CSB329H1 Study Guide - Summer 2018, Comprehensive Midterm Notes - Stem Cell, Cell Potency, Gene
12 Oct 2018
School
Department
Course
Professor
CSB329H1
MIDTERM EXAM
STUDY GUIDE
Fall 2018
Lecture 1(a): Introduction to Stem Cells
Cell Potency:
• Potency is the number of possible fates available to a cell
o “Potent” = having the power to achieve a certain fate
§ Few cells (i.e. blood stem cells); their potency decreases with age
Fertilized Eggs:
• First few cells making up the zygote in the morula stage
o Cells are known to being totipotent
§ Capable of reproducing the entire organism
• During the blastocyst stage, within them are inner mass
cells which are the source of embryonic stem cells
o Cells are known to being pluripotent
§ Can no longer reproduce an entire organism
but are capable of producing various cell
types (i.e. cardiac, nervous, immune cells)
• Afterwards, specific cell types (i.e. skin cells) are known to being unipotent
o Have ‘cell-cell character’ and are very limited to what type of cells they can give rise to
ð Normal development and tissue homeostasis and regeneration are dependent on stem cells
o ‘aka’ the survival of multicellular organisms are dependent on stem cells
Degrees of Potency:
a) Totipotent:
o Capable of generating new embryos
§ Zygote in mammals; remain totipotent until the morula stage (16 cell stage)
§ In mice, both cells of a two stage embryo are NOT totipotent
b) Pluripotent:
o Completely undifferentiated master cells that can make any tissue/cell in the body
i. Inner Cell Mass (ICM) of Blastocyst:
§ Regenerate the embryo - can make cells for all three basic layers, but
not the placenta; (greater than 200 different cell types)
ii. Induced Pluripotent Stem Cells (iPSCs)
§ Derived from a non-pluripotent stem cells; typically derived from an adult
somatic cell – reprogramed to acquire stem-like properties
c) Multipotent:
o More limited than pluripotent stem cells
i. Hematopoietic Stem Cells (HSCs):
§ Multipotent – give rise to all blood and immune cells
ii. Mesenchymal Stem Cells:
§ Multipotent – give rise to bone, cartilage and other connective tissue
find more resources at oneclass.com
find more resources at oneclass.com
Properties of Stem Cells:
1. Unspecialized cells capable of renewing themselves
through cell division
(occasionally after long quiescent periods)
o Renewing capabilities is required to
maintain stem cell population
ð Once a stem cell undergoes division it will
generate a new stem cell (self-renewal) and a progenitor cell (capable of differentiating)
o Prior to differentiation, progenitor cell will undergo rapid proliferation to generate a
large mass of progenitor cells
2. Cells can be induced to become tissue- or organ- specific cells with special functions
o Number of different cell types they can differentiate into is reflective of the ‘potency’
of the stem cell
Stem Cell ‘Activation’:
• How often a stem cell needs to be activated
(no longer quiescent) is a reflection of the
proliferation and turnover of cells in tissues
o Can be measured using a Pulse Chase Assay
Pulse Chase Assay:
• Two phase strategy capable of measuring the half-life cells or cell population within tissues;
which is indicative of how fast the cells are being remodeled
o Half-life = time required for half the labeled of cells to ‘disappear’
Phase 1:
• Adding 5-bromo-2’-deoxyuridine (Br-dU) is a thymidine analog which
incorporates to the DNA (instead of thymidine) – Pulse (labeling cells)
o Br-dU is incorporated in cells undergoing DNA replication (S phase)
Phase 2:
• Wash the cells to remove BrdU that is not incorporated following by the addition
of unlabeled thymidine and culture cells for a long period of time – Chase
o Any subsequent replication will not be tagged with BrdU
• After certain period time; tissue will be fixed and a primary antibody will be
added to label incorporated BrdU
o Primary antibody must be tagged with a fluorescent molecule to observe
it once it actually binds to incorporated BrdU
ð Cells can be fixed at different times (shorter/longer chase duration)
o Longer chase = more cells lose their ‘tag’ – therefore, more cells will
undergo turn-over
ð We must run parallel experiments; same tube but removing the same amount of
cells each time and placing it on a slide and see how much the decrease over time
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Lecture 1(a): introduction to stem cells: potency is the number of possible fates available to a cell, potent = having the power to achieve a certain fate. Few cells (i. e. blood stem cells); their potency decreases with age. Fertilized eggs: first few cells making up the zygote in the morula stage, cells are known to being totipotent. Capable of reproducing the entire organism: during the blastocyst stage, within them are inner mass cells which are the source of embryonic stem cells, cells are known to being pluripotent. Normal development and tissue homeostasis and regeneration are dependent on stem cells. Aka" the survival of multicellular organisms are dependent on stem cells. Degrees of potency: totipotent, capable of generating new embryos. Zygote in mammals; remain totipotent until the morula stage (16 cell stage) In mice, both cells of a two stage embryo are not totipotent: pluripotent, completely undifferentiated master cells that can make any tissue/cell in the body.
