checkpoints were significantly overexpressed in the GARS-high group. Besides, we found that GARS was enriched in myofibroblasts in the tumor microenvironment, and the enrichment was positively correlated with epithelial-mesenchymal transition (EMT)-related genes. This study also showed a positive correlation between GARS and BC RNA stemness. Patients in the GARS-high group had considerably higher rates of P53 and Titin (TTN) mutations than those in the GARS-low group. Drug Sensitivity analysis screened for drugs that were more sensitive to GARS-high patients. Further, we found that knockdown of GARS significantly inhibited the proliferation, migration and invasion ability both in vivo and in vitro. Finally, we found that in patients with high GARS the expression in uEVs was also at a high level. In summary, this study provided evidence that GARS can be used as a prognostic and therapeutic marker for BC, we can detect GARS in uEVs instead of tissue, to provide a new, simple, noninvasive way to obtain prognostic and therapeutic markers for BC patients.

Spatial whole exome sequencing reveals the genetic features of highly-aggressive components in lung adenocarcinoma

In invasive lung adenocarcinoma (LUAD), patients with micropapillary (MIP) or solid (SOL) components had a significantly poorer prognosis than those with only lepidic (LEP), acinar (ACI) or papillary (PAP) components. It is interesting to explore the genetic features of different histologic subtypes, especially the highly aggressive components.Based on a cohort of 5,933 patients, this study observed that in different tumor size groups, LUAD with MIP/SOL components showed a different prevalence, and patients with ALK alteration or TP53 mutations had a higher probability of developing MIP/SOL components. To control individual differences, this research used spatial whole-exome sequencing (WES) via laser-capture microdissection of five patients harboring these five coexistent components and identified genetic features among different histologic components of the same tumor. In tracing the evolution of components, we found that titin (TTN) mutation might serve as a crucial intratumor potential driver for MIP/SOL components, which was validated by a cohort of 146 LUAD patients undergoing bulk WES. Functional analysis revealed that TTN mutations enriched the complement and coagulation cascades, which correlated with the pathway of cell adhesion, migration, and proliferation.Collectively, the histologic subtypes of invasive LUAD were genetically different, and certain trunk genotypes might synergize with branching TTN mutation to develop highly aggressive components.

Identification of Novel Stemness-based Subtypes and Construction of a Prognostic Risk Model for Patients with Lung Squamous Cell Carcinoma.

Although cancer stem cells (CSCs) contribute to tumorigenesis, progression, and drug resistance, stemness-based classification and prognostic signatures of lung squamous cell carcinoma (LUSC) remain unclarified. This study attempted to identify stemness-based subtypes and develop a prognostic risk model for LUSC. Based on RNA-seq data from The Cancer Genome Atlas (TCGA), Gene-Expression Omnibus (GEO) and Progenitor Cell Biology Consortium (PCBC), mRNA expression-based stemness index (mRNAsi) was calculated by one-class logistic regression (OCLR) algorithm. A weighted gene coexpression network (WGCNA) was employed to identify stemness subtypes. Differences in mutation, clinical characteristics, immune cell infiltration, and antitumor therapy responses were determined. We constructed a prognostic risk model, followed by validations in GEO cohort, pan-cancer and immunotherapy datasets. LUSC patients with subtype C2 had a better prognosis, manifested by higher mRNAsi, higher tumor protein 53 (TP53) and Titin (TTN) mutation frequencies, lower immune scores and decreased immune checkpoints. Patients with subtype C2 were more sensitive to Imatinib, Pyrimethamine, and Paclitaxel therapy, whereas those with subtype C1 were more sensitive to Sunitinib, Saracatinib, and Dasatinib. Moreover, we constructed stemness-based signatures using seven genes (BMI1, CCDC51, CTNS, EIF1AX, FAM43A, THBD, and TRIM68) and found high-risk patients had a poorer prognosis in the TCGA cohort. Similar results were found in the GEO cohort. We verified the good performance of risk scores in prognosis prediction and therapy responses. The stemness-based subtypes shed novel insights into the potential roles of LUSC-stemness in tumor heterogeneity, and our prognostic signatures offer a promising tool for prognosis prediction and guide therapeutic decisions in LUSC.

