Pictured: me and my twin brother, just a few weeks old, synchronized napping somewhere in Medellin, Colombia.
Not pictured: our legs and feet don’t even come close to filling out those onesies…
I have an abiding interest in any and all research on the things our biological parents pass down to us — not just through genetics, but during pregnancy, and immediately after birth. I was born in a second-world ghetto, in a home for “troubled girls,” and adopted almost immediately by a first-world couple who flew in and kept vigil at my incubator. As soon as I was healthy enough, these new parents whisked me off to another country where they gave me an entirely different life than the one I was born into. My adoptive mom has been there almost from the start, in other words. And I never think of her as anything other than “mommy.”
But I do wonder a bit. About what happened in those hours (or maybe it was days?) before she arrived on the scene. About those very first moments of existence, when it was just me and this other woman (and ok, my twin brother too). This other woman who had created me, with the help of god-knows-who, and carried me around inside of her for 6.5-or-so months (I was premature). What did I take from her? I mean, obviously, half my genome. But what does that even mean? We learn more everyday about how genes are just a tiny part of the biological saga that makes us who we are. Their expression (or non-expression) is determined by a profoundly complicated array of factors, including the environments we live our lives in.
And what else besides genes, anyway?
Several news items from the past few days are either directly or tangentially related to that question. Posting them here.
Scientific American reports on a study published in the Journal of Neuroscience which found that, “the brain’s corticolimbic system, responsible for the regulation of emotion—and associated with the manifestation of depressive symptoms—is more likely to be passed down from mother to daughter than from mother to son or father to child.” The study was preliminary and correlational; it involved fMRI scans of just 35 families. But still, interesting:
Hoeft cites Dr. Seuss’s children’s book Horton Hatches the Egg—in which an elephant sits on a bird’s egg in lieu of its actual mother and a hybrid elephant–bird ends up hatching—as a cartoonish example of the inspiration for this research. The forces of both nature and nurture are at play. “What’s relevant is that it shows the profound influence of prenatal impact on offspring, which we often forget,” Hoeft adds. “Prenatal input is considered in the most severe cases, like alcohol and smoking. But it happens in everyone. A mom being stressed has an impact on her child’s outcome.”
Popular Science (and pretty much everyone else from NPR to the New York Times) reports on a study just published in Nature Medicine where researchers successfully transmitted mom’s microbiome (in this case the bacteria that populate her vaginal canal) to C-Section babies. This matters because:
that microbiome isn’t passed on if the baby is born via C-section, as are more than 30 percent of the babies born in the United States. Babies born this way have a higher incidence of asthma, obesity, and diabetes, and researchers think their lack of inherited microbiome might play a role.
The virus is transmitted through the bite of an infected mosquito. Scientists aren’t exactly sure just how, yet, but they know that if an infected mosquito bites a pregnant mother, the virus can be passed from her blood to the blood of her developing fetus, where it will go on to trigger a serious condition known as microcephaly. They are so certain of this link link that women in countries where Zika is endemic are being advised to avoid getting pregnant. But the virus is spreading quickly and not everyone had time to heed this advice. In Colombia (the country where I was born), more than 2,100 pregnant women are known to be infected with Zika right now.
Which means that our moms carry pieces of us inside of them, for life. (This is an older item, but I’m including it here because it’s relevant). Back in September the New York Times reported on a study published in Molecular Human Reproduction:
The new study suggests that women almost always acquire fetal cells each time they are pregnant. They have been detected as early as seven weeks into a pregnancy. In later years, the cells may disappear, but sometimes, the cells settle in for a lifetime. In a 2012 study, Dr. Nelson and her colleagues examined the brains of 59 deceased older women and found Y chromosomes in 63 percent of them. (Many studies on fetal microchimerism focus on the cells left behind by sons, because they are easier to distinguish from the cells of their mother.)
Experts now believe that microchimerism is far from rare. “Most of us think that it’s very common, if not universal,” Dr. Nelson said. But it remains quite mysterious.
In recent years, researchers have found many clues suggesting that microchimerism can affect a woman’s health. Tumors may be loaded with fetal cells, for example, suggesting that they might help drive cancer. Yet other studies have suggested that fetal microchimerism protects women against the disease.