Chapter 20 - Stem Cells

How do cells become different?

By differentiation and differential gene expression

Pathway of cells becoming terminally different

Totipotent → Pluripotent → Multipotent → Terminal Differentiation

What do gene expression and protein synthesis depend on?

Chromosome packing

What is chromosome packing dependent on?

Epigenetic modifications to histones and DNA

What modifications can DNA/Histones undergo to determine chromatin packing and gene expression?

1. DNA Methylation

2. Histone phosphorylation

   • Methylation

   • Acetylation

What do stem cells generate?

A continuous supply of terminally differentiated cells

What does asymmetrical division allow?

Two daughter cells to become different

What determines the rate at which tissues are renewed?

The lifespan of the terminal cell type

What functions do adult stem cells have?

• Pluripotency

• Undifferentiated cells

• Can renew themselves

• Can differentiate into specialized cells

• Can maintain and repair tissue

What cells are continuously renewed?

• Epidermal

• Blood cells

• Intestinal epithelia

What function do Wnt proteins have?

they are able to maintain a cells stem-cellness so that without Wnt present, the cells would differentiate

What is reproductive cloning?

Where an embryo is implanted into a surrogate mother and the embryo develops into a clone

What is therapeutic cloning?

When embryonic stem cells are used for tissue repair

Are embryonic stem cells totipotent?

No they are pluripotent

Why is reproductive cloning done?

To save good genes and allow for genetic modifications

What can embryonic stem cells be used for?

To repair damaged tissue

What part of embryonic stem cells allows for them to be used for tissue repair?

The cells in the inner cell mass blastocyst can become any body cell

What determines the rate of differentiation in embryonic stem cells?

Chemical signals like growth factors

What are the induced pluripotent stem cells factors?

Yamanaka factors - oct4, c-myc, sox2, Klf4

What do yamanaka factors do?

Cause de-differentiation of cells where they revert to a more primitive state

How is re-differentiation induced?

application of specific signaling molecules, altered microenvironments, or through reprogramming via induced pluripotent stem cells