Kiosk 6Q-FA-02 - A Rare Case of Primary Restrictive Cardiomyopathy Caused by a Titin Mutation

Kiosk 6Q-FA-02 - A Rare Case of Primary Restrictive Cardiomyopathy Caused by a Titin Mutation

Influence of sarcomeric protein mutations on myocardial function in a 3D-disease model of human iPSC-derived bioartificial cardiac tissue

Abstract Background Peripartum cardiomyopathy (PPCM) is a rare type of cardiomyopathy that occurs in women without prior history of heart disease at later stages of pregnancy or several months after childbirth (1). The disease is characterized by lowered left ventricular ejection fraction (LVEF<45%) and can lead to heart failure if left untreated (1). Approximately 20% of PPCM patients harbor sarcomeric mutations, from which titin truncating variants (TTNtv-s) have the highest pathogenic potential (2). However, the role of such genetic defects of the contractile apparatus on PPCM pathogenesis is not well understood. Purpose The study aims to establish an in vitro 3D disease model of PPCM to elucidate the role of sarcomeric mutations, including titin mutations, in its etiology. We hypothesize, that the disease phenotype can be uncovered in vitro via the stimulation of PPCM patient-derived Bioartificial Cardiac Tissues (BCTs), utilizing pregnancy-related factors in our custom-made bioreactors (3). Methods We selected three patients carrying previously unstudied mutations in the TTN gene for the study. The iPSC reprogramming was performed using a commercial, Sendai virus-based kit. Pluripotency was confirmed via flow cytometry and immunofluorescence stainings. The presence of mutations was confirmed by exome sequencing. Cardiomyocyte differentiation (4) and BCT generation (3) were carried out via established protocols. Following maturation, BCTs were stimulated with the pregnancy-related factors, and tissue forces were measured in the bioreactors. These forces include intrinsically generated (spontaneous) and electrically induced (paced) contraction forces (mN), as well as passive forces, which correlate with tissue stiffness. Results We successfully generated two clonal induced pluripotent stem cell (iPSC) lines from each patient. We confirmed that all of the cell lines were >90% positive for pluripotency markers. After differentiation, CMs contracted spontaneously from day 7 onwards and were >95% positive for cardiac markers (SA, MF20, cTnT). The BCTs remodeled and started contracting on days 1-2 after generation, similarly to wild-type tissues in the baseline conditions. Prolactin treatment of Patient A, harboring a missense mutation in titin, did not show significant functional effects. We confirmed, that patients B and C harbor TTNtvs, and tissues from these patients show a trend of altered stiffness after stimulation with repeated mechanical stretch cycles or β-adrenergic agonist isoprenaline. Further analysis of the underlying mechanisms investigating metabolic changes, signaling pathways, and transcriptomics are ongoing. Conclusion The established iPSC and tissue engineering technologies offer a valuable tool for the development of an iPS-CM-based 3D in vitro disease model for PPCM, which can be used for risk stratification of individual and combined sarcomeric mutations and the development of tailored therapeutic strategies.

Gene-echocardiography: refining genotype-phenotype correlations in hypertrophic cardiomyopathy.

