iPSCS: Disease Modeling and Therapy

Totipotent

Can form all embryonic & extra-embryonic tissues (eg. zygote)

Pluripotent

Can form all 3 germ layers (endo-, meso-, ectoderm)

Multipotent

Can form multiple cell types within one tissue

Unipotent

Can form one specific cell type

Core Properties of Stem Cells

• Self-renewal

• Proliferation

• Differentiation into specialised cell types

In Vivo Differentiation Eg.

Embryoid Body (EB) formation

Embryoid Body formation function

Mimics early development

• Differentiation into endo-, meso-, and ectoderm

Applications of ES cells

• Study of developmental biology

• Gene targeting and transgenic mice

Cre-loxP system

Enables conditional and tissue-specific knockout

Somatic Cell Nuclear Transfer (SCNT) applications

• Reproductive cloning (sheep, cow, mouse, etc.)

• Therapeutic cloning (generation of patient-specific stem cells)

Somatic Cell Nuclear Transfer (SCNT) problems

• Incomplete nuclear reprogramming

• Abnormal DNA methylation/imprinting

• Large offspring syndrome

Somatic Cell Nuclear Transfer (SCNT) ethical concerns

Human cloning debates; embryo destruction in SCNT

Reprogramming Factors (Yamanaka Factors)

• Oct3/4, Sox2, Klf4, c-Myc

• Convert differentiated somatic cells (eg. fibroblasts) → pluripotent iPSCs

Applications of iPSCs

• Gene correction

• Disease modeling

• Cell therapy

Which types of disease is gene correction used for?

Monogenic diseases (eg. sickle cell anaemia)

Gene Correction sequence (steps)

1. iPSCs generated

2. Gene repaired (homologous recombination)

3. Differentiated

4. Transplanted

5. Restored function

When is disease modeling used?

Using iPSCs from patients to study mechanisms in vitro eg. Schizophrenia iPSCs

Cell Therapy Parkinson’s Model

1. Mouse iPSCS

2. Dopaminergic neurons

3. Transplanted into rats

4. Partial recovery of motor function

Direct Cell Conversion (Transdifferentiation)

Conversion of one mature cell type directly into another without passing through a pluripotent state

What are the factors used for Induced Neuronal Cells (iNs) (fibroblast → neuron)

• Ascl1

• Brn2

• Myt1l