Sunday, 17 February, 2019

Baby mice with two mothers produced by scientists

The bimaternal mice offspring- born to two mothers- later produced pups of their own The bimaternal mice offspring- born to two mothers- later produced pups of their own
Theresa Hayes | 15 October, 2018, 03:30

While the researchers, from the Chinese Academy of Sciences, also created mice from two dads these only survived for a couple of days.

"We tried to find out whether normal mice with two female parents, or even mice with two male parents, could be produced using haploid embryonic stem cells with gene deletions".

A healthy adult "bimaternal" mouse.

Despite having success with mice, Li said the same technique can not easily be applied to other mammals - such as humans - since each species has a unique set of problematic imprinted genes, and identifying these takes time.

"We were interested in the question of why mammals can only undergo sexual reproduction".

Dr Tim Hore, Senior Lecturer, Department of Anatomy, University of Otago, comments:Note: This paper directly relates to an active area of investigation in Dr Tim's lab, which includes understanding if parent-specific gene expression can be altered by new stem cell culturing methods.

This early approach led to the production of bimaternal mice (mice born of two mothers) in a previous study.

Then CRISPR-Cas9 gene editing - which uses DNA and RNA sequences culled from bacteria to pinpoint and delete human genes - turns off the genes that tell the remaining cells to be female, encouraging the egg to behave like sperm.

Experts said that the concept was intriguing for its possible application to human reproduction.

The procedure generated 210 embryos, of which 29 survived to be born as healthy, normally developed mouse pups.

Scientists achieved this feat by taking an egg from one female mouse and a special cell called a haploid embryonic stem cell from another, and combining them, according to the BBC.

Female pairs of mice produced viable babies, whose offspring went on to have their own progeny.

Using gene editing techniques, the researchers created the mice with two mothers by deleting three imprinting regions of the genome from haploid ESCs containing a female parent's DNA and injected them into their eggs from another female mouse.

Traditionally, problems arise when attempting to reproduce clones using DNA from single-sex parents as certain gene expressions can be muted depending on the sex of their donor "parent"; running the risk of doubling-up on certain gene expressions but missing out on other critical genetic markers necessary for healthy development.

The final step involved the transfer of the embryo along with some placental material into surrogate mothers, who maintained the pregnancies to full term.

They survived only 48 hours after birth, despite a complicated process of gene manipulation meant to eliminate abnormalities resulting from the same-sex reproductive process. One mouse got the egg in the other Kaplan embryonic stem cells.

The leading scientist of the research team, Dr.Wei Li, stated "this result showed us what is actually possible scientifically: the errors in the genetic coding can be eradicated from mice bred with two mothers".

"[It seems that] compared to bimaternal reproduction, more obstacles need to be crossed at the bipaternal reproduction barrier", Li says.