This study aims to clarify the association between hypertrophic patterns and genetic variants in hypertrophic cardiomyopathy (HCM) patients, contributing to the advancement of personalized management strategies for HCM. A comprehensive evaluation of genetic mutations was conducted in 392 HCM-affected families using Whole Exome Sequencing. Concurrently, relevant echocardiographic data from these individuals were collected. Our study revealed an increased susceptibility to enhanced septal and interventricular septal thickness in HCM patients harbouring gene mutations compared with those without. Mid-septal hypertrophy was found to be associated predominantly with myosin binding protein C3 (MYBPC3) variants, while a higher septum-to-posterior wall ratio correlated with myosin heavy chain 7 (MYH7) variants. Mutations in MYH7, MYBPC3, and other sarcomeric or myofilament genes (troponin I3 [TNNI3], tropomyosin 1 [TPM1], and troponin T2 [TNNT2]) showed a relationship with increased hypertrophy in the anterior wall, interventricular septum, and lateral wall of the left ventricle. In contrast, alpha kinase 3 (ALPK3)-associated hypertrophy chiefly presented in the apical region, while hypertrophy related to titin (TTN) and obscurin (OBSCN) mutations exhibited a uniform distribution across the myocardium. Hypertrophic patterns varied with the type and category of gene mutations, offering valuable diagnostic insights. Our findings underscore a strong link between hypertrophic patterns and genetic variants in HCM, providing a foundation for more accurate genetic testing and personalized management of HCM patients. The novel concept of 'gene-echocardiography' may enhance the precision and efficiency of genetic counselling and testing in HCM.

Social, Genetics and Histopathological Factors Related to Titin (TTN) Gene Mutation and Survival in Women with Ovarian Serous Cystadenocarcinoma: Bioinformatics Analysis

Several factors may increase the risk of development of ovarian cancer. In this study, we investigated the relationship between social, genetic, and histopathologic factors in women with ovarian serous cystadenocarcinoma and titin (TTN) mutations, whether the TTN gene mutation may be a predictor, and its impact on mortality and survival in these patients. A total of 585 samples from patients with ovarian serous cystadenocarcinoma were collected from The Cancer Genome Atlas and PanCancer Atlas through the cBioPortal for analysis of social, genetic, and histopathological factors. Logistic regression was used to investigate whether TTN mutation could be a predictor, and the Kaplan-Meier method was applied to analyze survival time. TTN mutation frequency did not differ between age at diagnosis, tumor stage, and race, and was related to increased Buffa hypoxia score (p = 0.004), mutation count (p < 0.0001), Winter hypoxia Score (p = 0.030), nonsynonymous tumor mutation burden (TMB) (p < 0.0001), and reduced microsatellite instability sensor score (p = 0.010). The number of mutations (p < 0.0001) and winter hypoxia score (p = 0.008) were positively associated with TTN mutations, and nonsynonymous TMB (p < 0.0001) proved to be a predictor. Mutated TTN affects the score of genetic variables involved in cancer cell metabolism in ovarian cystadenocarcinoma.

Clinical and functional characterization of a long survivor congenital titinopathy patient with a novel metatranscript-only titin variant

Congenital titinopathies are an emerging group of a potentially severe form of congenital myopathies caused by biallelic mutations in titin, encoding the largest existing human protein involved in the formation and stability of sarcomeres. In this study we describe a patient with a congenital myopathy characterized by multiple contractures, a rigid spine, non progressive muscular weakness, and a novel homozygous TTN pathogenic variant in a metatranscript-only exon: the c.36400A > T, p.Lys12134*. Muscle biopsies showed increased internalized nuclei, variability in fiber size, mild fibrosis, type 1 fiber predominance, and a slight increase in the number of satellite cells. RNA studies revealed the retention of intron 170 and 171 in the open reading frame, and immunoflourescence and western blot studies, a normal titin content. Single fiber functional studies showed a slight decrease in absolute maximal force and a cross-sectional area with no decreases in tension, suggesting that weakness is not sarcomere-based but due to hypotrophy. Passive properties of single fibers were not affected, but the observed increased calcium sensitivity of force generation might contribute to the contractural phenotype and rigid spine of the patient. Our findings provide evidence for a pathogenic, causative role of a metatranscript-only titin variant in a long survivor congenital titinopathy patient with distal arthrogryposis and rigid spine.

Construction of a TTN Mutation-Based Prognostic Model for Evaluating Immune Microenvironment, Cancer Stemness, and Outcomes of Colorectal Cancer Patients.

