REVIEW AND COMMENTARY ON RECENT LITERATURE IN REPRODUCTIVE MEDICINE
Here, the staff of THE REPRODUCTIVE TIMES offers commentaries on recently published articles, primarily chosen for educational value—in the positive but also in the negative—for clinical purposes, and for their potential translational values to clinical medicine when addressing basic science issues.
September 9, 2024. Revised with permission from the September CHR VOICE.
SUBJECT: Genetics and Genomics
Preimplantation genetic testing for aneuploidy (PGT-A) and polygenic testing of embryos (PGT-M)
To a degree it is rewarding to see how much the discussion over PGT-A has changed over the last year. Commentaries regarding the procedure are getting more cautious – can we say more skeptical?1,2 Even Chinese colleagues, in the past unanimous in their admiration of PGT-A, now report that PGT-A does not improve cumulative live birth rates of a cycle cohort of embryos3 (how could anybody ever believe that it did?).
Somewhat amazingly, people, however, still publish papers on PGT-A from cell free spent culture media not understanding that, if PGT-A does not work for embryo biopsies, how can it work for cell-free spent media? (One of course feels sorry for all the investors in start-ups built on the idea of non-invasive PGT-A). But even those still trying to prove the unprovable at least no longer claim to have discovered the nirvana of IVF.4
Apparently, some colleagues have, however, still not given up: At least the question for those is now “to transfer or not to transfer mosaic embryos,” as a recent review article pretended to do.5 But they finally at least admit that some embryos they for many years described as untransferable and discarded, can safely be transferred. Interestingly, it is usually the members of “special interest groups” in reproductive genetics–i.e., the supposed “experts”–who take the longest to understand.
But what we are still missing in the still ongoing PGT-A discussion is the answer to a very simple question: if something does not work, why are we continuing to use it?
Paradoxically, we may, finally, have discovered a real “medical indication” for PGT-A, the new abortion laws in some states which prohibit abortions after 6 weeks gestational age (as information for the politicians who passed these laws, this means 4 weeks after conception), when most women don’t even know yet that they have conceived. One wonders what will remain for our still unconvinced colleagues to convince patients to undergo PGT-A once the courts end the 6-week restrictions? We can see only one
remaining argument: the fear of the unknown and that is not a real indication.
And then there is PGT-M, increasingly offered by IVF clinics and genetic testing laboratories. And why shouldn’t they? In contrast to PGT-A, PGT-M at least offers a logical proposition in claiming to be able to predict whether a given embryo carries in its few cells a special predilection toward a polygenic disease, like diabetes or heart disease. That PGT-A does not work in accurately differentiating between chromosomal -normal and -abnormal embryos should have been understood 20 years ago. To find out whether PGT-M is even able to predict the risks for a given disease accurately enough to reach a logical decision on whether to dispose of an embryo, will take probably at least 20 more years.
And all of this does not even start to address all the ethical concerns that come with PGT-M6 and, after several European societies (including ESHRE), now the American College of Medical Genetics and Genomics has also become concerned about the rapid integration of PGT-M into clinical IVF.7
REFERENCES
1. Barret F, Molinaro T. Fertil Steril 2024;122(1):68-69
2. Cooper AR, Viotti M. Fertil Steril 2024;122(1):74-75
3. Hu et al., Fertil Steril 2024;122(1):121129
4. Nakhuda et al., Dertil Steril 2024;122(1):42- 50
5. Muñoz et al., Reprod Biomed Online 2024;48(3):103664
6. Sierman et al., J Assist Reprod Genet 2024;41:1719-1726
7. Grebe et al., Genet Med 2024;26(4):10105
How RNA has been underestimated
A very interesting recent article in Scientific American made the point that RNAs – and not as widely believed, DNAs – really rule our genome.1 The article presented with this headline based on in recent years discovered thousands of active RNA molecules which in a variety of ways have controlling functions in our bodies.
It all started once it became clear that the initial belief that only 1-2% of our DNA was “working” in producing proteins by using RNA as a messenger that travels to cells where those proteins then are produced. Under this false assumption, 98-99% of DNA was considered so- called useless “junk DNA.” This, however, raised the question, if only 1-2% of DNA was through RNA encoding proteins, what was the rest doing?
