Leukocyte Nuclear Morphology Alterations in Dilated Cardiomyopathy Caused by a Lamin AC Truncating Mutation (LMNA/Ser431*) Are Modified by the Presence of a LAP2 Missense Polymorphism (TMPO/Arg690Cys).

The clinical phenotype of LMNA-associated dilated cardiomyopathy (DCM) varies even among individuals who share the same mutation. LMNA encodes lamin AC, which interacts with the lamin-associated protein 2 alpha (LAP2α) encoded by the TMPO gene. The LAP2α/Arg690Cys polymorphism is frequent in Latin America and was previously found to disrupt LAP2α-Lamin AC interactions in vitro. We identified a DCM patient heterozygous for both a lamin AC truncating mutation (Ser431*) and the LAP2α/Arg690Cys polymorphism. We performed protein modeling and docking experiments, and used confocal microscopy to compare leukocyte nuclear morphology among family members with different genotype combinations (wild type, LAP2α Arg690Cys heterozygous, lamin AC/Ser431* heterozygous, and LAP2α Arg690Cys/lamin AC Ser431* double heterozygous). Protein modeling predicted that 690Cys destabilizes the LAP2α homodimer and impairs lamin AC-LAP2α docking. Lamin AC-deficient nuclei (Ser431* heterozygous) showed characteristic blebs and invaginations, significantly decreased nuclear area, and increased elongation, while LAP2α/Arg690Cys heterozygous nuclei showed a lower perimeter and higher circularity than wild-type nuclei. LAP2α Arg690Cys apparently attenuated the effect of LMNA Ser431* on the nuclear area and fully compensated for its effect on nuclear circularity. Altogether, the data suggest that LAP2α/Arg690Cys may be one of the many factors contributing to phenotype variation of LMNA-associated DCM.

Homozygous Fukutin Missense Mutation in Two Mexican Siblings with Dilated Cardiomyopathy.

BACKGROUND: Fukuyama congenital muscular dystrophy (FCMD) is the most common form of a group of autosomal recessive disorders characterized by altered α-dystroglycan glycosylation and caused by FKTN gene mutations. However, mutations of this gene may cause a broad range of phenotypes, including Walker-Warburg syndrome, muscle-brain-eye disease, FCMD, limbgirdle muscular dystrophy without mental retardation, and cardiomyopathy with no or minimal skeletal muscle weakness. OBJECTIVE: Our purpose was to describe two siblings who died at a young age with dilated cardiomyopathy (DCM), no muscle weakness, or atrophy, and were homozygous for a FKTN missense mutation. METHODS: Site-directed next-generation sequencing (NGS) was performed. Pathogenicity of variants of interest was established according to the American College of Medical Genetics (ACMG) criteria, and all available first-degree relatives were screened for mutations by Sanger sequencing. RESULTS: NGS revealed a homozygous FKTN variant in the index case (p.Gly424Ser, rs752358445), classified as likely pathogenic by ACMG criteria. Both parents and an unaffected brother were heterozygous carriers. Since the siblings had no apparent skeletal muscle weakness or central nervous system involvement, FKTN mutations were not initially suspected. CONCLUSIONS: This is the first report demonstrating that heterozygous individuals for the FKTN p.Gly424Ser mutation were healthy, while two homozygous brothers suffered severe DCM, strongly suggesting that this FKTN mutation is a rare cause of autosomal recessive DCM.

Genes frequently associated with sudden death in primary hypertrophic cardiomyopathy.

Hypertrophic cardiomyopathy is characterized by left ventricular hypertrophy without apparent cardiac justification. Sudden cardiac death may be the first manifestation of the disease. It occurs mainly in adulthood and can be seen in childhood and adolescence where genetic origin predominates. Primary HCM ("familial") is inherited in an autosomal dominant pattern in the 25 subtypes informed in Online Mendelian Inheritance in Man. The proteins encoded by the mutated genes are part of the sarcomere in the cardiac cells, being the thick filament the most frequently affected, with the worst prognosis. In the present article, we describe the Mendelian inheritance of the disease and the two most associated genes with sudden death: MYBPC3 and MYH7.

