Pet cloning may be useful in treating patients who suffer from diseases that are currently untreatable or where treatment using an allogenic source is risky. It is also possible that the ability to clone genes using a somatic cell may serve as a platform for gene therapy. Gene therapy is an exciting area of research that has generated tremendous hopes in the medical community for treating untreatable diseases. In order for this potential therapy to be realized, however, specific tissue targeting must be available. Using somatic cell nuclear transfer, Dr. Dib's group has created human tissues in order to determine whether or not targeting of specific tissue types is feasible. Further development of somatic cell nuclear transfer for therapeutic purposes will require a more thorough understanding of the mechanism of reprogramming. One promising avenue of research is the identification of specific transcription factors that regulate reprogramming, and the identification of mechanisms that change the epigenetic landscape of somatic cells in order to make them more permissive for nuclear transfer. A major barrier to our understanding of the epigenetic mechanisms regulating nuclear reprogramming is the lack of methods to reliably and efficiently reprogram many individual cells within one experiment. In Dr. Dib's lab, his lab is developing a method to perform all steps of nuclear transfer in microwells in order to generate several hundred clones of each type of human cell in one experiment. By generating a library of each type of human cell in this manner, it will be possible to study how the epigenome of a cell is controlled in a controlled manner. These methods will also make it possible to investigate how chromatin packaging regulates reprogramming. Currently, methods to induce reprogramming within microwells of similar size and shape have only been published using stem cells and progenitor cells that reprogram extremely efficiently. These progenitor cells, however, are not normally found in nature, and do not directly parallel most of the differentiated cell types in human tissues. By demonstrating the efficiency of generation of differentiated cell types in microwells, Dr. Dib's lab will be able to better understand what mechanisms are necessary for nuclear reprogramming. A second major barrier to the application of somatic cell nuclear transfer for therapeutic purposes is the low success rate of the procedure. While most groups report at least partial success, the vast majority of the cloned embryos do not survive until the blastocyst stage, which is necessary for implantation. There are two possible reasons for the low cloning efficiency: (1) some nuclear reprogramming events may happen too slowly, thereby preventing proper embryonic development from the 2- to 4-cell stage; (2) some somatic cells may not be able to support full reprogramming, due to their epigenetic makeup, and are therefore not able to develop further than the 8-cell stage. As mentioned above, Dr. Dib's lab has developed methods to reprogram single cells in microwells that will allow the mechanisms of reprogramming to be studied in isolation. For more efficiently reprogramming a larger number of cells in microwells, Dr. Dib and his team have developed an array of microwells that can house up to 32 microwells per device. With these devices, they have developed a method to efficiently reprogram a large number of cells simultaneously. Additionally, Dr. Dib's group has identified some nuclear transfer reagents that are superior to the ones commonly used for reprogramming. Using these methods, Dr. Dib's lab will develop methods to improve cloning efficiency in order to produce more cloned embryos suitable for therapeutic cloning. Dr. Dib's lab, like all labs, can only do what it can with the resources available to it. Dr. Dib's group has developed a system of nuclear transfer with much higher efficiency than those commonly used by other researchers. But to achieve even higher efficiencies and ultimately perform all of the steps of nuclear transfer within a single experiment, Dr. Dib has developed an all-microwell cloning system that efficiently reprogram single cells within microwells and then transfer them into blastocysts. These methods will facilitate the analysis of the reprogramming process and allow his laboratory to develop therapeutic cloning in its early stages. Additionally, these methods are more amenable to larger scale screening for identification of transcription factors that may be necessary for the efficient generation of iPS cells or the control of epigenetic changes necessary for nuclear reprogramming. The techniques developed in Dr. Dib's lab are essential for studying somatic cell nuclear transfer and are relevant to the general field of epigenetics. Author's response * This research was supported by the NIH. The authors wish to thank Professor George Daley and the Department of Genetics and Complex Diseases of the Brigham and Women's Hospital for support and the NIAID for the P01 GM081619 award to G.D. The authors also wish to thank Dr. Bruce Blazar and the Harvard Stem Cell Institute for their support. The content of this publication does not necessarily reflect the views or policies of the Department of Health and Human Services, nor does mention of trade names, commercial products or organizations imply endorsement by the U.S. Government. Competing interests The authors declare that they have no competing interests. Review history Received 29 February 2013Accepted 24 April 2013Published 22 July 2013 This article has been cited by other articles in PMC. Our tools allow you to track citations across all of PMC. Similar articles Objective To assess an important but unresolved question: is the ability to clonally expand human embryonic stem (ES) cells from a single-cell equivalent to natural human development, in which clonal expansion is thought to occur very early on before implantation? Stem cells are by definition capable of being self-renewed and also of differentiating to different cell types. Such a cell may either be multipotent, so that it gives rise to only one cell type or lineage, or pluripotent, so that it gives rise to cell types found in all three germ layers and in both fetal and adult tissues. This characteristic makes these cells a very attractive cell source for regenerative medicine, where the aim is to repair or replace damaged tissues and organs in patients.