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Embryonic stem cells from adults move a step closer
In brief–
NATALIE FOBES/CORBIS
TWO salmon beget a trout. And the people who made it happen hope to use the strange parenting trick to conserve endangered fish species. A team led by Goro Yoshizaki of the Tokyo University of Marine Science and Technology in Japan began by manipulating male embryos of masu or cherry salmon. They did so by transplanting germ cells called spermatogonia from male rainbow trout into the salmon embryos. Within 17 months the salmon had grown into adults that produced pure trout sperm. They repeated the trick with female salmon embryos, which grew into adults that produced pure trout eggs. When Yoshizaki’s team fertilised these eggs with the sperm from the male salmon, just under 90 per cent of the resulting eggs hatched to produce healthy trout (Science, vol 317, p 1517). Salmon and trout belong to the same family – Salmonidae – and Yoshizaki says that it may be difficult to apply the technique across more distant species. “I do not think salmon can produce tuna or carp eggs,” he told New Scientist. He is collaborating with Penny Swanson of the Northwest Fisheries Science Center in Washington to try to repeat the experiments with germ cells from sockeye salmon – endangered in some parts of its range – in the hope that they can one day be bred from their less rare cousins.
20 | NewScientist | 22 September 2007
Good things come to stem cell creators who wait STEM cells derived from an adult’s own cells have come a step closer. Earlier this year, three independent teams reported reprogramming adult mouse cells into embryonic stem cell-like (ESC-like) cells by expressing the genes for four crucial factors (New Scientist, 6 June, p 8). However, a number of obstacles remained before this technique could be useful in humans. One of these was the method used to identify cells that had successfully reprogrammed. This involved accurately inserting
an antibiotic-resistance gene into the cells near an important ESC gene, so that only reprogrammed cells would be able to grow in a culture containing this antibiotic. “You can’t just go and grab a cell from a patient with a particular disease and have it have that marker in it,” says Robert Blelloch of the University of California, San Francisco. Now two teams have shown that reprogrammed cells can be isolated without introducing the antibiotic marker. Rudolf Jaenisch’s team at the Whitehead
Institute for Biomedical Research in Cambridge, Massachusetts, found that by simply waiting several weeks after introducing the genes for the four factors, rather than just a few days, colonies of ESC-like cells grew in a culture dish (Nature Biotechnology, DOI: 10.1038/nbt1335). Meanwhile, Blelloch’s team reports that if cells are placed in a culture medium that stem cells prefer, the ESC-like cells will grow, and they can then be identified visually (Cell Stem Cell, DOI: 10.1016/j.stem.2007.08.008).
Whiff is in the genes of the beholder
receptor, OR7D4. So the team collected blood samples from the sniffers to see if genes could explain the difference in how androstenone was perceived. They found two variants of OR7D4 that were involved. People with RT/RT allele were more likely to think androstenone stinks, while those with RT/WM think it smells like vanilla. Also people with RT/RT were much more likely to pick up its smell in the first place (Nature, DOI: 10.1038/ nature06162). The findings were similar for men and women. Since androstenone is used by some mammals to communicate sexual and social information, the researchers want to learn more about how it affects human behaviour – especially in people unable to detect it.
PUNCHSTOCK
Who’s your daddy, baby trout?
Yeast cells that never forget MEMORY is not something you would normally associate with yeast cells, but with a genetic “circuit” inside them the cells can “remember” exposure to a molecule of the sugar galactose. A team led by Pamela Silver at Harvard Medical School in Boston created the circuit to show that biological systems could be engineered in the same way as mechanical ones. They used the galactose to trigger expression of a gene, the product of which turned on a second gene. This gene then acted to turn itself on again and again, creating an infinite loop. So after the galactose triggers the circuit, the second gene stays activated indefinitely, regardless of whether galactose is still present. In Silver’s circuit, the second gene produces a fluorescent molecule, so the cells glow green if they have been exposed to galactose. The circuit stayed active for at least nine generations and possibly many more. The system could be used to flag up cells that have been exposed to a particular drug or suffered DNA damage, Silver says (Genes and Development, vol 21, p 2271).
