Question

Recently, it was reported that adult, differentiated cells can be made to behave as pluripotent stem cells by the introduction of a few genes, one of which was Oct What was the rationale for this experiment?

• A. Oct4 expression is one of the requisites for the maintenance of pluripotent embryonic stem cells in culture
• B. The Oct4 gene produces a cell-cell signaling protein that is used by stem cells to stimulate cell division
• C. Oct4 is only expressed in embryonic stem cells, and so its expression automatically reverses any differentiation that may have gone on in a cell
• D. Oct4 is a master switch gene that turns on the stem cell program

Hint:

Oct4 and Sox2 form a heterodimer that binds to specific DNA elements, acting as molecular gatekeepers to maintain pluripotency and prevent differentiation.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Induced Pluripotent Stem Cells (iPSCs) are adult somatic cells that have been genetically reprogrammed to an embryonic stem cell-like state.
This reprogramming is achieved by introducing a specific set of transcription factors, collectively known as Yamanaka factors: Oct4, Sox2, Klf4, and c-Myc.

Step 2: Detailed Explanation:
The rational design of the reprogramming experiment was based on decades of embryonic stem cell (ESC) research.
Oct4 (octamer-binding transcription factor 4, encoded by the Pou5f1 gene) is a homeodomain transcription factor.
In vivo, Oct4 is expressed in the inner cell mass of the blastocyst and is essential for maintaining pluripotency.
In vitro, maintaining pluripotency in embryonic stem cell cultures requires continuous Oct4 expression.
If Oct4 is downregulated, embryonic stem cells differentiate into trophectoderm.
If Oct4 is upregulated, they differentiate into primitive endoderm and mesoderm.
This strict requirement makes Oct4 a key marker and driver of pluripotency.
The researchers hypothesized that since Oct4 is essential for maintaining pluripotency in ESCs, introducing it into somatic cells would help reprogram them back to a pluripotent state.
While Oct4 works alongside other transcription factors (like Sox2 and Nanog) to regulate target genes, its presence is a primary requirement for establishing and maintaining the pluripotent state.

Step 3: Final Answer:
The rationale for using Oct4 was that its expression is required to maintain pluripotency in embryonic stem cells.