Lecture 6 - Stem cells
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What are the 4 major model organisms for differentiation?
Yest
C.Elegans
Drosophila
Mouse models
Q: What is yeast used to study?
A: Cell cycle and cell fate genes.
Q: Why is C. elegans an important model organism for studying differentiation?
A: Every cell's lineage can be mapped, and its transparent body allows researchers to observe cell development.
Q: What is Drosophila used to study?
A: Body-plan genes (Hox genes).
Q: What are mice used to study?
A: Mammalian development and gene knockouts.
Q: What is differentiation?
A: Progressive restriction of developmental potential to form specialized cells.
Q: What is a stem cell?
A: An unspecialized cell that can self-renew and form several different cell types.
Q: What is a progenitor cell?
A: A partly differentiated intermediate cell that forms more specialized cells.
Q: What is terminal differentiation?
A: An irreversible process in which cells become highly specialized and usually stop dividing.
Q: What two types of factors drive cell differentiation?
A: Cell-intrinsic and cell-extrinsic factors.
Q: What are the two major categories of cells mentioned in the lecture?
A: Germ cells and somatic cells.
Q: What is symmetric cell division?
A: Division that produces two daughter cells identical to the parent, which may differentiate later in response to different cues.
Q: What is asymmetric cell division?
A: Division that produces two daughter cells with different contents and gene expression.
Q: What happens to the daughter cells during asymmetric stem cell division?
A: One self-renews (remains a stem cell), while the other specializes.
Q: What are the three possible outcomes of stem cell division?
A: Maintain the stem cell population, expand the stem cell population, or increase differentiating cells.
Q: What is cell lineage?
A: The tracking of each cell's fate as its developmental potential narrows at each step.
Q: How does asymmetric division help maintain the stem cell population?
A: One daughter cell remains a stem cell while the other differentiates.
Q: What are totipotent stem cells?
A: Cells that can develop into a whole organism, including the embryo and placenta.
Zygote and early blastomeres are examples of?
Totipotent cells
Q: What are pluripotent stem cells?
A: Cells that can develop into any body cell type from all three germ layers.
Embryonic stem (ES) cells and induced pluripotent stem cells (iPSCs) are examples of?
pluripotent stem cells
Q: What are multipotent stem cells?
A: Cells that can develop into several related cell types.
Q: What are unipotent stem cells?
A: Cells that can self-renew but produce only one cell type.
Q: What happens to stem cell potency as cells specialize?
A: Potency progressively narrows as cells become more specialized.
Q: What type of potency do many adult stem cells have?
Multipotency
Q: What are the three germ layers formed during embryonic development?
A: Ectoderm, mesoderm, and endoderm.
Q: What does the ectoderm develop into?
A: Nervous system, retina and lens, epidermis, hair, pigment cells, and mammary glands.
Q: What does the mesoderm develop into?
A: Muscle, bone, heart, blood, kidney, connective tissue, dermis, and spleen.
Q: What does the endoderm develop into?
A: Gut lining, liver, lungs, pancreas, stomach, colon, urinary bladder, and epithelial parts of the trachea.
Q: Which germ layer gives rise to the nervous system, skin epidermis, and eye lens?
Ectoderm
Q: Which germ layer gives rise to muscle, bone, heart, blood, and kidneys?
Mesoderm
Q: Which germ layer gives rise to the gut lining, liver, lungs, and pancreas?
Endoderm
Q: What happens during progressive restriction in embryonic development?
A: Cells become increasingly specialized as their developmental potential narrows.
Q: What three germ layers form as the embryo develops beyond the early cleavage stages?
A: Ectoderm, mesoderm, and endoderm.
Q: What happens to each germ layer as development progresses?
A: Each layer divides into subpopulations that develop into specialized cells and tissues.
Q: When are germ-line cells set aside during embryonic development?
A: Early in development.
Q: What is the developmental progression from zygote to germ layers?
