Most of the genetic material in our cells is contained in the chromosomes which we inherit as a mixture from our mothers and fathers, but not all of it. A small amount of DNA is found in the mitochondria, the little structures in our cells that act like batteries. The only way to prevent the transmission of the genetic diseases of the mitochondria to date in couples who wants their own genetic children has been through the use of donor egg IVF. The problem is with donor egg is that the baby receives no genetic material from the the mother, and that only way around that problem would be to move the nucleus (which contains mom’s genetic material) from the mother’s egg into a donor egg. That process is called nuclear transfer and was banned by the US government because it involves cloning technologies. Now the FDA is considering lifting the ban to allow research into IVF with nuclear transfer for mitochondrial diseases. If successful, this would create babies with 3 genetic parents for the first time, a genetic mother, a genetic father and a mitochondrial mother. Quite a bit to ponder.
The use of Preimplantation Genetic Testing (PGD) enables fertility doctors to screen embryos for genetic diseases such as Cystic Fibrosis or Sickle Cell Anemia, permitting couples at high risk to avoid transmitting these diseases onto their children. PGD is done as part of an IVF cycle. A biopsy is taken when the embryo reaches the 8 cell or the blastocyst stage, and tested for the specific gene we are concerned about. This same technology can also be used to test for genes that do not necessarily cause a disease but put an individual at risk for other serious diseases. One such genetic mutation, called the BRCA 1 and 2 gene, puts affected women at very high risk for developing breast and ovarian cancer. The risk of developing these cancers in affected women is so high that many women (such as Angelina Jolie) chose to have their breasts and/or ovaries surgically removed just to prevent cancer. Since we know the genetic sequence of the BRCA mutation, it is possible to screen embryos for it, and prevent transmitting the gene onto one’s daughters. This article in the Wall Street Journal tells the story of a family who decided to go that route.
We know that in normal fertile couples it takes an average of 3 months to conceive. We also know that in successful IVF programs, most embryos will never implant. Even when genetic testing is performed on the embryos to eliminate the most common cause of IVF failure, 30% of embryos will still not stick. So, is the embryo sending some sort of message to the uterus that is OK to allow implantation or not? Researchers from the UK, discovered that embryos produce an enzyme called trypsin that facilitates the implantation process, but that embryos which are genetically abnormal produce less trypsin. This may be a way that embryos tells the uterus whether it ok to allow implantation. Perhaps a better understanding of this process may help develop ways to make IVF more successful.
It has been known for some time that couples suffering from infertility, including those who get pregnant using assisted reproductive techniques such as IVF, are more likely to have complicated pregnancies.: more high blood pressure, diabetes, miscarriages, preterm births and likely birth defects as well. This is true even with singleton pregnancies. What is not so clear is why this is so. Is it the patient population? Women who have infertility tend to be older and have more medical and metabolic problems. Is it the fertility medications such as clomid and injectables? Is it something in the process of IVF or IUI that causes problems? Researchers at Cedars Sinai Hospital in Los Angeles have received a large grant from the National Institute of Child Health and Development to help study the molecular events the underlie an early pregnancy after IVF. They will be looking at both genetics (the DNA in the chromosomes) and epigenetics (changes in gene expression that occur outside the chromosomes) to try to discover an explanation for these problems
In Reproductive Medicine we are comfortable in offering our IVF patients Preimplantatation Genetic Testing (PGD) and Screening (PGS) to prevent the transmission of genetic diseases and reduce miscarriages. Many of us in the field are concerned that there is also a slippery slope, and that advances in genomics may make it too easy to cross that line. Researchers in China are now trying to use these new tools to help couples select smarter babies. To many of us in the west this sounds like Brave New World, the novel by Aldous Huxley, but in China this idea is not so controversial. If their project is ultimately successful, it should raise enormous ethical concerns for all of us, and more importantly is the potential that our patients will insist on access to this technology regardless our ethical concerns.
Coenzyme Q-10 is a naturally occurring chemical found in the parts of the cells (mainly the mitochondria) that produce energy, and is thought by some to be helpful for certain diseases such as cancer, heart disease and some neurologic diseases. A recent study suggests that using Coenzyme Q-10 as part of IVF (In vitro fertilization) may increase the percentage of embryos that are genetically normal. We know that genetically abnormal embryos (which is actually most embryos transferred) explain most IVF failures and miscarriages, so anything that might increase the number of generically normal embryos may improve a couple’s odds for success. A word of caution: this study is too small to draw any conclusions. Further research is needed to determine if Coenzyme Q10 is effective or not.
This article which appeared recently in our local paper The Trenton Times (and originaly in the Star Ledger) profiled a laboratory we work with at Princeton IVF called Reprogenetics. The test they discussed called Array cGH involves removing some cells from embryos created during IVF and testing them to compare the amount of genetic material they contain from each of the chromosomes. It enables us to diagnose disorders such as Down Syndrome and Turner Syndrome, avoid putting back most abnormal embryos and select embryos for gender. In comparison to earlier methods it is a more comprehensive chromosome screening technique. Click here to read the article.