Abstract
The dorsal root ganglia (DRG) and trigeminal ganglia (TG) are clusters of cell bodies of highly specialized sensory neurons which are responsible for relaying information about our environment to the central nervous system. Despite previous efforts to characterize sensory neurons at the molecular level, it is still unknown whether those present in DRG and TG have distinct expression profiles and therefore a unique molecular fingerprint. To address this question, we isolated lumbar DRG and TG neurons using fluorescence-activated cell sorting from Advillin-GFP transgenic mice and performed RNA sequencing. Our transcriptome analyses showed that, despite being overwhelmingly similar, a number of genes are differentially expressed in DRG and TG neurons. Importantly, we identified 24 genes which were uniquely expressed in either ganglia, including an arginine vasopressin receptor and several homeobox genes, giving each population a distinct molecular fingerprint. We compared our findings with published studies to reveal that many genes previously reported to be present in neurons are in fact likely to originate from other cell types in the ganglia. Additionally, our neuron-specific results aligned well with a dataset examining whole human TG and DRG. We propose that the data can both improve our understanding of primary afferent biology and help contribute to the development of drug treatments and gene therapies which seek targets with unique or restricted expression patterns.
Highlights
Among the different types of cells present in the central (CNS) and peripheral (PNS) nervous systems, sensory neurons are of particular importance as they are continually relaying information about our environment
Lumbar dorsal root ganglia (DRG) and trigeminal ganglia (TG) were dissociated, the cells were exposed to propidium iodide (PI) and isolated using fluorescence-activated cell sorting (FACS) (Figure 1B; for gating strategies, please refer to section “Materials and Methods” and Supplementary Figure 2)
We carried out Quantitative real-time PCR (qPCR), where we showed a higher amount of calcitonin gene-related peptide (CGRP) messenger ribonucleic acid (RNA) (mRNA) in the DRG in an independent cohort of animals (n = 3 DRG; n = 4 TG; p = 0.056; Figure 5A)
Summary
Among the different types of cells present in the central (CNS) and peripheral (PNS) nervous systems, sensory neurons are of particular importance as they are continually relaying information about our environment. There is large heterogeneity, whereby different types of neurons have their own special perceptual modalities and distinct cellular and molecular identities (Snider and McMahon, 1998; Devor, 1999; Marmigere and Ernfors, 2007; Dubin and Patapoutian, 2010; Reichling et al, 2013). Despite their functional similarities and capability to sense innocuous and noxious stimuli, DRG and TG neurons are very distinct in their location and connectivity. The distinction in cell fate at embryonic stages, together with some of the already mentioned exclusive functional characteristics and different connectivity patterns, suggests the existence of different molecular identities underlying either of these ganglia
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