What are Stem Cell Markers?
Stem cell markers are highly unique which helps scientists to determine the type and function of various stem cells. They are named based on the molecules they bind to. Stem cells are also given identifiable names based on the markers present on their surface which can sometimes be a combination of markers. They are also given a (+) or (-) sign to indicate the marker's presence or absence.
There are several techniques by which scientists can identify the stem cell using signaling molecules that adhere specifically to certain markers. One technique is to attach a molecule to the signaling molecule that can emit light or fluorescence in the presence of an energy source such as UV rays. These can be adjusted to provide light of a particular desired color or intensity.
They may also Fluorescence-activated cell sorting (FACS) to sort rare stem cells from a large population of stem cells using fluorescent tags. They can also apply fluorescent tags to the markers and visually sort them using a fluorescent microscope from a thin slice of tissue.
Besides surface markers, genetics markers which are special identifying genes and transcription factors present in stem cells can help sort stem cells using advanced genetic techniques such as polymerase chain reaction (PCR). This can help researchers understand how genes are regulated within an organism's stem cells throughout life and how the cells become specialized during development.
Advances in genetic engineering technology have allowed scientists to forgo the utilization of cell surface markers in a process where they insert a reporter gene into the cell itself. An example of this gene is the green fluorescent protein or GFP which is activated and emits green fluorescence when the cells are undifferentiated and turns off when the cells start differentiating.
Some of the stem cell markers are as follows:
C - kit
C-kit- C-kit is alternatively known by many names such as mast/stem cell growth factor receptor (SCFR), proto-oncogene c-Kit or tyrosine-protein kinase Kit or CD117 (cluster of differentiation 117). It is a receptor tyrosine kinase protein type III that is encoded by the KIT gene. CD117 or C-kit is expressed on the surfaces of hematopoietic stem cells. Altered forms of this receptor may be associated with some types of cancer including gastrointestinal stromal tumors and melanoma. CD117 binds to stem cell factor (a substance that causes growth of certain types of cells), also known as "steel factor" or "c-kit ligand" forming a dimer that activates its intrinsic tyrosine kinase activity, which then phosphorylates and activates the signal transduction molecules that propagate the signal in the cell. The signaling process through CD117 plays an important role in cell survival, proliferation, and differentiation.
Oct - 4
Oct-4 (octamer-binding transcription factor 4) is a protein that in humans is encoded by the POU5F1 gene. Oct-4 is a homeodomain transcription factor belonging to the POU family which plays a large role in the development and functioning of the nervous system in both vertebrates and invertebrates. This protein is critically involved in the self-renewal of undifferentiated embryonic stem cells. It’s frequently used as a marker for undifferentiated cells. The expression of Oct-4 must be closely regulated as too much or too little will lead to differentiation of the cells.
Nestin is a protein marker for neural stem cells that is encoded by the NES gene. Nestin is expressed mostly in nerve cells where it is concerned with the radial growth of the axon.
Nestin is also expressed in follicle stem cells and their direct, differentiated progeny. The hair follicle area is a rich, easily accessible source of actively growing pluripotent adult stem cells that can differentiate into neurons, glia, keratinocytes, smooth muscle cells, and melanocytes. Therefore, hair follicle stem cells contribute towards providing an effective, easily available, autologous source of stem cells for the treatment of disorders such as peripheral nerve injury
Hematopoietic progenitor cell antigen CD34 also known as CD34 antigen is a protein that is encoded by the CD34 gene. It is a cell surface glycoprotein and functions as a cell-cell adhesion factor. It may also be involved in the attachment of stem cells to the bone marrow extracellular matrix or directly to the stromal cells.
CD38 (cluster of differentiation 38), which is also known as cyclic ADP ribose hydrolase is a glycoprotein that is found on the surface of many immune cells, such as CD4+, CD8+, B lymphocytes, as well as natural killer cells. CD38 also plays a role in signal transduction, calcium signaling, and cell adhesion. In human beings, the CD38 protein is encoded by the CD38 gene which is situated on the fourth chromosome. CD38 has also been used as a prognostic marker and as a therapeutic target in the treatment of leukemia.
CD44 antigen is a cell-surface glycoprotein that is a valuable marker is many types of cancer stem cells. It plays a role in cell-cell interactions, cell adhesion, and migration and is encoded by the CD44 gene present on Chromosome 11. CD44 has been referred to as HCAM (homing cell adhesion molecule)