A: Zygote → Blastocyst → Gastrula → Ectoderm, mesoderm, and endoderm.
Q: Why is C. elegans an important model organism for studying cell differentiation?
A: It is transparent, allowing researchers to observe every cell division and map each cell's lineage.
Q: What makes it possible to track every cell division in C. elegans?
A: Its transparent body allows researchers to directly observe cell divisions.
Q: What is unique about the cell lineage of C. elegans?
A: Every cell's lineage has been mapped, creating a complete cell family tree.
Q: What can influence cell fate during C. elegans development?
A: External signals can change cell fate.
Q: What does a complete cell lineage allow researchers to track?
A: The developmental history of each cell, including its divisions and eventual fate.
Q: What stage of embryonic development is used to obtain embryonic stem (ES) cells?
A: The blastocyst stage.
Q: From which part of the blastocyst are embryonic stem cells isolated?
A: The inner cell mass.
Q: What are isolated inner cell mass cells grown on?
A: A feeder layer of fibroblast cells.
Q: What happens after the inner cell mass is grown on a feeder layer?
A: The cells are dissociated into single cells to form ES cell colonies.
Q: What can be done with established embryonic stem cell lines?
A: They can be maintained, cryopreserved, differentiated in vitro, or injected into embryos in vivo.
Q: What is the pathway for establishing embryonic stem (ES) cell cultures?
A: Cleavage-stage embryo → Blastocyst → Isolate inner cell mass → Grow on fibroblast feeder layer → Dissociate into single cells → Form ES cell colonies → Maintain or cryopreserve cell lines → Differentiate in vitro or inject into embryos in vivo.
Q: What happens when embryonic stem (ES) cells are grown in suspension culture?
A: They form embryoid bodies.
Q: What happens when embryonic stem cells are grown on a surface?
A: They can differentiate into many different cell types.
Q: What is an embryoid body?
A: A cluster of embryonic stem cells formed in suspension culture.
Q: What are the five regulators that determine cell fate?
A: Signaling proteins, transcription factors, DNA methylation, chromatin regulators (histone acetylation), and miRNAs.
Q: What three germ layers can embryonic stem cells differentiate into?
A: Ectoderm, mesoderm, and endoderm.
Q: What cell types can embryonic stem cells form through the mesoderm?
A: Cardiac muscle, skeletal muscle, kidney tubule cells, red blood cells, and smooth muscle cells.
Q: What cell types can embryonic stem cells form through the endoderm?
A: Lung cells, thyroid cells, and pancreatic cells.
Q: What cell types can embryonic stem cells form through the ectoderm?
A: Epidermal skin cells, neurons, and pigment cells.
Q: What are synthetic embryos (sEmbryos)?
A: Embryo-like structures that self-assemble from stem cells.
Q: What type of stem cells were used to create synthetic mouse embryos in the Tarazi et al. (2022) study?
A: Naive mouse embryonic stem (ES) cells.
Q: What did Tarazi et al. (2022) demonstrate about naive mouse ES cells?
A: They can self-assemble into embryo-like structures outside the uterus.
Q: What type of culture system was used to grow synthetic embryos outside the uterus?
A: An electronically controlled ex utero culture device.
Q: What are the two levels of gene control?
A: Transcriptional control and post-transcriptional control.
Q: What is transcriptional control?
A: Regulation of gene expression at the level of transcription.
Q: What factors regulate transcriptional control?
A: Transcription factors, chromatin state, co-factors, and alternative promoters.
Q: What factors regulate transcriptional control?
A: Transcription factors, chromatin state (DNA methylation, histone acetylation), co-factors, and alternative promoters.
Q: What chromatin modifications regulate transcriptional control?
A: DNA methylation and histone acetylation.
Q: What is post-transcriptional control?
A: Regulation of gene expression after mRNA has been transcribed.
Q: What mechanisms regulate post-transcriptional control?
