Type I diabetes is a form of diabetes that is due to the loss of insulin-producing cells of the pancreas. The potential of stem cells—in particular, induced pluripotent stem (iPS) cells—for therapy has gotten a lot of press.
If researchers were attempting to stimulate the differentiation of iPS cells, which of the following would they most likely add to the cell-culture medium (the liquid surrounding the cells)?
a. Activin A, an extracellular signal protein
b. Sox-2, a transcription factor active in early development
c. Grb-2, an intracellular signal transduction protein
d. Lactase, an enzyme that catalyzes the breakdown of lactose

Verified step by step guidance

1. Understand the problem: Researchers are trying to stimulate the differentiation of induced pluripotent stem (iPS) cells to potentially replace insulin-producing cells in Type I diabetes therapy.
2. Identify the role of each option: Activin A is an extracellular signal protein involved in cell differentiation, Sox-2 is a transcription factor active in early development, Grb-2 is an intracellular signal transduction protein, and lactase is an enzyme that breaks down lactose.
3. Consider the differentiation process: Differentiation of stem cells often requires specific signaling molecules that can guide the cells to develop into a particular cell type.
4. Evaluate the options: Activin A, as an extracellular signal protein, is known to play a role in the differentiation of various cell types, including pancreatic cells. This makes it a likely candidate for inclusion in the cell-culture medium.
5. Conclude the reasoning: Based on the need for differentiation signals, researchers would most likely add activin A to the cell-culture medium to stimulate the differentiation of iPS cells into insulin-producing cells.

Key Concepts

Induced Pluripotent Stem (iPS) Cells

Induced pluripotent stem (iPS) cells are a type of stem cell that can be generated directly from adult cells. They have the ability to differentiate into various cell types, making them a promising tool for regenerative medicine. iPS cells are created by reprogramming somatic cells to a pluripotent state, similar to embryonic stem cells, allowing them to potentially replace damaged or lost cells in diseases like Type I diabetes.

Cell Differentiation

Cell differentiation is the process by which a less specialized cell becomes a more specialized cell type. This process is crucial in the development of multicellular organisms and is guided by specific signals and factors that influence gene expression. In the context of iPS cells, differentiation is essential to produce insulin-producing cells that could be used to treat Type I diabetes.

Extracellular Signal Proteins

Extracellular signal proteins, such as activin A, play a critical role in cell communication and differentiation. These proteins bind to receptors on the cell surface, triggering a cascade of intracellular events that lead to changes in gene expression and cell behavior. In stem cell research, extracellular signals are often used to direct the differentiation of stem cells into specific cell types, such as insulin-producing cells for diabetes therapy.