Lesson 1 of 2 / Stem cells and differentiation
Self-renewal and developmental potential
What can a stem cell do that a specialised cell usually cannot?
In this lesson: Distinguish totipotent, pluripotent and multipotent stem cells.
About 6 min
The key ideaStem cells self-renew and produce differentiated descendants; potency describes the range of cell types they can form.
Explore the idea
Compare the possible descendants
In the syllabus model, a zygotic cell can give rise to body and extraembryonic cell types needed for a complete organism. Development still requires appropriate conditions and signals.
Potency describes the range of possible descendants. Self-renewal is a separate property: maintaining a stem-cell population through division.
The range is not a promise that every descendant appears in every culture. Evidence needs appropriate developmental conditions. Differentiation normally changes gene expression; it does not remove all unused genes.
Original lineage model. Arrows show developmental relationships, not physical cell movement or one fixed division pattern. The tree is simplified and does not show every progenitor or blood-cell type.
Explanation
A stem cell can divide while maintaining a stem-cell population and can give rise to specialised descendants. Self-renewal is not the same as potency: a cell may divide repeatedly yet remain restricted to a narrow lineage. Differentiation usually changes which genes are expressed rather than deleting all genes for other cell types.
A totipotent cell, such as the zygote in the syllabus model, can give rise to all cell types needed for the organism, including extraembryonic tissues. Pluripotent embryonic stem cells can generate the body's major cell types but do not independently form all the supporting extraembryonic tissues required for a complete organism.
Multipotent stem cells have a more restricted developmental range within related lineages. Blood stem-cell pathways include lymphoid and myeloid branches. Lymphoid progenitors generate lymphocyte lineages; myeloid progenitors generate several other blood-cell types. Restricted does not mean able to make only one mature cell type.
Potency is inferred from experimentally demonstrated developmental capacity, not from how large a cell looks. A diagram of narrowing branches represents possible descendants; it does not imply that a mature blood cell normally reverses spontaneously into an embryo.
Step by step
- 1
Ask about renewal
Can the population retain stem cells through division?
- 2
Ask about descendants
Which demonstrated cell types can it produce?
- 3
Assign potency
Use the range, not the cell's age or division speed.
Worked example
Work through the evidence
Cell A forms many body tissues but not all extraembryonic tissues; cell B forms several blood-cell types only. Classify them.
One way to explain it
A is pluripotent. B is multipotent. Neither description establishes totipotency.
Why this answer works
- Body-wide potential and complete organismal potential differ.
- Multiple blood types still belong to a restricted developmental system.
Is this true? "Pluripotent means a cell can independently make a complete organism."
That requires the broader extraembryonic potential included in totipotency.