La miocardiopatía hipertrófica (MCH) es el aumento de grosor de la pared ventricular izquierda no relacionada con otras alteraciones cardíacas. Es una enfermedad que puede presentar como primera manifestación clínica la muerte súbita y de ahí su relevancia clínica. Aunque se presenta sobre todo en la edad adulta, puede aparecer durante la infancia y adolescencia, en las que predominan los casos de origen hereditario. La MCH primaria, de causa genética, muestra en particular un patrón de herencia autosómico dominante en los 25 subtipos reconocidos en OMIM (Online Mendelian Inheritance in Man). Las proteínas codificadas por los genes mutantes forman parte del sarcómero en células musculares cardíacas, y las variantes patogénicas de filamentos gruesos son las de mayor frecuencia y peor pronóstico. En este artículo se describen la herencia mendeliana de la enfermedad y la relación con muerte súbita de los genes más frecuentemente encontrados en ella: MYBPC3 y MYH7.

Genomic study of dilated cardiomyopathy in a group of Mexican patients using site-directed next generation sequencing.

BACKGROUND: Dilated cardiomyopathy (DCM) is a major cause of nonischemic heart failure and death in young adults. Next generation sequencing (NGS) has become part of the diagnostic workup in idiopathic and familial DCM. More than 50 DCM genes have been identified, revealing great molecular heterogeneity and variable diagnostic yield. Interpretation of variant pathogenicity is challenging particularly in underrepresented populations, as pathogenic variant databases include studies mainly from European/Caucasian populations. To date, no studies on genomic diagnosis of DCM have been conducted in Mexico. METHODS: We recruited 55 unrelated DCM patients, 22 familial (F-DCM), and 33 idiopathic (I-DCM), and performed site-directed NGS seeking causal mutations. Diagnostic yield was defined as the proportion of individuals with at least one pathogenic (P) or likely pathogenic (LP) variant in DCM genes. RESULTS: Overall diagnostic yield was 47.3%, and higher in F-DCM (63.6%) than in I-DCM (36.4%, p = 0.047). Overall, NGS disclosed 41 variants of clinical interest (61.0% novel), 27 were classified as P/LP and 14 of unknown clinical significance. Of P/LP variants, 10 were A-band region TTN truncating variants, five were found in DSP (18.5%), five in MYH7 (18.5%), two in LMNA (7.4%), and one in RBM20, ABCC9, FKTN, ACTA1, and TNNT2. NGS findings suggested autosomal recessive inheritance in three families, two with DSP loss of function mutations in affected individuals. The increasing number of mutation reports in DCM, increasing knowledge on the functional consequences of mutations, mutational hotspots and functional domains of DCM-related proteins, the recent refinement ACMG/ClinGen Guidelines, and co-segregation analysis in DCM families helped increase the diagnostic yield. CONCLUSION: This is the first NGS study performed in a group of Mexican DCM patients, contributing to understand the mutational spectrum and complexity of DCM molecular diagnosis.

Homozygous Fukutin Missense Mutation in Two Mexican Siblings with Dilated Cardiomyopathy

