Variable Phenotype Research Articles

Diabetes Mellitus Associated with Maternally Inherited Diabetes and Deafness (MIDD): From Pathogenic Variant to Phenotype.

Maternally inherited diabetes and deafness (MIDD) is a monogenic mitochondrial disorder caused by a pathogenic variant in the MT-TL1 gene encoding for a leucine transfer RNA. We propose a new hypothesis that explains how the MT-TL1 variant causes impaired glucose tolerance and diabetes in MIDD. We suggest that diabetes in MIDD primarily depends on a variable combination of insulin resistance and impaired beta cell function that seems more likely to occur in the presence of high skeletal muscle heteroplasmy and moderate beta cell heteroplasmy for m.3243A>G. The underlying genetic defect generates oxidative stress and disrupts the tricarboxylic acid cycle, leading to mTORC1 hyperactivity and modifying mitochondrial retrograde signalling. mTORC1 hyperactivity contributes to insulin resistance and beta cell dysfunction and to an increased load of the m.3243A>G phenotypic variant. Abnormal mitochondrial signalling affects the nuclear epigenome and influences MIDD phenotype. Despite being an apparent pathogenic factor, we highlight evidence showing that heteroplasmy in the blood and in tissues, does not fully explain the phenotypic variability of this condition, and that other factors, including mtDNA copy number, additional nuclear or mitochondrial variants, environmental factors and metabolic characteristics of the patient may be contributing factors. A better understanding of the mechanisms leading to MIDD diabetes will help inform novel management strategies for this form of diabetes.

Case Report: Allelic and biallelic variants in coagulation factor XI cause factor XI deficiency

Factor XI deficiency is a rare inherited coagulation disorder with an estimated prevalence of affecting 1 in 1 million. It is characterized by mild and variable bleeding phenotypes, including bruises, nosebleeds, hematuria, and postpartum hemorrhage. It can be caused by either allelic or biallelic variants in coagulation factor XI (F11). Coagulation factor XI is a glycoprotein that circulates in plasma as a non-covalent complex with high-molecular-weight kininogen. It is converted to an active protease, coagulation factor XIa, which participates in blood coagulation as a catalyst. In this study, we recruited a family with Factor XI deficiency and identified two F11 variants using whole-exome sequencing. One (NM_000128.4: c.841C>T, p.Q281X) was a known variant, and the other (NM_000128.4: c.1832T>G, p.V611G) had not been reported. In addition, we compiled the characteristics of known missense variants in coagulation factor XI. Our findings enriched the variant spectrum of Factor XI deficiency and contributed to the genetic counseling and molecular diagnostics of Factor XI deficiency.

Impact of Sublethal Disinfectant Exposure on Antibiotic Resistance Patterns of Pseudomonas aeruginosa.

The problem of hospital cross-infection due to contamination of disinfectants has been recognized elsewhere. The passage of bacteria through diluted disinfectants may not only bring about phenotypic changes in their antibiograms but also changes in phage susceptibility patterns. Contact with disinfectants in sublethal concentrations allows survival and multiplication of bacteria. Serial passage, through disinfectants at subminimal inhibitory concentrations, induced antibiotic resistance in 18% of derived phenotypic variants of fifty strains of Pseudomonas aeruginosa which were isolated from diarrheal stools of infants in children's hospital. A proportion of these strains became susceptible to an increased number of antibiotics. The present study revealed that all the isolates were resistant to tetracycline and carbenicillin and 40% of these isolates became sensitive to both antibiotics after exposure to disinfectants. The exposure to disinfectants induced neomycin resistance among two isolates. The resistance patterns were three before disinfectants exposure which increased to be nine different patterns after exposure. No antibiotic resistance was transferred between P. aeruginosa and Escherichia coli K12 as a recipient strain. Almost 50% of the isolates tested became sensitive to tetracycline, carbenicillin and co-trimoxazole after exposure to disinfectants. The resistance patterns among the 50 isolates were three which changed to be nine different patterns after exposure to disinfectants. Unjustifiable use of disinfectants might give a chance for survival and multiplication of pathogenic bacteria to develop new resistance patterns to antibiotics in use with a short time. These new resistance variants of bacteria which multiply in hospital environment could lead to serious epidemic conflicts particularly the epidemiological reporting and management.

