Stem Cells and Tissues Quiz

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Questions and Answers

Which type of cells are responsible for producing insulin in the pancreas?

Hepatocytes

Paneth cells

Pancreatic Beta cells (correct)

Germ cells

What role do Paneth cells play in the stem-cell niche?

They secrete Wnt proteins. (correct)

They maintain Lgr5-expressing cells. (correct)

They differentiate into retinal cells.

They initiate meiosis.

Which process is essential for maintaining stem-cell identity in the C.elegans gonad?

Apoptosis signaling

Growth factor stimulation

Wnt signaling

Notch signaling (correct)

How does the microenvironment affect stem cells?

It supplies necessary signal molecules for self-renewal. Signup and view all the answers

What occurs when a stem cell in the C.elegans gonad moves out of reach of the distal tip cell processes?

It initiates meiosis and begins differentiation. Signup and view all the answers

What is a primary characteristic of tissues lacking stem cells?

They are incapable of regeneration. Signup and view all the answers

How do stem cells choose between self-renewal and differentiation?

Based on environmental signals and niches. Signup and view all the answers

Which signaling pathway is cell contact dependent for maintaining stem-cell identity?

Notch signaling pathway Signup and view all the answers

What happens to the label of a stem cell after a recombination event occurs?

The label persists over time. Signup and view all the answers

What type of cells do Lgr5-expressing stem cells give rise to?

All types of differentiated cells and persistent Lgr5-expressing cells. Signup and view all the answers

What role do satellite cells play in skeletal muscle?

They are quiescent but can proliferate and fuse with existing muscle cells. Signup and view all the answers

Why is a blood stem cell considered multipotent?

It can reconstitute the entire hematopoietic system. Signup and view all the answers

Which statement is true regarding tissues that do not require stem cells for maintenance?

They can renew and regenerate through fully differentiated cells. Signup and view all the answers

What is a key characteristic of satellite cells?

They serve as a self-renewing source for myoblasts. Signup and view all the answers

What distinguishes Lgr5-expressing cells in the small intestine?

They are multipotent, giving rise to differentiated cell types. Signup and view all the answers

What is the fate of a clonal lineage marked in a stem cell after a recombination event?

It will persist as long as the stem cell self-renews. Signup and view all the answers

What process helps maintain tissue homeostasis in self-renewing adult tissues?

Constant flow of new cells through cell division Signup and view all the answers

How do stem cells contribute to the tissue structure?

They can either self-renew or differentiate, maintaining the stem cell pool. Signup and view all the answers

What defines a multipotent stem cell?

It can produce a limited number of differentiated cell types. Signup and view all the answers

Which cell type is most abundant in the epithelial lining of the small intestine?

Absorptive (brush-border) cells Signup and view all the answers

What is the role of progenitor cells in tissue regeneration?

They undergo many divisions before differentiating. Signup and view all the answers

What feature distinguishes the epidermal cells at the skin surface?

They are all dead cells. Signup and view all the answers

What is the main function of microvilli on the apical surface?

They increase surface area for nutrient absorption and enzyme anchorage. Signup and view all the answers

What type of receptor is expressed by stem cells in the gut epithelial lining?

Lgr5 G-protein coupled receptor Signup and view all the answers

Which cells are responsible for secreting cryptdins that kill bacteria?

Paneth cells Signup and view all the answers

What role do enteroendocrine cells play in the gut?

They secrete hormones that regulate various gut activities. Signup and view all the answers

What happens to cells as they move from the basal layer of the epidermis to the surface?

They differentiate and eventually die. Signup and view all the answers

What is the purpose of cell lineage tracing in stem cell identification?

To create a visible genetic mark in cells. Signup and view all the answers

What activates Cre recombinase in the technique for identifying stem cells?

Tamoxifen administration. Signup and view all the answers

What happens to dividing progenitor cells in cell lineage tracing?

