The researchers hypothesize that tumors could arise when stem cells in the cerebellum become inappropriately activated and multiply uncontrollably. Identifying the source of medulloblastoma could enable researchers to more effectively disrupt the genes and proteins that fuel its growth.
Stem cells are immature cells that have the potential to differentiate into multiple types of adult cells. They are known for their unique ability to proliferate extensively and give rise to both new stem cells as well as a host of specialized cells that perform designated tasks in a particular tissue or organ. But when stem cells become activated at the wrong time or place, rapid proliferation can give rise to cancer, said Wechsler-Reya.
The researchers discovered the stem cells while studying the development of granule cells, the most abundant type of neuron in the cerebellum. While purifying granule cell precursors, they discovered what they believed to be contaminating cells. But upon closer examination, these turned out to include a small population of neural stem cells, said Audra Lee, a research associate in Wechsler-Reya's lab who carried out the majority of the work.
The stem cells they isolated represented less than one percent of the total number of cells in the cerebellum, said Lee. Yet they were clearly identified as stem cells based on three distinct properties: their expression of a protein called Prominin-1 or CD133, which is commonly found on stem cells; their ability to divide indefinitely in response to stem cell growth factors; and their ability to generate all the major cell types in the cerebellum when transplanted into the cerebellum of neonatal mice.
Identifying stem cells in the cerebellum provides the research team with a target for studying both normal development and can