Editing Transdifferentiation (section)

==Methods==

=== Lineage-instructive approach ===

In this approach, [[transcription factor]]s from [[progenitor cell]]s of the target cell type are [[transfection|transfected]] into a somatic cell to induce transdifferentiation.<ref name="Forcing cells to change lineages"/> There exists two different means of determining which transcription factors to use: by starting with a large pool and narrowing down factors one by one<ref name="ReferenceB">{{Cite journal 
| last1 = Ieda | first1 = M. 
| last2 = Fu | first2 = J. D. 
| last3 = Delgado-Olguin | first3 = P. 
| last4 = Vedantham | first4 = V. 
| last5 = Hayashi | first5 = Y. 
| last6 = Bruneau | first6 = B. G. 
| last7 = Srivastava | first7 = D. 
| doi = 10.1016/j.cell.2010.07.002 
| title = Direct Reprogramming of Fibroblasts into Functional Cardiomyocytes by Defined Factors 
| journal = Cell 
| volume = 142 
| issue = 3 
| pages = 375–386 
| year = 2010 
| pmid = 20691899 
| pmc =2919844 
}}</ref> or by starting with one or two and adding more.<ref>{{Cite journal 
| last1 = Vierbuchen | first1 = T. 
| last2 = Ostermeier | first2 = A. 
| last3 = Pang | first3 = Z. P. 
| last4 = Kokubu | first4 = Y. 
| last5 = Südhof | first5 = T. C. 
| last6 = Wernig | first6 = M. 
| doi = 10.1038/nature08797 
| title = Direct conversion of fibroblasts to functional neurons by defined factors 
| journal = Nature 
| volume = 463 
| issue = 7284 
| pages = 1035–1041 
| year = 2010 
| pmid = 20107439 
| pmc =2829121 
| bibcode = 2010Natur.463.1035V 
}}</ref> One theory to explain the exact specifics is that [[ectopia (medicine)|ectopic]] Transcriptional factors direct the cell to an earlier progenitor state and then redirects it towards a new cell type. Rearrangement of the [[chromatin]] structure via [[DNA methylation]] or [[histone]] modification may play a role as well.<ref>{{Cite journal 
| last1 = Ang | first1 = Y. S. 
| last2 = Gaspar-Maia | first2 = A. 
| last3 = Lemischka | first3 = I. R. 
| last4 = Bernstein | first4 = E. 
| title = Stem cells and reprogramming: Breaking the epigenetic barrier? 
| doi = 10.1016/j.tips.2011.03.002 
| journal = Trends in Pharmacological Sciences 
| volume = 32 
| issue = 7 
| pages = 394–401 
| year = 2011 
| pmid = 21621281 
| pmc =3128683 
}}</ref> Here is a list of in vitro examples and [[Examples of in vivo transdifferentiation by lineage-instructive approach|in vivo examples]]. [[In vivo]] methods of transfecting specific mouse cells utilize the same kinds of vectors as [[in vitro]] experiments, except that the vector is injected into a specific organ. Zhou et al. (2008) injected Ngn3, Pdx1 and Mafa into the dorsal splenic lobe (pancreas) of mice to reprogram pancreatic [[exocrine]] cells into β-cells in order to ameliorate hyperglycaemia.<ref>{{Cite journal 
| last1 = Zhou | first1 = Q. 
| last2 = Brown | first2 = J. 
| last3 = Kanarek | first3 = A. 
| last4 = Rajagopal | first4 = J. 
| last5 = Melton | first5 = D. A. 
| title = In vivo reprogramming of adult pancreatic exocrine cells to β-cells 
| doi = 10.1038/nature07314 
| journal = Nature 
| volume = 455 
| issue = 7213 
| pages = 627–632 
| year = 2008 
| pmid = 18754011 
| pmc = 9011918 
| bibcode = 2008Natur.455..627Z 
| s2cid = 205214877 
}}</ref>

