A comparison of human brain dissection by drill versus saw on nucleic acid quality

This study examined the effect of two dissection techniques on the quality of human brain specimens. Frozen cerebellar samples were obtained from postmortem brains of 10 subjects free from neurological and psychiatric disease. These tissues were tested for RNA and DNA concentration and quality after being dissected with either an electric dental drill or a small handsaw. RNA and DNA were extracted separately from each sample, and the concentrations and quality of each were measured. We found that dissection technique does not significantly affect RNA or DNA quality/yield. RNA and DNA yields, as well as RNA integrity showed no significant differences between the two dissection techniques. Therefore, these results support the use of a high-speed hand-held electric dental drill as an efficient and anatomically precise means of human brain dissection without compromising tissue quality. Published by Elsevier B.V

Development of Knock-in Mutant Mice Carrying Human Catechol-O-Methyltransferase Met Mutation Mimicking the Functional Val158Met Polymorphism

The functional Val158Met polymorphism in human catechol-O-methyltransferase (COMT) gene affects cognition, arousal, pain sensitivity, and has been associated with psychiatric disorders including schizophrenia, obsessive-compulsive disorder and anxiety. The best characterized role of COMT in brain function is in termination of dopamine action in prefrontal cortex. Other than termination of dopamine action, it may play other roles in brain development and function related to its methyl transferase activity. COMT consumes S-adenosylmethionine (SAM), a key substrate for DNA methylation, and might affect epigenetic regulation of other genes in the brain. In addition, the dominant form of COMT in human brain is the membrane-bound COMT (MB-COMT), which is located on the cell membrane and might affect cell to cell communication involved in cell migration and survival. Although the complete COMT gene knockout mouse is a useful animal model for studying the roles of COMT in cognitive and emotional behaviors, the complete gene knockout mutation is quite different from the functional Val158Met polymorphism in terms of the effect on gene expression. Another problem with the complete COMT knockout mouse model is that the COMT gene is located in a high gene density region and the complete knockout of COMT might affect adjacent genes and complicate the interpretation of results. To mimic the Val158Met polymorphism, we replaced two nucleotides in the mouse COMT gene to replace the Leu, equivalent to Val in human COMT, with Met at the 158th amino acid position using knock-in targeted mutation technology. The knock-in mutant mice showed dramatic decreases in COMT protein and enzyme activity, which is very similar to the consequence of the Val\uf0e0Met mutation in human COMT. Our results suggest that the mutation in the COMT Met knock-in mutant mice resemble the functional Val/Met polymorphism better than the complete knockout and could be a better animal model for analyses of the molecular and cellular mechanisms underlying the differences in the cognitive and emotional controls due to the functional Val158Met polymorphism

Expression of HDAC2 but Not HDAC1 Transcript Is Reduced in Dorsolateral Prefrontal Cortex of Patients with Schizophrenia

Postmortem brain studies support dysregulated expression of the histone deacetylase enzymes, HDAC1 and HDAC2, as a central feature in diseases including schizophrenia, bipolar disorder, and depression. Our objective was to investigate HDAC expression in a large postmortem sample set representing healthy and disease brains. We used >700 well-characterized samples from patients diagnosed with schizophrenia (n = 175), major depressive disorder (n = 135), and bipolar disorder (n = 61) to measure HDAC1 and HDAC2 transcript levels by quantitative real-time PCR in dorsolateral prefrontal cortex (DLPFC) and caudate compared to control samples. HDAC expression was calculated relative to the geometric mean of β-2-microglobulin, β-glucuronidase, and β-actin. In adult-age DLPFC, HDAC2 was decreased by 34% in schizophrenia samples compared to controls (p < 10–4). HDAC2 was significantly upregulated in major depressive disorder samples by 17% versus controls (p = 0.002). Neither smoking history nor therapeutic drugs impacted HDAC2 levels and no HDAC1 patient-control differences were observed. In caudate, HDAC levels were unchanged between patient and control groups. In control DLPFC, age fetal week 14 to 97 years (n = 326), both HDAC1 and HDAC2 levels sharply declined around birth and stabilized thereafter. Using by far the largest postmortem sample set on this topic, our major finding (decreased HDAC2 transcript) showed notable specificity in disease (schizophrenia but not major depressive disorder), HDAC subtype (HDAC2 but not HDAC1) and brain region (DLPFC but not caudate). These differences shape understanding of regional components of neural circuitry in the diseased brain and set a benchmark to quantify HDAC density and distribution using in vivo neuroimaging tools