A new stem cell source to build the retina identified

A new stem cell source to build the retina identified

Scientists have long believed that, in mammals, the retina—a thin layer of tissue in the eye that captures light and converts it into nervous signals—develops from a single stem cell population. The director of the Cellular Neurobiology research unit at the Institut de recherches cliniques de Montréal (IRCM) / Montreal Clinical Research Institute, Michel Cayouette, and his team recently challenged this belief. They have uncovered a new population of stem cells that produces retinal neurons during embryonic development.

A well-kept secret
Dr. Cayouette, also a professor at the University of Montreal and McGill University, and PhD student Marie Claude Bélanger discovered the stem cells in the peripheral zone of the retina. They used a technique called genetic lineage tracing to monitor the development of these cells in mice.

“We found a gene, Msx1, which is expressed specifically in some cells of the peripheral retina,” explains Dr. Cayouette. “We then tagged those cells with a fluorescent molecule so we could see their entire progeny after the mouse embryo developed,” said Dr. Cayouette, who was recently granted the Gaëtane and Roland Pillenière Research Chair in Retina. When studying this “cellular family tree”, the researchers noticed that the cells contributed to building the nervous tissue of the retina. In fish, this same cell source generates new neurons throughout their lives. “In mammals, the ability to do this appears restricted to developmental stages, but it will be interesting to see if these cells can be stimulated to produce neurons in adults.”

During the lineage tracing experiment, the pair of IRCM researchers also noted that these cells played a dual role during eye development: “Not only can this stem cell population generate retinal neurons (cells that send nerve signals)—its daughter cells were also found in tissue that is not part of the central nervous system: the iris of the eye, for example, which is more mechanical in nature,” said Marie-Claude Bélanger. This was a surprising finding, as there are few examples of stem cells in the central nervous system that have this dual role. 

Important issue
According to the Canadian National Institute for the Blind (CNIB), nearly half a million people in Canada have enough vision loss to be considered blind or partially sighted. This number will increase considerably with the aging population.

Many diseases that cause vision loss, such as those affecting the retina, are incurable. The damage caused is permanent, because the retina cannot regenerate. By better understanding how stem cells in the retina form the different neurons that make it up, Dr. Cayouette hopes to help develop techniques to repair this precious tissue. 

About the study
Published in Developmental Cell, this research project was conducted in the Cellular Neurobiology research unit by Marie Claude Bélanger and Michel Cayouette. Benoit Robert of the Institut Pasteur was also involved in the study. The research was funded by the Canadian Institutes of Health Research, the Brain Canada Foundation and the Fonds de recherche Québec–Santé [Quebec health research fund]. 

About the IRCM
Founded in 1967, the Institut de recherches cliniques de Montréal (IRCM) / Montreal Clinical Research Institute is a non-profit organization that conducts fundamental and clinical biomedical research in addition to training high-level young scientists. With its cutting-edge technology facilities, the institute brings together 33 research teams, which work in cancer, immunology, neuroscience, cardiovascular and metabolic diseases, systems biology and medicinal chemistry. The IRCM also operates a research clinic specialized in hypertension, cholesterol, diabetes and cystic fibrosis, as well as a research centre on rare and genetic diseases in adults. The IRCM is affiliated with the Université de Montréal and associated with McGill University. Its clinic is affiliated with the Centre hospitalier de l’Université de Montréal (CHUM). The IRCM is supported by the Ministère de l’Économie, de la Science et de l’Innovation (Quebec ministry of Economy, Science and Innovation).
 
Source: 
Anne-Marie Beauregard, Communication Advisor
Institut de recherches cliniques de Montréal (IRCM) / Montreal Clinical Research Institute
514 987-5555 | anne-marie.beauregard@ircm.qc.ca

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