Assessing Drug Sensitivity in Fission Yeast Using Half-Maximal Inhibitory Concentration (IC50) Assays.

Fission yeast is an excellent model organism in which to study mammalian drug sensitivities. In addition to building a mechanistic picture of drug effect, fission yeast screens may be valuable in determining compounds that show synthetic lethality effects. While compounds might be screened for a variety of phenotypes, an effective method is to detect the proliferative effects of a new compound on a yeast culture. This is traditionally performed in acute viability assays or spot tests; both methods require some knowledge of concentration to observe an effect. Mammalian cell culture experiments that assess proliferation to indicate drug dose and effect are well described. However, differences between S. pombe growth characteristics and mammalian cells mean that importing a mammalian viability assay requires consideration of potential effects on fission yeast biology. We describe the half-maximum inhibitory (IC50) dose as a method of rapid proliferation effect screening. IC50 determination is performed on liquid cultures in 96-well plates and may be developed for initial compound library uses or in synthetic lethality screening of drug effects.

Abstract 4136394: Elucidation of a novel genetic substrate responsible for genetically elusive ring-like arrhythmogenic cardiomyopathy

Background: Arrhythmogenic cardiomyopathy (ACM) is a genetic heart disease characterized by fibrofatty replacement of ventricular myocardium. Arrhythmogenic left ventricular (LV) cardiomyopathy (ALVC) is a phenotypic variant of ACM predominantly involving the LV. Mutations in genes encoding for desmosome proteins and filamin C have been implicated in ALVC, especially in the setting of a ring-like late gadolinium enhancement (LGE) imaging pattern. Objective: To identify the underlying genetic substrate responsible for genetically elusive ring-like ALVC in a patient with seemingly sporadic/recessive disease. Methods: A 38-year-old male was referred for genetic investigation to determine the underlying genetic substrate responsible for his ALVC phenotype. The patient fulfilled both electrocardiographic (low voltage in the limb leads and anterolateral T-wave inversions) and imaging (>1 segment of subepicardial LGE) criteria for ALVC. Additionally, the patient experienced unexplained episodes of tachycardia, shakiness, sweating, and nausea prompting concern for an underlying neuromuscular disease. Genome sequencing (GS) was performed on DNA isolated from the affected patient and both of his unaffected parents. Variants were filtered assuming either a sporadic de novo occurrence or an autosomal recessive inheritance pattern. Results: GS identified compound heterozygous GNPTAB variants in the affected patient. A previously reported maternally derived p.Leu257Leu (c.771G>A) variant involving the last nucleotide of exon 7 of the GNPTAB gene and a novel paternally inherited Lys834fs*5 frame-shift variant were identified. The p.Leu257Leu variant has been reported to cause aberrant splicing and exon skipping of the GNPTAB mRNA transcript. Pathogenic variants in the GNPTAB encoded N-acetylglucosamine-1 (GlcNAc)-phosphotransferase subunits alpha/beta cause mucolipidosis type III, a rare recessive lysosomal storage disease characterized by coarse facial features, developmental delay, short stature, skeletal deformities, and cardiac involvement including valvular thickening and cardiomyopathy. Conclusions: Here, using a genome sequencing trio analysis we identified a compound heterozygous GNPTAB pathogenic variants as the underlying genetic substrate in a patient with ring-like ALVC and concomitant neuromuscular disease manifestation. Genome sequencing may identify the genetic etiology responsible for an otherwise undifferentiated diagnosis of cardiomyopathy.

The Great Controversy of Obstructive Sleep Apnea Treatment for Cardiovascular Risk Benefit: Advancing the Science Through Expert Consensus. An Official American Thoracic Society Workshop Report.

