1. Cell Differentiation and Specialization
How cells become tissues and organs
Interactions between external stimuli and regulated gene expression result in specialization of cells, tissues and organs

2. Overview Atoms  Molecules  Cells  Tissues  Organs
Cells becomes specialized (for one purpose).
This occurs through the differentiation of cells.
There are 220 types of cells in the human body.

3. What causes cell specialization?
Differentiation is triggered in 3 ways:
Internal cues from the cell its that turn genes on/off
Thereby changing proteins made / phenotype expressed
External cues from adjacent cells that turn genes on/off
Environmental cues / stimuli that turn genes on/off

4. In the beginning… All cells begin as stem cells (baby cells)
Not specialized yet
Can become any of the 220 types of human cells
Have the exact same DNA
After the fertilization of egg & sperm,
Becomes a zygote

5. Life continues… A zygote is totipotent
Has the ability to generate a whole organism
As the zygote becomes a blastula,
Becomes pluripotent
Can development any cell
But cannot become a whole organism
Then, differentiation happens
Becomes unipotent
Cannot become any other cell

6. Development Summary

7. What causes differentiation?
Internal cues
Based on cell’s location in the organism (or body)
Express only certain genes in the genome
Other genes will methylate (add CH3) – turn off
Cues are called transcription factors
Chemical that causes DNA  mRNA
Makes amino acids then proteins

8. What causes differentiation?
External cues (from adjacent cells)
Example: At 6 weeks, all embryos are female
At this time, the Y chromosome becomes activated
SRY gene turns on (sex-determining Y region)
In males, the gonads will start to produce male hormones
Act as a signal to be sent to all cells
Make male proteins
Controls gene regulation

9. What causes differentiation?
Environmental Stimuli
Examples: Heat Shock Factor
Cell sense a change in temperature
Changes physical properties of the cell to protest itself
Examples can occur with lack of oxygen too
Galapagos Tortoise Eggs
Incubation at a particular time in embryo development trigger protein production on the Y chromosomes
Temp can change gender

10. Using this technology today…
Therapeutic Cloning (tissues and organs for transplant)
Embryological sources of stem cells are controversial because of “when does life begin?” issues

11. However…good news
We can do this WITHOUT the use of embryonic stem cells!
iPS cells
Turns adult cells back into pluripotent stem cells
Use the same transcription factors to give cell signals

12. Videos to watch…
_organs_engineering_tissue.html
a_human_kidney.html
Bozeman Science – Cellular Specialization