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#stem cells

34 public questions tagged with this topic.

Stem Cell -l

A key characteristic distinguishing stem cells from progenitor cells is:

The fundamental distinction lies in lifespan and self-renewal capacity. Stem cells maintain indefinite self-renewal through telomerase activity, DNA repair proficiency, and symmetric self-renewing divisions, persisting throughout organismal lifetime. Progenitor or transit-amplifying cells exhibit limited proliferative potential, typically fewer than ten divisions, before senescence or terminal differentiation. Stem cells also retain broader potency and ability to regenerate tissue after injury, while progenitors are more fate-restricted. Both can differentiate, but only stem cells combine lifelong persistence with self-renewal, making them true reservoir for tissue turnover.

Ref: Gilbert, Developmental Biology, 12th ed., Chapter 6: Stem vs progenitor self-renewal.

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Stem Cell -l

Which of the following statements about stem cell differentiation is incorrect?

Stem cell differentiation is highly orchestrated, not stochastic uncontrolled process. Lineage commitment involves progressive restriction through transcription factor networks, chromatin remodeling, and repression of alternative fates. Niche signals such as Wnt, BMP, Notch, and FGF provide positional information, while intrinsic epigenetic modifiers like Polycomb and Trithorax establish memory. Under specific experimental conditions, differentiation can be reversed via induced pluripotency or transdifferentiation using defined factors. Random differentiation would disrupt tissue architecture and cause tumorigenesis. Therefore regulated, stepwise commitment with reversible plasticity under defined reprogramming defines contemporary differentiation paradigms.

Ref: Gilbert, Developmental Biology, 12th ed., Chapter 6: Regulation of differentiation.

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Stem Cell -l

Which of the following is an example of a stem cell niche?

A functional niche must provide structural support, adhesive contacts, and signaling milieu that maintains stemness. The intestinal crypt exemplifies this model: Paneth cells intercalated with Lgr5-positive stem cells at crypt base secrete Wnt3, EGF, and Notch ligands DLL1 and DLL4, creating high Wnt environment. Stromal telocytes and basement membrane contribute R-spondin and BMP inhibitors. This arrangement promotes proliferation and suppresses differentiation upward along villus. Mature red blood cells, trophoblast, and apoptotic cells lack stem-supporting signaling capacity, thus not considered niches. Crypt architecture demonstrates niche control of division mode and lineage output.

Ref: Gilbert, Developmental Biology, 12th ed., Chapter 6: Intestinal crypt as niche example.

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Stem Cell -l

Which statement about induced pluripotent stem cells (iPSCs) is false?

Induced pluripotent stem cells are engineered by ectopic expression of Yamanaka factors Oct4, Sox2, Klf4, c-Myc in somatic fibroblasts or blood cells, resetting epigenome to embryonic-like state. They self-renew indefinitely and differentiate into derivatives of three germ layers, useful for disease modeling and regenerative medicine without embryo destruction. Unlike embryonic stem cells isolated from blastocyst inner cell mass, iPSCs do not exist naturally in embryos; they require artificial reprogramming. They retain epigenetic memory and potential tumorigenicity, highlighting distinction between natural embryonic pluripotency and laboratory-induced pluripotency.

Ref: Takahashi & Yamanaka, Cell 2006; Gilbert, 12th ed., Chapter 6: iPSC reprogramming.

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Stem Cell -l

What is the correct sequence of lineage commitment in hematopoietic differentiation?

Developmental potency narrows progressively as epigenetic restrictions and lineage-specific transcription factors accumulate. The zygote and early morula are totipotent, producing embryo plus placenta. With blastocyst formation, inner cell mass becomes pluripotent, forming all three germ layers ectoderm, mesoderm, endoderm but not trophectoderm. Subsequently, tissue-specific multipotent stem cells such as hematopoietic stem cells arise, limited to lineages within one germ layer. Finally, unipotent progenitors differentiate into single cell types like erythrocytes or spermatids. This totipotent to pluripotent to multipotent to unipotent hierarchy reflects irreversible chromatin condensation and loss of plasticity.

Ref: Gilbert, Developmental Biology, 12th ed., Chapter 6: Hierarchy of potency restriction.

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Stem Cell -l

In which organism is each individual cell totipotent?

Totipotency denotes ability to generate complete organism including embryonic and extraembryonic tissues. While mammalian totipotency is limited to zygote and early blastomeres up to eight-cell stage, certain lower metazoans retain organism-wide cellular plasticity. Hydra, a cnidarian, contains interstitial stem cells distributed throughout body that remain totipotent, capable of forming ectoderm, endoderm, nematocytes, neurons, and germ cells. Each fragment containing interstitial cells can regenerate entire animal. Mice, Drosophila, and zebrafish show lineage-restricted somatic cells early, so individual differentiated cells cannot regenerate whole organisms spontaneously.

Ref: Bosch, Stem Cells 2009; Gilbert, 12th ed., Chapter 6: Totipotency in Hydra interstitial cells.

