My dissertation project investigated protein expression in the brains of humans and chimpanzees as a way of understanding modifications in molecular composition that underlie differences in cognition between these two species. Proteins are derived from gene transcripts, so the abundance of one is often thought to be predictive of the quantity of the other molecule. While many studies have compared the molecular compositions of humans and chimpanzees using gene transcripts, recent technological advancements allow protein expression to be examined.
I sought to determine the extent to which the expression levels of gene transcripts are indicative of the downstream expression levels of their protein products in the brains of humans and chimpanzees. Overall, results indicate an extremely low correlation between gene transcript and protein expression abundances, indicating a lack of correspondence between these two molecules in both species. Moreover, I found that different biological signals are accessible by studying gene expression changes between species compared to protein expression, suggesting that these molecules should not be used interchangeably when studying species differences.
Additionally, I studied the distribution of proteins in the brains of humans and chimpanzees using matrix-assisted laser desorption ionization mass spectrometry, a technology that allows tissue sampling at a fine spatial resolution. I found that, in general, the pattern of protein expression is similar within the layers of neocortex between humans and chimpanzees, reflecting consistency in the fundamental cytoarchitecture of cortical lamina regardless of the region of the brain. Furthermore, the human neocortex and caudate nucleus exhibit higher expression of proteins supporting aerobic metabolism than regions of the chimpanzee brain. A higher density of proteins supporting energetic function may underlie enhanced connectivity in the human neocortex and caudate nucleus compared to the same regions in the chimpanzee.
These insights are indicative of extensive research value in the study of protein expression when investigating the differences in molecular composition of the brain between species and provide new avenues for examining the biological basis of behavioral novelty in humans.
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|Advisor:||Sherwood, Chet C.|
|Commitee:||Babbitt, Courtney C., Hof, Patrick R., Wood, Bernard A., Wray, Gregory A.|
|School:||The George Washington University|
|School Location:||United States -- District of Columbia|
|Source:||DAI-A 76/01(E), Dissertation Abstracts International|
|Subjects:||Biology, Neurosciences, Physical anthropology|
|Keywords:||Gene expression, Human brain evolution, Protein, Proteome, Transcriptome|
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