Tagging Stem Cells - Online Exhibit
This exhibit is about an ingenious experiment published in 1963 by Drs. Till, McCulloch and their graduate student Dr. Becker, at the Ontario Cancer Institute & University of Toronto.(1) Their primary area of research was leukemia, which is a cancer involving blood cells in the bone marrow. Using radiation technology and microscopy work, they became the first scientists to identify stem cells which significantly advanced the study of stem cells and cancer therapy worldwide.
In the 1960s, scientists could readily identify several types of bone marrow blood cells under the microscope. But Becker, Till & McCulloch were looking for the elusive blood stem cell. Hypothetically, a stem cell would give rise to all the other cells but no research lab had any evidence to demonstrate its existence.
Step 2 was to grow colonies from the irradiated cells. After 11 days they saw colonies containing multiple cell types. And the cells within a colony all had the identical chromosomal marking, demonstrating that they must be descendants of an original cell.
This was the first positive evidence that a single cell could indeed give rise to all the different types of blood cells.
From this experiment, they were able to establish two key properties about stem cells.
1. Stem cell can proliferate to become more stem cells and
2. Stem cells can differentiate to become many different types of cells.
(1) Read the original publication at this link tspace.library.utoronto.ca/bitstream/1807/2779/2/Nature_1963_197_452.pdf .
Special thanks to Dr. Till for his correspondence.