The prevalence of obstructive sleep apnea (OSA) is on the rise, driven by various factors including more sensitive diagnostic criteria, increased awareness, enhanced technology through at-home testing enabling easy and cost-effective diagnosis, and a growing incidence of comorbid conditions such as obesity. Treating symptomatic patients with OSA syndrome to enhance quality of life remains a cornerstone approach. However, there is a lack of consensus regarding treatment to improve cardiovascular disease (CVD) outcomes, particularly in light of overall negative results from several randomized controlled trials (RCT) indicating no benefit of positive airway pressure (PAP) therapy on primary and secondary CVD events. These RCTs were limited by suboptimal PAP adherence, use of composite CVD outcomes, and limited diversity and generalizability to Sleep Clinic patients. As such, this workshop assembled clinical experts, as well as researchers in basic and translational science, epidemiology, clinical trials, and population health to discuss the current state, and future research directions to guide personalized therapeutic strategies and future research directions in OSA. There was overall consensus among workshop participants that OSA represents a heterogeneous disease with variable endotypes and phenotypes, and heterogeneous responses to treatment. Future research should prioritize employing multi-modal therapeutic approaches within innovative and adaptive trial designs, focusing on specific subgroups of OSA patients hypothesized to benefit from a CVD perspective. Future work should also be inclusive of diverse populations and consider the life-course of OSA to better comprehend treatment strategies that can address the disproportionate impact of OSA on racially minoritized groups. Further, a more holistic approach to sleep must be adopted to include broader assessments of symptoms, sleep duration, and comorbid sleep and circadian disorders. Finally, it is imperative to establish a sleep research consortium dedicated to collecting raw data and biospecimens categorized by OSA subtypes. This will facilitate mechanistic determinations, foster collaborative research, and help bolster the pipeline of early-career researchers.

Characteristics of stem sings of EpCAM-negative and EpCAM-positive tumor cells in primary tumor and 2D and 3D cultures in breast cancer

One of the predictors of adverse prognosis in breast cancer is the overexpression of the EpCAM protein. However, a signifcant part of tumor cells have low or no EpCAM expression. The molecular features and the ability to grow in 2D and 3D cultures, indirectly refecting metastatic potential of tumor cells without EpCAM expression, have not been sufficiently studied.The aim of the study was to compare phenotypic variants of stem cells and EMT depending on the EpCAM expression in the primary tumor of breast cancer and 2D and 3D cultures.Material and Methods. The study included 7 patients with invasive breast carcinoma of no special type. Luminal A subtype was found in 2/7 patients (29 %), and luminal B HER2-negative molecular subtype was found in 5/7 patients (71 %). The patients didn’t have neoadjuvant chemotherapy. Cells from the primary tumor were cultured in 2D and 3D. The primary tumor cells, 2D and 3D cultures were phenotyped using fow cytometry with antibodies targeting: CD45, EpCAM (CD326), CD44, CD24, N-cadherin (CD325), and CD133, CK7/8, EpCAM (CD326).Results. No significant differences were found in the frequency of detection and the number of cells exhibiting stem cell features among EpCAM- and EpCAM+ tumor cells, 2D and 3D cultures. All phenotypic variants of co-expression of stemness markers CD44, CD24, CD133, and ALDH were present both in the primary tumor and 2D/3D cultures. Stem cells in mammospheres had features of both epithelial and hybrid EMT phenotypes. In primary tumors and 2D/3D cultures, the smallest proportion consisted of stem cells with the CD44+CD24- phenotype and cells co-expressing CD44+CD24- with other stemness markers, while the largest proportion comprised stem cells with ALDH+ and ALDH+CD133+ phenotypes. Marked intra- and inter-tumor heterogeneity in the phenotypic composition of primary tumors, 2D, and 3D cultures was noted.Conclusion. The results indicate that EpCAM-negative and EpCAM-positive tumor cells of luminal molecular subtype of breast cancer are capable of exhibiting various phenotypic variants of stemness and EMT in the primary tumor and 2D and 3D cultures. In most cases, individual tumor cells show co-expression of several stemness markers. The phenotypic composition of primary tumors, 2D and 3D cultures is characterized by pronounced intra- and inter-tumor heterogeneity.

Biliary, Renal, Neurological, and Skeletal syndrome in a Chinese boy.

Biliary, Renal, Neurological, and Skeletal syndrome (BRENS syndrome) is a very rare ciliopathy caused by variants in the TTC26 (OMIM 617453) gene. There are only a few case reports of BRENS syndrome in the literature. We report here a Chinese case of BRENS syndrome who presented with kidney, neurological, skeletal, and other features. It is the first description of BRENS syndrome without biliary involvement. Gene testing revealed three novel compound heterozygous variants in the TTC26 gene, c.1069 + 5G > A in one allele from the mother and c.511A > G (p.Ile171Val) and c.1099T > C (p.Ser367Pro) in another allele from the father. We suggest that patients with BRENS syndrome may exhibit variable phenotypes.