Colorectal cancer (CRC) is one of the commonest cancers worldwide. As conventional biomarkers cannot clearly define the heterogeneity of CRC, it is essential to establish novel prognostic models. For the training set, data pertaining to mutations, gene expression profiles, and clinical parameters were obtained from the Cancer Genome Atlas. Consensus clustering analysis was used to identify the CRC immune subtypes. CIBERSORT was used to analyze the immune heterogeneity across different CRC subgroups. Least absolute shrinkage and selection operator regression was used to identify the genes for constructing the immune feature-based prognostic model and to determine their coefficients. A gene prognostic model was then constructed to predict patient outcomes; the model was then externally validated using data from the Gene Expression Omnibus. As a high-frequency somatic mutation, the titin (TTN) mutation has been identified as a risk factor for CRC. Our results demonstrated that TTN mutations have the potential to modulate the tumor microenvironment, converting it into the immunosuppressive type. In this study, we identified the immune subtypes of CRC. Based on the identified subtypes, 25 genes were selected for prognostic model construction; a prediction model was also constructed, and its prediction accuracy was tested using the validation dataset. The potential of the model in predicting immunotherapy responsiveness was then explored. TTN-mutant and TTN-wild-type CRC demonstrated different microenvironment features and prognosis. Our model provides a robust immune-related gene prognostic tool and a series of gene signatures for evaluating the immune features, cancer stemness, and prognosis of CRC.

Structural basis of domain destabilization by dilated-cardiomyopathy-causing missense mutations in titin.

Truncating variants in the titin gene are the most common cause of familial dilated cardiomyopathy (DCM), accounting for 25% of the genotype-positive cases. Similar to other genetic diseases triggered by gene loss of function, it has been proposed that destabilizing titin missense mutations can also result in DCM. Indeed, the highly destabilizing C3575S mutation targeting immunoglobulin-like (Ig) 21 domain of cardiac titin has been recently identified as a cause of DCM. However, the effects of the mutation on the structure of the parent domain and whether altered disulfide bond formation contribute to the destabilizing properties of the mutation remain unexplored. Here, using high-resolution X-ray crystallography, we report that the structure of the C3575S mutant domain is largely unperturbed (RMSD: 0.538 Å). In addition, using gel-shift assays, we have ruled out that the lower thermal stability of the mutant domain results from its inability to establish intramolecular disulfide bonds. Instead, we propose that the lower hydrophobicity of serine is not well accommodated in the core of mutant domains, causing their destabilization. Finally, we have observed that similar missense mutations, which cause a decrease in hydrophobicity in buried positions of titin Ig domains, are enriched in DCM patients. Altogether, our results illustrate that subtle physicochemical changes induced by titin missense mutations can cause domain destabilization, even in the absence of remarkable structural alterations, resulting in development of DCM.

Genomic and RNA-Seq profiling of patients with HFrEF unraveled OAS1 mutation and aggressive expression

BackgroundHeart failure (HF) is a complex pathophysiological state characterized by inadequate delivery of blood and nutrients to the cardiac tissues. It is rarely curable and is commonly associated with a poor prognosis. In this study, we aimed to analyse exomic and RNA-Seq data from patients with HF to identify the key altered pathways in HF. MethodsWhole blood samples were collected from patients with HF and subjected to whole exome sequencing (WES) and RNA-Seq analysis. The gene expression and RNA-Seq data obtained were verified using gene chip analysis and RT-PCR. ResultsBoth exomic and RNA-Seq data confirmed the dysregulation of phosphorylation and immune signalling in patients with HF. Specifically, exomic analysis showed that TITIN, OBSCURIN, NOD2, CDH2, MAP3K5, and SLC17A4 mutations were associated with HF, and RNA-Seq revealed that S100A12, S100A8, S100A9, PFDN5, and TMCC2, were upregulated in patients with HF. Additionally, comparison between RNA-seq and WES data showed that OAS1 mutations are associated with HF. ConlcusionOur findings indicated that patients with HF show an overall disruption of key phosphorylation and immune signalling pathways. Based on RNA-seq and WES, OAS1 mutations may be primarily responsible for these changes.

