Chemogenetic Tools and their Use in Studies of Neuropsychiatric Disorders.

Chemogenetics is a newly developed set of tools that allow for selective manipulation of cell activity. They consist of a receptor mutated irresponsive to endogenous ligands and a synthetic ligand that does not interact with the wild-type receptors. Many different types of these receptors and their respective ligands for inhibiting or excitating neuronal subpopulations were designed in the past few decades. It has been mainly the G-protein coupled receptors (GPCRs) selectively responding to clozapine-N-oxide (CNO), namely Designer Receptors Exclusively Activated by Designer Drugs (DREADDs), that have been employed in research. Chemogenetics offers great possibilities since the activity of the receptors is reversible, inducible on demand by the ligand, and non-invasive. Also, specific groups or types of neurons can be selectively manipulated thanks to the delivery by viral vectors. The effect of the chemogenetic receptors on neurons lasts longer, and even chronic activation can be achieved. That can be useful for behavioral testing. The great advantage of chemogenetic tools is especially apparent in research on brain diseases since they can manipulate whole neuronal circuits and connections between different brain areas. Many psychiatric or other brain diseases revolve around the dysfunction of specific brain networks. Therefore, chemogenetics presents a powerful tool for investigating the underlying mechanisms causing the disease and revealing the link between the circuit dysfunction and the behavioral or cognitive symptoms observed in patients. It could also contribute to the development of more effective treatments.

Portal hypertension is the main driver of liver stiffness in advanced liver cirrhosis.

Liver stiffness (LS) is a novel non-invasive parameter widely used in clinical hepatology. LS correlates with liver fibrosis stage in non-cirrhotic patients. In cirrhotic patients it also shows good correlation with Hepatic Venous Pressure Gradient (HVPG). Our aim was to assess the contribution of liver fibrosis and portal hypertension to LS in patients with advanced liver cirrhosis. Eighty-one liver transplant candidates with liver cirrhosis of various aetiologies underwent direct HVPG and LS measurement by 2D shear-wave elastography (Aixplorer Multiwave, Supersonic Imagine, France). Liver collagen content was assessed in the explanted liver as collagen proportionate area (CPA) and hydroxyproline content (HP). The studied cohort included predominantly patients with Child-Pugh class B and C (63/81, 77.8%), minority of patients were Child-Pugh A (18/81, 22.2%). LS showed the best correlation with HVPG (r=0.719, p< 0.001), correlation of LS with CPA (r=0.441, p< 0.001) and HP/Amino Acids (r=0.414, p< 0.001) was weaker. Both variables expressing liver collagen content showed good correlation with each other (r=0.574, p<0.001). Multiple linear regression identified the strongest association between LS and HVPG (p < 0.0001) and weaker association of LS with CPA (p = 0.01883). Stepwise modelling showed minimal increase in r2 after addition of CPA to HVPG (0.5073 vs. 0.5513). The derived formula expressing LS value formation is: LS = 2.48 + (1.29 x HVPG) + (0.26 x CPA). We conclude that LS is determined predominantly by HVPG in patients with advanced liver cirrhosis whereas contribution of liver collagen content is relatively low.

Large copy-number variations in patients with statin-associated myopathy affecting statin myopathy-related loci.

Some patients are susceptible to statin-associated myopathy (SAM) either because of genetic variations affecting statin uptake and metabolism, or because they predispose their carriers to muscular diseases. Among the frequent variants examined using the genome-wide association study approach, SLCO1B1 c.521T>C represents the only validated predictor of SAM in patients treated with high-dose simvastatin. Our aim was to ascertain the overall contribution of large copy-number variations (CNVs) to SAM diagnosed in 86 patients. CNVs were detected by whole genome genotyping using Illumina HumanOmni2.5 Exome BeadChips. Exome sequence data were used for validation of CNVs in SAM-related loci. In addition, we performed a specific search for CNVs in the SLCO1B region detected recently in Rotor syndrome subjects. Rare deletions possibly contributing to genetic predisposition to SAM were found in two patients: one removed EYS associated previously with SAM, the other was present in LARGE associated with congenital muscular dystrophy. Another two patients carried deletions in CYP2C19, which may predispose to clopidogrel-statin interactions. We found no common large CNVs potentially associated with SAM and no CNVs in the SLCO1B locus. Our findings suggest that large CNVs do not play a substantial role in the etiology of SAM.