A Novel DLG1 Variant in a Family with Brugada Syndrome: Clinical Characteristics and In Silico Analysis

Background: Brugada syndrome (BrS) is an inherited primary channelopathy syndrome associated to sudden cardiac death. Overall, variants have been identified in eighteen genes encoding for ion channel subunits and seven genes for regulatory proteins. Recently, a missense variant in DLG1 has been found within a BrS phenotype-positive patient. DLG1 encodes for synapse associated protein 97 (SAP97), a protein characterized by the presence of multiple domains for protein–protein interactions including PDZ domains. In cardiomyocytes, SAP97 interacts with Nav1.5, a PDZ binding motif of SCN5A and others potassium channel subunits. Aim of the Study: To characterize the phenotype of an Italian family with BrS syndrome carrying a DLG1 variant. Methods: Clinical and genetic investigations were performed. Genetic testing was performed with whole-exome sequencing (WES) using the Illumina platform. According to the standard protocol, a variant found by WES was confirmed in all members of the family by bi-directional capillary Sanger resequencing. The effect of the variant was investigated by using in silico prediction of pathogenicity. Results: The index case was a 74-year-old man with spontaneous type 1 BrS ECG pattern that experienced syncope and underwent ICD implantation. WES of the index case, performed assuming a dominant mode of inheritance, identified a heterozygous variant, c.1556G>A (p.R519H), in the exon 15 of the DLG1 gene. In the pedigree investigation, 6 out of 12 family members had the variant. Carriers of the gene variant all had BrS ECG type 1 drug induced and showed heterogeneous cardiac phenotypes with two patients experiencing syncope during exercise and fever, respectively. The amino acid residue #519 lies near a PDZ domain and in silico analysis suggested a causal role for the variant. Modelling of the resulting protein structure predicted that the variant disrupts an H-bond and a likelihood of being pathogenic. As a consequence, it is likely that a conformational change affects protein functionality and the modulating role on ion channels. Conclusions: A DLG1 gene variant identified was associated with BrS. The variant could modify the formation of multichannel protein complexes, affecting ion channels to specific compartments in cardiomyocytes

Mutation of angiopoietin-1 gene (ANGPT1) associates with a new type of hereditary angioedema

Hereditary angioedema (HAE) is a rare genetic disease usually due to mutation within the C1 inhibitor or the coagulation Factor XII gene. However, in a series of patients with HAE no causative variants have been described and the pathophysiology of the disease remains unknown (U-HAE). Identification of causative genes in U-HAE is valuable for understanding the cause of the disease. Objective: We conducted genetic studies in Italian patients with U-HAE to identify novel causative genes. Methods: Among patients belonging to 10 independent families and unrelated index patients with U-HAE disease recruited from the Italian network for C1-INH-HAE (ITACA), we selected a large multiplex family with U-HAE and performed whole-exome sequencing. The angiopoietin-1 gene(ANGPT1) was investigated in all patients with familial or sporadic U-HAE. The effect of ANGPT1 variants was investigated by in silico prediction and using patients and control plasmas and transfected cells. Results: We identified a missense mutation (ANGPT1, c.807G>T, p.A119S) in a family with U45 HAE. The ANGPT1 p.A119S variant was detected in all members of the index family with U-HAE but not in asymptomatic family members, nor in an additional 20 patients with familial U-HAE, 22 patients with sporadic U-HAE, and 200 controls. Protein analysis of the plasma of patients revealed a reduction of multimeric forms and a reduced ability to bind the natural receptor “tunica interna endothelial cell kinase-2” (TIE2) of the ANGPT1 p.A119S variant. The recombinant mutated ANGPT1 p.A119S formed a reduced amount of multimers and showed a reduced binding capability to its receptor. Conclusion: ANGPT1 impairment is associated with angioedema and ANGPT1 variants can be the basis of HAE

Capillary Malformation-Arteriovenous Malformation Type 2, A Report of 6 Cases and Main Differential Diagnosis

Objectives: Capillary malformation-arteriovenous malformation (CM-AVM) is a rare disorder characterized by multifocal CMs associated with AVMs. While the phenotype of CMAVM1 has been well established in the literature, there are limited published reports documenting the clinical features of CMAVM2. Our aim is to highlight this phenotype, and the distinctive features of CMAVM2 compared with CMAVM1 and hereditary hemorrhagic telangiectasia, as prompt recognition is crucial to screen for fast-flow vascular malformations, which, if left untreated, can sometimes be life-threatening. Methods: This is a retrospective review of cases seen at multiple tertiary care centers in the United States and Argentina. Results and Conclusions: We report 6 pediatric patients with CMAVM2 presenting with diffuse multifocal cutaneous CMs, telangiectases favoring the lips, perioral area and upper trunk, and Bier spots. Three patients had epistaxis. One patient had an extracranial AVM and 1 patient had Parkes Weber syndrome. EPHB4 pathogenic variants were identified in all patients. CMAVM2 remains an underrecognized condition. Genetic testing and imaging studies are recommended to guide management

RASA1 mutations and associated phenotypes in 68 families with capillary malformation-arteriovenous malformation

Capillary malformation-arteriovenous malformation (CM-AVM) is an autosomal-dominant disorder, caused by heterozygous RASA1 mutations, and manifesting multifocal CMs and high risk for fast-flow lesions. A limited number of patients have been reported, raising the question of the phenotypic borders. We identified new patients with a clinical diagnosis of CM-AVM, and patients with overlapping phenotypes. RASA1 was screened in 261 index patients with: CM-AVM (n = 100), common CM(s) (port-wine stain; n = 100), Sturge-Weber syndrome (n = 37), or isolated AVM(s) (n = 24). Fifty-eight distinct RASA1 mutations (43 novel) were identified in 68 index patients with CM-AVM and none in patients with other phenotypes. A novel clinical feature was identified: cutaneous zones of numerous small white pale halos with a central red spot. An additional question addressed in this study was the "second-hit" hypothesis as a pathophysiological mechanism for CM-AVM. One tissue from a patient with a germline RASA1 mutation was available. The analysis of the tissue showed loss of the wild-type RASA1 allele. In conclusion, mutations in RASA1 underscore the specific CM-AVM phenotype and the clinical diagnosis is based on identifying the characteristic CMs. The high incidence of fast-flow lesions warrants careful clinical and radiologic examination, and regular follow-up