Mouse pups with same-sex par­ents cre­ated by Chi­nese sci­en­tists

Tehran Times - - SCIENCE -

Us­ing ad­vanced new gene-edit­ing tech­niques, sci­en­tists from the Chi­nese Academy of Sciences have pro­duced healthy, vi­able mouse ba­bies us­ing DNA taken from two moth­ers — without a fa­ther in sight.

Ac­cord­ing to a pa­per pub­lished in the jour­nal Cell Stem Cell, the team also cre­ated mice with two dads, but these off­spring only sur­vived for a cou­ple of days. The idea be­hind the re­search was to in­ves­ti­gate why it’s so chal­leng­ing for mam­mals of the same sex to pro­duce off­spring and how these bar­ri­ers can be over­come.

“Al­though an­i­mals have three dif­fer­ent re­pro­duc­tion modes, known as asex­ual re­pro­duc­tion, uni­sex­ual re­pro­duc­tion and sex­ual re­pro­duc­tion, mam­mals can only un­dergo sex­ual re­pro­duc­tion,” Qi Zhou, a se­nior au­thor of the study, told Newsweek. “How does this hap­pen? We got in­ter­ested in this ques­tion.”

While some rep­tiles, am­phib­ians, fish and other an­i­mals can re­pro­duce with one par­ent of the same sex, mam­mals do not have this ca­pa­bil­ity. Even with lab fer­til­iza­tion tech­nolo­gies, it is very dif­fi­cult to achieve.

The re­pro­duc­tion in mam­mals

“It had been thought that re­pro­duc­tion in mam­mals was pred­i­cated on re­ceiv­ing DNA from both ma­ter­nal and pa­ter­nal ori­gin as eggs and sperm have a dif­fer­ent yet com­ple­men­tary pat­tern of cod­ing,” Me­gan Mun­sie, Deputy Di­rec­tor of the Cen­tre for Stem Cell Sys­tems at the Univer­sity of Mel­bourne, who was not in­volved in the study, said in a state­ment. “This pat­tern­ing is re­ferred to as im­print­ing and is im­posed dur­ing sperm and egg de­vel­op­ment in mam­mals.”

As a re­sult, mam­mal off­spring that don’t re­ceive ge­netic ma­te­rial from both a mother and a fa­ther could ex­pe­ri­ence de­vel­op­men­tal ab­nor­mal­i­ties or may not be vi­able.

How­ever, the Chi­nese re­searchers were able to cre­ate pups solely from fe­male ge­netic ma­te­rial us­ing em­bry­onic stem cells—which are ca­pa­ble of turn­ing into any other cell—that con­tained only a sin­gle set of chro­mo­somes rather than the pairs that are usu­ally present in mouse cells.

The re­searchers deleted sev­eral re­gions of the genome in the hap­loid stem cells to re­move the im­print­ing genes. These mod­i­fied stem cells were then in­jected into nor­mal eggs (from an­other mouse) to cre­ate em­bryos that were trans­planted into a sur­ro­gate mouse.

Healthy pups

This re­sulted in the birth of 29 healthy pups, which lived to adult­hood and were even able to have off­spring of their own. The process was in­ef­fi­cient, how­ever, with only a small pro­por­tion of the 210 em­bryos used de­vel­op­ing into a pup.

Pre­vi­ously, re­searchers have pro­duced bi­ma­ter­nal mice—mice with two moth­ers— how­ever, the tech­nique used in this case was not as prac­ti­cal as the lat­est method and the off­spring dis­played sev­eral ab­nor­mal­i­ties.

To cre­ate the pups from only male ge­netic ma­te­rial, the team used a sim­i­lar process to how they cre­ated the bi­ma­ter­nal pups, al­beit slightly more com­pli­cated.

“Again, they in­jected the nu­cleus from ge­net­i­cally mod­i­fied male hap­loid stem cells, along­side sperm from an­other mouse, into eggs where the fe­male chro­mo­somes were re­moved,” Mun­sie said. The “re­sult­ing em­bryos were then al­lowed to de­velop in the lab for sev­eral days.”

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