Stem Cells and Pluripotency (2C) Practice Test

A team studies colony heterogeneity in a human pluripotent stem cell line. They sort cells into two fractions based on surface marker intensity: Fraction High and Fraction Low. Both fractions are returned to identical maintenance conditions for one week, then assessed for (i) ability to reconstitute the original mixed distribution of marker intensity and (ii) ability to generate derivatives from multiple germ layers when placed into distinct differentiation cues.

Which result most strongly supports that Fraction High contained cells with greater pluripotency?

In a laboratory study of myocardial repair, researchers cultured human induced pluripotent stem cells (iPSCs) under two conditions for 10 days: Condition 1 used a medium designed to maintain an undifferentiated state; Condition 2 included signaling factors intended to promote differentiation. The team measured expression of OCT4 (associated with an undifferentiated state), SOX17 (endoderm-associated), and TNNI3 (cardiomyocyte-associated). Results are shown below.

Based on these results, which characteristic would be expected of a pluripotent stem cell in this context?

Table 1. Relative mRNA expression (fold-change vs baseline)

• Condition 1: OCT4 = 5.2, SOX17 = 0.6, TNNI3 = 0.4
• Condition 2: OCT4 = 0.7, SOX17 = 3.8, TNNI3 = 4.1