Four putative pathogenic ARHGAP29 variants in patients with non-syndromic orofacial clefts (NsOFC).

The pathophysiological basis of non-syndromic orofacial cleft (NsOFC) is still largely unclear. However, exome sequencing (ES) has led to identify several causative genes, often with reduced penetrance. Among these, the Rho GTPase activating protein 29 (ARHGAP29) has been previously implicated in 7 families with NsOFC. We investigated a cohort of 224 NsOFCs for which no genetic pathogenic variant had been identified by diagnostic testing. We used ES and bioinformatic variant filtering and identified four novel putative pathogenic variants in ARHGAP29 in four families. One was a missense variant leading to the substitution of the first methionine with threonine, two were heterozygous frameshift variants leading to a premature termination codon, and one was a nonsense variant. All variants were predicted to result in loss of function, either through mRNA decay, truncated ARHGAP29, or abnormal N-terminal initiation of translation of ARHGAP29. The truncated ARHGAP29 proteins would lack the important RhoGAP domain. The variants were either absent or rare in the control population databases, and the loss of intolerance score (pLI) of ARHGAP29 is 1.0, suggesting that ARHGAP29 haploinsufficiency is not tolerated. Phenotypes ranged from microform cleft lip (CL) to complete bilateral cleft lip and palate (CLP), with one unaffected mutation carrier. These results extend the mutational spectrum of ARHGAP29 and show that it is an important gene underlying variable NsOFC phenotypes. ARHGAP29 should be included in diagnostic genetic testing for NsOFC, especially familial cases, as it may be mutated in ∼4% of them (4/97 in our cohort) with high penetrance (89%).

Identification and genetic dissection of convergent persister cell states.

Persister cells, rare phenotypic variants that survive normally lethal levels of antibiotics, present a major barrier to clearing bacterial infections1. However, understanding the precise physiological state and genetic basis of persister formation has been a longstanding challenge. Here we generated a high-resolution single-cell2 RNA atlas of Escherichia coli growth transitions, which revealed that persisters from diverse genetic and physiological models converge to transcriptional states that are distinct from standard growth phases and instead exhibit a dominant signature of translational deficiency. We then used ultra-dense CRISPR interference3 to determine how every E. coli gene contributes to persister formation across genetic models. Among critical genes with large effects, we found lon, which encodes a highly conserved protease4, and yqgE, a poorly characterized gene whose product strongly modulates the duration of post-starvation dormancy and persistence. Our work reveals key physiologic and genetic factors that underlie starvation-triggered persistence, a critical step towards targeting persisters in recalcitrant bacterial infections.

Revolutionizing medicine: Recent developments and future prospects in stem-cell therapy.

Stem-cell therapy is a revolutionary frontier in modern medicine, offering enormous capacity to transform the treatment landscape of numerous debilitating illnesses and injuries. This review examines the revolutionary frontier of treatments utilizing stem cells, highlighting the distinctive abilities of stem cells to undergo regeneration and specialized cell differentiation into a wide variety of phenotypes. This paper aims to guide researchers, physicians, and stakeholders through the intricate terrain of stem-cell therapy, examining the processes, applications, and challenges inherent in utilizing stem cells across diverse medical disciplines. The historical journey from foundational contributions in the late 19th and early 20th centuries to recent breakthroughs, including ESC isolation and iPSC discovery, has set the stage for monumental leaps in medical science. Stem cells' regenerative potential spans embryonic, adult, induced pluripotent, and perinatal stages, offering unprecedented therapeutic opportunities in cancer, neurodegenerative disorders, cardiovascular ailments, spinal cord injuries, diabetes, and tissue damage. However, difficulties, such as immunological rejection, tumorigenesis, and precise manipulation of stem-cell behavior, necessitate comprehensive exploration and innovative solutions. This manuscript summarizes recent biotechnological advancements, critical trial evaluations, and emerging technologies, providing a nuanced understanding of the triumphs, difficulties, and future trajectories in stem cell-based regenerative medicine. Future directions, including precision medicine integration, immune modulation strategies, advancements in gene-editing technologies, and bioengineering synergy, offer a roadmap in stem cell treatment. The focus on stem-cell therapy's potential highlights its significant influence on contemporary medicine and points to a future in which individualized regenerative therapies will alleviate various medical disorders.