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Stem Cell -l

Which of the following is NOT an essential property of a stem cell?

Essential stem cell properties include prolonged self-renewal, maintenance of an undifferentiated state with open chromatin, and capacity to differentiate into specialized functional cells under niche cues. Self-renewal involves asymmetric or symmetric divisions preserving stem pool while generating progeny. Limited division potential characterizes transit-amplifying progenitors and differentiated somatic cells subject to Hayflick limit and telomere attrition. True stem cells divide extensively throughout life, expressing telomerase and checkpoint evasion mechanisms. Recognizing unlimited self-renewal versus limited progenitor amplification separates stemness from more restricted proliferative populations during tissue homeostasis.

Ref: Gilbert, Developmental Biology, 12th ed., Chapter 6: Properties of stem versus progenitors.

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Stem Cell -l

The term stem cell niche refers to:

The stem cell niche concept introduced by Schofield defines a specific anatomic and biochemical compartment that anchors stem cells and controls their behavior. It comprises supporting stromal cells, extracellular matrix, blood vessels, neural inputs, soluble factors like Wnt, BMP, Notch ligands, oxygen tension, and adhesion molecules. Niche signals suppress differentiation, regulate symmetric versus asymmetric division, and protect genome integrity. Disruption leads to stem cell loss or tumorigenic hyperplasia. Examples include intestinal crypt base, hair follicle bulge, and bone marrow endosteal zone, illustrating how location dictates fate.

Ref: Schofield, Blood Cells 1978; Gilbert, 12th ed., Chapter 6: Stem cell niche definition.

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Stem Cell -l

Which of the following statements about progenitor cells is correct?

Progenitor cells, often termed transit-amplifying or intermediate progenitors, derive from rare stem divisions and exhibit rapid proliferation but limited self-renewal, undergoing finite mitoses before obligatory terminal differentiation and cell cycle exit. They express lineage-specific transcription factors committing them to particular path such as myeloid progenitors expressing PU.1 and C/EBPalpha or basal keratinocyte progenitors expressing Krt5 but not sustaining lifelong pool. Unlike genuine stem cells they lack indefinite telomerase, cannot long-term reconstitute ablated tissue upon serial transplantation, and are not totipotent, serving mainly as amplification stage increasing output without endangering stem genome integrity.

Ref: Potten, Stem Cells 1990; Watt, J Cell Sci 1998: Transit-amplifying progenitor transient proliferation committed lineage.

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Stem Cell -l

The ability of hematopoietic stem cells to differentiate into blood cells makes them:

Hematopoietic stem cells residing in specialized bone marrow niches generate diverse mature blood lineages including erythroid, megakaryocytic, myeloid and lymphoid branches but do not produce neural, skeletal muscle, or extraembryonic trophoblast under physiological conditions in vivo. This pattern of generating multiple differentiated types related within one physiological system but limited outside defines multipotency precisely. Multipotent stem cells are lineage-restricted compared with pluripotent embryonic stem cells, yet maintain extensive self-renewal and produce several distinct terminal types through successive oligopotent progenitor intermediates regulated by master transcription factors GATA, PU.1, and Ikaros governing commitment.

Ref: Orkin & Zon, Cell 2008; Seita & Weissman 2010: Hematopoietic multipotency restricted to blood lineages.

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Stem Cell -l

Stem cell asymmetry refers to:

Asymmetry elegantly describes fundamental process generating cellular diversity from one parental stem cell during renewal. It refers specifically to division producing one daughter retaining mother stem identity with intact self-renewal machinery including telomerase and niche adhesion, and another losing stem markers entering differentiation program toward particular tissue type such as keratinocyte or erythrocyte. Intrinsic polarity Par complex and extrinsic niche gradients orchestrate determinant segregation. Processes producing only committed progenitors or multiple lineages simultaneously or loss without preservation do not capture balanced self-preservation coupled with differentiation output.

Ref: Knoblich, Nat Rev Mol Cell Biol 2010; Gilbert, Chapter 6: Asymmetry producing stem and differentiated daughters mechanism.

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Stem Cell -ll

What is the key feature that distinguishes stem cells from progenitor cells?

Stem cells are defined functionally by sustained ability to self-renew over extended time, frequently spanning whole organismal lifespan, contrasting sharply with transient amplifying progenitors that perform limited rounds of rapid division before terminal differentiation and exhaustion. Unlimited self-renewal is supported by high telomerase activity, avoidance of cellular senescence via Bmi1 polycomb repression of Ink4a locus, and asymmetric segregation of damaged proteins and old mitochondria. Multipotency alone does not guarantee stemness, as multipotent progenitors can exhaust quickly. Hence long-term repopulating capacity and serial transplantation remain functional gold standards distinguishing genuine stem cells from short-lived progenitors in experimental biology.

Ref: Shenghui et al., Birth Defects 2005; Gilbert, Chapter 6: Self-renewal unlimited distinguishes stem from progenitor.

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