SCN5A compound heterozygosity mutation in Brugada syndrome: Functional consequences and the implication for pharmacological treatment.

AIMS: SCN5A gene encodes the α-subunit of Nav1.5, mainly found in the human heart. SCN5A variants are the most common genetic alterations associated with Brugada syndrome (BrS). In rare cases, compound heterozygosity is observed; however, its functional consequences are poorly understood. We aimed to analyze the functional impact of de novo Nav1.5 mutations in compound heterozygosity in distinct alleles (G400R and T1461S positions) previously found in a patient with BrS. Moreover, we evaluated the potential benefits of quinidine to improve the phenotype of mutant Na+ channels in vitro. MATERIALS AND METHODS: The functional properties of human wild-type and Nav1.5 variants were evaluated using whole-cell patch-clamp and immunofluorescence techniques in transiently expressed human embryonic kidney (HEK293) cells. KEY FINDINGS: Both variants occur in the highly conservative positions of SCN5A. Although all variants were expressed in the cell membrane, a significant reduction in the Na+ current density (except for G400R alone, which was undetected) was observed along with abnormal biophysical properties, once the variants were expressed in homozygosis and heterozygosis. Interestingly, the incubation of transfected cells with quinidine partially rescued the biophysical properties of the mutant Na+ channel. SIGNIFICANCE: De novo compound heterozygosis mutations in SNC5A disrupt the Na+ macroscopic current. Quinidine could partially reverse the in vitro loss-of-function phenotype of Na+ current. Thus, our data provide, for the first time, a detailed biophysical characterization of dysfunctional Na+ channels linked to compound heterozygosity in BrS as well as the benefits of the pharmacological treatment using quinidine on the biophysical properties of Nav1.5.

Identification of nuclear factor-κB sites in the Slc2a4 gene promoter.

Glucose transporter GLUT4 protein, codified by Slc2a4 gene plays a key role in glycemic homeostasis. Insulin resistance, as in obesity, has been associated to inflammatory state, in which decreased GLUT4 is a feature. Inflammatory NF-κB transcriptional factor has been proposed as a repressor of Slc2a4; although, the binding site(s) in Slc2a4 promoter and the direct repressor effect have never been reported yet. A motif-based sequence analysis of mouse Slc2a4 promoter revealed two putative κB sites located inside -83/-62 and -134/-113 bp. Eletrophoretic mobility assay showed that p50 and p65 NF-κB subunits bind to both putative κB sites. Chromatin immunoprecipitation assay using genomic DNA from adipocytes confirmed p50- and p65-binding to Slc2a4 promoter. Moreover, transfection experiments revealed that NF-κB binds to the -134/-113bp region of the mouse Slc2a4 gene promoter, inhibiting the Slc2a4 gene transcription. The current findings demonstrate the existence of two κB sites in Slc2a4 gene promote, and that NF-κB has a direct repressor effect upon the Slc2a4 gene, providing an important link between insulin resistance and inflammation.

Essential regulatory elements for NHE3 gene transcription in renal proximal tubule cells

The objectives of the present study were to identify the cis-elements of the promoter absolutely required for the efficient rat NHE3 gene transcription and to locate positive and negative regulatory elements in the 5’-flanking sequence (5’FS), which might modulate the gene expression in proximal tubules, and to compare this result to those reported for intestinal cell lines. We analyzed the promoter activity of different 5’FS segments of the rat NHE3 gene, in the OKP renal proximal tubule cell line by measuring the activity of the reporter gene luciferase. Because the segment spanning the first 157 bp of 5’FS was the most active it was studied in more detail by sequential deletions, point mutations, and gel shift assays. The essential elements for gene transcription are in the region -85 to -33, where we can identify consensual binding sites for Sp1 and EGR-1, which are relevant to NHE3 gene basal transcription. Although a low level of transcription is still possible when the first 25 bp of the 5’FS are used as promoter, efficient transcription only occurs with 44 bp of 5’FS. There are negative regulatory elements in the segments spanning -1196 to -889 and -467 to -152, and positive enhancers between -889 and -479 bp of 5’FS. Transcription factors in the OKP cell nuclear extract efficiently bound to DNA elements of rat NHE3 promoter as demonstrated by gel shift assays, suggesting a high level of similarity between transcription factors of both species, including Sp1 and EGR-1.

