epithelia II B

Question 1

Epithelia undergo continuous development though:

Answer 1

Epithelial stem cells, cell division, and differentiation

Question 2

epithelia generally contain stem cells that are capable of cell division, and that serve to

Answer 2

1. self renew: regeneration of stem cells with each division

2. produce differentiated cell types specific to each epithelia.

Question 3

Like all stem cells, epithelial stem cells:

Answer 3

replace cells that die and can flexibly regulate (change) the form and function of tissues

Question 4

Stem cells produce

Answer 4

differentiated cell types by cell division coupled with specific pathways of cell specification imposed on some of their daughter cells.

Question 5

Many stem cells produce

Answer 5

daughters that also proliferate themselves (undergo cell division cycles), often at faster rates; these transitional intermediates are called transit amplifying cells.

Question 6

transit amplifying cells produce:

Answer 6

differentiated cells, either directly or through several steps of specification

At each step, specific changes in protein expression patterns and activities occur.

Question 7

______ determines the constellation of cell types, their relative proportions, and their arrangements.

Answer 7

The developmental state of stem cells

Question 8

A specific stem cell type, its intermediate progeny, and their differentiated progeny are collectively called a _____

Answer 8

cell lineage

Question 9

Both division and differentiation in stem cell lineages are tightly regulated by ______.

Answer 9

cell to cell communication and cell signaling pathways, which are activated or inhibited by physiological and developmental cues

Question 10

Because of tight regulation, stem cells typically divide _____

Answer 10

very slowly, or infrequently in some tissues.

they are usually much less abundant than their differentiated offspring.

Question 11

Loss of tight regulation of stem cells is at the

Answer 11

heart of the many diseases of stem cell systems.

Question 12

A typical cell signaling pathway consists of:

Answer 12

1. an extracellular ligand (signal) secreted by signaling cells,
2. a receptor in receiving cells that binds and is activated/inactivated by the ligand,
3. downstream effector proteins in the cytoplasm and nucleus,
4. numerous modulator proteins that promote or suppress pathway components.

Question 13

Cell signaling of epithelial stem cells may be local involving _____.

Answer 13

ligands secreted by cells within the same epithelia or by cells in neighboring connective tissue

Question 14

epithelial turn-over may be controlled by:

Answer 14

long-distance signaling between tissues.

Question 15

Long distance signals are typically secreted from

Answer 15

endocrine glands into the blood stream (described below), or may be produced by the nervous system or other tissues.

Question 16

Some of the most important signaling systems that control epithelial stem cell renewal and differentiation are:

Answer 16

1. Wnt
2. Sonic Hedgehog
3. TGFβ
4. Notch
5. receptor tyrosine kinase family
   (RTK; for example the EGF receptors)
6. FGF receptor

Question 17

Each pathway is used by _____.

Answer 17

multiple, very distinct stem cell systems in different organs/tissues

Question 18

Some pathway proteins may be ______

Answer 18

unique to certain stem cell subsets

Question 19

most pathway components are ____

Answer 19

shared by several distinct stem cell lineages

Question 20

stem cell lineages=

Answer 20

stem cells and all their daughters, granddaughters, etc

Question 21

A single signaling pathway often triggers _____.

Answer 21

different developmental outcomes in different stem cell lineages

Question 22

The pathway differences result from combinations of:

Answer 22

1. Different developmental histories of each stem cell type (cells can inherit and maintain unique differences in nuclear (chromatin) and cytoplasmic states that are generated earlier in development, which dramatically impact how a cell responds to a ligand)
2. Different environments stem cells reside in (or to put another way, the different combinations of signaling inputs a cell is exposed to).
3. Differences in the levels of the extracellular ligands, receptors, and/or downstream components.

Question 23

Defects in the______ lead to disease, particularly cancer. =

Answer 23

regulation, expression, or structure of signaling components (ligands, receptors, effectors)

Question 24

Drugs that specifically target several components of these pathways are now in use as _____
one example:

Answer 24

anti-tumor agents

Tarceva (erlotinib) inactivates the EGF receptor and is commonly used to treat lung and pancreatic cancers