They will eventually disappear. Signup and view all the answers

How do stem cells in adult tissues typically manifest in conventional sections?

They are rare and challenging to identify without specific markers. Signup and view all the answers

The apical surface of epithelial cells is primarily involved in which of the following?

Increasing nutrient absorption surface area. Signup and view all the answers

What initiates meiosis and the differentiation program in certain cells?

Movement out of reach of distal tip cell processes Signup and view all the answers

In asymmetric stem-cell division, what is localized to one side of the cell before division?

Stem-cell fate determinants Signup and view all the answers

Which outcome is associated with a daughter cell losing contact with the niche in stem-cell division?

It commits to differentiation Signup and view all the answers

What does the independent-choice mechanism indicate about stem-cell fate decisions?

They can be influenced by local environmental factors Signup and view all the answers

What is the probability that both daughters will differentiate if the choice is made randomly at the first division?

25% Signup and view all the answers

What can influence the decision of a stem cell daughter to remain a stem cell or differentiate?

Changing environmental conditions Signup and view all the answers

In symmetric stem-cell division, what happens to both daughter cells?

Both cells remain stem cells Signup and view all the answers

What might happen to a stem cell clone if both daughters choose to differentiate at the first division?

The clone will eventually disappear Signup and view all the answers

Study Notes

BIOS 367 Cell Biology, Fall 2024, Chapter 22 Part 1

Stem Cells in Tissue Homeostasis and Regeneration: Tissue homeostasis is like a river, with new cells flowing in and differentiated cells flowing out, maintaining dynamic equilibrium.
Tissue Homeostasis: A constant flow of new cells, generated by cell division, and a constant loss of differentiated cells, due to normal turnover or injury, create a dynamic equilibrium.
Epidermis Example: The epidermis, a type of epithelial tissue, demonstrates this. Dead cells are sloughed off, while new epidermal cells mature and push up from underneath. Mitosis is frequent in the lower layers, generating new skin cells.
Stem Cell Defining Characteristics: Stem cells can either remain a stem cell, during self-renewal, or commit to differentiation after multiple divisions. Stem cell self-renewal maintains the stem cell pool within a tissue.
Stem Cell Hierarchy: Stem cells, progenitor cells, and differentiated cells are arranged in a hierarchy. Tissue-specific stem cells produce progenitor cells that divide a limited number of times before differentiating. Different cells can be unipotent (produce only one type) or multipotent (produce multiple types).
Gut Epithelial Lining Renewal: Stem cells in the gut epithelial lining exhibit a 3 - 5 day transit time from the crypt to the villus. Specific G-protein coupled receptor Lgr5 is expressed in these stem cells. Rapidly dividing cells have a 12-hour cycle time. Nondividing differentiated cells make up the villus.
Four Main Differentiated Cell Types in Small Intestine: Absorptive, goblet, Paneth, and enteroendocrine cells.
Absorptive Cells: High number, microvilli provide a significant surface area to import nutrients and aid in the final stages of extracellular digestion.
Goblet Cells: Secrete mucus, which covers the epithelium and provides protective coating.
Paneth Cells: Secrete cryptdins (defensins) to kill bacteria and some growth factors.
Enteroendocrine Cells: Numerous subtypes, secrete serotonin and peptide hormones, affect gut wall neurons and regulate growth/proliferation/digestive activities.

Identifying Stem Cells

Methodologies for Identifying Stem Cells: Stem cells are usually rare in adult tissues and challenging to identify in conventional tissue sections unless a specific marker is available. Recombinant DNA technology provides a powerful tool using cell lineage tracing.
Cell Lineage Tracing: This technique uses transgenic animals to mark specific cells, and tracks their progeny, leading to a clonal lineage that includes stem cells and differentiated cells.

Recombination Methods

CreERT2 System: Cre recombinase is inactive unless activated by tamoxifen. Adding tamoxifen activates the recombinase. In some cells, it removes a blocking sequence, leading to GFP expression.
Stem Cell Label Example: If recombination happens within a stem cell, the labeling will remain consistent with time; if within another cell type, the label will vanish as the cell differentiates.

