Research News
Counting Gene Expression in Single Cells to Identify Stem Cells
Using a technique that can track the expression of multiple genes in a single cell, a team of investigators from the Massachusetts Institute of Technology (MIT) and the Royal Netherlands Academy of Arts and Sciences have demonstrated that they can identify and track individual stem cells from fixed samples of intestinal tissues. The researchers believe that this approach will be useful for studying the role of stem cells in the development of cancer.
Alexander van Oudenaarden of MIT led the team that conducted this study and published its work in the journal Nature Cell Biology. Dr. van Oudenaarden is the principal investigator of the MIT Physical Science-Oncology Center, one of 12 such centers created by the National Cancer Institute’s Physical Sciences in Oncology initiative.
In 2008, Dr. van Oudenaarden and his research group developed the technique now known as single-molecule fluorescence in situ hybridization (FISH) for detecting single messenger RNA (mRNA) molecules in individual cells. In this study, his team used three-color single-molecule FISH to follow the expression of a number of intestinal stem cell markers in intestinal crypt cells throughout development, aging, and recovery from radiation treatment.
Under the microscope, the outer layer of intestinal tissue, known as the epithelium, resembles corrugated paper, and crypt cells lie at the bottom of the valleys formed by two adjacent projections, which are known as villi. Since the mammalian intestinal epithelium regenerates itself over the course of several days, stem cells in these crypts continually generate new cells that travel out of the crypts and become the cells that absorb nutrients and secrete a variety of chemicals. Research suggests that colon cancer may develop when these stem cells begin proliferating in an uncontrolled manner.
In this study, the researchers showed that they could follow the expression of multiple stem cell markers in cells as they moved away from the crypts, and the results of these studies showed that the distribution of the expression of these markers varied little in normal or ageing intestinal epithelium. These experiments also demonstrated that single-molecule FISH can identify the precise location of cells that co-express any combination of the five markers. In addition, the researchers showed that following irradiation, which damages the intestinal epithelium, the expression program of these genes changed markedly, suggesting that each of these genes plays a unique role during damage repair.
This work, which is detailed in a paper titled, "Single-molecule transcript counting of stem-cell markers in the mouse intestine," was supported in part by the National Cancer Institute's Physical Sciences in Oncology initiative, a program that aims to foster the development of innovative ideas and new fields of study based on knowledge of the biological and physical laws and principles that define both normal and tumor systems. An abstract of this paper is available at the journal's Web site.
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