Cells from male mice are able to be grown into egg cells and produce babies

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Image by Karsten Paulick from Pixabay
Image by Karsten Paulick from Pixabay

International researchers have bred baby mice using implanted egg cells that were once cells taken from male mice. The researchers took skin cells from the tail of mature male mice and turned them into stem cells - which are cells that can develop into a range of other cell types. By growing these stem cells in the lab, some cells begin to lose their Y chromosome, and duplicate their remaining X chromosome, meaning they slowly changed from having 'male' XY chromosomes to 'female' to XX chromosomes.  The researchers then got these stem cells to grow into egg cells. When fertilised and planted into a mouse uterus, about 1% of the embryos produced babies (7 out of 630). The researchers say this could help push fertility research forward, though there will need to be much more research into the impact of using this method to reproduce.

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From: Springer Nature

Stem cells: Functional egg cells generated from male mice (N&V) 

A method of converting male (XY) mouse stem cells into female (XX) cells to produce functional egg cells is published in Nature today. These egg cells were then fertilized and around 1% of the resulting embryos produced healthy offspring. The research provides insights that could facilitate fertility research.

Male and female gametes — sperm and oocytes (eggs), respectively — are produced from a type of stem cells known as primordial germ cells. Differentiation of these stem cells into gametes requires proper functioning of sex chromosomes. Previous research looking into the possibility of altering the sex of primordial germ cells has found the production of gametes either diminished or produced cells with low fertility. Katsuhiko Hayashi and colleagues report that using pluripotent stem cells (including both embryonic stem cells and induced pluripotent stem cells) might have the potential to produce more robust egg cells.

The authors took skin cells from the tail of mature male mice (with XY chromosomes) and turned them into induced pluripotent stem cells. These stem cells were grown in culture, a process that leads to the loss of the Y chromosome in rare subsets of cells (approximately 6% of the cultured cells), generating ‘XO’ cells. Further growth in culture of these XO cells induced duplication of the X chromosome. Treating cells with reversine, a drug that interferes with cell division, increased the efficiency of X chromosome duplication. The resulting cells with two X chromosomes were induced to differentiate into primordial germ cell-like cells and then into egg cells, which — when fertilized and implanted into a mouse uterus — produced viable offspring. Around 1% of the implanted embryos gave rise to pups (7 out of 630).

The authors note that a more rigorous evaluation of the impact of this method of converting male cells into female on genome integrity will be necessary for future research and application.

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Research Springer Nature, Web page
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conference:
Nature
Research:Paper
Organisation/s: Kyushu University, Japan
Funder: This study was supported in part by Grant-in-Aid for Scientific Research on Innovative Areas from JSPS (grants 18H05544 and 18H05545 to K.H. and 18H05549 to T.S.K.); by a Grant-in-Aid for Specially Promoted Research from JSPS (grants 17H06098 and 22H04920 to M.S.); by the Takeda Science Foundation (K.H.); by the Luca Bella Foundation (K.H.); and by a Grant-in-Aid from The Open Philanthropy Project (K.H.).
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