Early Diagnosis of Abnormal Left Ventricular Systolic Functions of Rare Pathogenic Titin Mutation Gene Carriers in FHCM by Three-Dimensional Speckle Tracking Echocardiography Combined with Gene Detection.

Objective This study aimed to explore the early diagnosis of abnormal left ventricular systolic function of rare pathogenic titin (TTN) mutation gene carriers in familial hypertrophic cardiomyopathy (FHCM) by three-dimensional speckle tracking echocardiography (3D-STE) combined with gene detection. Methods Eighteen members of a Hui nationality family in Ningxia province of China were enrolled in this study in July 2019. The proband was tested with high-throughput sequencing of gene detection technology to detect the whole exome, and the mutation locus of pathogenic TTN gene was analyzed. According to the result, 16 subjects were divided into two groups: carrier group (n = 4) and noncarrier group (n = 12). Related indicators from 2DE were obtained, and myocardial strain indicators from 3D-STE were analyzed by postprocessing software of Tomtec. Strain indicators included global longitudinal strain (GLS), global circumference strain (GCS), global radial strain (GRS), regional longitudinal strain (RLS), regional circumference strain (RCS), and regional radial strain (RRS). All those indicators were compared between the two groups, and a receiver operating characteristic (ROC) curve was used for further analysis. Results There were 4 subjects diagnosed as asymptomatic TTN gene carriers with the mutation locus of Val135643Ile. Compared with the noncarrier group, GLS and partial RLS were significantly reduced in the carrier group. The ROC curve shows that GLS has the largest AUC, and its sensitivity was better than LVPWD and specificity was better than IVSD and LVMI obtained from 2DE in the carrier group. Conclusions There were 4 subjects diagnosed as asymptomatic TTN gene carriers with the mutation locus of Val135643Ile, and their GLS and partial RLS were significantly reduced; GLS had the better sensitivity and specificity than LVPWD, IVSD, and LVMI.

VP.03 Diagnosing Titinopathy: lessons from a multi-omics pilot study

Titinopathy, or skeletal muscular dystrophy caused by autosomal recessive mutations in Titin (<i>TTN</i>), poses a unique diagnostic challenge because of A) significant variation in clinical manifestation, B) presence of rare putative deleterious <i>TTN</i> variants amongst healthy individuals which increases likelihood of incidental findings. Altogether, this makes establishing a definite diagnosis of Titinopathy based solely on phenotypic and genotypic information virtually impossible in the absence of corroborative evidence. We report six patients with Titinopathy from four unrelated families. In each case, prior genomics-based efforts had failed to reach a conclusive diagnosis and a confirmed diagnosis was reached by co-analyzing patient genomic and transcriptomic data. The multi-omics approach provided direct evidence confirming or dismissing impact of plausible candidate variants in TTN and other genes. This clarity of information was critical in solving these cases. The phenotypic diversity of the cohort highlights the diagnostic challenge. The first family included two siblings presented with adolescent onset multiple joint contractures, slowly progressive spine rigidity and elevated Creatine Kinase (CK). The severity of condition varied amongst the siblings with elder brother exhibited mild limb girdle weakness not seen in the younger sister. The second and third families comprise of a girl and boy respectively. Both unrelated patients had similar symptoms characterized by early onset hypotonia, delayed walking and elevated CK. Both had limb girdle muscle weakness and mild scoliosis. Their motor performance had been stable, and both continued to walk independently in adulthood. The fourth family included two siblings presented with arthrogryposis multiplex congenita and hypotonia after birth. Their mother reported decreased fetal movement during both pregnancies. Both elder sister and younger brother had delayed walking and limb girdle weakness. However, their joint contractures improved with age and regular stretching. The younger brother also had autistic features. Both siblings had normal CK. All patients in the study had normal echocardiogram suggesting lack of cardiac involvement. Our multi-omics findings link individualized patient condition to the specific functional impact of their implicated mutations.