ABSTRACT Background: Fukuyama congenital muscular dystrophy (FCMD) is the most common form of a group of autosomal recessive disorders characterized by altered α-dystroglycan glycosylation and caused by FKTN gene mutations. However, mutations of this gene may cause a broad range of phenotypes, including Walker-Warburg syndrome, muscle-brain-eye disease, FCMD, limb-girdle muscular dystrophy without mental retardation, and cardiomyopathy with no or minimal skeletal muscle weakness. Objective: Our purpose was to describe two siblings who died at a young age with dilated cardiomyopathy (DCM), no muscle weakness, or atrophy, and were homozygous for a FKTN missense mutation. Methods: Site-directed next-generation sequencing (NGS) was performed. Pathogenicity of variants of interest was established according to the American College of Medical Genetics (ACMG) criteria, and all available first-degree relatives were screened for mutations by Sanger sequencing. Results: NGS revealed a homozygous FKTN variant in the index case (p.Gly424Ser, rs752358445), classified as likely pathogenic by ACMG criteria. Both parents and an unaffected brother were heterozygous carriers. Since the siblings had no apparent skeletal muscle weakness or central nervous system involvement, FKTN mutations were not initially suspected. Conclusions: This is the first report demonstrating that heterozygous individuals for the FKTN p.Gly424Ser mutation were healthy, while two homozygous brothers suffered severe DCM, strongly suggesting that this FKTN mutation is a rare cause of autosomal recessive DCM.

Genes frequently associated with sudden death in primary hypertrophic cardiomyopathy / Genes frecuentemente asociados con muerte súbita en miocardiopatía hipertrófica primaria

Abstract Hypertrophic cardiomyopathy (HCM) is characterized by left ventricular hypertrophy without apparent cardiac justification. Sudden cardiac death may be the first manifestation of the disease. It occurs mainly in adulthood and can be seen in childhood and adolescence where genetic origin predominates. Primary HCM (“familial”) is inherited in an autosomal dominant pattern in the 25 subtypes informed in Online Mendelian Inheritance in Man. The proteins encoded by the mutated genes are part of the sarcomere in the cardiac cells, being the thick filament the most frequently affected, with the worst prognosis. In the present article, we describe the Mendelian inheritance of the disease and the two most associated genes with sudden death: MYBPC3 and MYH7.

Resumen La miocardiopatía hipertrófica (MCH) es el aumento de grosor de la pared ventricular izquierda no relacionada con otras alteraciones cardíacas. Es una enfermedad que puede presentar como primera manifestación clínica la muerte súbita y de ahí su relevancia clínica. Aunque se presenta sobre todo en la edad adulta, puede aparecer durante la infancia y adolescencia, en las que predominan los casos de origen hereditario. La MCH primaria, de causa genética, muestra en particular un patrón de herencia autosómico dominante en los 25 subtipos reconocidos en OMIM (Online Mendelian Inheritance in Man). Las proteínas codificadas por los genes mutantes forman parte del sarcómero en células musculares cardíacas, y las variantes patogénicas de filamentos gruesos son las de mayor frecuencia y peor pronóstico. En este artículo se describen la herencia mendeliana de la enfermedad y la relación con muerte súbita de los genes más frecuentemente encontrados en ella: MYBPC3 y MYH7.

Caspase-12 activation is involved in amyloid-ß protein-induced synaptic toxicity.

Synapse loss is considered to be the best correlate of cognitive impairments in Alzheimer's disease (AD), and growing evidence supports the notion that certain events that trigger neuronal death in AD can be initiated by the local activation of caspases within the synaptic compartment. We have demonstrated previously that presynaptic terminals are particularly vulnerable to endoplasmic-reticulum (ER)-stress depending of amyloid-ß protein (Aß). This toxicity included a notable reduction of actin and synaptophysin protein and mitochondrial dysfunction. This synaptic damage was prevented by incubation with a wide range of caspase inhibitor, suggesting the activation of local synaptic apoptotic mechanisms. The ER-resident caspase-12 was initially identified as a mediator of Aß neurotoxicity. Thus, the current study was conducted to explore the presence and local activation of the caspase-12 in cortical and hippocampal synaptosomes isolated from rat and from the triple transgenic mouse model of AD (3xTg-AD) in the presence of Aß and ryanodine. Under these conditions, we found mitochondrial failure accompanied by a reduction in actin levels which was dependent on caspase-12 activation suggesting its participation in Aß-induced synaptic toxicity.