P

ORTLAND, Ore. — The next great advance in fertility treatments may rest with five young monkeys in a lab outside of town.

Each of the five carries genes from three parents instead of two, because they were conceived using a novel — and controversial — gene therapy. They seem to be completely ordinary. But researchers are watching them closely to make sure they age normally, can reproduce, and have healthy children.

If so, the three-parent fertilization technique will likely be tried in humans, potentially helping women with certain genetic glitches give birth to healthy children. The same approach might also someday provide older women a chance to extend their fertility by freshening up their eggs with contributions from another woman.

advertisement

Such genetic manipulation sounds uncomfortably like “playing God” to some critics. But the scientist behind the fuzzy-haired monkeys pushes on, as he always has, in a career spent on the scientific frontier.

At age 54, Shoukhrat Mitalipov has a wrestler’s build and jet-black hair that stands up in spikes. He also has a fierce desire to get results in the here and now.

“You don’t want to say ‘My science will help 100 years from now.’ Maybe it will, but I want it while I’m here,” said Mitalipov, who directs the Center for Embryonic Cell and Gene Therapy at Oregon Health & Science University.

In interviews at his lab in downtown Portland and his office at the Oregon National Primate Research Center — where a stuffed monkey, a gift to the lab, is one of the few personal touches — Mitalipov laid out his vision for his research and discussed the uproar it’s caused, and what makes it all worthwhile.

The son of two teachers, Mitalipov was born in Kazakhstan, then part of the Soviet bloc, and went to college in Moscow. His first research lab was the only one in Moscow studying embryonic stem cells, back when the field was embryonic itself.

Now, he’s one of the few researchers in the world to study a type of genetic manipulation — essentially cloning — in hopes of eventually improving human health.

And he is a devotee of a genome that few others bother to explore: The mitochondria that provide energy — and their own 37 genes — to every cell in our bodies.

Mitochondria are particularly fascinating, Mitalipov said, because they are meticulous timekeepers.

“We came to this [mitochondrial] DNA as a genome that probably affects a lot more than we think,” he said with a thick accent and grammatical structure that still betray his Soviet upbringing. “Not only disease, not only aging. … It seems like there was a niche that no one studied … so we built a program around it.”

The path to ‘three-parent embryos’

In freshman biology, most of us learned that mitochondria are the “powerhouse of the cell,” floating around outside the nucleus and serving as living batteries.

The iconic drawings of cells show a few ovals with squiggles inside — but in truth, a normal, healthy cell might have upward of 1,000 mitochondria, each with its own DNA. These genes are inherited only from mothers. (The vastly bigger nuclear genome, of 20,000 genes, is a relatively even mix from mother and father.)

Newsletters

Sign up for The Readout: A guide to what's new in biotech

Please enter a valid email address.

Serious mutations in these 37 mitochondrial genes doom a fetus; slightly milder mutations can lead to muscle weaknesses, heart problems, and intellectual disabilities. Symptoms can turn up at birth or later in life. It isn’t possible to identify a mitochondrial disease in an embryo, so most women who know they are carriers of mitochondrial mutations decide not to have biological children.

Hoping to offer them a chance to have genetically related children, Mitalipov has pioneered a method dubbed “three-parent embryos.”

Step one: He takes the nucleus out of the egg of the mother-to-be.

Step two: He strips a donor egg of its nucleus.

Step three: He implants the mother’s nucleus into the donor egg. The resulting cell now contains DNA from two women: The mother’s DNA in the nucleus (where the bulk of genetic material resides) and the donor’s DNA in the mitochondria.

The egg is then fertilized in vitro, adding the man’s DNA and — if all goes well — creating an embryo.

So far, Mitalipov has tried this only on mice and a handful of monkeys. He is eager to try the technique to prevent human disease.

Potential patients are excited, too.

“It has given many mitochondrial disease families a lot of hope,” said MaryBeth Hollinger, a New York-based nurse navigator for the advocacy group MitoAction.

Of course, families want the procedure to be safe, Hollinger said, but they are willing to take some risks to avoid passing on a devastating disease to their children.

‘Too many question marks’

Both Mitalipov and his friendly rival in the field, Dieter Egli of the New York Stem Cell Foundation, maintain that changing an egg’s mitochondrial DNA is different from tinkering with the bulk of the genetic material in the nucleus.

And Mitalipov believes his energetic young monkeys — Mito, Tracker, Spindler, Spindy, and Chrysta, all rhesus macaques — are living proof that the technique is safe.

The UK government approved use of the three-parent technique in humans last year, though no research group has yet done it. In the United States, however, Congress is contemplating banning the approach, known as mitochondrial replacement therapy.

And some scientists worry it’s too soon for human trials.

“If someone were to proceed with it now, my own view is that’s probably irresponsible. There are so many question marks. I just think it’s premature,” said Paul Knoepfler, a stem cell biologist at the University of California, Davis.

At minimum, Knoepfler said, the offspring of these “three-parent” families should be limited to males, so they can’t pass on their mitochondria to the next generation.

Despite his hesitations, Knoepfler said he doesn’t doubt that Mitalipov’s heart is in the right place, and praised him for continuing the research.

“I appreciate the fact that he’s willing to tackle some really tough things,” Knoepfler said. “He’s been willing to take risks, to really push and invest time and energy into this cool stuff that almost nobody else has been even trying to do until just recently.”

Other peers of Mitalipov also respect his work, calling him a serious scientist who isn’t afraid of controversy, but also isn’t out to feed his own ego. They uniformly refer to him as “nice,” though none said they knew him well enough to describe him further.

