Stem Cells and Pluripotency (2C) - MCAT Biological and Biochemical Foundations of Living Systems

A cell that self-renews and can differentiate into specialized cell types. Stem cells maintain populations through self-renewal while producing differentiated progeny to form or repair tissues.

The range of cell types a stem cell can generate. Potency classifies stem cells based on their differentiation potential, from totipotent to unipotent.

Can form all embryonic and extraembryonic tissues (entire organism). Totipotent cells have the broadest potential, enabling development of a complete organism including supportive structures.

Can form all three germ layers but not extraembryonic tissues. Pluripotent cells generate all body cell types from the three germ layers but cannot form extraembryonic structures.

Can form multiple related cell types within a specific tissue/lineage. Multipotent cells are tissue-specific, differentiating into various related types within one lineage.

Can form a few closely related cell types within a lineage. Oligopotent cells have narrower potential than multipotent, limited to a few related types in a lineage.

Can form one cell type while retaining self-renewal capacity. Unipotent cells self-renew but are restricted to producing only one differentiated cell type.

Pre-implantation cleavage stage (zygote through early blastomeres). Early embryonic cells before compaction retain totipotency, allowing formation of an entire organism.

Forms extraembryonic tissues, especially much of the placenta. The trophoblast supports embryonic development by forming structures like the placenta for nutrient exchange.

Ectoderm, mesoderm, and endoderm. Gastrulation organizes the embryo into germ layers that specify tissue and organ formation.

Mesoderm. Mesoderm develops into supportive and circulatory systems as the middle germ layer.

Endoderm. Endoderm creates internal linings and organs as the innermost germ layer.

Pluripotent cell derived from the inner cell mass of a blastocyst. ESCs are isolated from pre-implantation embryos and retain ability to form all germ layer derivatives.

Usually multipotent; maintains and repairs specific tissues. Adult stem cells reside in tissues to enable regeneration and homeostasis within specific lineages.

More lineage-restricted with limited self-renewal capacity. Progenitors are committed precursors with finite divisions, bridging stem cells and differentiated cells.

Somatic cells reprogrammed back to a pluripotent state. iPSCs are created by reprogramming to restore pluripotency, mimicking embryonic stem cells.

Oct4, Sox2, Klf4, and c-Myc. Yamanaka factors activate pluripotency gene networks to dedifferentiate somatic cells.

Differentiation into derivatives of ectoderm, mesoderm, and endoderm. In vitro differentiation to all germ layers confirms pluripotent capacity without ethical issues of in vivo tests.

Local microenvironment signals that maintain stemness and regulate division. The niche provides extrinsic cues to preserve stem cell identity and control proliferation versus differentiation.

One daughter remains a stem cell and the other becomes a differentiating cell. Asymmetric division ensures stem cell maintenance while generating committed progenitors for tissue needs.

Multipotent. HSCs are multipotent as they produce all blood cells but are restricted to the hematopoietic lineage.

Totipotent. Totipotency encompasses all embryonic and extraembryonic lineages for complete organism development.

Pluripotent. Pluripotency allows derivation of diverse somatic cells from all germ layers but excludes extraembryonic tissues.

Ectoderm. Ectoderm forms external and neural tissues as the outermost germ layer.