IVF used by some to avoid passing on genetic diseases to offspring
In vitro fertilization (IVF), widely known as a way to help infertile couples have babies, has taken on another remarkable use: It has become part of a procedure to help families keep from passing on serious genetic diseases to their children.
Parents who know they carry genetic mutations for muscular dystrophy, cystic fibrosis, sickle cell anemia, breast cancer, Huntington's disease, Alzheimer's and other inherited diseases can undergo IVF, where the mother's eggs are collected and combined with sperm in a dish, and another procedure called preimplantation genetic testing (PGT), in which embryos are screened for the particular mutation and only disease-free embryos can be implanted in the mother.
"I don't know why more people don't embrace these technologies," said Greg McGuire, 38, of Fishers, Ind., who was diagnosed with Becker muscular dystrophy when he was 8 years old, one of several family members with the inherited genetic mutation. Because it is passed down from mother to son - and his mother only had sisters - no one in the family knew anything about Becker or the effects of being a mutation carrier until McGuire's condition was discovered.
Once McGuire was diagnosed, his mother had her two other children tested, and his sister Maggie Camporese came up positive as a carrier for the genetic mutation. McGuire's brother does not have the mutation. It took years before they knew that Camporese could develop symptoms caused by the mutation that are unrelated to Becker: cardiomyopathy, or weakness of her heart muscle.
To stop this devastating family legacy, both McGuire and Camporese turned to assisted reproductive technologies to make sure they gave birth only to children who would not carry the Becker genetic mutation. A first cousin, a woman also identified as a carrier, similarly had two children using these modern techniques.
"This disease began with me, and it ends with me," said McGuire, whose condition has progressively weakened his leg and hand muscles so that he is now using a walker and scooter to navigate.
Since PGT was developed more than 20 years ago to screen for genetic abnormalities, it has been a source of some controversy among those who believe parents should not make life-altering decisions about what kind of child is born to them, whether that means the sex of a child or eliminating the possibility of a familial disease.
Yet the procedure has been transformative for many people with family histories of debilitating diseases, those who want to have children but fear what they might inherit in childhood - or later in adulthood. Because the testing happens before any embryo is implanted, the technology for many people is less fraught than discovering that an embryo growing in a mother's uterus is carrying a genetic mutation.
"When we started offering IVF services for any number of single gene mutations, people would question the ethics of allowing parents to make decisions about their unborn child," said Svetlana Rechitsky, president and director for PGT and IVF at Reproductive Genetics Innovations (RGI) in Illinois and an early pioneer in the technology. "But it is their decision to make."
Since the 1990s, her laboratory has conducted over 8,000 genetic tests for 700 different human conditions involving thousands of gene mutations. "People come to us to have healthy kids," she said. The techniques are not just used for identifying childhood-onset conditions but diseases that could take decades for the first clinical signs to develop. And no one knows whether there could be medical treatments by then to prevent or slow the course of those adult-onset diseases.
"We are not just testing for childhood-onset conditions," added Joe Leigh Simpson, an obstetrician-gynecologist and medical geneticist at Florida International University who is also clinical director at RGI. "The world has changed. Many more couples are turning to IVF and PGT to select an embryo for implantation so they are not faced with having a child develop clinical signs of a disease decades or longer down the line."
One of the earliest cases of using preimplantation screening for adult-onset heritable diseases occurred about 20 years ago when a woman in her 30s discovered she carried a genetic mutation for early-onset Alzheimer's.
She and her husband turned to Rechitsky and the then-new combination of IVF and PGT to identify embryos that would not carry the mutation that causes Alzheimer's.
The technique enabled the couple, who chose to remain anonymous, to create several embryos that testing showed were free of the genetic mutation, and they eventually had three children using those embryos.
Deeply impaired for years by Alzheimer's, the mother died in 2019.
McGuire understands the controversy surrounding these assisted reproductive technologies.
He recalls attending a muscular dystrophy meeting where he said he intended to defy his genetics and use IVF to have children without the disease. Some bristled at that, saying he should leave it to nature, not science.
Today, he watches his twin boys, born with the help of IVF, wrestle and play baseball. The muscles in his legs have grown too weak for him to get around on his feet. A scooter offers him protection from falls, which are now common.
Although men can't pass on Becker directly - since the mutation that causes it must be carried on two x-chromosomes, which only women have - McGuire could still pass his copy of the genetic mutation to any daughters, who could then potentially continue the cycle of disease if they have children. For that reason, McGuire and his wife used the PGT to select only male embryos.
He tells people who question his decision to select only sons: "It's not like I want to eliminate me. I wanted to get rid of this genetic disease. I knew that using in vitro fertilization and only selecting the male embryos meant that I would not have to teach my sons how to live with muscular dystrophy. If we had a daughter with the mutated gene, she would have been a carrier."
His sister Camporese and her husband opted for IVF and PGT to ensure the Becker mutation wouldn't transfer to their children.
Using hormone treatments, Camporese produced 31 eggs, of which 19 were fertilized. Only four of them reached the blastocyte stage that begins five days after gestation. Of those, two had the Becker mutation: one female and one male. The other two, one female and one male, were mutation free.
Her daughter Chloe is now 4; her son Lucas is now 2.
"I am extremely emotional and grateful," Camporese said.
- The steps of IVF and PGT
Here is how in vitro fertilization and preimplantation genetic testing are done:
With IVF, hormone treatments are used to trigger a woman's eggs to ripen and then be released from the ovaries. They are collected and fertilized in the lab with the husband's (or donor) sperm. Donor eggs can also be used.
The fertilized eggs are then allowed to grow into a five-day embryo.
At that point, genetic testing is done to identify any chromosomal problems or specific genetic mutations.
Only an embryo free of the known disease/mutation is selected for implantation into the woman's uterus and, hopefully, it will then grow into a baby.
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