Hematopoietic Stem Cells, Di erentiation and
Development
Lecture 1
Granulocytes have short lifespan; approx half a day
Mature blood cells are regenerated from progenitors that
stem from hematopoietic stem cells
LT-HSC can regenerate a whole new blood system once transplanted
What are the determinants of asymmetry as induced by cell division? (One di erentiates
and one does self-renewal)
- gene expression -> expression of stemness-related genes in the self-renewal one
- DNA -> imortal strand hypothesis = the original strand will stay in the self-renewal cells;
and the new copies (with possible mutations) will go into the di erentiating cell
- Proteins and metabolites
The physical position of cells in the niche can already be enough to
de ne asymmetry/symmetry
Orientation of centrosomes is dictated by age -> old cells: often more
misorientation; e.g. due to loss of adhesion proteins for the centrosomes
Embryonic stem cells: pluripotent (totipotent
actually); only exist during the formation of the
blastocyst; can form all di erent lineages
Adult stem cells: multipotent stem cells; can
only form cells within its own lineage
Mesenchymal stem cells form the niches for the stem cells: bone tissue, fat tissue, etc
Generate / obtain embryonic stem cells
1. Embryonic stem cells derived from embryos (blastocysts): ethical
issues, and tissue does not match = not patient speci c
2. Embryonic stem cells derived from nuclear transfer: get genetically
identical clone to the donor of the nucleus
3. Embryonic stem cells derived from induced pluripotency (iPS):
reprogram cells (you can use your own cells and is not unethical)
ES / iPS are useful for
- Cell and tissue replacement therapies: generate HSCs from ES or iPS
- Vehicle for gene therapy; therapeutic cloning
- Cell-based models of human disease
- Drug discovery and toxicology tests
fi ff ff fi ff ff
,You can push di erentiation of ES into HSC by injecting
them with HSC transcription factors; e.g. HOXB4
Requirements for hematopoiesis
- Hematopoietic stem cells
- Growth factors
- Microenvironment
Why do stem cells need a niche?
- oxygen presence is an important determinant how cells
generate their energy -> low O2 in bone marrow; stem cells
often use glycolysis
- If O2 is low, there is low ROS
- If O2 is low, there is a lot of HIF transcription factors -> that
drive glycolysis
- Stem cells in the niche are quite quiescence; only divide
once a month or so; could be because it is risky to divide
- There is also a lot of telomerase enzyme present because
stem cells need to bypass senescence as induced by
telomere shortening
Molecules that can be found in the stem cell niche
1.Could be involved in correct positioning
of the centrosome as well
2. Involved in correct gene expression of
whatever is needed; cell type-speci c
Erythrocytes
- nuclei shrink and are pushed out eventually
- Look like disks
- Life aprox 120 days
- Are loaded with hemoglobin: the iron-containing oxygen-transport metalloprotein in the red
blood cells
- ^ hemoglobin = polycythemia; low hemoglobin = anemia
Sickle cell anemia: somatic mutations in hemoglobin
ff fi
, Di erent hemoglobins are expressed throughout development = globin
switches
- Locus Control Region (LCR) interacts via long-range chromatin
interactions
- During fetal stage it interacts with alpha-gamma globulin genes
- Throughout development, more BCL11 is expressed -> LCR will now interact with
beta globulin genes
Megkaryocytes: platelets (thrombocytes)
-have multiple nuclei = endomitosis
-Eventually the cells explode and release platelets
-Platelets help in blood clotting
White blood cells: leukocytes (innate & adaptive)
- ght infection
- Innate: neutrophil, eosinophil, basophil, monocytes/macrophages
- Adaptive: B cells, T cells
Innate
Neutrophil
- Primary defense against infection, phagocytes microorganisms
- Segmented nuclei: 3-5 lobes
- Cytoplasm with ne granules
Eosinophils
- Against allergic and parasitic infection; rst in action
- Two lobes connected by slender thread of chromatin
- Loaded with granules
Basophils
- Also against parasitic
- Large granules; very purple
- Granules obscure the nucleus
Monocytes/macrophages
- Phagocytosis
- Mononuclear leukocyte
- Kidney shaped nucleus
Phagocytosis
fi ff fi fi
, Adaptive
Lymphocyte
- Mononuclear leukocyte
- Minimal cytoplasm
B cells
VDJ is important in immunoglobulin splicing
1. For B cell development, transcription factor
Pax-5 is most important -> opens up the
chromatin
2. After which the endonucleases com in -> make double strand breaks and splice
3. Make new combination of DJ parts
T cells
