The somatosensory nervous system is critical for the organism's ability to respond to
mechanical, thermal, and nociceptive stimuli. Somatosensory neurons are functionally
and anatomically diverse but their molecular profiles are not well-defined. Here, we
used transcriptional profiling to analyze the detailed molecular signatures of dorsal
root ganglion (DRG) sensory neurons. We used two mouse reporter lines and surface IB4
labeling to purify three major non-overlapping classes of neurons: 1)
IB4−SNS-Cre/TdTomato+, and 3)
Parv-Cre/TdTomato+ cells, encompassing the majority of
nociceptive, pruriceptive, and proprioceptive neurons. These neurons displayed
distinct expression patterns of ion channels, transcription factors, and GPCRs.
Highly parallel qRT-PCR analysis of 334 single neurons selected by membership of the
three populations demonstrated further diversity, with unbiased clustering analysis
identifying six distinct subgroups. These data significantly increase our knowledge
of the molecular identities of known DRG populations and uncover potentially novel
subsets, revealing the complexity and diversity of those neurons underlying
In the nervous system, a network of specialized neurons—known as the
somatosensory system—carries information about sensations including touch,
muscle position, temperature and pain. Distinct sets of somatosensory neurons are
thought to carry information about the different types of sensations. In young
animals, the precise switching on, or ‘expression’, of genes controls
the formation of the network of neurons. However, it is not known exactly which genes
are expressed in what types of neurons, where, or when.
Here, Chiu et al. used a technique called flow cytometry using different fluorescent
markers to isolate a group of cells called Dorsal Root Ganglion (DRG) neurons in
mice. These neurons have long thread-like fibers that extend from the spinal cord to
the skin, muscles and joints all over the body. These fibers carry sensory
information to the spinal cord, where it can be relayed to the brain and processed.
The experiments compared three distinct types of DRG neuron and found that they
differed in their ability to send information to other cells.
Chiu et al. analyzed the expression of all the genes in the three types of DRG
neurons. Each type of neuron had distinct groups of genes that were being expressed.
Also, several genes that are known to be important for sensation were expressed at
different levels in the different types of cells. Next, large numbers of single cells
were analyzed to find out the finer details about the three types of neuron. These
findings made it possible to further divide the DRG neurons into six distinct subsets
that matched previously known groups of somatosensory neurons, and also identified
Chiu et al.'s findings reveal the complexity and diversity of the neurons involved in
carrying information about sensations towards the brain. This is an important step in
classifying the nervous system, and uncovers many genes previously not linked to
sensation. The next challenges lie in understanding how the expression of these genes
in each type of neuron relates to their unique roles.