Distinct patterns of gene expression in the left and right hippocampal formation of developing rats

Abstract

A central problem in neurobiology is the elucidation of the mechanisms that underlie left-right asymmetries in brain structure and function. Using a transcriptome screening approach, we found asymmetric gene expression patterns in the right when compared with the left hippocampal formation at postnatal days (P) 6, 9, and 60 in the rat. Of those genes that were differentially expressed, most were predominantly expressed in the right hippocampus at P6, whereas most were predominantly expressed in the left at P9 and P60. Real-time PCR analysis of genes associated with synaptic vesicle trafficking confirmed this pattern. At P6, 9 of 13 such genes were more robustly expressed in the right hippocampus, while only 1 gene was predominantly expressed in the left. Conversely, at P9, 5 of the 13 genes were more highly expressed in the left hippocampus and only 1 gene was predominantly expressed in the right. This pattern persisted at P60: eight genes were more robustly expressed in the left hippocampus, and the remaining five showed no hemispheric preference. These data demonstrate a pattern of early lateralized gene expression that is likely to underlie the establishment of functional asymmetry in the adult hippocampus.

Neuropilin asymmetry mediates a left-right difference in habenular connectivity

“…and M.E.H., unpublished). However, some recent reports have identified L-R differences in gene expression programs in the rodent cortex (Sun et al, 2006;Sun et al, 2005) and hippocampus (Moskal et al, 2006), and in the size of white-matter fiber tracts associated with language regions of the human brain (Nucifora et al, 2005). Our study suggests that the asymmetric distribution of axon-guidance cues could be an important mechanism to establish patterns of connectivity in the developing embryonic CNS that underlie functional specialization.…”

Social defeat, a paradigm of depression in rats that elicits 22-kHz vocalizations, preferentially activates the cholinergic signaling pathway in the periaqueductal gray

“…Importantly, although smaller changes may actually demonstrate statistical significance, a 10-13% change, in our hands, is currently the limit of discrimination for qRT-PCR quantitation [41,56].…”

“…Notwithstanding, in-house design and fabrication allows a stringent level of quality control, exquisite sensitivity, and economy that typically constrains the number of arrays required to conduct experiments with sufficient numbers of biological samples/replicates and provide statistically acceptable sensitivity and specificity. This approach has reliably identified transcripts having as low as 10% differences in transcript expression between RNA samples observed in heterogeneous tissue sources such as neocortex and hippocampus [41,56]. In sum, our approach of highly selective yet broad ontological coverage of the rat transcriptome facilitates the generation of high quality data from systems/paradigms sensitive to small regulatory changes that can be confirmed by independent measurements.…”

Effects of alcohol and combined marijuana and alcohol use during adolescence on hippocampal volume and asymmetry

“…Given that other studies have found reduced left hippocampal and amygdale, but not right, volumes associated with other pathological processes (e.g., Chen et al, 2004;Saylam et al, 2006), there may be neurotoxic or pre-existing developmental trajectory differences between the hemispheres that account for these differences. For example, left versus right hippocampi may differ in drug effects due to gene expression or neurotransmitter receptor discrepancies (e.g., Mostal et al, 2006).…”