- Produced in bone marrow & mature in thymus
Development
Lecture 1
Granulocytes have short lifespan; approx half a day
Mature blood cells are regenerated from progenitors that
stem from hematopoietic stem cells
LT-HSC can regenerate a whole new blood system once transplanted
What are the determinants of asymmetry as induced by cell division? (One di erentiates
and one does self-renewal)
- gene expression -> expression of stemness-related genes in the self-renewal one
- DNA -> imortal strand hypothesis = the original strand will stay in the self-renewal cells;
and the new copies (with possible mutations) will go into the di erentiating cell
- Proteins and metabolites
The physical position of cells in the niche can already be enough to
de ne asymmetry/symmetry
Orientation of centrosomes is dictated by age -> old cells: often more
misorientation; e.g. due to loss of adhesion proteins for the centrosomes
Embryonic stem cells: pluripotent (totipotent
actually); only exist during the formation of the
blastocyst; can form all di erent lineages
Adult stem cells: multipotent stem cells; can
only form cells within its own lineage
Mesenchymal stem cells form the niches for the stem cells: bone tissue, fat tissue, etc
Generate / obtain embryonic stem cells
1. Embryonic stem cells derived from embryos (blastocysts): ethical
issues, and tissue does not match = not patient speci c
2. Embryonic stem cells derived from nuclear transfer: get genetically
identical clone to the donor of the nucleus
3. Embryonic stem cells derived from induced pluripotency (iPS):
reprogram cells (you can use your own cells and is not unethical)
ES / iPS are useful for
- Cell and tissue replacement therapies: generate HSCs from ES or iPS
- Vehicle for gene therapy; therapeutic cloning
- Cell-based models of human disease
- Drug discovery and toxicology tests
fi ff ff fi ff ff
,You can push di erentiation of ES into HSC by injecting
them with HSC transcription factors; e.g. HOXB4
Requirements for hematopoiesis
- Hematopoietic stem cells
- Growth factors
- Microenvironment
Why do stem cells need a niche?
- oxygen presence is an important determinant how cells
generate their energy -> low O2 in bone marrow; stem cells
often use glycolysis
- If O2 is low, there is low ROS
- If O2 is low, there is a lot of HIF transcription factors -> that
drive glycolysis
- Stem cells in the niche are quite quiescence; only divide
once a month or so; could be because it is risky to divide
- There is also a lot of telomerase enzyme present because
stem cells need to bypass senescence as induced by
telomere shortening
Molecules that can be found in the stem cell niche
1.Could be involved in correct positioning
of the centrosome as well
2. Involved in correct gene expression of
whatever is needed; cell type-speci c
Erythrocytes
- nuclei shrink and are pushed out eventually
- Look like disks
- Life aprox 120 days
- Are loaded with hemoglobin: the iron-containing oxygen-transport metalloprotein in the red
blood cells
- ^ hemoglobin = polycythemia; low hemoglobin = anemia
Sickle cell anemia: somatic mutations in hemoglobin
ff fi
, Di erent hemoglobins are expressed throughout development = globin
switches
- Locus Control Region (LCR) interacts via long-range chromatin
interactions
- During fetal stage it interacts with alpha-gamma globulin genes
- Throughout development, more BCL11 is expressed -> LCR will now interact with
beta globulin genes
Megkaryocytes: platelets (thrombocytes)
-have multiple nuclei = endomitosis
-Eventually the cells explode and release platelets
-Platelets help in blood clotting
White blood cells: leukocytes (innate & adaptive)
- ght infection
- Innate: neutrophil, eosinophil, basophil, monocytes/macrophages
- Adaptive: B cells, T cells
Innate
Neutrophil
- Primary defense against infection, phagocytes microorganisms
- Segmented nuclei: 3-5 lobes
- Cytoplasm with ne granules
Eosinophils
- Against allergic and parasitic infection; rst in action
- Two lobes connected by slender thread of chromatin
- Loaded with granules
Basophils
- Also against parasitic
- Large granules; very purple
- Granules obscure the nucleus
Monocytes/macrophages
- Phagocytosis
- Mononuclear leukocyte
- Kidney shaped nucleus
Phagocytosis
fi ff fi fi
, Adaptive
Lymphocyte
- Mononuclear leukocyte
- Minimal cytoplasm
B cells
VDJ is important in immunoglobulin splicing
1. For B cell development, transcription factor
Pax-5 is most important -> opens up the
chromatin
2. After which the endonucleases com in -> make double strand breaks and splice
3. Make new combination of DJ parts
T cells
- Produced in bone marrow & mature in thymus
