SLC7A3: In Silico Prediction of a Potential New Cause of Childhood Epilepsy

We report an in-depth genetic analysis in an 11-year-old boy with drug-resistant, generalized seizures and developmental disability. Three distinct variants of unknown clinical significance (VUS) were detected by whole exome sequencing (WES) but not by initial genetic analyses (microarray and epilepsy gene panel). These variants involve the SLC7A3, CACNA1H, and IGLON5 genes, which were subsequently evaluated by computational analyses using the InterVar tool and MutationTaster. While future functional studies are necessary to prove the pathogenicity of a certain VUS, segregation analyses over three generations and in silico predictions suggest the X-linked gene SLC7A3 (transmembrane solute carrier transporter) as the likely culprit gene in this patient. In addition, a search via GeneMatcher unveiled two additional patients with a VUS in SLC7A3. We propose SLC7A3 as a likely candidate gene for epilepsy and/or developmental/cognitive delay and provide an overview of the 27 SLC genes related to epilepsy by other preclinical and/or clinical studies.

Reconstitution of GABA, Glycine and Glutamate Transporters

In contrast to water soluble enzymes which can be purified and studied while in solution, studies of solute carrier (transporter) proteins require both that the protein of interest is situated in a phospholipid membrane and that this membrane forms a closed compartment. An additional challenge to the study of transporter proteins has been that the transport depends on the transmembrane electrochemical gradients. Baruch I. Kanner understood this early on and first developed techniques for studying plasma membrane vesicles. This advanced the field in that the experimenter could control the electrochemical gradients. Kanner, however, did not stop there, but started to solubilize the membranes so that the transporter proteins were taken out of their natural environment. In order to study them, Kanner then had to find a way to reconstitute them (reinsert them into phospholipid membranes). The scope of the present review is both to describe the reconstitution method in full detail as that has never been done, and also to reveal the scientific impact that this method has had. Kanner’s later work is not reviewed here although that also deserves a review because it too has had a huge impact.

Deletion of Kvβ2 (AKR6) Attenuates Isoproterenol Induced Cardiac Injury with Links to Solute Carrier Transporter SLC41a3 and Circadian Clock Genes

Kvβ subunits belong to the aldo-keto reductase superfamily, which plays a significant role in ion channel regulation and modulates the physiological responses. However, the role of Kvβ2 in cardiac pathophysiology was not studied, and therefore, in the present study, we hypothesized that Kvβ2 plays a significant role in cardiovascular pathophysiology by modulating the cardiac excitability and gene responses. We utilized an isoproterenol-infused mouse model to investigate the role of Kvβ2 and the cardiac function, biochemical changes, and molecular responses. The deletion of Kvβ2 attenuated the QTc (corrected QT interval) prolongation at the electrocardiographic (ECG) level after a 14-day isoproterenol infusion, whereas the QTc was significantly prolonged in the littermate wildtype group. Monophasic action potentials verified the ECG changes, suggesting that cardiac changes and responses due to isoproterenol infusion are mediated similarly at both the in vivo and ex vivo levels. Moreover, the echocardiographic function showed no further decrease in the ejection fraction in the isoproterenol-stimulated Kvβ2 knockout (KO) group, whereas the wildtype mice showed significantly decreased function. These experiments revealed that Kvβ2 plays a significant role in cardiovascular pathophysiology. Furthermore, the present study revealed SLC41a3, a major solute carrier transporter affected with a significantly decreased expression in KO vs. wildtype hearts. The electrical function showed that the decreased expression of SLC41a3 in Kvβ2 KO hearts led to decreased Mg2+ responses, whereas, in the wildtype hearts, Mg2+ caused action potential duration (APD) shortening. Based on the in vivo, ex vivo, and molecular evaluations, we identified that the deletion of Kvβ2 altered the cardiac pathophysiology mediated by SLC41a3 and altered the NAD (nicotinamide adenine dinucleotide)-dependent gene responses.

Clinical significance of high expression of a specific solute carrier transporter in HCC.

303 Background: Hepatocellular carcinoma (HCC) is the third cause of cancer-related death. GNS561 (Genoscience Pharma, France) is a small molecule inducing apoptosis by lysosome inhibition and caspase activation. GNS561 has high hepatotropism and anti-tumorigenic capacity on tumor bulk and cancer stem cells. Its main target is a specific solute carrier transporter (SLCt). We describe here the clinical relevance of the overexpression of SLCt in HCC patients. Methods: The expression of SLCt was investigated by iQRT-PCR in surgically resected HCC tumors (T) and the matched non-tumor (NT) liver tissues (n=180) as well as healthy livers (HL) devoid of chronic or acute disease (n=10). Pearson's chi-squared test was employed for significant correlation tests while univariate and multivariate survival analysis were performed by Cox proportional hazard ratio (HR) method. Results: SLCt was overexpressed in 40.5% of T and 30.3% of NT as compared to HL. High SLCt in T was associated with microvascular emboli (p=0.034) and expression of the cancer stem cell markers Sox2 (p=0.025) and CD133 (p=0.034). High SLCt in NT correlated with cirrhosis (p=0.009) and presence of satellite nodules (p<0.001). Univariate analysis showed association between high SLCt in T and shortened overall survival (OS) (HR=1.08, p=0.020), lower progression-free survival (PFS) (HR=1.76, p=0.006) as well as early recurrence-free survival (ERFS) (within 2 years post-surgery) (HR=1.88, p=0.008). In multivariate analysis, high SLCt tended to be an independent factor for OS, and this was strongly significant for PFS and ERFS. High SLCt in NT, is quite a poor outcome factor on late recurrence-free survival (HR=2.33, p=0.056) together with cirrhosis in univariate analysis, but remained dependent of cirrhosis in multivariate analysis. Late recurrence is linked to the intrinsic tumorigenic status of the liver. Conclusions: Overexpression of the SLCt in HCC tumors is associated to stemness features and appears as a poor outcome factor impacting on early recurrence. Further, SLCt in NT is associated with development of de-novo HCC. Validation cohorts and prospective assessments are needed to define high SLCt as a potential biomarker of HCC stemness and patient outcome.