Sinoatrial node pacemaker cells share dominant biological properties with glutamatergic neurons

Activation of the heart normally begins in the sinoatrial node (SAN). Electrical impulses spontaneously released by SAN pacemaker cells (SANPCs) trigger the contraction of the heart. However, the cellular nature of SANPCs remains controversial. Here, we report that SANPCs exhibit glutamatergic neuron-like properties. By comparing the single-cell transcriptome of SANPCs with that of cells from primary visual cortex in mouse, we found that SANPCs co-clustered with cortical neurons. Tissue and cellular imaging confirmed that SANPCs contained key elements of glutamatergic neurotransmitter system, expressing genes encoding glutamate synthesis pathway (Gls), ionotropic and metabotropic glutamate receptors (Grina, Gria3, Grm1 and Grm5), and glutamate transporters (Slc17a7). SANPCs highly expressed cell markers of glutamatergic neurons (Snap25 and Slc17a7), whereas Gad1, a marker of GABAergic neurons, was negative. Functional studies revealed that inhibition of glutamate receptors or transporters reduced spontaneous pacing frequency of isolated SAN tissues and spontaneous Ca

Evaluation of Accessibility of Road Traffic Sidewalks Using the Codes for Accessibility Design in the Mega-city: a Case of Shanghai / 中国康复理论与实践

Objective:To evaluate the accessibility construction status of road traffic sidewalks in Shanghai. Methods:From July to September, 2019, 46 road traffic sidewalks in Shanghai were selected using a convenience sampling, and evaluation tools were designed based on the Codes for Accessibility Design (GB 50763-2012) and Standards for Design on Accessibility of Buildings and Facilities (DGJ08-103-2003). After field check and experience for the sidewalks, the compliance rates of evaluation dimensions and evaluation contents of sidewalks were analyzed using the descriptive analysis. The weights of each dimension were calculated using the principal component analysis to construct the sidewalk comprehensive barrier score model, and to compare the sidewalk comprehensive barrier scores in different areas of Shanghai. From September to November 2019, in-depth interviews were conducted with eleven persons with disabilities to understand the sidewalk barriers for them. Results:The overall compliance rate of sidewalk accessibility was 4.35%. Among the evaluated contents, 93.5% sidewalks had a curb ramp, 91.3% had a height difference between the ramp and the carriageway, 26.1% were not paved with tactile ground surface indicators; 71.7% tactile ground surface indicators were blocked by poles, etc., and 84.8% were occupied by obstacles. The warning indicator was the greatest weight among the evaluated dimensions. The barrier of sidewalks was high (36.7%) and medium (20.0%) in the central area, which was higher than that in the sub-central area (both 6.3%) (P < 0.05). There were many obstacles during the experience of sidewalks using, resulting in less using of the barrier-free facilities. Conclusion:Most of the sidewalks in Shanghai do not meet the standards of the Codes for Accessibility Design. It is urgent to construct and maintain the barrier-free facilities.

Dynamin-mediated endocytic process contributes to neuronal nitric oxide synthase-mediated regulation of cardiac contraction / 生理学报

Nitric oxide synthases (NOSs) play complex roles in the regulation of cardiac excitation contraction coupling under basal and stressed conditions. Herein, using the recording approach for intracellular calcium transient and synchronous myocyte contraction, the potential mechanism for NOSs-mediated cardiomyocyte contraction was explored. We found that selective inhibition of neuronal NOS (nNOS) with 100 µmol/L spermidine markedly enhanced the cardiomyocyte twitch [control: (10.5 ± 0.21)%; nNOS inhibition: (12.4 ± 0.18)%] and calcium transient [control: (0.27 ± 0.03)%; nNOS inhibition: (0.42 ± 0.01)%], but slowed the relengthening of twitch [control: (25.2 ± 1.3) ms; nNOS inhibition: (53 ± 2.8) ms] and the calcium transient decay [control: (129 ± 4.3) ms; nNOS inhibition: (176 ± 7.1) ms], which was similar to that by dynamin inhibition with 30 µmol/L dynasore. The nNOS inhibition- or dynasore-mediated effects could be rescued by an NO donor, S-Nitroso-N-acetylpenicillamine (SNAP). Our data suggest that the selective nNOS-mediated regulation of cardiac contractile activity may partly involve the dynamin-mediated endocytic mechanism.