Hidradenitis Suppurativa from a Multi-Omic Scope.

Hidradenitis suppurativa (HS) is recognized as a systemic immune-mediated disease (IMID), sharing genetic and environmental risk factors with other IMIDs such as inflammatory bowel disease and psoriasis. Over time, correlating clinical findings with genetic, proteomic, and metabolomic results has been challenging due to diverse sampling methods, analysis techniques, and the use of variable clinical phenotype descriptions across studies. This review aims to summarize the results from various omics fields to explore the etiopathology of HS. Genetic studies highlight defects in Notch and γ-secretase signaling and inflammasome function. Syndromic HS involves specific mutations in autoinflammatory syndromes such as pyogenic sterile arthritis, pyoderma gangrenosum, and acne (PAPA) and pyoderma gangrenosum, acne, and HS (PASH). Proteomic analyses reveal key inflammatory pathways indicating activation of both innate and adaptive immunity. Additionally, microbiome studies show an increased presence of anaerobes like Prevotella in HS lesions and a decreased presence of commensals such as Staphylococcus epidermidis. Gut microbiota dysbiosis, particularly involving Ruminococcus gnavus and Clostridium ramosum, is associated with HS. Moreover, metabolomic profiling indicates dysregulated tryptophan catabolism and lipid metabolism, with increased 5-lipoxygenase-derived metabolites and odd-chain fatty acids suggesting bacterial involvement. In summary, despite advances, robust associations between genetics, proteomics, microbiome, and metabolomics in HS are still lacking. Integrating these datasets could identify new clinical phenotypes, genetic predispositions, microbial signatures, and therapeutic targets, enhancing personalized treatment strategies and biomarker discovery for HS classification, prognosis, and treatment response.

Comparing One Stage, Chromogenic Assay Results and Discrepancies with Bleeding Phenotype and Genetic Variants in Females with Hemophilia A

Increasing evidence in females with Hemophilia A has shown significant bleeding symptoms. Accurate factor VIII activity (FVIII:C) measurement is essential to assign correct diagnosis/severity. Assay discrepancies reported in Hemophilia A male patients, are not well studied in females. Our research sought to assess the association of FVIII:C levels by one-stage versus chromogenic assays and the assay discrepancy with bleeding phenotype and genetic mutation in females with hemophilia A. Data from 64 females with hemophilia A from our center were reviewed with center's IRB approval. Descriptive statistics, Chi-square, Fisher's exact and Bland-Altman plot analysis were applied. Abnormal ISTH BAT score was seen in 52% (FVIII:C<40 IU/dL: 72%/73%; FVIII:C>40 IU/dL: 41%/45%; by OSA/CSA respectively), more often in adults and post-menarchal patients. Assay discrepancies were present, direct more often than inverse. Based on one assay result only, 11 (17%) patients would have been incorrectly diagnosed and 1 (1.5%) patient would have been assigned incorrect hemophilia severity. No association of genetic variants with FVIII:C levels and bleeding phenotype were found. Our study emphasizes the importance of evaluating female hemophilia A patients for bleeding phenotype. Our study is the first to document prevalence of assay discrepancies exclusively in females with Hemophilia A, which can lead to inaccurate diagnosis/severity assignment. Future larger, multi-center studies are needed to validate our findings, to help develop recommendations regarding the appropriate use of assays for accurate diagnosis and to further elucidate the association of genetic variants with bleeding phenotype and assay discrepancies.

Comparison of Genetic, Auditory Features, and Systemic Clinical Phenotype in 14 Families with Syndromic Hearing Loss.