For his part, Mitalipov said he has no real hobbies outside of work and his family. He used to play blues guitar, but now is excited to listen to his favorite music on Pandora. His teenagers showed him how to work the app so he can listen to Stevie Ray Vaughn during his commute.

“I cannot keep up with all this technology,” he said.

A delicate touch on egg cell surgery

It takes a very delicate hand to do intricate surgery on egg cells, and in Mitalipov’s lab, only he and one other researcher can do it. He said his eyes are not as good as they used to be, so his colleague recently came in to do research on a freshly donated human egg — just a week after giving birth to her own baby.

Mitalipov learned the techniques in Moscow and then honed them as a young PhD student at Utah State University.

His first project was aimed at understanding why embryonic stem cells are essentially immortal. “The female germline doesn’t have a clock — it’s always zero,” he said. “That’s why when we get mitochondria from our mother, it’s set at zero, not her age.”

An early mentor was Keith Campbell, then in the process of cloning Dolly the sheep — born 20 years ago this week. The young Mitalipov, who still had just a rudimentary command of English, met Campbell at a conference in Utah, and was enthralled. The senior scientist was generous with his time and his tips, and the two bonded over their common interests in science and beer.

His whole career, Mitalipov said, has consisted of tinkering with the nuclear transfer techniques that Campbell, who died a few years ago, developed in the mid-90s.

“My clinical goal was to use some of the basic knowledge to improve human reproduction,” Mitalipov said. “The IVF platform can be used now to remanufacture gametes, to treat infertility, but also as a platform for gene therapy, which is probably where the future will go.”

Macaques
Spindler and Spindy, two of the monkeys created from the DNA of three parents. Oregon Health & Science University

Red flags from recent studies

Mito, Tracker, Spindler, and Spindy are now 7; Chrysta has turned 4. Mitalipov said he’s been asked by the US Food and Drug Administration and the UK government to follow them as they age to make sure they remain normal.

He also hopes to breed Chrysta to see how her offspring fare, and to study the mitochondrial DNA she passes on to them.

Monkeys don’t reproduce until they’re 6 or 7 — and they live 15 to 20 years in captivity — so it will be a long wait to figure out if these animals have any health problems.

“So far, nothing,” Mitalipov said.

Research in mice suggests there could be some reason for concern.

A study published last month in Cell Stem Cell found that even if 99 percent of a mother’s flawed mitochondria were removed through mitochondrial replacement, the remaining 1 percent could still be passed down to future generations and expand to essentially take over the mitochondrial genes.

Another study out this week in Nature shows that mice whose nuclear and mitochondrial DNA come from different mothers — in other words, those with three genetic parents — age faster than normal mice, “resulting in profound differences in health longevity.”

The studies don’t concern Mitalipov. He focuses on the successes.

But he struggles to keep his cutting-edge work funded; he’s entering an American research competition, hoping to win enough money to eventually breed Chrysta and study the third generation of offspring. He jokes about bringing pictures of irresistibly cute monkey babies to convince the judges.

He’s also keeping a wary eye on congressional debate about whether to allow mitochondrial replacements in humans.

“We’d like to be the first people to do it, since we were the first people to do it in [monkeys],” said Dr. Paula Amato, a fertility specialist and obstetrician at OHSU who collaborates with Mitalipov.

There’s simply no way to eliminate all the risks before trying the technique in people, she said.

“We’ve done everything we can to show that it likely would be safe, but ultimately you never know until you do it,” Amato said.

A humble rock star

Mitalipov remains fascinated by the area of a woman’s egg cell that falls outside the nucleus. It’s filled with mitochondria, fluid, and the secret ingredients of humanity.

“It’s a woman’s egg cytoplasm that gives life, not its nucleus,” he said. Scientists still don’t know what makes a good or bad egg, but it’s clear that “with aging, something goes wrong with cytoplasm activity.”

That’s why older women are less fertile than younger ones. “Women in their 40s, their eggs, no matter what you do, doesn’t seem like they’re producing a viable embryo,” he said.

But an older woman can successfully carry a pregnancy from a younger woman’s egg. “So everybody knows it’s an egg problem, but people don’t realize which part of the egg is the problem,” he said. “In my lab, we think it is the maturation of the cytoplasm that is the major issue.”

The mitochondria we get from this cytoplasm may also determine how long we live.

Mitalipov believes his rising blood pressure has something to do with the aging of his mitochondria. After about age 50, mitochondrial mutations rise; after 70, they go through the roof. Mice that are bred to have lots of these genetic errors die substantially sooner than normal mice.

Newsletters

Sign up to our Weekend Reads newsletter

Please enter a valid email address.

The best way to rein in these glitches is to maximize the number of healthy mitochondria, Mitalipov said. Exercise may do that when we’re young, but probably won’t do much to reverse damage once it’s done, he said. He takes “a whole bunch of antioxidants,” hoping to improve his mitochondrial health, though he’s not sure it will make a difference.

The more he learns about mitochondria, the more he’ll be able to help people live long, healthy lives, Mitalipov said.

Amato, his obstetrician colleague, said Mitalipov deserves more credit for such vision than he’s gotten.

“He’s a very understated kind of person,” she said. “He’s sort of a humble guy and goes about his business and doesn’t have to be the rock star. But he really is.”

Leave a Comment

Please enter your name.
Please enter a comment.

Sign up for our Morning Rounds newsletter

Your daily dose of news in health and medicine