Proteomics reveal rat hippocampal lateral asymmetry

Abstract

Brain laterality has been observed in animals and humans structurally, functionally, and behaviorally. MRI and CT scans have revealed pathological and normal brain asymmetry. A coarse assessment of rat or human brain fails to expose profound left/right differences, while a finer examination of its structure reveals an array of asymmetric features. This lateralization may be derived from evolutionary, genetic, developmental, epigenetic, and pathologic factors. However, brain structure and function is complex and macroscopic or microscopic asymmetries may be hard to discern from random fluctuations. This study concentrated on the hippocampus and we explored lateralization employing a molecular high-throughput approach. Using proteomic analysis based on a combined approach of 2-D PAGE and MS, we examined differential protein expression in the hippocampi (left vs. right) of young adult male rats. Initial proteomic analysis demonstrated quantitative differences of approximately eighty proteins between the right (RH) and left hippocampus (LH). These were primarily energy-, cell metabolism-, stress-inducible chaperone proteins and cytoskeleton- proteins. Analysis revealed higher abundance of metabolic enzymes related to cellular energy metabolism, in the RH than the LH. In contrast, higher concentrations of proteins which are located mainly in astrocytes were shown in the LH than the RH. Immunoblotting of brain-specific proteins, on single animal hippocampal lysates confirmed the expression of Dynamin-1, DRP2, synapsin-1 and others, to be higher in the RH than LH lysates. These findings demonstrate major laterality in the expression of protein molecules between the two hippocampi providing a fertile field for mapping studies relating molecular, neuroimaging and functional data. Undoubtedly, asymmetries found at the animal level are hard to extrapolate to humans; however, studies in animal models will increase our understanding of the developing and adult brain and the healthy and diseased brain.

Effects of an Early Experience of Reward through Maternal Contact or its Denial on Laterality of Protein Expression in the Developing Rat Hippocampus

“…Lack of complete agreement between the results of the proteomic analysis and those of the western blotting could be partially due to the fact that the linearity in the dynamic range of the Coomassie-Blue assay is restricted. Furthermore similar inconsistencies have also been reported by others [8], [30].…”

“…For each experimental group (RER, CTR, DER) 2 samples were prepared, in each of which 5, either left or right, hippocampi were pooled. Tissue homogenization was performed as previously described [30], [47]: Hippocampi were suspended in 350 µl sample buffer containing 20 mM Tris, 7 M urea, 2 M thiourea, 4% CHAPS, 10 mM 1,4-dithioerythritol, 1 mM EDTA, and a mixture of protease inhibitors (1 mM PMSF and 1 tablet CompleteTM (Roche Diagnostics, Basel, Swiss) per 50 ml of suspension buffer) and phosphatase inhibitors (0.2 mM Na 2 VO 3 and 1 mM NaF). The suspension was sonicated for ∼30 s and centrifuged at 150,000 g for 20 min.…”

“…Peptide analysis and protein identification were performed as previously described [30], [47]. The selected spots were manually detected on the gels by Melanie 4.02 software (GeneBio, Geneve Bioinformatics S.A., Geneva, Swiss).…”

“…Furthermore a proteomic analysis of adult hippocampus revealed that the expression of a variety of proteins was asymmetrically distributed between the left and right hippocampi [30].…”

Osteopontin Expression during Early Cerebral Ischemia-Reperfusion in Rats: Enhanced Expression in the Right Cortex Is Suppressed by Acetaminophen

“…Functional asymmetries have been reported in the rat brain over several decades [36]. Major laterality has been noted in the expression of protein molecules between the right and the left hippocampi in rats [37]. Thus there is precedent for the right and the left hemispheres responding differently to a cerebral insult and that the right cortex could be more susceptible to injury from I-R when compared to the left cortex.…”