Stem Cell Biology

• Stem cell differentiation involves changes to the genes and proteins expressed by stem cells as they develop into specialized cell types.
• Stem cells can be a therapeutic to mitigate potential diseases.
• Stem cells have two main properties to distinguish themselves from other eukaryotic cells: the ability to differentiate and the ability to undergo self-renewal.
• Stem cells typically have a good reserve to maintain its quantity and avoid depletion.
• The process of mitosis replenishes damaged or dead cells by dividing into two diploid daughter cells that contain the same number of chromosomes as their parent cell.
• Meiosis involves division into four daughter haploid cells that contain half the number of chromosomes as their parent cell.
• Both cycles of division are fairly similar but the primary difference being that in the process of meiosis, division occurs twice.
• In mitosis, the sister chromatids are identical to their parent.
• As the daughter cells are genetically identical to the parent, the same cell will be regenerated.
• In meiosis, homologs will pair but are separated during anaphase I, which results in a reduction division.
• These daughter cells will be genetically distinct from each other and their parent cell due to the crossing over of genes that occurs during the stages of meiosis.
• The possible fates of a stem cell include quiescence, cell division, apoptosis/senescence, and progenitor cells.
• Embryonic stem cells (ES cells) are derived from the blastocyst stage of the embryo and existed when we were a fetus.
• Maternal and fetal circulation never mix as the placenta acts as a physical barrier to ensure nutrients are taken up and waste is properly excreted during pregnancy.
• Adult stem cells are associated with newly forming tissues and provide a source of replacement cells.
• Many adult stem cells spend a large duration in quiescence as they have no DNA damage (they do not accumulate damaging mutations).
• Cell potency is the cell's ability to differentiate into other cell types.
• Levels of potency include totipotency, pluripotent, multipotent, unipotent, and progenitor cells.
• The heart and brain typically don't experience turnover as they are unable to carry out mitosis.
• The niche and physical orientation is critical for the correct functioning of stem cells.
• You don't need a blastocyst to generate (induced) pluripotent stem (iPS) cells.
• The economical importance of stem cells is that they can improve crop and livestock by mitigating certain diseases.
• The Yamanaka factors (there are 4) can be added to any type of lineage via a viral vector.
• The cells require growth factors to be able to differentiate.
• Meristem is a tissue found in plants and meristematic cells are undifferentiated plant stem cells.
• Enucleated cells are cells that contain all cellular components except the nucleus.
• The nucleus is removed in order to remove DNA.
• The process of adult sheep cells being fused with enucleated eggs involved (Dolly the Sheep experiment) involves the removal of the nucleus from egg cells and the removal of mammary cells from the donor, followed by the implantation of the mammary cells infused with the enucleated egg cell into surrogate mothers (recipient).
• Dolly the Sheep died early due to disease, which makes us question whether Dolly died due to natural causes or if Dolly was more susceptible to disease as she was a clone.
• In the First Cloned Drosophila experiment, it is important to note that the possible reason as to why isolated nuclei from GFP-strain embryos were injected into 820 host embryos is that the process of implantation is very difficult and failure is very likely.
• The placenta may not have developed properly in the First Cloned Drosophila experiment as it arises from the donor's isolated nuclei (enucleated cells).
• Regeneration is the process of repairing or replacing damaged or diseased organs using cells.
• Three strategies are involved with regeneration: Implantation of stem cells to build new structures, Implantation of pre-primed cells (cells that require cues to differentiate), and Stimulation of endogenous stem cells (these stem cells already reside in the individual; however, these cells require growth factors to differentiate).
• Autonomy is essentially self-amputation and it is a defence mechanism employed by animals to evade predation.
• The African spiny mouse loses its skin upon predation; however, they can replace up to 60% of their skin, including all appendages.
• Dedifferentiation is the reversal in the phenotype of a cell to an earlier state, it follows one cell lineage and can revert back to an earlier state within that lineage.
• Transdifferentiation is the switching to a cell type that is that is on a distinct pathway of differenation, for example, switching from skin cell to neuronal cell.
• Regeneration of animals consists of morphallaxis and epimorphosis.
• Morphollaxis does not go through the proliferative stage, for example, in Hydra.
• Epimorphosis goes through the proliferative stage as there needs to be sufficient amount of cells for differentiation to occur, for example, in the process of cardiac regeneration in zebrafish, where 20% of their heart is removed (apex portion).