Exploring the Potential of Symmetric Exon Deletion to Treat Non-Ischemic Dilated Cardiomyopathy by Removing Frameshift Mutations in TTN.

Non-ischemic dilated cardiomyopathy (DCM) is one of the most frequent pathologies requiring cardiac transplants. Even though the etiology of this disease is complex, frameshift mutations in the giant sarcomeric protein Titin could explain up to 25% of the familial and 18% of the sporadic cases of DCM. Many studies have shown the potential of genome editing using CRISPR/Cas9 to correct truncating mutations in sarcomeric proteins and have established the grounds for myoediting. However, these therapies are still in an immature state, with only few studies showing an efficient treatment of cardiac diseases. This publication hypothesizes that the Titin (TTN)-specific gene structure allows the application of myoediting approaches in a broad range of locations to reframe TTNtvvariants and to treat DCM patients. Additionally, to pave the way for the generation of efficient myoediting approaches for DCM, we screened and selected promising target locations in TTN. We conceptually explored the deletion of symmetric exons as a therapeutic approach to restore TTN’s reading frame in cases of frameshift mutations. We identified a set of 94 potential candidate exons of TTN that we consider particularly suitable for this therapeutic deletion. With this study, we aim to contribute to the development of new therapies to efficiently treat titinopathies and other diseases caused by mutations in genes encoding proteins with modular structures, e.g., Obscurin.

Clinical and molecular genetic analysis of early-onset myopathy with fatal cardiomyopathy: Novel biallelic M-line TTN mutation and review of the literature

Early-onset myopathy with fatal cardiomyopathy (EOMFC), also known as Salih myopathy (SALMY) is a rare, heterogeneous, and severe form of titinopathies with autosomal recessive inherited neuromuscular disorders that affects both skeletal and cardiac muscles. It was previously identified only in the Arab population with unknown incidence. Titin (TTN) mutations that have been reported in congenital myopathies are associated with a variety of phenotypic spectrum of titinopathies, which are scattered along with the 364 exons of the gene. In this study, we report a consanguineous Moroccan female child aged 29 months who presented with congenital myopathy associated to dilated cardiomyopathy. Clinical Exome Sequencing identified a novel homozygous truncating mutation c.106541delA p.(Asp35514Valfs*32) in exon 361 of the TTN gene. Sanger sequencing confirmed the mutation in a homozygous state in the proband and in a heterozygous state in both of her parents. Clinical and molecular data of the proband were correlated with 15 patients reported in the literature for congenital myopathy associated to a heart defect or development of dilated cardiomyopathy with at least one mutant allele in the M-band titin protein as inclusion criteria. In conclusion, the application of NGS in rare genetic heterogeneous forms as EOMFC provides more evidently an increasing proportion of congenital myopathies than currently recognized and expands the mutation spectrum of the TTN gene for better guiding the genetic diagnosis with adequate genetic counseling to the Moroccan families.

Truncated titin is incorporated into the sarcomere in human cardiac samples with dilated cardiomyopathy

The most common genetic cause of dilated cardiomyopathy (DCM) is mutations in titin gene, TTN, with truncating variants (TTNtv). TTN encodes the giant protein titin, a large (3-4 MDa) and abundant protein that forms the third myofilament type of striated muscle. Titin spans half the sarcomere, from the Z-disk to the M-line. The underlying mechanisms by which titin mutations induce DCM are poorly understood.

Mutations in the TTN Gene are a Prognostic Factor for Patients with Lung Squamous Cell Carcinomas.