Syndromic hearing loss (SHL) is characterized by distinctive clinical phenotypes as well as genetic and phenotypic heterogeneity. More than 400 species of SHL have been described, the majority of which are autosomal dominant. 11 forms of SHL were obtained from 14 unrelated families with probands ranging in age from 5 to 78 months. The results of whole exome sequencing(WES), audiological characteristics, middle and inner ear radiological findings, and additional clinical phenotype characteristics were retrospectively analyzed. Fourteen people with SHL were found. Two of them had Waardenburg syndrome, two had Branchio-Oto-Renal syndrome, two had CHARGE syndrome, and one had Treacher Collins syndrome, Kleefstra syndrome, Muenke syndrome, Osteopathia Striata with Cranial Sclerosis, Ayme-Gripp syndrome, Tatton-Brown-Rahman syndrome, Stickler syndrome, or Stapes Ankylosis with Broad Thumbs and Toes. In this investigation, ten variants were first reported. The combination of a neonatal hearing screening and WES can diagnose syndrome-type hearing loss in infancy and childhood, according to our findings, expansion of the gene variant spectrum and phenotype for various age groups of SHL is essential and can provide valuable guidelines for clinical intervention decisions. It is imperative for medical practitioners to conduct diligent and prolonged patient monitoring due to the inherent variability in both the auditory impairment and the comprehensive clinical manifestation of SHL.

Clinical phenotype and functional influence of GRIN2A variants in epilepsy-aphasia syndrome.

N-methyl-D-aspartate receptors are glutamate-gated ion channels that play a crucial role in brain function. Numerous inherited or de novo variants in the GRIN2A gene, encoding the GluN2A subunit of the receptor, have been identified in patients with epilepsy. In addition, it is worth noting that GRIN2A variants exhibit a strong correlation with epilepsy-aphasia syndromes, a group of age-dependent epileptic, cognitive, and language disorders with a characteristic electroencephalographic pattern. Whole exome sequencing was conducted in enrolled patients with epilepsy-aphasia syndromes, and GRIN2A variants were screened. The conservation of substituted residues, conformational changes of mutant subunits, and in silico predictions of pathogenicity were thoroughly assessed in our study. Functional alterations of the variants were examined using whole-cell voltage-clamp current recordings while the relative surface expression levels of subunit proteins were assessed via immunofluorescence assays. A summary of previously published GRIN2A missense variants was conducted to investigate the genotypic-phenotypic-functional correlations. Two missense GRIN2A variants (c. 2482A >G/p. M828V, c.2627 T >C/p. I876T) were identified, which are located in the transmembrane helix M4 and C-terminus domain of the GluN2A subunit, respectively. Both variants exhibited reduced current density of NMDARs and surface/total expression levels of GluN2A subunits, while M828V showed a decreased extent of desensitization as well. A further summary of the previously reported GRIN2A variants demonstrated that more variable phenotypes were observed for variants situated in the C-terminus domain or those with loss-of-function effects. Our study expands the phenotypic and functional range of GRIN2A-related disorders. In order to optimally establish the domain-function-phenotype correlations in GRIN2A variants, it is imperative to gather a more extensive set of clinical and functional data. This study has identified two genetic variants of the GRIN2A gene in patients with epilepsy-aphasia syndrome. We assess the variants' harmfulness through a variety of functional experiments, including evaluating the expression level of the mutated protein and the resulting changes in electrophysiological activities. Also, we reviewed previously published papers about GRIN2A variants in epilepsy to learn more about the correlations between their locations, functional changes, and clinical manifestations.

Epigenetic Study of Cohort of Monozygotic Twins With Hypertrophic Cardiomyopathy Due to MYBPC3 (Cardiac Myosin-Binding Protein C).

