Lecture 17 - the development of complexity

Question 1

How many cells & cell types are found in humans?

Answer 1

10-50 trillion cells & >200 cell types

Question 2

What is cell differentiation?

Answer 2

generation of different cell types - which occurs via mitosis.
- same DNA but changes in Gene expression and proteome

Question 3

What is pattern formation?

Answer 3

• the concept of positional information proposes that cells acquire positional values as in a coordinate system, which they interpret by developing in particular ways to give rise to spatial patterns

Question 4

Polarity is fundamental to development - what events define these polarities?

Answer 4

molecular events

Question 5

Why are stem cell described the front of everything?

Answer 5

an undifferentiated cell of a multicellular organism which is capable of giving rise to indefinitely more cells of the same type, and from which certain other kinds of cell arise by differentiation

Question 6

How do stem cells undergo self-renewal?

Answer 6

• self-renewal maintains stem cell population
• progenitor cell gives rise to differentiated cell
• asymmetric division: a mitotic cell division that gives rise to progeny with different fates

Question 7

Define totipotent

Answer 7

can form whole new organism
- mammals: can form embryo, extra embryonic membrane & placenta

Question 8

Define pluripotent

Answer 8

can form many cell types but not all
- mammals: can form embryo

Question 9

Define multipotent

Answer 9

• can form fewer but still many cell types

Question 10

How do you generate embryonic stem cells?

Answer 10

• from blastocyst
• inner cell mass (ICM cells)
• tissue culture conditions
• embryonic stem cells (ESCs)
• ESCs are not totipotent as cannot generate all cells of the embryo

Question 11

What are uses of embryonic stem cells?

Answer 11

• introduce genes
• knockout genes
• chromosomal rearrangements/deletions
• make specific genome edits

Question 12

How can you create a transgenic mice from embryonic stem cells?

Answer 12

embryo contained ICM from original embryo + introduced embryonic stem cells

Question 13

What are ethical issues for embryonic stem cells?

Answer 13

Significant research tool in rice
- same methodology in humans would require human blastocysts
- so would have to sacrifice human embryos
- BUT - have been approved for limited experimentation - including human-animal hybrids (must terminate early in development)

Question 14

What can happen to somatic nuclei?

Answer 14

can be reprogrammed to be totipotent

Question 15

How do you create induced pluripotent stem cells?

Answer 15

using transcription factors:
- Oct3/4, Sox2. Klf4, c-Myc

Question 16

Summarise the development of complexity

Answer 16

Development encompasses several processes that are interlinked:
- cell differentiation - how cells acquire different fates
- pattern formation - how cells, tissues and organs are positioned
- polarity - often established early & encodes information

Question 17

Summarise stem cells

Answer 17

• different types with different generational capacities
• embryonic stem cells are valuable tools for researchers
• embryonic stem cells enable regeneration of transgenic mice
• induced pluripotent stem cells are derived from somatic cells