A: MicroRNAs, alternative splicing, alternative polyadenylation, and RNA-binding proteins.
Q: What type of RNA can regulate gene expression through RNA interference?
A: MicroRNAs (miRNAs).
Q: What is the role of non-coding RNAs in gene control?
A: They help regulate gene expression at the post-transcriptional level.
Q: What four signaling pathways are important in regulating stem cell niches?
A: TGF-β, BMP, Notch, and Wnt.
What do the 4 signaling pathways (TGF-β, BMP, Notch, and Wnt) help control
They help control whether stem cells:
Self-renew — remain stem cells.
Differentiate — become specialized cells.
Proliferate — divide to produce more cells.
Q: What is the role of signaling pathways in stem cell niches?
A: They help regulate stem cell self-renewal, differentiation, and proliferation.
Q: What is the difference between signaling proteins and transcription factors?
A: Signaling proteins bind cell-surface receptors to initiate signals, while transcription factors bind DNA to turn genes on or off.
Q: What is epigenetics?
A: Regulation of gene expression without changing the DNA sequence.
Q: Does epigenetic regulation change the DNA sequence?
A: No. It changes gene expression without altering the DNA sequence.
Q: What are the three epigenetic mechanisms discussed in the slide?
A: DNA methylation, histone acetylation, and microRNAs (miRNAs).
Q: What is the effect of DNA methylation on gene expression?
A: Methylation of cytosines in promoter CpG islands silences gene expression.
Q: What enzyme adds methyl groups to DNA?
A: DNA methyltransferase (DNMT).
Q: What is the effect of histone acetylation on chromatin?
A: It opens chromatin, promoting transcription.
Q: What enzymes add acetyl groups to histones?
A: Histone acetyltransferases (HATs).
Q: What enzymes remove acetyl groups from histones?
A: Histone deacetylases (HDACs).
Q: What is the effect of histone deacetylation on gene expression?
A: It promotes chromatin condensation and decreases transcription.
Q: What is the role of microRNAs (miRNAs) in gene regulation?
A: They block translation of specific mRNAs and can promote mRNA degradation.
Q: What happens when histone methylation and DNA methylation contribute to gene silencing?
A: The gene can become stably silenced.
Q: What are the two major uses of embryonic stem (ES) cells?
A: Therapy and research.
Q: How are embryonic stem (ES) cells used in therapy?
A: To replace damaged cells in various diseases.
Q: How are embryonic stem (ES) cells used in research?
A: To create mutant mice and study the effects of specific gene knockouts.
Q: What can pluripotent embryonic stem cells develop into for therapeutic use?
A: Specialized cells such as heart muscle cells, neurons, blood cells, liver cells, pancreatic islet cells, and intestinal cells.
A: Specialized cells such as heart muscle cells, neurons, blood cells, liver cells, pancreatic islet cells, and intestinal cells.
A: Very little.
Q: Where are adult stem cells found?
A: In many different tissues throughout the body.
Q: What is a stem cell niche?
A: A specialized environment containing intrinsic and extrinsic signals that regulate stem cells.
Q: What is the normal state of adult stem cells until they are stimulated?
A: Quiescent (inactive).
Q: What causes quiescent adult stem cells to become active?
A: Stimulation by signals within their niche.
Q: What do germ-line stem cells produce?
A: Eggs and sperm.
Q: What type of stem cell is responsible for producing different blood cell types?
A: Hematopoietic stem cells.
Q: Where are hematopoietic stem cells found?
A: Bone marrow.
_____________: adult somatic cells treated with a cocktail of transcription (and growth) factors become pluripotent again.
Induced pluripotent stem cells
_______ stem cells have many fates and are very plastic
bone marrow
Q: Where are epithelial stem cells located in the hair follicle?
A: In the hair follicle bulge.
Q: What type of division occurs in hair follicle bulge stem cells?
A: Asymmetric division.