Hypertrophic cardiomyopathy is an autosomal dominant cardiac disease. The mechanisms that determine its variable expressivity are poorly understood. Epigenetics could play a crucial role in bridging the gap between genotype and phenotype by orchestrating the interplay between the environment and the genome regulation. In this study we aimed to establish a possible correlation between the peripheral blood DNA methylation patterns and left ventricular hypertrophy severity in patients with hypertrophic cardiomyopathy, evaluating the potential impact of lifestyle variables and providing a biological context to the observed changes. Methylation data were obtained from peripheral blood samples (Infinium MethylationEPIC BeadChip arrays). We employed multiple pair-matched models to extract genomic positions whose methylation correlates with the degree of left ventricular hypertrophy in 3 monozygotic twin pairs carrying the same founder pathogenic variant (MYBPC3 p.Gly263Ter). This model enables the isolation of the environmental influence, beyond age, on DNA methylation changes by removing the genetic background. Our results revealed a more anxious personality among more severely affected individuals. We identified 56 differentially methylated positions that exhibited moderate, proportional changes in methylation associated with left ventricular hypertrophy. These differentially methylated positions were enriched in regions regulated by repressor histone marks and tended to cluster at genes involved in left ventricular hypertrophy development, such as HOXA5, TRPC3, UCN3, or PLSCR2, suggesting that changes in peripheral blood may reflect myocardial alterations. We present a unique pair-matched model, based on 3 monozygotic twin pairs carrying the same founder pathogenic variant and different phenotypes. This study provides further evidence of the pivotal role of epigenetics in hypertrophic cardiomyopathy variable expressivity.

Gene-echocardiography: refining genotype-phenotype correlations in cardiomyopathy patients with restrictive phenotype

Abstract Background The restrictive phenotype, the least frequent and genetically complex form of cardiomyopathy, is the focus of this investigation. The aim is to clarify the association between restrictive phenotype and genetic variants in cardiomyopathy patient. Methods We utilized whole-exome sequencing in a cohort of 568 cardiomyopathy patients and performed echocardiographic evaluations to identify restrictive phenotypes. Comprehensive analysis of cardiac characteristics and functionality was also undertaken. Results Among the cohort, 33 patients exhibited a restrictive phenotype. These patients were distributed as follows: 7 within the restrictive cardiomyopathy group (RCM), 20 in the hypertrophic cardiomyopathy group (HRCM), and 6 in the dilated cardiomyopathy group (HDRCM). A notable prevalence of gene mutations, mainly in the MYBPC3 gene, was found in these individuals. We observed that mutation carriers, characterized by smaller aortic sinus dimension, demonstrated an association with the mutation and diminished myocardial work. Furthermore, MYBPC3 mutation carriers showed a thicker ventricular wall and a higher predisposition for septal hypertrophy. Both HRCM and HDRCM groups displayed consistent hypertrophic manifestations, with the latter demonstrating a higher frequency of interventricular septal hypertrophy. The 5-year survival rate was calculated at 54.5%, with gene mutations not significantly affecting longevity. Conclusion Genetic factors profoundly influence the restrictive phenotype of cardiomyopathy. There is a strong link between restrictive phenotype and genetic variants in cardiomyopathy, providing a foundation for more accurate genetic testing and personalized management of patients. The emerging "gene-echocardiography" concept may refine the accuracy and productivity of genetic counseling and testing in cardiomyopathy.

Routine application of cardiac magnetic resonance imaging in patients with suspected myocarditis from immune checkpoint inhibitor therapy

Abstract Background Cardiovascular adverse events including myocarditis associated with immune checkpoint inhibitor (ICI) therapy remain a challenge in clinical practice. Diagnostic assessment of ICI-related myocarditis (ICI-M) is challenging due to a variable phenotype, confounding effects and limited sensitivity of diagnostic tools. Cardiac magnetic resonance imaging (CMR) is used to diagnose non-ICI myocarditis, but evidence on diagnostic sensitivity is low, particularly in patients with a discrete phenotype. Here, we aim to assess the impact of CMR in patients with suspected ICI-related myocarditis and relate to final diagnosis including endomyocardial biopsy findings. Methods All consecutive patients receiving CMR for suspected ICI-M between September 2019 and January 2024 were included and retrospectively analysed. CMR parameters were correlated with clinical, laboratory and echocardiographic parameters and stratified for presence or absence of myocarditis as per final diagnosis. Results A total of 55 patients who received CMR for suspected ICI-related myocarditis were analysed, including 25 patients with confirmed ICI-M as per final diagnosis and 30 patients with cardiotoxicity other than myocarditis or no cardiotoxicity (ICI-O). The mean age (ICI-M versus ICI-O) was 65.7±13.6 versus (vs.) 67.3±9.9 (p=0.61) years, 32.0% vs. 26.7% (p=0.67) were female, and 40.0% vs. 26.7% (p=0.29) had pre-existing coronary heart disease. Cardiac biomarkers and echocardiographic data did not differ between the groups. In CMR analysis, presence of late gadolinium enhancement (LGE) was associated with ICI-M (56.0% vs. 26.7%, p=0.027). Myocardial oedema was generally rare and not associated with ICI-M. Endomyocardial biopsy (EMB) was used in 6 out of 55 patients (10.9%) with suspected ICI-M. In 4 of these 6 patients (66.7%) EMB confirmed ICI-M diagnosis. Of note, only 2/4 patients with EMB-confirmed myocarditis showed abnormal CMR findings. Conclusion The diagnostic assessment of ICI-M is challenged by low sensitivity of common diagnostic measures, often requiring a multimodal approach. Presence of LGE in CMR was associated with ICI-M, but sensitivity and specificity are low. Our data emphasize the high value of EMB in patients with clinically suspected ICI-M despite inconspicuous CMR. Prospective data to improve diagnostic criteria are needed.

