Stem Cells and Differentiation

What does genome of fertilized egg determine

the ultimate structure of the clone of cells that will develop from it

What are tissues

organized mixtures of many cell types like the skin

What are totipotent cells

can become any cell in the body like a zygote including the extra-embryonic tissue like the placenta

What are pluripotent cells

Found in the inner cell mass of the blastocyst and can become any cell in the body except extra-embryonic tissues like placenta

What are multipotent cells

can develop into a limited range of cell types within a specific lineage

What are unipotent cells

can only differentiate into a single cell type but can still self-renew

What is differentiation

the process by which a cell becomes specialized for a particular function, like erythrocyte or red blood cell

What are stem cells

they are undifferentiated self-renewing cells that produce daughter cells that can either differentiate or retain the stem cell potential of the parental cell

What do stem cells give rise to

Proliferating precursor cells.

What does cell division before differentiation do

amplifies the number of differentiated cells that are produced

What are terminally differentiated cells

differentiated cells that are at the end of their developmental path

What is asymmetric cell division

a process that generates two daughter cells with different fates

What is symmetric cell division

a process that generates two daughter cells that are identical

What is intrinsic asymmetric cell division

the mother cell has an internal polarity causing it to divide unevenly and produce daughter cells that are already distinct at the time of division.

What is extrinsic asymmetric cell division

daughter cells are initially equivalent but develop different fates later due to signals from their environment or stochastically. The daughter cells interact with their surroundings or with each other to receive signals that induce different outcomes

What does intrinsic asymmetric cell division rely on

The asymmetric distribution of internal factors like proteins, organelles, and other molecules within the mother cell before division

Embryonic stem cells versus adult stem cells: potency levels

Embryonic: totipotent/pluripotent
Adult Stem: multipotent/unipotent

Embryonic stem cells versus adult stem cells: derived from what

Embryonic: inner cell mass of blastocyst
Adult Stem: rare population delivered from adult tissues

Embryonic stem cells versus adult stem cells: what do they differentiate into

Embryonic: cells of the three germ layers
Adult Stem: limited types terminally cells

Embryonic stem cells versus adult stem cells: used for what

Embryonic: development
Adult Stem: repair and maintenance

Do all types of tissues renew at the same rate

No, some tissues have constant turnover like the intestine or interfollicular epidermis, but other tissues like brain and skeletal muscle have low to no turnover

What do villi do

project into the intestinal lumen

What is the surface of each villus

a single-layered epithelium

What does epithelium include

goblet cells and brush-border cells

What do goblet cells do

secrete mucus

What do brush-border cells do

function in absorption

How are crypts formed

the epithelium extends into the underlying connective tissue

What is the crypt

a stem-cell niche which is a microenvironment required for continued stem cell renewal

What do stem cells give rise to in the lining of the small intestine

proliferating precursor cells

What happens to proliferating precursor cells in lining of small intestine

slide continuously upward and terminally differentiate into secretory or absorptive cells, which are shed from the tip of the villus

The speed at which the lining of small intestine renews

rapidly

What do stem cells in crypts do

divide to generate precursor cells which then divide and differentiate into specialized cells of the epithelium, which then travel upwards and are lost at top of the villus

What else do stem cells generate in addition to precursor cells

Paneth cells at the bottom of the crypts

Do paneth cells divide

no

What do paneth cells do

secrete antibacterial proteins and support stem cell renewal

What regulates intestinal crypt cells

Wnt signaling

Why must stem cells must be tightly regulated

to ensure that new cells are generated at the right place and at the right time

When is Wnt signaling active

in the intestinal stem cell niche (crypt)

When is Wnt signaling inactive

villi

Where is wnt ligand produced (Wnt3a)

Paneth cells

What does Wnt ligand promote

cell proliferation in the crypt

In the colon, what do mutations that inactive APC (adenomatous polyposis cell) initiate

initiate tumors by causing excessive activation of the Wnt signaling pathway.