PurposeTo analyze the relationship between titin (TTN) mutation gene and tumor mutational burden (TMB) and the with prognosis of lung squamous cell carcinomas (LUSC), and to explore the feasibility of TTN as a potential prognostic marker of for LUSC.MethodsWe analyzed the somatic mutation landscape of LUSC samples using datasets obtained from The Cancer Genome Atlas (TCGA) and International Cancer Genome Consortium (ICGC) databases. Sequence data were divided into wild and mutant groups, and differences in TMB values between the groups compared using a Mann–Whitney U-test. The Kaplan Meier method was used to analyze the correlation between TTN mutation and LUSC prognosis, whereas CIBERSORT algorithm was used to calculate the degree of relative enrichment degree of among tumor-infiltrating lymphocytes in LUSC.ResultsAnalysis of both datasets revealed high mutations in the TTN gene, with mutants exhibiting a significantly higher TMB value relative to the wild-type (P < 0.001). Prognosis of the TTN mutant group in LUSC was significantly better than that of wild-type (P = 0.009). Kaplan Meier curves showed that TTN mutation may be an independent prognostic factor in LUSC patients (HR: 0.64, 95% CI 0.48–0.85, P = 0.001), while GSEA analysis revealed that TTN mutation plays a potential role in the development of LUSC. Finally, analysis of LUSC immune microenvironment revealed that TTN mutation was significantly associated with enrichment of macrophages M1 (p < 0.05).ConclusionTTN mutation is associated with TMB, and is positively correlated with prognosis of LUSC. Therefore, this mutation may serve as a potential prognostic indicator of LUSC.

418 Titin mutations and female sex characterize dilated cardiomyopathy in the elderly

Abstract Aims Dilated cardiomyopathy (DCM) is frequently caused by genetic factors. Studies identifying deleterious rare variants have predominantly focused on early-onset cases, and little is known about the genetic underpinnings of the growing numbers of patients with DCM who are diagnosed after 60 years of age (i.e. late-onset DCM). The aim is to investigate the prevalence, type, and prognostic impact of disease-associated rare variants in late-onset DCM patients. Methods and results We analysed a population of late-onset DCM patients who had undergone genetic testing in seven international tertiary referral centres worldwide. A positive genotype was defined as the presence of ‘pathogenic’ or ‘likely pathogenic’ (P/LP) variants. The study outcome was all-cause mortality. 184 patients over age 60 years (56% females, mean age 67 ± 6 years, mean left ventricular ejection fraction 32 ± 10%) were studied. Sixty-six patients (36%) were carriers of a P/LP variant. Titin truncating variants (TTNtv) were the most prevalent (present in 25% of the total population and accounting for 69% of all genotype-positive patients). During a median follow-up of 42 months (interquartile range: 10–115), 23 patients (13%) died; 17 of these (25%) were carriers of P/LP variants while six patients (5.1%) were genotype-negative (P &amp;lt; 0.001). Conclusions In the largest series worldwide, to date, of patients with late-onset DCM, we found a high prevalence of female sex and a high genetic mutation burden, largely due to TTNtv. Patients with a positive genetic test had higher mortality than genotype-negative patients. These findings support the extended use of genetic testing also in the elderly.

Functional impact of titin (TTN) mutations in ocular surface squamous neoplasia

Mutations in the titin (TTN) gene are among the most common genomic aberrations in ocular surface squamous neoplasia (OSSN), the most common cancer of the external eye. Further, TTN mutations are associated with resistance to standard therapy with topical interferon alpha-2b (IFN-α2b). However, it remains unclear how TTN mutations drive OSSN pathogenesis and treatment resistance. TTN encodes the largest protein in the human body and its best understood function is as a myofibril scaffold in striated muscle. However, recent evidence indicates that TTN has additional functions in non-muscle cells and in cancer. Here, we performed a disorder-based bioinformatics analysis which revealed that intrinsically disordered protein regions are abundant in TTN and provide mechanistic insights into its function as a nuclear protein in epithelial cells. Specific mutations found in OSSN are predicted to affect its intrinsically disordered protein regions (IDPRs), promoting chromosomal instability, oncogenesis, and altered response to IFN-α2b treatment.