Sunday Science had a brief hiatus last week, due to workload and family commitments, but we’re back this week instead, with gene edited humans, how your birth affected your brain, how MRSA can evade the immune system, brainwaves in a dish, and spiders that nurse their young…

A fascinating study has revealed that how you are born may affect your brain cell survival: a study in mice showed that those born by caesarean section showed greater brain cell death than those born vaginally, despite C-sections generally being considered less stressful for the infant. A certain amount of controlled cell death is an essential and normal part of embryo development, including in the brain, but this rise is concerning. It’s not certain what triggers the pause in cell death seen in those mice born vaginally – it could be due, ironically, to stress-induced maternal hormones, or to the microbiome in the vagina. C-sections are in many cases a life-saving intervention, and every woman should have the choice as to how she gives birth. However, in many countries such as the US, a rise in C-sections has in part been due to doctors unwilling to risk being sued if a vaginal delivery develops complications. This study underscores that the decision to perform a C-section must be an informed choice that is based on the welfare of mother and infant. Original study here (paywalled).

Some big news that has caused controversy in and out of the world of science is the announcement by He Jiankui, a Chinese scientist who claims to have used CRISPR gene editing technology in humans. This made largely negative headlines around the world (see here, for example) and for good reason. Twin girls have been born that carry a deliberately mutated version of CCR5, the cell surface receptor that HIV exploits to enter cells. Let’s be clear: this research was unethical, dangerous and pointless. Gene editing in human embryos is currently banned, and with good reason: the technology is incredibly new, with not nearly enough study into its safety and long-term effects. Moreover, CRISPR is know to have “off-target” effects – these children could have had another mutations introduced. Finally, his choice of trying to confer HIV resistance is frankly baffling. The best way to avoid HIV infection is through avoiding exposure, for which simple and effective methods exist (like condoms and not re-using needles). Additionally, HIV can be treated relatively successfully. It’s not completely known what other effects the CCR5 mutation has – but it is known that it makes you more likely to get flu. So this isn’t exactly helping these children as much as he thinks. If he had instead engineered a gene containing a mutation causing a fatal disease – like Huntingdon’s, for example – I could almost understand it. Condemnation from the scientific world has been universal. Let’s hope those children don’t suffer any long-term effects.

This week’s featured image is a slice through a brain “organoid” – a complex tissue grown in culture that resembles a simple, miniature organ. Researchers have been growing a number of these over recent years: they by no means are like complete mini brains. At best, they show some organisation of one part of the brain (e.g. the cortex), and a range of different brain cell types. They are proving useful for studying development and disease, however, being more complicated and realistic than cell culture, and more accessible (and ethical) than animal models, particularly when human stem cells are used. This particular advance is significant because for the first time, brain organoids have spontaneously produced brainwaves, and they’re rather like those seen in premature babies. And no, before you ask, they are nowhere near to consciousness, but they are certainly interesting.

What does Theresa May’s negotiated Brexit deal mean for science? Well, it’s still unclear – apart from the fact that it will never be as good as the deal with have in the EU. It would be business largely as usual during the transition period, but afterwards much remains to be negotiated, including our participation in huge EU funding streams like Horizon, and how easy it will be to have free movement of scientists. We will leave Euratom, leaving the future of the Joint European Torus near Oxford uncertain. Nature summarises what little is known here.

MRSA, or methicillin-resistant Staphylococcus aureus, is a “superbug” resistant to most antibiotics, notorious for causing potentially fatal hospital infections. But S. aureus, ordinarily, is a harmless bacterium that lives on our skin and doesn’t usually cause problems – but it can opportunistically cause infections if the host is injured or ill. What tips the balance between it being harmless or causing disease? Researchers are now pointing the finger at a surprising culprit: a virus that infects the bacterium itself. Phage DNA in the bacterium codes for an enzyme which alters the bacterial cell wall, allowing it to evade the immune system. Article here.

And finally, a spider mother that goes the extra mile – by feeding her baby spiders milk until they’re nearly adults. Maternal milk to feed offspring, once thought to be largely confined to mammals such as ourselves, is actually more widespread than we’d appreciated. Nevertheless, the length of time this spider gives its spiderlings milk is highly unusual. NOriginal (paywalled) study here.


Featured image

A slice through a brain organoid shows more mature cortical neurons on the outer edge of the structure. Credit: Muotri Lab/UC San Diego, via Nature.



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