Phenotypic variability of RP1-related inherited retinal dystrophy associated with the c.5797 C > T (p.Arg1933*) variant in the Japanese population

The phenotypes of RP1-related inherited retinal dystrophies (RP1-IRD), causing autosomal dominant (AD) and autosomal recessive (AR) diseases, vary depending on specific RP1 variants. A common nonsense mutation near the C-terminus, c.5797 C > T (p.Arg1933*), is associated with RP1-IRD, but the exact role of this mutation in genotype-phenotype correlation remains unclear. In this study, we retrospectively analyzed patients with RP1-IRD (N = 42) from a single center in Japan. AR RP1-IRD patients with the c.5797 C > T mutation (N = 14) mostly displayed macular dystrophy but rarely retinitis pigmentosa or cone-rod dystrophy. Conversely, AR RP1-IRD patients without the c.5797 C > T mutation, including those with other pathogenic RP1 variants, were mostly diagnosed with severe retinitis pigmentosa. Full-field electroretinograms were significantly better in patients homozygous or compound heterozygous for the c.5797 C > T mutation than in those without this mutation, corresponding to their milder phenotypes. Clinical tests also revealed a slower onset of age and a better mean deviation value with the static visual field in AR RP1-IRD patients with the c.5797 C > T mutation compared to those without. Therefore, the presence of c.5797 C > T may partly account for the phenotypic variety of RP1-IRD and may yield milder phenotypes. These findings may be useful for predicting the prognosis of RP1-IRD patients.

CACNA1A haploinsufficiency leads to reduced synaptic function and increased intrinsic excitability.

Haploinsufficiency of the CACNA1A gene, encoding the pore-forming α1 subunit of P/Q-type voltage-gated calcium channels, is associated with a clinically variable phenotype ranging from cerebellar ataxia, to neurodevelopmental syndromes with epilepsy and intellectual disability. To understand the pathological mechanisms of CACNA1A loss-of-function variants, we characterized a human neuronal model for CACNA1A haploinsufficiency, by differentiating isogenic induced pluripotent stem cell lines into glutamatergic neurons, and investigated the effect of CACNA1A haploinsufficiency on mature neuronal networks through a combination of electrophysiology, gene expression analysis, and in silico modeling. We observed an altered network synchronization in CACNA1A+/- networks alongside synaptic deficits, notably marked by an augmented contribution of GluA2-lacking AMPA receptors. Intriguingly, these synaptic perturbations coexisted with increased non-synaptically driven activity, as characterized by inhibition of NMDA and AMPA receptors on micro-electrode arrays. Single-cell electrophysiology and gene expression analysis corroborated this increased intrinsic excitability through reduced potassium channel function and expression. Moreover, we observed partial mitigation of the CACNA1A+/- network phenotype by 4-aminopyridine, a therapeutic intervention for episodic ataxia type 2. Positive modulation of KCa2 channels could reverse the CACNA1A+/- network electrophysiological phenotype. In summary, our study pioneers the characterization of a human induced pluripotent stem cell-derived neuronal model for CACNA1A haploinsufficiency, and has unveiled novel mechanistic insights. Beyond showcasing synaptic deficits, this neuronal model exhibited increased intrinsic excitability mediated by diminished potassium channel function, underscoring its potential as a therapeutic discovery platform with predictive validity.