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Mouse placental cells contain dozens, even hundreds, of copies of genes key for pregnancy

19452628685_98cca6511f_zPeering inside a mouse placental cell is a bit like looking at a fun-house mirror. Rather than the standard two copies of each chromosome (mice have 20), there are as many as 900 copies of each genome segment.

What gives?

A team led by Julie Baker, PhD, associate professor of genetics, has found one clue: Genes that produce critical developmental proteins supporting the pregnancy are among the replicated regions. Baker, and first author Roberta Hannibal, PhD, published their results today in Current Biology.

"The placenta is a really fascinating organ," Baker told me. "It's a transient organ, so it doesn't need to invest that much energy in conserving the genome. What it really needs is to get proteins and (placental) attachment molecules up and running really, really fast."

And the best way to do that, rather than wasting energy cleaving the genome and producing a new cell with each division, may be to just jam many copies of the critical genes in one cell, Baker says.

This is the first time anyone has found genomic amplification of selective regions in mammals, the researchers write. That's because no one has looked before, Baker said: "The placenta has been largely ignored."

Next, she and her team are investigating the role of extra genome copies in human placentas. They're also studying the particular mouse placental cells they examined, called trophoblast giant cells, in the lab, Baker said.

Previously: Species-specific differences among placentas due to long-ago viral infection, say Stanford researchers, Scientists create a placenta-on-a-chip to safely study process and pitfalls of pregnancy and NIH puts focus on the placenta, the "fascinating" and "least understood" organ
Photo by Michael Pardo

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