Hey Steemians,

You may all know that many time in science we discover something which was not intended to or something came out by chance that’s what serendipity is and same happens to a group from Sungkyunkwan University, Korea.

"Protein from E.coli can combine with small molecule and act synergistically to push pluripotent cells into the functional neurons.”

Yamanaka has given four factors which are expressed in the embryonic stem cells (Oct3/4, Sox2, Klf4, c-Myc) (1) and while working in lab Kim group has found that one of the factors Sox2 has the ability to bind to the bacterial chaperone protein (Skp) (2). This leads them to investigate what change does it bring to the rate of differentiation.

Before going into the details, let’s just clear some of the basics for those who missed some of the terms.

Stem Cells and Embryonic Stem Cells

As Rudolf Virchow has said “Omnis Cellula e Cellula” means every cell is born from the previous one and that was born from the previous (Life comes from life).

In our body, some cells can differentiate themselves to give rise to many other. These stem cells can be categorized in two types: Embryonic Stem Cells (present in blastocysts) and Adult Stem cells (present in various tissues). Embryonic stem cell in the developing embryo differentiates and produces all the cell type which further differentiates into Ectoderm, Mesoderm and Endoderm (3).

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Stem cells can also be harvested at the time of birth from the umbilical cord blood and can be stored as for further medical therapies (4). These stem cells can be used in certain therapies where the immune system is involved and can have an effective stand on it. Now, in the recent advancements Stem cells can be grown artificially and can be differentiated into different cell type (5). Here comes the Yamanaka discovery.

Yamanaka factors

Shinya Yamanaka gave the induced Pluripotent Stem Cell (iPSC) and proved that by integrating four gene encoding transcription factors Oct3/4, Sox2, Klf4, c-Myc are capable of converting the normal adult cell into stem cell (1). For this discovery, he and Sir John Gurdon shared the Nobel Prize in Medicine 2012 for the “Adult cell can be Reprogrammable to pluripotent cell”.

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Sox2 genes are mainly associated with the multi and unipotent stem cells (6). Among all four transcription factors Sox2 was the first to be used for induction; other families of these genes were also known for the induction process but were less efficient as compared to the Sox2 (7).

Sox2 has a major role play in the suppression of neuronal differentiation of pluripotent stem cells and also known as gatekeeper of stemness. Once the function of Sox2 is finished or been removed, all the pluripotent stem cells starts differentiating and proliferating. This the reason why Sox2 is been so much in demand to supress.

Bacterial Chaperons

Chaperons are the proteins involved in folding of the other protein molecules. All the newly synthesized proteins are made to fold so as to attain their structure and be functional. The whole chaperons molecule works in a set of process where the newly synthesized linear protein comes inside it and in the hydrophobic patches get folded then come out of the chaperone molecule (The molecule is of barrel structure, which has an opening) (8). The chaperone we are going to discuss is from E.coli and are named as hsp60, hsp70, hsp90 etc. (9) (hsp stands for heat shock proteins) and skp chaperone (seventeen kilodalton protein) (10).

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Molecular Chaperones in bacteria has a wide range and the molecular proteins are being synthesized during the stress condition, for example when the bacterial cells are exposed to high temperature of hidh salinity etc. The whole unit is comprise of several proteins (mainly Gro EL/Gro ES in E.coli). GroEL is basically a ring like structure present on the top of barrel and GroES is a heptamer present on the barrel body which attaches to the opening. This opening and closing of the Molecular Chaperone is mediated by ATP utilization.

Binding to the Transcription Factor

The bacterial protein skp was used to bind to the Sox2 transcription factor and suppresses its activity. skp is a 17KDa protein from E.coli which on binding to the Sox2 factor resulted in the premature impression of the neuronal and cardiacn progenator cell. So, the bacterial chaperone induced cell formation was not totally specific, Kim group has tried some chemical inducer supplement that can turn them to specific cell type. In an attempt to do so they used P19 cells to convert into the functional neuronal cells by treating them with Skp and small inducer molecules.

Although the research have made it so far that we can change the adult cells to pluripotent stem cell, but still there is still so much to work on the efficiency of these cells and their transcription factors. There is need to look for more advanced and efficient way to make it happen – Says Kyeong Kim.

Further working on, they concluded that to make the cell pluripotent two simple and basic steps can be involved: first, if the stem cell begin differentiation and stay no longer a stem cell; second, or it decide itself which type of cell it want to be (11). The bacterial chaperon skp in the first step bind to the transcriptional gene (Sox2) and inhibits their function of inducing the cells to differentiate to neurons. In second step, an inducer for neuron differentiation Neuradazine (Nz) and Neurodazole (Nzl) is been used to guild the stem cell to differentiate into stem cells. By this, more functional neurons with higher rate can be produced.

The synergy thus mainly arises from combining suppression of stemness by these protein and directing lineage-specific commitment by chemical inducers (Nz and Nzl). Hence, this process stands as an example of rationally designed cell differentiation to achieve a high level of lineage commitment efficiency - Shin says.

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Pluripotent stem cells usually grow in suspension and further differentiate into specific cell type based following the lineage of three germ layers. It was recently reported that suppressing the activity of Sox2 gene can give the self-renewable power to the stem cells.

Advantages and Disadvantages

Using protein instead of any virus-mediated gene is always advantageous, because protein can never cause any gene alteration or cause any genetic modification while viral genome for the gene delivery can always be suspicious.

Well, using a bacterial protein in a human system is always have a safety concern and will never be that much easy to implement for therapeutics.

Future Prospect

The current research always hope to encourage the next generation to develop something more advanced using the same approach. Now, study is been carried to explore the same combinatorial approach to efficiently differentiate other cell types. The use of small molecule to suppress the stemness can be applied to the system. There could be lots of other small molecules other than the bacterial chaperones and more effective one, just need to find out.