The answers started coming in as recently as in 2012, when papers first appeared in the literature suggesting that much more of the genome was “functional” in that a much larger percentage of DNA was producing so-called noncoding RNAs (i.e. does not encode proteins as mRNA does) but, still, engages with other molecules, in the process fulfilling a huge array of biochemical tasks. As the article notes, by 2020, the so-called ENCODE project had identified at least 37,600 noncoding DNAs in DNA stretches with instructions for RNA molecules that do not code for proteins (ncRNA). If correct – and final numbers are still awaiting confirmation – this would mean that non-coding DNA genes are almost twice as common as genes that code for proteins.
Once again nature has in this way created a thermostat effect for coding genes (we previously have used this analogy in explaining the effects of environmental factors on coding gene functions in a process called epigenetics; see also next section) because what ncRNA does is fine-tuning the functions of coding genes, in the process becoming the final determinator of whether protein is made and at what quantities. Unsurprisingly ncRNAs have also been found to play important roles in diseases. The argument that RNA – and not DNA –rules our genome, therefore, has considerable merit.
REFERENCE
1. Ball P. Scientific America, May 14, 2024. https://www.scientificamerican.com/article/ evolutionary-genetics-research-shows-rna- may-rule-our-genome/
Epigenetics
And since we are already talking about epigenetics, Mitinori Saitou’s lab at Kyoto University in Japan published another important paper in Nature magazine, reporting on the in vitro reconstitution of epigenetic reprogramming in the human germ line,1 which has remained a fundamental challenge. It resets parental epigenetic memories and differentiates primordial germ cells (PGCs) into mitotic pro-spermatogonia or pro-oogonia, thereby ensuring sexually dimorphic germ cell development for totipotency.
In the paper the authors report on epigenetic reprogramming and differentiation of pluripotent stem-cell-derived human PGC-like cells into mitotic pro-spermatogonia and -pro-oogonia, followed by extensive amplification (~>1010-fold). So-produced cells still failed to fully activate genes vital for spermatogenesis and oogenesis. The study, however, provided a remarkable framework for epigenetic reprogramming in humans and represented an important step forward in the potential ability to produce human gametes from stem cells sometime in the not-too-distant future.
REFERENCE
1. Murase et al., Nature 2024;631:170178
Female mosaic chromosome loss
As recently has become known as a side product of studies of age-related changes in clonal hematopoiesis, healthy adults experience with advancing age increased sex chromosome aneuploidies. In females this especially includes loss of one X chromosome (mostly the inactivated one), producing in peripheral leukocytes a mosaic XO (Turner syndrome) karyotype, usually in low single digit percentages. Because it primarily (though not exclusively) affects the inactivated X chromosomes and, likely, because the mosaicism affects only a very small percentage of cells (the percentages can vary between organs), patients are clinically generally not likely to be affected, though this mosaicism apparently increases the risk of developing leukemia. That observation alone, of course, opens the possibility that this kind of low-level X0 mosaicism may also have other medical effects (especially if the mosaicism affects the active X chromosome).
Since the X chromosome represents ca. 5% of the genome and contains several genes relevant to immune function and cancer susceptibility, one can also not preclude Turner syndrome-like effects on fertility at older ages in association with this age-dependent mosaicism, and we have anecdotally seen at the CHR over the years a handful of women with low functional ovarian reserve for age who during karyotyping surprisingly were found to demonstrate this kind of low-level mosaicism.
Valid associations with infertility have thus far, however, not been demonstrated. Interestingly, these X chromosome losses are in women much more frequent than losses in autosomes. Losses of the X chromosomes in men are much rarer.
All of this information is meant as introduction of a paper by a large number of authors from many
universities around the world that reported on genetic drivers and cellular selection of female mosaic X chromosome loss.1 Using data from 883,574 females from 8 biobanks, 12% demonstrates detectable X0 mosaicism in on average 2% of leukocytes. They, indeed, demonstrated an increased prevalence
of myeloid and lymphoid leukemias. They also demonstrated 56 common genomic variants associated with X0, implicating genes with roles in in chromosomal missegregation, cancer predisposition, and autoimmune diseases. A polygenic risk score including 44 allelic shift loci correctly inferred the lost X chromosome in 80.7% of mosaic X0 cases in the top decile.