A novel GATA4 mutation leading to congenital ventricular septal defect / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To identify the GATA4 gene mutation of congenital ventricular septal defect (VSD) and study the molecular mechanism of a novel mutation.</p><p><b>METHODS</b>The clinical data and blood samples from 185 unrelated subjects with congenital VSD were collected and evaluated together with 200 healthy individuals. The coding exons and the flanking intron regions of the GATA4 gene were amplified by PCR and sequenced using the di-deoxynucleotide chain termination approach. The GATA4 gene was cloned and the corresponding mutant was acquired by site directed mutagenesis. The recombinant plasmid expressing GATA4 and the reporter vector expressing enhanced green fluorescence protein (EGFP) driven by the promoter of atrial natrium peptide (ANP) gene were transfected into HeLa cells with Lipofectamine. The effect of mutated GATA4 gene on the transcriptional activity of encoded transcriptional factor was analyzed by reverse transcription (RT)-PCR.</p><p><b>RESULTS</b>A novel heterozygous missense GATA4 mutation, c.191G>A was identified in 1 VSD patient. The mutation leads to glycine to glutamic acid change at amino acid residue 64 (G64E) in the GATA4 protein. Functional analysis showed that GATA4 G64E mutation decreased the transcriptional activity of GATA4 transcriptional factor.</p><p><b>CONCLUSION</b>A novel heterozygous missense GATA4 mutation, G64E, was identified in 1 VSD patient. The mutation might cause VSD by impairing the transcriptional activity of GATA4 transcriptional factor.</p>

Novel GATA4 mutations identified in patients with congenital atrial septal defects / 中华心血管病杂志

<p><b>OBJECTIVE</b>To identify the genetic defects in patients with congenital atrial septal defects (ASD).</p><p><b>METHODS</b>The clinical data and blood samples from 180 unrelated subjects with congenital ASD were collected and evaluated. Two hundred healthy individuals served as controls. The coding exons and the flanking introns of GATA4 gene were amplified by polymerase chain reaction and sequenced using the di-deoxynucleotide chain termination approach. The acquired sequences were aligned with the sequences publicized in GenBank by the aid of programme BLAST to identify the sequence variations. Clustal W software was applied for analysis of the conservation of altered amino acids.</p><p><b>RESULTS</b>Two novel heterozygous missense GATA4 mutations were identified in 2 out of 180 ASD patients. Namely, the triplet substitutions of GTC for GGC at codon 21 and TCG for CCG at codon 87 were detected, predicting the conversions of glycine into valine at amino acid residue 21 (G21V) and proline into serine at amino acid residue 87 (P87S). None of the two mutations were detected in 200 healthy controls. Across-species alignment of GATA4 encoded protein sequences displayed that the mutated amino acids were highly conserved evolutionarily. Additionally, a single nucleotide polymorphism c.99G>T was observed. However, the polymorphic frequency distribution in ASD cases was similar with that in healthy controls (for genotype GT, χ(2) = 0.7556, P = 0.3847; for allele T, χ(2) = 0.7235, P = 0.3950).</p><p><b>CONCLUSIONS</b>Two novel mutations of GATA4 gene are identified in two unrelated ASD patients. This finding provides new insight into the molecular etiology responsible for ASD.</p>

Mutation of NKX2-5 gene in patients with atrial septal defect / 中华儿科杂志

<p><b>OBJECTIVE</b>The purpose of this investigation was to identify the novel genetic mutations in patients with a congenital atrial septal defect (ASD).</p><p><b>METHODS</b>Clinical data and blood specimens from a total of 12 unrelated ASD pedigrees and a cohort of 168 unrelated subjects with sporadic ASD were collected and evaluated in contrast to 200 healthy individuals. The whole exons and partial flanking introns of NKX2-5 gene were amplified by polymerase chain reaction and sequenced using the di-deoxynucleotide chain termination approach. The acquired sequences were aligned with those publicized in GenBank by the aid of programme BLAST to identify the sequence variations. The software ClustalW was applied for analysis of the conservative of the altered amino acids.</p><p><b>RESULTS</b>A novel heterozygous mutation of NKX2-5 gene, i.e., a substitution of thymine for cytosine at nucleotide 536, predicting the conversion of serine into phenylalanine at amino acid residue 179, was identified initially in a proband. The same missense mutation was thereafter detected in other 3 affected members of the identical family but neither in the healthy members of the kindred nor in the 200 normal controls. A cross-species alignment of the protein sequences encoded by NKX2-5 gene displayed that the mutated amino acid was highly conserved evolutionarily. No mutation of NKX2-5 gene was observed in the other 11 ASD pedigrees or in 168 patients with sporadic ASD. Additionally, a common synonymous single nucleotide polymorphism, a transition of adenine (A) into guanine (G) at nucleotide 63, was found in NKX2-5 gene. However, there were no significant differences in the prevalence of alleles A and G between ASD patients and healthy controls (chi(2) = 2.8641, P = 0.0906).</p><p><b>CONCLUSION</b>A novel mutation of NKX2-5 gene identified in an ASD family suggests that mutated NKX2-5 gene is responsible for familial ASD.</p>