What does dysregulated Wnt signaling do

disrupts intestinal morphology and function

What does increased Wnt signaling by APC removal in the crypt lead to

increased proliferation and expansion of the crypt compared to control animals

How is epidermis renewed

by stem cells in the basal layer

What is the epidermis

a stratified epithelium

Where do stem cells reside in adult mammalian skin

basal layer

Cell potency of epidermal stem cells

unipotent

What regulates epidermal stem cells

Wnt/b-catenin signaling

What stem cells generate all blood cell types

hematopoietic stem cells (HSCs)

Cell potency of HSCs

multipotent

Where do HSCs reside

in the bone marrow

What state are 80% of adult HSCs in and what can they do

quiescent state and can rapidly respond to a challenge

What are quiescent HScs

cells that have exited the cell cycle

What do adult HSCs undergo in response to acute inflammation

differentiation

What do stem cell niches in bone marrow provide

signals to reinforce quiescence of HSCs

What does Wnt signaling do to HScs niche

maintains it

Do stem cells function alone

No

What do bone marrow transplants depend on

HSCs

Types of transplants and what they mean

Autologous: donor and recipient are the same individual

Syngeneic: recipient receives cells from a twin

Allogeneic: recipient receives cells from a (nontwin) family member or other individual.

What happens in bone marrow transplant

patient’s stem cells are first destroyed by chemotherapy or radiation and then the grafted stem cells restore the functional bone marrow

cell potency of stem cells in brain

multipotent

What are neurons

cells in the brain that receive, integrate, and transmit signals

What is the process by which neurons are formed

neurogenesis

What are astrocytes

“star-like cells” with many functions, including removing excess signaling molecules, regulating synapse formation and maintenance

What are oligodendrocytes

Glial cells that produce myelin to insulate neuronal axons and help with neural signaling

What do microglia do

act as the first and main form of active immune defense in the central nervous system

Where do neural stem cells (NSCs) reside

in two regions of the adult brain: the subventricular zone (SVZ) and the dentate gyrus (part of the hippocampus)

What do NSCs in SVZ and dentate gyrus give rise to

neurons and other cell types in the brain

What do radial glia-like neural stem cells generate in NSC niche of SVZ

transit amplifying cells

What do C cells generate in NSC niche of SVZ

neuroblasts

What do neuroblasts do in NSC niche of SVZ

migrate down the rostral migratory stream to the olfactory bulb, where they differentiate into olfactory bulb neurons

What do astrocytes and microglia contribute to in NSC niche of SVZ

the cellular architecture of the niche

What do radial glia-like cells generate in the NSC niche of the dentate gyrus

intermediate progenitor cells (IPCs)

What do IPCs generate in the NSC niche of the dentate gyrus

neuroblasts

What do neuroblasts differentiate into in the NSC niche of the dentate gyrus

dentate granule cells

What do astrocytes, microglia, and interneurons contribute to in the NSC niche of the dentate gyrus

the cellular architecture of the niche

What molecular niche signals contribute to both adult NSC niches

morphogens (BMPs, SHH, Wnts, Notch), growth factors (EGF, IGF, EGF), and neurotransmitters (GABA, 5-HT, Ach, dopamine)

What are the three approaches to reprogramming in pluripotency

(1) somatic nuclear transfer or nuclear transfer, (2) cell fusion, (3) transcription-factor transduction

Whats somatic nuclear transfer or nuclear transfer

The nucleus of a somatic cell (which is diploid, 2n) is transplanted into an enucleated oocyte

Whats cell fusion

Two distinct cell types are combined to form a single entity.

Whats transcription-factor transduction and what does it form

Can be used to form induced pluripotent stem (iPS) cells, which have similar properties to ES cells and can be generated from almost any cell type in the body through the introduction of four genes (Oct4, Sox2, Klf4 and c-Myc) by using retroviruses

Example of somatic cell nuclear transfer in frogs

Destroy nucleus of unfertilized frog egg through UV light then inject the nucleus of adult frog skin cells into that egg. The frog will create normal embryo and turn into tadpole

What was the timeline in nuclear reprogramming (how quickly were Gurdon experiments replicated in mammals)

Took long time to before Gurdon experiments could be replicated

Who was the first mammal cloned and how did they do it

Dolly was cloned using transfer from a cell taken from a mammary gland. They fused the nucleus of a mammary gland cell with an enucleated egg cell and gave the egg cell an electrical shock, which triggered the start of cell division.

What is Dolly an example of

reproductive cloning

Was Dolly’s reproductive capacity affected

No, Bonnie was born through normal conception

Example of cell fusion

fusion between mouse ESC (mESC) and a somatic human B cell (hB)

What is heterokaryon and what is it caused by

it’s where two nuclei share a cytoplasm but don’t cycle. It’s caused by cell fusion

What was used for nuclear stain in cell fusion

5-hydroxymethylcytosine and DAPI

What does phalloidin do in cell fusion

delineates cytoplasmic membrane

How is mESC nucleus distinguished from human nucleus

by the presence of heterochromatic γ-satellite DNA at murine centromeric clusters