Muscle Repair

Skeletal Muscle Repair: Skeletal muscle cells are long, multinucleated. Quiescent satellite cells proliferate and fuse with existing muscle cells when damaged or stimulated to grow. Satellite cells are a self-renewing source of terminally differentiated myoblasts.

Blood Cells

Blood Cell Functions and Concentrations: Blood cell types, such as erythrocytes (red blood cells), leukocytes (white blood cells), monocytes, granulocytes (neutrophils, basophils, eosinophils), lymphocytes (B cells, T cells, and NK cells), and platelets, are presented with their concentrations and main functions in the human blood.

Bone Marrow Rescue

Bone Marrow Transfusion: Injecting stem cells from a healthy donor into an irradiated mouse can rescue the mouse's blood cell production. A single blood stem cell can reconstitute the entire mouse hematopoietic system, producing differentiated blood cell types.

Hematopoiesis

Hematopoiesis Scheme: A simplified scheme of mouse/human blood cell development (hematopoiesis). Stem cells, multipotent progenitors, and committed progenitors are shown with their differentiation pathways into mature blood cells.

Stem Cell-Free Tissues/Examples

Tissues that Do Not Require Stem Cells: Some tissues, like pancreatic beta cells and hepatocytes, can regenerate without stem cell involvement due to division abilities of fully differentiated cells.
Tissues Lacking Stem Cells: Examples of tissues without active stem cell populations and incapable of regeneration, such as auditory epithelium and retinal photoreceptors

Stem Cell Identity

Signalling Molecules (Niches). Stem cells maintain identity within specialized microenvironments (niches). Signaling molecules from supporting cells or extracellular matrices concentrate within the niche. Niche-supporting environments can be small, and some cells within a short distance from a niche can still engage in self-renewal.

Cultivation of Lgr5 Expressing Cells: A single Lgr5 expressing cell within a cell-free matrix produces a minigut over time. Differentiated Paneth cells will emerge from certain cells; these secrete Wnt proteins that maintain Lgr5 stem-cell expression in neighboring cells.

Stem Cell Niche: C. elegans Gonad

Distal Tip Cells in C. elegans Gonad: The distal tip cell in the C. elegans gonad plays a key role in the stem-cell niche. Distal tips of the cell extend across multiple stem-cell diameters to maintain stem-cell identity through Notch signaling, which is cell-contact dependent. Cells detach from the distal tip and go through meiosis, producing eggs or sperm.

Asymmetric/Symmetric Divisions

Asymmetric vs. Symmetric Divisions: Asymmetric stem-cell divisions result from a cell-fate determinant that is localized to one side of the cell. Only one daughter cell inherits this determinant and remains a stem cell; the other undergoes differentiation. Symmetric stem-cell divisions result in both daughter cells inheriting determinants and remaining as stem cells. These two division models are visually depicted.
Plane of Division in Drosophila Testis: The plane of division of germ-line stem cells in the Drosophila testis is a critical determinant for which daughter cell maintains contact with the niche. The daughter cell oriented so to remain in contact with the somatic niche retains the self-renewal capacity, while the other doesn't.

Independent Choices for Stem-Cell Daughters

Environmental Influence: Daughter cells' choice of self-renewal or differentiation might depend on the local environment a daughter cell is exposed to.
Stochastic Outcomes: In some cases, the choice is made randomly (stochastically), with potential outcomes including whether a daughter cell commits to differentiation or remains as a stem cell. Factors such as environmental conditions may influence this randomness.

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Test your knowledge on stem cells, their functions, and their role in various tissues. Explore questions about the classifications of stem cells, the significance of microenvironments, and the implications of stem cell behavior in organisms like C. elegans. This quiz is designed for those interested in cell biology and regenerative medicine.