REFERENCE
1. Liu et al., Nature 2024;631:134-141
Do we finally have a treatment for Huntington’s disease?
There are not many worse diseases than Huntington’s, an inherited neurodegenerative disease that causes nerve cells in the brain to break down and die. The disease usually becomes clinically symptomatic in middle age and causes involuntary muscle movements (chorea) and changes in cognition and behavior. After diagnosis, life expectancy is between 15-25 years. It is dominantly inherited from either mother or father (which means one parent usually has the disease) and women as well as men can get it.
A company based in the Netherlands called uniQure recently received FDA Regenerative Medicine Advanced Therapy Designation for an investigational gene therapy (AMT-130 for Huntington’s disease1) and preliminary reports on this treatment have been very positive, leading to a rise in the company’s stock price by over 60%.2
The gene therapy involved in the trial is designed to thwart production of a protein called huntingtin. It normally is helpful in brain function but, when it is mutated, becomes toxic to brain cells. The most recently published interim data suggest that AMT-130 is slowing progression of disease in a dose-dependent way, and so-far has data on 20 patients followed over 24 months. But this is just the beginning of a tall mountain to climb before a final judgment about this treatment can be made.
REFERENCES
1. UniQure. June 3, 2024. https://uniqure.gcs- web.com/news-releases/news-release-details/ uniqure-receives-fda-
regenerative-medi- cine-advanced-therapy-rmat
2. Bell J. Biopharma Dive. July 9, 2024. https://www.biopharmadive.com/ news/uniqure-huntingtons-gene-thera- py-
stock-neurofilament/720856/
SUBJECT: Infectious diseases
Is bird flu the next pandemic?
So far reported cases in the U.S. are sparse, but at least one report suggests that a good number of cases of bird flu are going undetected because it seems almost impossible to assume that only 13 cases have so far occurred in humans. In a small study of farmworkers’ blood samples two of fourteen supposedly never infected individuals demonstrated antibodies to the virus; that is 15.4%. Both had a history of respiratory complaints in the past. It, therefore, increasingly seems that the known cases are only the tip of the iceberg.1
And now, for a change, some good news: Studies suggest that some people, because of prior flu exposure, may be better protected from bird flu.2 The H5N1 strain that is now running the show turned out to be highly lethal in birds, but for now it does not seem to spread easily between people, though it clearly made the jump to humans and experts worry that it could easily become more contagious and spark a pandemic, especially since it is genetically very different from seasonal flu viruses circulating now or in recent years.
But here is some further good news, at least for some people: A 2016 paper in Science magazine found, after analyzing almost 20 years of severe infections caused by H5N1 and H7N9 flu strains, that people remain largely unaffected by flu strains that best matched their first exposure in life to a flu virus, while remaining vulnerable if a strain is mismatched with their first infection. This is important for people born
before 1968 because H5N1 infections were then predominant. In contrast, people born after 1968 can expect to be the lucky ones should a H7N9-like strain start circulating because this is when the H7N9 strain was prevalent.
Should the current bird flu expand, older people, therefore, can expect to be spared, and younger people can expect to be affected.
REFERENCE
1. Maxmen A. KFF Health News. July 31, 2024 2. Kozlov M. Nature 2024;631:491-492
COVID-19
For two reasons, the literature about COVID-19 has been overabundant over the last few months: A first was an unexpected summer wave of infections, when expert expected a flu-like late fall-early winter wave1,2 (so much again about COVID experts!). The second major reason was the increasing attention long COVID is receiving, which now is assumed to have affected at least 7% of all U.S. adults.3
Together, KP.3 and KP.3.1.1 now account for over half of all new cases in the U.S. and long COVID is still only relatively poorly understood.4 It now is, however, increasingly obvious that the immune system plays an important role,5,6 likely involving rogue antibodies.7 At least partially motivated by long COVID, The Lancet recently argued in an editorial that medicine must take persistent physical symptoms more seriously (rather than assuming they were supratentorial).8-10
And if all of this were not already more than enough, here is a little more bad news: As it turns out, those who have recovered from long COVID often suffer relapses or flare-ups not only from fresh COVID infections but also from other viral infections, like cold or flu viruses. Called “viral interreference” this phenomenon has also been seen in patients with HIV and other infections and is characterized by myalgias and the so-called encephalomyelitis/chronic fatigue syndrome.11
Finally, another excellent and important study in the American Journal of Obstetrics & Gynecology reporting on INTERCOVID-2022, a large prospective observational study between November 2021 and June 2022, when the omicron variant of the COVID virus was dominant, deserves mention: During that study period, newborns of unvaccinated mothers had an increased risk of neonatal death. Neonates of vaccinated mothers, in contrast, had a decreased risk of preterm deliveries and adverse neonatal outcomes. Because the protective effect of anti-COVID vaccines declines over time, the authors of this study recommend that to protect newborns, mothers should receive vaccine boosters no more than 14 weeks before any expected delivery.12
A lesson to be remembered in the current COVID wave, even though disease expression is milder than during omicron, is there may be another fall-winter wave on the way, and who knows how malignant the dominant strain(s) will be.
