Highway to the brain: cells responsible for touch need a support system to grow really long distances during development

or technically,

Roof Plate-Derived Radial Glial-like Cells Support Developmental Growth of Rapidly Adapting Mechanoreceptor Ascending Axons

[See Original Abstract on Pubmed]

Authors of the study: Kim Kridsada, Jingwen Niu, Zhiping Wang,Parthiv Haldipur, Long Ding, Jian J. Li, Anne G. Lindgren, Eloisa Herrera, Gareth M. Thomas, Victor V. Chizhikov, Kathleen J. Millen, and Wenqin Luo

Have you ever thought about going on a cross-country road trip, perhaps from Washington D.C to San Francisco? To make traveling such a long distance easier, you may need road signs telling you where to go and highways to make your journey more direct. In the same way that we need directions and fuel for a long trip, the neuronsA nerve cell that uses electrical and chemical signals to send information to other cells including other neurons and muscles that mediate our sense of touch (also known as mechanoreceptorA type of neuron (nerve cell) that senses mechanical stimuli like touch cells) need a way to get their axonsA specialized part of a neuron that sends electrical and chemical signals to other cells. Axons are typically long and thin like a wire. from the periphery of your body (e.g., hands, toes, and legs) to their final destination, the brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals.! During nervous system development, it’s really important for these cells to reach the brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. in order to provide us with a proper sense of touch; these cells help you feel the carpet under your feet as you get out of bed, the fork in your hand as you eat your lunch, and even that light tap on your shoulder when somebody is trying to get your attention. So how exactly do these touch neuronA nerve cell that uses electrical and chemical signals to send information to other cells including other neurons and muscles axonsA specialized part of a neuron that sends electrical and chemical signals to other cells. Axons are typically long and thin like a wire. travel so far to ultimately reach the brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals.? Kim Kridsada, a neuroscience graduate student in Wenqin Luo’s lab, sought to figure this out.

Kim noticed that during development, the mechanoreceptorA type of neuron (nerve cell) that senses mechanical stimuli like touch (“touch”) cell axonsA specialized part of a neuron that sends electrical and chemical signals to other cells. Axons are typically long and thin like a wire. that had to travel the farthest (e.g. from hands and feet to the brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals.) also seemed to grow closer to a group of specialized cells in the spinal cord compared to cells that didn’t have as far to go. She thought that maybe these specialized cells could be guiding cells (aka acting as a highway) and also sending signals (aka “road signs”) out to the touch cell axonsA specialized part of a neuron that sends electrical and chemical signals to other cells. Axons are typically long and thin like a wire. that helped them grow through the spinal cord to eventually reach the brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals.. Kim found that these support cells indeed sent out signals, in the form of specific growth-promoting proteinsAn essential molecule found in all cells. DNA contains the recipes the cell uses to make proteins. Examples of proteins include receptors, enzymes, and antibodies., that could be used by the touch neuronsA nerve cell that uses electrical and chemical signals to send information to other cells including other neurons and muscles to grow in the correct directions. The support cells that Kim found surrounding these touch cells were part of a particular class of cells known as radial glial-like cells (RGLCs), which are cells that can help with growth and development of neuronal cells. Kim wondered how important these RGLCs were for the touch cells - did the touch cells need them to grow along this highway to reach the brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals.? She hypothesized that without this RGLC highway, the touch cells wouldn't grow as far. To test whether RGLCs are truly needed in the body for touch cells to grow long distances, Kim studied mice that did not have any RGLCs but still had touch cells that were capable of growing. Interestingly, she found that in mice that had no RGLCs, their touch cells axonsA specialized part of a neuron that sends electrical and chemical signals to other cells. Axons are typically long and thin like a wire. were much shorter and 40% of their touch cells did not grow long enough to reach their correct destination in the brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals.! Taken together, these findings suggest that RGLCs are really important in the body for helping touch cells axonsA specialized part of a neuron that sends electrical and chemical signals to other cells. Axons are typically long and thin like a wire. eventually make their way to the brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals..

Overall, Kim discovered a previously unknown group of support cells (RGLCs) in the spinal cord that help touch cell axonsA specialized part of a neuron that sends electrical and chemical signals to other cells. Axons are typically long and thin like a wire. make connections over long distances, from the periphery of the body to eventually the brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals.. These findings are really important not only for our understanding of how we develop a very important sense (touch), but could also be used to improve regeneration in people who have suffered injuries and have, as a result, lost their sense of touch. Thanks to Kim’s work, we now know that these spinal cord cells help certain touch cells grow long distances, so we could try to develop drugs or therapies that target them so that growth of touch cells during regeneration happens more easily.
About the brief writer: Elelbin Ortiz  Elelbin is a PhD Candidate in  Michael Granato’s lab . She is interested in understanding how animals set behavioral thresholds, or ways to decide whether information from the environment requires a response or not. She is interested in understanding how an animal's genes (DNA) influence how these behavioral thresholds are set.

About the brief writer: Elelbin Ortiz

Elelbin is a PhD Candidate in Michael Granato’s lab. She is interested in understanding how animals set behavioral thresholds, or ways to decide whether information from the environment requires a response or not. She is interested in understanding how an animal's genes (DNA) influence how these behavioral thresholds are set.

Do you want to learn more about touch, RGLCs, and development? You can read Kim’s whole paper here.