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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