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.1  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.2 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.3

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….4

  1. Wernig et al. 2007. In vitro reprogramming of fibroblasts into a pluripotent ES-cell-like state. Nature. []
  2. Hübner et al. 2003. Derivation of oocytes from mouse embryonic stem cells. Science 300:1251-56. []
  3. 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. []
  4. Contributed by H. Michael Kubisch []

Ethiopia and the ITPGRFA

Ethiopia’s Institute of Biodiversity Conservation (IBC) has a nice new website. Interestingly, it includes an interactive feature called BioForum. I was surprised, however, to see no reference to the Standard Material Transfer Agreement (SMTA) in the section on access. Since Ethiopia has been a Party to the International Treaty on Plant Genetic Resources for Food and Agriculture since 2003, IBC should be using the SMTA for transfers of Annex 1 material, surely.

Carolina Gold

In the early 1700’s, rice was South Carolina’s main export — no wonder the variety grown was called Carolina Gold. But where did it come from?

The first reported import in the New World of what is thought to be Carolina Gold occurred in 1685, when a slave ship from Madagascar unloaded a cargo of rice in Charleston, South Carolina.

So was that Indian Ocean island the ultimate source of Carolina Gold? USDA geneticists think they know, and have written about it in a new paper. Anna McClung and Robert Fjellstrom looked for molecular markers for Carolina Gold among the material in USDA rice germplasm collection. The best genetic fit — confirmed by close morphological similarity — was actually with an accession from Ghana, not Madagascar.

Questions remain. Maybe material from Carolina — originally derived from somewhere else — found its way back to Africa.

But geographer Judith Carney of the University of California, Los Angeles, says a Ghanaian origin of Carolina Gold fits with the idea that Carolina Gold arrived in the colony as food on slave ships and was then planted by the slaves.

Efforts are underway to bring this historical variety back into commercial cultivation.

A maize tour

SIRGEALC over, Marleni, David and I headed for CIMMYT, the International Maize and Wheat Improvement Centre. That’s in Texcoco, about an hour’s drive from the hotel where we were staying in Mexico City (or three hours, unfortunately, on the way back). It turned out to be something of a maize odyssey. I’ll tell the story in pictures.

When we got to Texcoco, it was too early for lunch, but that didn’t stop us spending some time in the market sampling the local cuisine, as the quesadillas there are famous. This lady certainly made us some great ones. Note the two types of maize she’s using.


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