=== Initial epigenetic activation phase approach ===

Somatic cells are first transfected with pluripotent reprogramming factors temporarily ([[Oct4]], [[Sox2]], [[Homeobox protein NANOG|Nanog]], etc.) before being transfected with the desired inhibitory or activating factors.<ref>{{Cite journal 
| last1 = Efe | first1 = J. A. 
| last2 = Hilcove | first2 = S. 
| last3 = Kim | first3 = J. 
| last4 = Zhou | first4 = H. 
| last5 = Ouyang | first5 = K. 
| last6 = Wang | first6 = G. 
| last7 = Chen | first7 = J. 
| last8 = Ding | first8 = S. 
| doi = 10.1038/ncb2164 
| title = Conversion of mouse fibroblasts into cardiomyocytes using a direct reprogramming strategy 
| journal = Nature Cell Biology 
| volume = 13 
| issue = 3 
| pages = 215–222 
| year = 2011 
| pmid = 21278734 
| s2cid = 5310172 
}}</ref> Here is a list of [[Examples of in vitro transdifferentiation by initial epigenetic activation phase approach|examples in vitro]].

===Pharmacological agents===
The DNA methylation inhibitor, 5-azacytidine is also known to promote phenotypic transdifferentiation of cardiac cells to skeletal myoblasts.<ref>{{cite journal|last1=kaur|first1=keerat|last2=yang|first2=jinpu|last3=eisenberg|first3=carol|last4=eisenberg|first4=leonard|title=5-azacytidine promotes the transdifferentiation of cardiac cells to skeletal myocytes.|journal=Cellular Reprogramming|date=2014|volume=16|issue=5|pmid=25090621|url=https://www.researchgate.net/publication/264462290|doi=10.1089/cell.2014.0021|pages=324–330}}</ref>

In [[prostate cancer]], treatment with [[androgen receptor]] targeted therapies induces neuroendocrine transdifferentiation in a subset of patients.<ref>{{cite journal |last1=Usmani |first1=S |last2=Orevi |first2=M |last3=Stefanelli |first3=A |last4=Zaniboni |first4=A |last5=Gofrit |first5=ON |last6=Bnà |first6=C |last7=Illuminati |first7=S |last8=Lojacono |first8=G |last9=Noventa |first9=S |last10=Savelli |first10=G |title=Neuroendocrine differentiation in castration resistant prostate cancer. Nuclear medicine radiopharmaceuticals and imaging techniques: A narrative review. |journal=Critical Reviews in Oncology/Hematology |date=June 2019 |volume=138 |pages=29–37 |doi=10.1016/j.critrevonc.2019.03.005 |pmid=31092382|s2cid=131934021 }}</ref><ref>{{cite journal |last1=Davies |first1=AH |last2=Beltran |first2=H |author3=[[Amina Zoubeidi]]|title=Cellular plasticity and the neuroendocrine phenotype in prostate cancer. |journal=Nature Reviews. Urology |date=May 2018 |volume=15 |issue=5 |pages=271–286 |doi=10.1038/nrurol.2018.22 |pmid=29460922|s2cid=4732323 }}</ref> No standard of care exists for these patients, and those diagnosed with treatment induced neuroendocrine carcinoma are typically treated palliatively.<ref>{{cite journal |last1=Aggarwal |first1=R |last2=Zhang |first2=T |last3=Small |first3=EJ |last4=Armstrong |first4=AJ |title=Neuroendocrine prostate cancer: subtypes, biology, and clinical outcomes. |journal=Journal of the National Comprehensive Cancer Network |date=May 2014 |volume=12 |issue=5 |pages=719–26 |doi=10.6004/jnccn.2014.0073 |pmid=24812138}}</ref>

=== Mechanism of action ===

The transcription factors serve as a short term trigger to an irreversible process. The transdifferentiation liver cells observed 8 months after one single injection of pdx1.<ref name="nature.com"/>