REFERENCES
1. CDC, National Wastewater Surveillance System. July 7-11, 2024. https:/www.cdc.gov/nwss/rv/COVID19-
currentlevels.html
2. Edwards E, Syal A. NBC News,July 25, 2024, https://www.nbcnews.com/health/health- news/covid-isolation-guidelines-
cdc-updat- ed-positive-cases-rcna163292
3. Fang et al., JAMA 2024;332(1):5-6
4. Perry Wilson F. Impact factor, Medscape, June 18, 2024. https://www.medscape.com/ viewarticle/we-wont-solve-long-
covid-until- we-decide-what-it-2024a10000b9g?form=fpf
5. Israelow B, Iwasaki A. Nature 2024;631:33-35 6.
6. Lindeboom et al., Nature 2014;631:189
7. Wong C. Nature 2024;630:798-799
8. Editorial. Lancet 2024;403:2565
9. Endresen Reme S. Lancet 2024;403:2569
10. Lõwe et al., Lancet 2024; 403:2649-2662
11. Ready T. Medscape Medical News. July 3, 2024. https://www.medscape.com/view article/cold-flu-virus-can-trigger-long-
covid-relapses-2024a1000cau
12. Barros et al., on behalf of the INTER COVID -2022 International Consortium. Am J Obstet Gynecol 2024; https://
doi.org/10.1016/j.ajog.2024.02.008; on line.
Are infections going bonkers on us?
Doesn’t it suddenly seem like viruses in our environment are out of control? Besides all the above-described viral problems, Dengue fever is reaching historical levels in the Americas, including in the U.S., where close to 3000 cases have been reported to the CDC (real numbers can, of course, be expected to be even higher), inducing the CDC to issue an official Health Advisory.2
A little-known virus, called Oropouche fever, linked to brain malformations and stillbirths, is also surging in Brazil,3 sounding very similar to when the Zika virus started in Brazil several years ago and caused fear in the whole hemisphere. And – though a bacterium and not a virus – even Chlamydia trachomatis, very frequently encountered in gynecology, is surging in the U.S., in Las Vegas demonstrated through wastewater surveillance to peak after holidays and major sporting events.4
And then there is the mosquito-transmitted eastern equine encephalitis, a viral disease with considerable mortality which has put all of New England on high alert, with some communities having established a curfew after 6pm. Another viral disease transmitted by mosquitos, West Nile fever paralyzed a teenager in Missouri and led to the hospitalization of infamous Dr. Anthony Fauci.
All of this raises the question whether this overabundance of infectious diseases is caused by pure coincidence, more virulent infectious agents, or weaker immune systems in the population. Time to find out!
REFERENCES
1. CDC, Cuevas E. USA Today. July 18, 2024.https://www.usatoday.com/story/news/ health/2024/07/18/dengue-fever-us-
symp- toms-transmission/74373970007/
2. CDC Health Alert Network, June 25, 2024.https://www.cdc.gov/locs/2024/06-27- 2024-Lab Advisory_CDC_Issues_Alert
_In- creased_Risk_Dengue_Virus_Infections_ United_States.html
3. Moutinho S. Science 2024.385(6707):355
4. Curtin C. Genomweb. Hune 17, 2024.https://www.genomeweb.com/infectious-dis- ease/wastewater-surveillance-chlamyd- ia-las-vegas-finds-peaks-after-holidays-major