Using stem cell technology, Texas researchers have created mice who have two genetic fathers – an advance that could give same-sex couples their own genetic children one day.
Rather than have the usual chromosomal assemblage from a father (XY) and a mother (XX), these mouse babies carry daddy-only chromosomes from two males.
“It has been a weird project, but we wanted to see if it could be done” in mice, says developmental biologist Richard Behringer from the University of Texas M.D. Anderson Cancer Center.
Indeed. Birds, bees, storks, mice from Maine, fancy lab manipulations, the works.
Step 1: The researchers took cells from a male mouse (Dad #1) and reprogrammed them to act like embryonic stem cells.
Step 2: They grew these special ‘to-be-determined’ cells in a culture. Sometimes, when these cells are copied, a mistake happens in the cell division process, and about 1% of them will spontaneously lose their Y chromosomes.
Step 3: They took cells containing just Dad #1’s X chromosome (that is, XO cells) and injected them into early-stage embryos (which were created from an egg and sperm, the old fashioned way).
Step 4: They transplanted those embryos into a surrogate mouse mother, who gave birth to female mice. These baby girls were chimeras with cells from at least two genetically distinct cell types. Some of their eggs contain just the single X chromosome from Dad #1.
Step 5: When these chimeric girls came of age, the scientists mated them with a normal male (Dad #2).
And presto stork-o! A few weeks later, sons (XY) and daughters (XO and XX) were born who only have DNA from Dads #1 and #2.
The researchers say this double-daddy DNA technique could be used to combine traits of two males to possibly, one day, create offspring from either two fathers or two mothers. But it’s still a long way before this technique can be applied in humans. For starters, when a human embryo inherits just one X chromosome (rather than one from each parent), it will likely die. Sometimes, girls (XO) are born this way but cannot have children – this is called Turner syndrome. And then there’s the whole separate issue of human chimeras.
“If this is possible, then some day two men could produce their own genetic sons and daughters,” the authors write. It may also be possible to “generate sperm from a female donor (converting XX to XO to XY) and produce viable male and female progeny with two mothers.”
The study was published in Biology of Reproduction last week.
Image by Snaphappy#1 via Flickr
