Selective Gene Expression

• Once a cell becomes differentiated it only expresses the genes that produce the proteins characteristic for that type of cell.

• So which would be turned on ......

Pancreas cell Eye lens cell(in embryo)

Nerve cell

Glycolysis enzyme genes (for respiration for energy)

Crystallin gene (keep transparency &refractive index for lens clear)

Insulin gene (needed for regulationOf glucose in blood)

Haemoglobin gene (protein for oxygen transportation)

Extension – can you think of other genes that would be needed to be expressed or

other cells and gene?

Patterns of gene expression in specialized human cells

Pancreascell

Eye lens cell(in embryo)

Nerve cell

Glycolysisenzymegenes

Crystallingene

Insulingene

Hemoglobingene

Key:

Activegene

Inactivegene

What are stem cells?

Stem cells are unspecialised cells that have the ability to reproduce and differentiate into a diverse range of

specialised cells.

Learning Outcomes

• Identify the different types of stem cells • Understand the requirements for specialised

cells and examine different tissues • Define the term somatic cell• Explore the ethical, financial and progress

made in stem cell research

Stem cell jargon/definitionsPotency A measure of how many types of specialized cell a stem

cell can make

Stem cell Stem cell typetype DescriptionDescription ExamplesExamples

TotipotentTotipotent Each cell can develop into a Each cell can develop into a new individualnew individual

Cells from early (1-3 Cells from early (1-3 days) embryos days) embryos (zygote)(zygote)

PluripotentPluripotent Cells can form any (over Cells can form any (over 200) cell types200) cell types

Some cells of Some cells of blastocyst (5 to 14 blastocyst (5 to 14 days)days)

MultipotentMultipotentCells differentiated, but can Cells differentiated, but can form a number of other form a number of other tissuestissues

Fetal tissue, cord Fetal tissue, cord blood, and adult stem blood, and adult stem cellscells

UnipotentUnipotent ????????Spermatogonial cells Spermatogonial cells in testicles only make in testicles only make spermsperm

Stem cell jargon/definitionsPotency A measure of how many types of specialized cell a stem

cell can make

Stem cell Stem cell typetype DescriptionDescription ExamplesExamples

TotipotentTotipotent Each cell can develop into a Each cell can develop into a new individualnew individual

Cells from early (1-3 Cells from early (1-3 days) embryos days) embryos (zygote)(zygote)

PluripotentPluripotent Cells can form any (over Cells can form any (over 200) cell types200) cell types

Some cells of Some cells of blastocyst (5 to 14 blastocyst (5 to 14 days)days)

MultipotentMultipotentCells differentiated, but can Cells differentiated, but can form a number of other form a number of other tissuestissues

Fetal tissue, cord Fetal tissue, cord blood, and adult stem blood, and adult stem cellscells

UnipotentUnipotent Can only differentiate into 1 Can only differentiate into 1 type of specialized cell.type of specialized cell.

Spermatogonial cells Spermatogonial cells in testicles only make in testicles only make spermsperm

Where are stem cells found?

embryonic stem cellsblastocyst - a very early

embryo about 50-100 cells

tissue stem cellsfetus, baby and throughout life

zygote stem cellsTotipotent can diffrerentiate into all cells and

placenta/ umbilical cord etc.

What is a stem cell?

Identical stem cells

Stem cell

SELF-RENEWAL(copying)

Stem cell

Specialized cells

DIFFERENTIATION(specializing)

1 stem cell

Self renewal - maintains the stem cell pool

4 specialized cells

Differentiation - replaces dead or damagedcells throughout your life

Why self-renew AND differentiate?1 stem cell

stem cell

What is a stem cell?

stem cell

SELF-RENEWAL(copying)REPRODUCE

specialized celle.g. muscle cell, nerve cell

DIFFERENTIATION(specializing)

Repeated mitosis and cell division while remaining undifferentiated

Differentiation in somatic cells• All differentiated cells (except reproductive cells)

derived from stem cells are called somatic cells.

• Somatic cells form several different types of body tissues;

• Epithelial cells cover the body surface and line body cavities.

• Connective tissue includes blood, bone and cartilage cells,

• Muscle cells form muscle tissue • Nerve cells form nervous tissue.

Epithial into goblet cells, ciliated cells, skin cells – all cells lining including blood vessels.

Tissue stem cells:Mesenchymal stem cells (MSCs)

MSC

bone marrow

committed progenitors

Bone (osteoblasts)

Cartilage (chondrocytes)

Fat (adipocytes)

specialized cells

Tissue stem cells:Haematopoietic stem cells (HSCs)

HSC

committed progenitors

neutrophil

NK cell

erythrocytes

dendritic cell

plateletsmegakaryocyte

macrophage

eosinophil

basophil

B cell

T cell

specialized cells

bone marrow

Tissue stem cells:Neural stem cells (NSCs)

NSC

brain

committed progenitorsspecialized cells

Neurons

Interneurons

Oligodendrocytes

Type 2 Astrocytes

Type 1 Astrocytes

Tissue stem cells:Gut stem cells (GSCs)

GSC

Small intestine

committed progenitors

Paneth cells

Columnar cells

Goblet cells

Endocrine cells

specialized cells

Stem cell researchStem cell research provides us with a wealth of information and can be studied in a variety of ways, including:

•how cell processes such as growth, differentiation and gene regulation work•the study of diseases and their development•drug testing•therapeutic uses in the treatment of diseases such as leukaemia (bone marrow transplant), Hunter’s disease and heart disease•therapeutic uses in medicine, including skin grafts for burns and stem cell grafts for cornea repair.

Issues with stem cells

Therapeutic uses stem cells

Research of stem cells

Issues with stem cells

Therapeutic uses stem cells e.g. Repair damaged or

diseased tissue

Research of stem cells

Information on how cell processes work (e.g.cell growth, differentiation and gene regulation)

Model cells to study how diseases occur/ develop or for drug testing

Skin grafts for burns

Stem cell grafts for cornea repair

Bone marrow transplants Ethics of embryo – when does life start?

Expensive

Unknown potential risk

Reduces alternative research into cures/therapies