Cell Interactions and Stem Cells• Recognize the importance of cell interactions, cell signaling and cell-cell

interactions, for coordination of functions in a multi-cellular organism. • Learn the three stages of cell signaling, the different types of first messengers

(external signals including hormones), internal messengers, and different cellular responses.

• Explain why different body cells respond in specific yet different ways to the same chemical signal.

• Review the steps of early embryonic development from the fertilized egg to a multi-cellular organism with differentiated cells.

• Distinguish between stem, progenitor, and differentiated cells in terms of ability to self renew (replicate) and gene expression.

• Define and explain the difference between totipotent, pluripotent, and multi-potent cells with examples.

• Learn the three general sources of stem cells, and how they differ.

Figure 2.3

Cell Communication

Make multi-cellular life possible through coordination of cellular activities

Two broad types of cell interaction1) Cell Signaling at a distance2) Cell-cell interactions close proximity

Defects cause certain inherited disorders

Cell signaling: allows cells to receive and respond to surrounding biochemical signals

The same basic cellular function is involved in:• Sensing pain • Inflammation & wound healing• Diabetes• Anxiety• Learning & memory• Psychoactive substances- caffeine, nicotine, marijuana, etc…

Figure 2.19

Cell Signaling

Reception

Signal Transduction

Response

Figure 2.3

Signal TransductionThe process of transmitting a signal from the

environment to a cell

- Receptor binds to “first messenger”- Interacts with regulator

- Causes an enzyme to produce “second messenger”

- Elicits cellular response, which is typically enzyme activation

Cell Signaling

Leads to • Specific response to a specific signal• Amplified responses due to cascade

http://www.learner.org/courses/biology/units/cancer/images.html

Cell signaling in apoptosis http://www.youtube.com/watch?v=hqhxnWty5jc&feature=relat

edStages of Apoptosis

• Destroy enzymes the replicate and repair DNA• Activate enzymes that cut DNA into similar sizes• Disassemble the cytoskeleton and the nuclear lamina,

condense DNA• Signal the mitochondria to increase caspase activity and

end the energy supply• Abolish the cell’s ability to adhere to other cells• Attract phagocytes to remove the cell remnants

The response of a particular cell to a signal depends on its particular collection of receptor proteins, and other

cellular proteins needed to carry out the response

Insulin Signaling

Figure 2.20

Cell-cell interactions: - Adhesion proteins

- Gap junctions

The inner life of the cellshttp://www.studiodaily.com/main/searchlist/6850.html

orhttp://www.dnatube.com/video/551/The-Inner-Life-Of-A-Cell-HQ

Stem CellsFrom a Fertilized egg (zygote) to a multi-cellular organism

Sperm cell

NucleicontainingDNA

Egg cell

Fertilized eggwith DNA fromboth parents

Embyro’s cells with copies of inherited DNA

Offspring with traitsinherited fromboth parents

Inner Cell Mass

Figure 2.3

Stem Cells

All cells in the human body descend from Embryonic stem cells via mitosis and differentiation

Cells differentiate down cell lineages by differential gene expression

Adult Stem cells are present throughout life and provide growth and repair

Figure 2.3

Stem Cells

A stem cell divides by mitosis- Produces daughter cells that retain the ability to divide and some that specialize

Progenitor cells do not have the capacity of self-renewal

Figure 2.20

Figure 2.3

Stem & Progenitor Cells

Described in terms of their developmental potential

Totipotent – Can give rise to every cell typeEmbryonic Stem (ES) Cells

Pluripotent – Have fewer possible fates

Multipotent – Have only a few fates Daughters of Pluripotent cells

Figure 2.3Figure 2.23

Pluripotentcells

Totipotent(Embryonic stem cells)

Multipotentcells

Differentiation produces a variety of cell types, each expressing a different combination of genes

Muscle cell Pancreas cells

Blood cells Nerve cell

Figure 2.3

Stem Cells in Health CareThere are 3 general sources of human stem cells

1) Embryonic stem cells – Created in a lab dish using the inner cell mass (ICM) of an embryo

2) Adult stem cells – Tissue-specific or somatic stem cells

3) Induced pluripotent stem (iPS) cells – Somatic cells reprogrammed by genes or chemicals to differentiate into any of several cell types

Under the right conditions, cultured stem cells derived from either source can differentiate into specialized cells.

Stem Cells uses

• Therapeutic- Tissues & OrgansOrgan engineering

https://www.ted.com/talks/anthony_atala_growing_organs_engineering_tissue?language=en

• Reproductive- Organism (Animal Cloning)

Induced Pluripotent Stem Cells (iPSC)

Figure 2.24

Stem Cells in Health Care

Figure 2.22

Organ engineeringhttps://www.ted.com/talks/anthony_atala_growing_organs_engineering_tissue?language=en

https://www.ted.com/talks/anthony_atala_printing_a_human_kidney?language=en

Cloning of a Mammal

In 1997 by Ian Wilmut

http://learn.genetics.utah.edu/units/cloning/whatiscloning/