A MAN can smell as sweet as vanilla or a foul as a urinal – and it depends largely on a single gene in the sniffer. Androstenone, a steroid derived from testosterone, is found in higher concentrations in the urine and sweat of men than of women. Some people think it reeks, others think it smells sweet, and some can’t detect it at all. Leslie Vosshall at Rockefeller University in New York and her colleagues asked 391 volunteers to sniff 66 odours of either high or low intensity and rate their pleasantness. Two of the odours had a steroid component that activated a particular
www.newscientist.com
NATALIE FOBES/CORBIS
TWO salmon beget a trout. And the people who made it happen hope to use the strange parenting trick to conserve endangered fish species. A team led by Goro Yoshizaki of the Tokyo University of Marine Science and Technology in Japan began by manipulating male embryos of masu or cherry salmon. They did so by transplanting germ cells called spermatogonia from male rainbow trout into the salmon embryos. Within 17 months the salmon had grown into adults that produced pure trout sperm. They repeated the trick with female salmon embryos, which grew into adults that produced pure trout eggs. When Yoshizaki’s team fertilised these eggs with the sperm from the male salmon, just under 90 per cent of the resulting eggs hatched to produce healthy trout (Science, vol 317, p 1517). Salmon and trout belong to the same family – Salmonidae – and Yoshizaki says that it may be difficult to apply the technique across more distant species. “I do not think salmon can produce tuna or carp eggs,” he told New Scientist. He is collaborating with Penny Swanson of the Northwest Fisheries Science Center in Washington to try to repeat the experiments with germ cells from sockeye salmon – endangered in some parts of its range – in the hope that they can one day be bred from their less rare cousins.
20 | NewScientist | 22 September 2007
Good things come to stem cell creators who wait STEM cells derived from an adult’s own cells have come a step closer. Earlier this year, three independent teams reported reprogramming adult mouse cells into embryonic stem cell-like (ESC-like) cells by expressing the genes for four crucial factors (New Scientist, 6 June, p 8). However, a number of obstacles remained before this technique could be useful in humans. One of these was the method used to identify cells that had successfully reprogrammed. This involved accurately inserting
an antibiotic-resistance gene into the cells near an important ESC gene, so that only reprogrammed cells would be able to grow in a culture containing this antibiotic. “You can’t just go and grab a cell from a patient with a particular disease and have it have that marker in it,” says Robert Blelloch of the University of California, San Francisco. Now two teams have shown that reprogrammed cells can be isolated without introducing the antibiotic marker. Rudolf Jaenisch’s team at the Whitehead
Institute for Biomedical Research in Cambridge, Massachusetts, found that by simply waiting several weeks after introducing the genes for the four factors, rather than just a few days, colonies of ESC-like cells grew in a culture dish (Nature Biotechnology, DOI: 10.1038/nbt1335). Meanwhile, Blelloch’s team reports that if cells are placed in a culture medium that stem cells prefer, the ESC-like cells will grow, and they can then be identified visually (Cell Stem Cell, DOI: 10.1016/j.stem.2007.08.008).
Whiff is in the genes of the beholder
receptor, OR7D4. So the team collected blood samples from the sniffers to see if genes could explain the difference in how androstenone was perceived. They found two variants of OR7D4 that were involved. People with RT/RT allele were more likely to think androstenone stinks, while those with RT/WM think it smells like vanilla. Also people with RT/RT were much more likely to pick up its smell in the first place (Nature, DOI: 10.1038/ nature06162). The findings were similar for men and women. Since androstenone is used by some mammals to communicate sexual and social information, the researchers want to learn more about how it affects human behaviour – especially in people unable to detect it.
PUNCHSTOCK
Who’s your daddy, baby trout?
Yeast cells that never forget MEMORY is not something you would normally associate with yeast cells, but with a genetic “circuit” inside them the cells can “remember” exposure to a molecule of the sugar galactose. A team led by Pamela Silver at Harvard Medical School in Boston created the circuit to show that biological systems could be engineered in the same way as mechanical ones. They used the galactose to trigger expression of a gene, the product of which turned on a second gene. This gene then acted to turn itself on again and again, creating an infinite loop. So after the galactose triggers the circuit, the second gene stays activated indefinitely, regardless of whether galactose is still present. In Silver’s circuit, the second gene produces a fluorescent molecule, so the cells glow green if they have been exposed to galactose. The circuit stayed active for at least nine generations and possibly many more. The system could be used to flag up cells that have been exposed to a particular drug or suffered DNA damage, Silver says (Genes and Development, vol 21, p 2271).
A MAN can smell as sweet as vanilla or a foul as a urinal – and it depends largely on a single gene in the sniffer. Androstenone, a steroid derived from testosterone, is found in higher concentrations in the urine and sweat of men than of women. Some people think it reeks, others think it smells sweet, and some can’t detect it at all. Leslie Vosshall at Rockefeller University in New York and her colleagues asked 391 volunteers to sniff 66 odours of either high or low intensity and rate their pleasantness. Two of the odours had a steroid component that activated a particular
www.newscientist.com