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

Gene expression imputation across multiple brain regions provides insights into schizophrenia risk

Transcriptomic imputation approaches combine eQTL reference panels with large-scale genotype data in order to test associations between disease and gene expression. These genic associations could elucidate signals in complex genome-wide association study (GWAS) loci and may disentangle the role of different tissues in disease development. We used the largest eQTL reference panel for the dorso-lateral prefrontal cortex (DLPFC) to create a set of gene expression predictors and demonstrate their utility. We applied DLPFC and 12 GTEx-brain predictors to 40,299 schizophrenia cases and 65,264 matched controls for a large transcriptomic imputation study of schizophrenia. We identified 413 genic associations across 13 brain regions. Stepwise conditioning identified 67 non-MHC genes, of which 14 did not fall within previous GWAS loci. We identified 36 significantly enriched pathways, including hexosaminidase-A deficiency, and multiple porphyric disorder pathways. We investigated developmental expression patterns among the 67 non-MHC genes and identified specific groups of pre- and postnatal expression

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