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.
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.
Molecular diagnosis in dilated cardiomyopathy (DCM) is challenging, particularly in underrepresented populations. We obtained a relatively high diagnostic yield in familial DCM (63.6%) and in idiopathic DCM (47.3%) in a group of Mexican patients. The increasing number of reports of mutations in DCM patients, the increasing knowledge on the functional consequences of mutations, mutational hotspots and functional domains of some DCM‐related proteins, the refinement ACMG/ClinGen Guidelines and co‐segregation analysis helped achieve this higher diagnostic yield.
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-β protein (Aβ). 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 Aβ 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 Aβ 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 Aβ-induced synaptic toxicity.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
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.
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.
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.
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.
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.
PDF