The ectopic transcription factors turn off the host repertoire of gene expression in each of the cells. However, the alternate desired repertoire is being turned on only in a subpopulation of predisposed cells.<ref>{{Cite journal 
| last1 = Meivar-Levy | first1 = I. 
| last2 = Sapir | first2 = T. 
| last3 = Gefen-Halevi | first3 = S. 
| last4 = Aviv | first4 = V. 
| last5 = Barshack | first5 = I. 
| last6 = Onaca | first6 = N. 
| last7 = Mor | first7 = E. 
| last8 = Ferber | first8 = S. 
| doi = 10.1002/hep.21766 
| title = Pancreatic and duodenal homeobox gene 1 induces hepatic dedifferentiation by suppressing the expression of CCAAT/enhancer-binding protein β 
| journal = Hepatology 
| volume = 46 
| issue = 3 
| pages = 898–905 
| year = 2007 
| pmid = 17705277 
| doi-access = free 
}}</ref> Despite the massive dedifferentiation – lineage tracing approach indeed demonstrates that transdifferentiation originates in adult cells.<ref>{{Cite journal 
| last1 = Mauda-Havakuk | first1 = M. 
| last2 = Litichever | first2 = N. 
| last3 = Chernichovski | first3 = E. 
| last4 = Nakar | first4 = O. 
| last5 = Winkler | first5 = E. 
| last6 = Mazkereth | first6 = R. 
| last7 = Orenstein | first7 = A. 
| last8 = Bar-Meir | first8 = E. 
| last9 = Ravassard | first9 = P. 
| last10 = Meivar-Levy | first10 = I. 
| last11 = Ferber | first11 = S. 
| editor1-last = Linden 
| editor1-first = Rafael 
| title = Ectopic PDX-1 Expression Directly Reprograms Human Keratinocytes along Pancreatic Insulin-Producing Cells Fate 
| doi = 10.1371/journal.pone.0026298 
| journal = PLOS ONE 
| volume = 6 
| issue = 10 
| pages = e26298 
| year = 2011 
| pmid = 22028850 
| pmc =3196540 
| bibcode = 2011PLoSO...626298M 
| doi-access = free 
}}</ref>

=== Mogrify algorithm ===
Determining the unique set of cellular factors that is needed to be manipulated for each cell conversion is a long and costly process that involved much trial and error. As a result, this first step of identifying the key set of cellular factors for cell conversion is the major obstacle researchers face in the field of cell reprogramming. An international team of researchers have developed an algorithm, called Mogrify(1), that can predict the optimal set of cellular factors required to convert one human cell type to another. When tested, Mogrify was able to accurately predict the set of cellular factors required for previously published cell conversions correctly. To further validate Mogrify's predictive ability, the team conducted two novel cell conversions in the laboratory using human cells, and these were successful in both attempts solely using the predictions of Mogrify.<ref>[http://www.eurekalert.org/pub_releases/2016-01/dms-moc011516.php  Mapping out cell conversion]</ref><ref>{{cite journal | last1 = Owen | first1 = Rackham | last2 = Gough | first2 = Julian  | year = 2016 | title = A predictive computational framework for direct reprogramming between human cell types | journal = Nature Genetics| volume =  48| issue = 3| pages =  331–335| doi = 10.1038/ng.3487 | pmid=26780608| url = https://research-information.bris.ac.uk/en/publications/a-predictive-computational-framework-for-direct-reprogramming-between-human-cell-types(e6490a78-f3e8-4253-acc4-7ee181c79168).html | hdl = 1983/e6490a78-f3e8-4253-acc4-7ee181c79168 | s2cid = 217524918 | hdl-access = free }}</ref><ref>Jane Byrne (Jul 2021). [https://www.biopharma-reporter.com/Article/2021/07/01/Mogrify-looks-to-transform-cell-therapy-development  Mogrify looks to transform cell therapy development]. BIOPHARMA-REPORTER.COM</ref> Mogrify has been made available online for other researchers and scientists.