Question about cloning via 'ECNT'

[deleted-301508]

Dear all

Actually, I've two questions about embryonic cell nuclear transfer (ECNT). (1) What is its current success rate? Is it greater than that of somatic cell nuclear transfer (SCNT)? (2) SCNT seems preferred, for reproductive cloning, over ECNT. Why? Solely because it circumvents ethical worries about manipulating and destroying embryos?

Thanks for your time. (I'll be teaching a class on the ethics of cloning, and so I need to get the science right.)

EDIT: Although I am a teacher, I teach philosophy, not science - and my scientific knowledge is not what it could be. So please keep answers fairly simple - thanks!

[SciB]

Hi,

I’m not a cloning wizard but I do have some experience with cell culture, gene transfer and molecular biology.

The scientists who pioneered the nuclear transfer method of artificially producing an embryo naturally chose an embryonic cell as the donor of the nucleus containing the DNA because an embryonic cell is already programmed to turn into an embryo. The likelihood that a given transfer will be successful and an embryo will form is much greater with ECNT than SCNT (http://learn.genetics.utah.edu/content/ ... clonezone/).

When the donor DNA comes from a somatic cell—a cell from any part of the adult body—it has to be reprogrammed to initiate embryo formation by manipulating the components of the solution that the cells are cultured in. Discovering the correct recipe for this is difficult and even then SCNT may not produce a viable embryo or live birth. In the case of the famous cloned sheep, Dolly, it took 277 SCNTs before one lamb was born and survived to adulthood (https://en.wikipedia.org/wiki/Somatic_c ... r_transfer).

There are also serious questions about the health of SCNT-cloned offspring. Dolly only lived to the age of 6 ½ years which is about half the normal lifespan (https://www.newscientist.com/article/dn ... ies-young/). She had arthritis and lung disease and seemed to be aging prematurely. Experiments with cloned lab mice have shown similar earlier deaths. The accelerated aging may be caused by the presence of shorter telomeres on the chromosomes. Telomeres are the small sequences of DNA at the ends of mammalian chromosomes that protect them from loss during cell division. Telomeres gradually shorten with age so if an animal starts off life with shorter than normal telomeres, they will age more quickly. This has not been proven as the cause for Dolly’s early demise but it is possible.

In regard to your second question, yes the main reason that researchers have begun to use non-embryonic human cells as DNA donors is to avoid potential ethical and legal concerns over growing human embryos as a source of donor cells. Somatic cells can be taken from any tissue of the animal being cloned so are identical to it. The cells can also be cultured in the lab and genetically manipulated to correct a hereditary disease like muscular dystrophy or Down syndrome.

Since you are preparing to teach a course on the ethics of genetics in the 21st century you must have already read about the latest concern of bio-ethicists, the CRISPR/Cas9 technology. This technique allows a person to change the DNA sequence in a very precise way at a single chosen location. The CRISPR (clustered regularly interspaced short palindromic repeats) method is quite simple and could easily be used to alter the DNA of somatic donor cells which could then be used to provide the DNA for a SCNT and produce a genetically-modified embryo.

I was in college when the old technique of recombinant DNA manipulation using restriction enzymes and ligases was developed and there were huge concerns about the outcomes and safety of this technique. The whole scientific community met at the Asilomar conferences to draft strict rules for those wishing to use recombinant DNA. The newer technologies such as CRISPR and SCNT make the old recombinant issues look trivial by comparison. I’m afraid the genies are out of the bottle in force now and laws can only do so much to prevent unethical or unwise use of these cloning methods. There is a tremendous potential for good in terms of improved health and freedom from disease inherent in these new genetic techniques. It’s the other side of the coin that worries me.

I hope this helps to answer your questions. Please feel free to continue this thread with more questions. I am learning more by helping you!

Good luck!

Sybee

[deleted-301508]

Dear Sybee

This is helpful stuff. Thank you very much for providing it.

Here's a thing: I should have been more precise (a galling admission for a philosopher)! I said I was teaching a 'class' on the ethics of cloning. I should have said: I am teaching one single session on the ethics of cloning.

As of today I have taught that class - before, unfortunately, reading your excellent post - and it went fairly well. (Actually, though - another thing/another imprecision - it is more of a seminar than a class.) Since that was my only class, and since, as it happens and perhaps regrettably - I am not especially interested in the subject (I do feel I should be . . ) - I will leave matters here (unless you'd like to see the materials I used and comment upon them). (I should perhaps add that I am interested in the idea that reproductive - and perhaps other forms of - cloning might be part of a trend that treats humans too instrumentally. My reference points here are Kant, Heidegger and Adorno.)

I can add that I pursued some other avenues of knowledge - viz., I found I biologist I know, and buttonholed him; and I did a bit more superficial research-by-Internet - and what I discovered fits with what you say.

[SciB]

Hello and thank you for the interesting reply. It is a rare pleasure to speak to a real live 21st century philosopher!

Although I am a scientist, I am old enough to have had a good course in the humanities in college that included lectures on philosophy--at least through the 18th century. I have doubts that Aristotle's Ethics would have much bearing on the rights and wrongs of cloning humans, however.

I was interested by your suggestion that genetic manipulation of humans would result in their being treated 'instrumentally'. I am not sure what you mean by the term but it conjured up in my mind visions of a race of humans 'enhanced', shall we say, for a variety of purposes. Electronic implants are already being used in people who are paralyzed or blind and this might be construed as treating a human as a machine whose parts can be replaced or upgraded as needed. But genetically altering a human to give them new powers or enhanced senses--is that ethical?

I would like to see you and your colleagues teach a philosophy course in 21st century ethics--Aristotle updated. Bring in good outside speakers, design an interactive course website and I'll bet the students will be clamoring to sign up. At our college of medicine we have a mandatory course in the ethics of research where we delve a little into the question of human cloning, but more from a legal than a moral or philosophical standpoint. As a scholar of the continuing philosophical conversation you might lend your voice to the debate that needs to be happening now while we are still at the beginnings of the genetic revolution.

Scibuddies is specifically a site for helping K-12 students with science fair projects, so we cannot pursue this discussion, but thanks for being interested enough to send a query.

All the best,

Sybee