Monday, April 23, 2007

Conservation of expression in human and mouse brains   posted by p-ter @ 4/23/2007 05:01:00 PM

Speaking of human brain evolution, PLoS Genetics gives us this, "Conservation of Regional Gene Expression in Mouse and Human Brain":
Here we compare gene expression profiles of human motor cortex, caudate nucleus, and cerebellum to one another and identify genes that are more highly expressed in one region relative to another. We separately perform identical analysis on corresponding brain regions from mice. Within each species, we find that the different brain regions have distinctly different expression profiles. Contrasting between the two species shows that regionally enriched genes in one species are generally regionally enriched genes in the other species. Thus, even when considering thousands of genes, the expression ratios in two regions from one species are significantly correlated with expression ratios in the other species. Finally, genes whose expression is higher in one area of the brain relative to the other areas, in other words genes with patterned expression, tend to have greater conservation of nucleotide sequence than more widely expressed genes. Together these observations suggest that region-specific genes have been conserved in the mammalian brain at both the sequence and gene expression levels. Given the general similarity between patterns of gene expression in healthy human and mouse brains, we believe it is reasonable to expect a high degree of concordance between microarray phenotypes of human neurodegenerative diseases and their mouse models. Finally, these data on very divergent species provide context for studies in more closely related species that address questions such as the origins of cognitive differences.
Long story short-- the human brain is not some freak/miracle; studying mouse brains will be worthwhile as a tool for understanding human brains in general. This is also a step towards understanding what exactly it is that makes a human brain so different genetically from a mouse brain-- which developmental pathways have been altered, which parts of the brain most diverged? Previous studies of gene expression evolution have treated the "brain" as a single organ; now we can get in at its finer details.

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