enucleation

pipetteload

nuclear transfer

developmental stages after mouse cloning

Michele Boiani at the microscope
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Michele Boiani’s homepage on nuclear transfer

 

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What is nuclear transfer?

Nuclear transfer describes the transplantation of a nucleus from one cell into another. On this website I refer specifically to the nucleus of a somatic (body) cell transplanted into an egg cell that has been stripped of its own nuclear material. This setting is commonly known as "cloning". It should be noted that there are other kinds of nuclear transfer too, such as intracytoplasmic sperm injection (ICSI) and germinal vesicle (GV) transfer, which are used in assisted reproduction and have nothing to do with cloning except the skills and the costs involved. In yet other settings, nuclei are transferred across somatic cells (The EMBO Journal 25, 5329 - 5338, 2006).

Why performing nuclear transfer?

In the "somatic nucleus to egg" setting, nuclear transfer is a powerful method conceived over a century ago in order to investigate the basis of cell differentiation (Int‘l J Dev Biol 48:607-612, 2004). Now that the original questions have been answered and alternative methods can be deployed, nuclear transfer is held by many as technically obsolete and burdened with ethical problems. I am going to challenge these views and introduce some fundamental biologic questions that cloning still can answer, such as: what is it that makes the egg cell so powerful at restoring in somatic nuclei a ground state of pluripotency ("reprogramming‘
")? How many pathways of reprogramming exist? May somatic cell nuclear transfer be seen as a way to restore a feature our ancestors lost during evolution i.e. the ability of any body cell to serve as a reproductive agent? Does cloning accelerate the pace of evolution by bringing somatic mutations back into the germline? Is cloning a Lamarckian process?