Essential regulatory elements for NHE3 gene transcription in renal proximal tubule cells.

The objectives of the present study were to identify the cis-elements of the promoter absolutely required for the efficient rat NHE3 gene transcription and to locate positive and negative regulatory elements in the 5'-flanking sequence (5'FS), which might modulate the gene expression in proximal tubules, and to compare this result to those reported for intestinal cell lines. We analyzed the promoter activity of different 5'FS segments of the rat NHE3 gene, in the OKP renal proximal tubule cell line by measuring the activity of the reporter gene luciferase. Because the segment spanning the first 157 bp of 5'FS was the most active it was studied in more detail by sequential deletions, point mutations, and gel shift assays. The essential elements for gene transcription are in the region -85 to -33, where we can identify consensual binding sites for Sp1 and EGR-1, which are relevant to NHE3 gene basal transcription. Although a low level of transcription is still possible when the first 25 bp of the 5'FS are used as promoter, efficient transcription only occurs with 44 bp of 5'FS. There are negative regulatory elements in the segments spanning -1196 to -889 and -467 to -152, and positive enhancers between -889 and -479 bp of 5'FS. Transcription factors in the OKP cell nuclear extract efficiently bound to DNA elements of rat NHE3 promoter as demonstrated by gel shift assays, suggesting a high level of similarity between transcription factors of both species, including Sp1 and EGR-1.

Síndrome do túnel do tarso: relato de 11 casos / Tarsal tunnel syndrome: report of 11 cases

Na atualidade, apesar de pouco conhecida, a síndrome do túnel do tarso, pelos recursos eletroneurofisiológicos e de imagem, se impoe no diagnóstico diferencial das patologias que determinem sintomas álgicos nos pés. Objetivo. Sao apresentados e discutidos pacientes com queixa de dor nos pés cujo quadro clínico permitiu o diagnóstico de síndrome do túnel do tarso. MÉTODOS. Onze pacientes foram submetidos e exame eletroneuromiográfico conclusivo de compressao nervosa e, em seguida, foram submetidos a cirurgia específica, quando foi feita a descompressao do túnel do tarso pela secçao do retináculo dos flexores. Resultados. Nos casos apresentados, importante espessamento fibroso foi observado na maioria dos casos, e a melhora da sintomatologia dolorosa foi verificada nas primeiras semanas do pós-operatório, sendo os pacientes observados por intervalo de 3 meses a 5 anos, nao apresentando recorrência do quadro de dor.

[Tarsal tunnel syndrome: report of 11 cases]. / Síndrome do túnel do tarso: relato de 11 casos.

UNLABELLED: Little is know on tarsal tunnel syndrome by means of image and electrophysiological access. It is imperative the differential diagnosis on diseases which present foot pain. PURPOSE: To present patients with foot pain complaints, whose clinical pattern allowed the diagnosis of tarsal tunnel syndrome. METHODS: Eleven patients underwent nerve velocity conduction examination concluding for entrapment. They were submitted to tarsal tunnel surgical decompression by sectioning the flexor retinaculum. RESULTS: Most of the cases showed a marked fibrous thickening. The improvement of symptoms was noted in the first weeks. No recurrence was observed from three months to five years. CONCLUSION: The main question was the presentation of the tarsal tunnel syndrome and some adequate procedures.

Management of tarsal tunnel syndrome. Report of seven cases.

Seven patients with clinical and electroneurographic evidence of tarsal tunnel syndrome were managed surgically, after failed attempts for non-surgical treatment. Post-operative results were more satisfactory than the previous responses to non-surgical therapies. Tarsal tunnel syndrome appears to respond better to surgical intervention than to conservative management.