This week in bizarre new forms of mammal reproduction: mice who have genetic material from two fathers but nary a mother, the next step in a progression of scientific efforts to get more creative with sex and reproduction.
“It has been a weird project, but we wanted to see if it could be done” in mice, says Richard Behringer, lead author of the study and a developmental geneticist at M.D. Anderson in Houston. [Wall Street Journal]
Weird, and also complex: The process requires several generations and some creative genetic trickery. To make it happen, Behringer’s team started with a single male mouse. Let’s call him Fred. Scientists took cells from Fred and transformed them into a line of induced pluripotent stem cells, which can grow into any kind of cell in the body. Normally, of course, a male’s sex chromosomes are X and Y. But when the researchers created these stem cells, some of them—about 1 percent—lost the Y chromosome through ordinary mistakes that happen in cell division.
Thus, the scientists had a batch of Fred-derived stem cells that had no Y, and thus were labeled XO cells. The next step was to take ordinary mice blastocysts—early stage embryos that had been conceived in the traditional fashion—and inject the XO cells into them. When this XO-injected embryo was implanted into a normal female mouse, she gave birth to offspring called chimera—what we call animals with two or more genetically distinct populations of cells. In this case the mouse possessed, in addition to the normal cells from its mother and father, some XO cells derived from Fred.
Finally, the last step. Some of the chimera mice would be female. And some of those females would have egg cells that derived from the XO cells. Let’s say a female mated with a typical male mouse, Tom, and conceived with an XO egg: The resulting little one, be it a male or a female, would have been born of a female but possess genetic material from two males: Fred and Tom, mice two dads.
Researchers said that with a variation of their technique, “it may also be possible to generate sperm from a female donor and produce viable male and female progeny with two mothers.” However, the study cautioned that the ability to replicate the findings in humans was a long way off. The “generation of human iPS cells still requires significant refinements prior to their use for therapeutic purposes,” the study said. [AFP]
A long, long, long way off might be a better way to put it. Even if one could imagine skirting the mad science aura and ethical quandaries of attempting such a thing, there are huge scientific hurdles to making it a safe way to conceive children.
When a human embryo inherits only one X chromosome (instead of one chromosome from each parent) it tends to die. Rarely, females are born this way, called Turner syndrome, and all are infertile. And scientists would also have to find a way to create eggs without creating human chimeras, which is ethically contentious. [Wall Street Journal]
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