Category: Biotechnology

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Stem cells and endangered livestock breeds

A group of scientists at the Massachusetts Institute of Technology has managed to turn fibroblasts, cells abundant in connective tissues, back into pluripotent, i.e. non-differentiated, stem cells. ((Wernig et al. 2007. In vitro reprogramming of fibroblasts into a pluripotent ES-cell-like state. Nature.))  This has caused quite a stir — and for good reason.

Because stem cells are pluripotent, they can in theory be turned into virtually any cell type in the body. Needless to say, such cells have tremendous potential for therapeutic intervention in all sorts of human maladies that result from cellular death or injury. Until now there have been mainly two ways to obtain stem cells: one involves the generation and subsequent destruction of  an embryo to extract embryonic (ES) stem cells,  the other relies on  isolation of adult stem cells, which have been found in all sorts of locations from the spinal chord to dental pulp.

But there are limitations and issues with both approaches: the derivation of ES cells evokes moral objections from many quarters because it necessitates the destruction of an embryo, while the use of adult stem cells is at present fraught with doubts about whether such cells are truly pluripotent. This is why this new development is considered such a breakthrough.

Why would a method to generate stem cells be relevant for saving endangered animal breeds? What if it were possible to turn pluripotent stem cells into eggs and sperm cells? Impossible, you say? Well, consider this: an article appeared in 2003 in the journal Science claiming that scientists had, indeed, managed to generate what seemed to look like egg cells from embryonic mouse stem cells. ((Hübner et al. 2003. Derivation of oocytes from mouse embryonic stem cells. Science 300:1251-56.)) Several other groups meanwhile seem to have coaxed stem cells to turn into primitive sperm cells, and at least one report has described the use of such sperm cells to generate live mouse offspring. ((Nayernia et al. 2006. In vitro-differentiated embryonic stem cells give rise to male gametes that can generate offspring mice. Developmental Cell 11:125-32.))

Much of this remains to be worked out and confirmed by other scientists, and given the incredibly complicated process of meiosis and maturation that egg and sperm cells have to undergo before becoming truly functional, many doubt this kind of approach will ever be feasible. Even the conversion of fibroblasts into stem cells is at present still very complicated and this recent report represents mostly a proof of principle. 

But just imagine if this were all to work: it might then be possible to go out into a field, pick a few small chunks of ear tissue from as many endangered cattle, goats or pigs as you want,  isolate the fibroblasts, turn them into stem cells, coax those into becoming eggs and sperm, make embryos, and put them into your freezer, where they could remain indefinitely. You could do this probably with a lot less effort than it often takes to ensure preservation of  rare animals in situ and would, moreover, be able to bank as much of a breed’s genomic variation as you’d like.

Maybe this will remain science fiction. Then again, nobody thought a sheep could be cloned either…. ((Contributed by H. Michael Kubisch))

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Nuts for makapuno

The redoutable Coconut Google Group has a great story from Roland Bourdeix about the Philippines’ makapuno coconut variety, ((Now, you may have to join the Google Group to read Roland’s post. But that would be no bad thing.)) drawing from an article in the Philippine Star. Makapuno nuts have a delicious and very valuable jelly instead of water, but can’t germinate. A makapuno palm will only have 15-20% or so makapuno fruits. The only way to get makapuno nuts is to plant a normal coconut from a palm with makapuno fruits and harvest that precious 15-20%. But that meets only 3% of demand. So in the 1960s Dr Emerita de Guzman came up with a way of rescuing makapuno embryos in tissue culture. When she planted the resulting seedlings, all the coconuts were makapuno. There are now nine labs in the Philippines churning out makapuno seedlings, but they’re expensive and few farmers can afford to buy them. I’ll let Roland tell the rest of the story, but here’s a little spoiler to whet your appetite: tissue culture makapuno palms were planted on a kind of artificial island in Thailand and something wonderful happened there…

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Mutant teff

Sometimes a crop just doesn’t have the genes for it, as a good friend of mine who dabbled in taro breeding used to say. So then you have to try something else. “Zerihun Tadele is using the latest biotechnological methods to produce dwarf tef lines in order to prevent lodging, which causes significant yield losses.” The technique involved is TILLING (Targeting Induced Local Lesions IN Genomes), an automated methods for inducing, and then detecting, potentially useful point mutations. But is there really no short(ish) teff variety among the 4743 accessions in the genebank of Ethiopia’s Institute of Biodiversity Conservation? By the way, IBC has just won the Sultan Qaboos Environmental Preservation Prize. Congratulations!