In this newsletter we describe how experiments have shed light on the relationship between the tendency to associate small numbers with the left, and large numbers with the right, and differences between the two sides of the brain. Plus, the evolutionary origins of the Wnt signaling pathway, and why being sick makes you feel sleepy.
– Peter Rodgers, Chief Magazine Editor
Confocal image showing cytokine-response signaling (in magenta) in both the gut (middle) and brain (bottom right) of an adult female Drosophila. Image credit: Malita et al. (CC BY 4.0)
Humans tend to associate small numbers with the left, and large numbers with the right. Some researchers have proposed that this left-to-right ‘mental number line’ is associated with brain lateralization – that is, with differences between the left and right sides of the brain – but this has not been verified. Now, as highlighted in this Insight article, experiments on young domestic chicks have shown that brain lateralization and the left-to-right mental number line are related. The researchers exploited the fact the right eye of the developing chick points outward between embryonic days 18 and 21, while the left points inward, so exposure to light results in an asymmetry in how the two sides of the brain develop.
When we are sick, we often feel tired or sleepy. This is a deeply conserved response across species that helps the body recover. However, we still do not fully understand how the immune system communicates with the brain to make this happen. Now, based on experiments with fruit flies, research published in eLife reveals that this communication happens via small proteins called cytokines that are released by endocrine cells in the gut. The cytokines travel in the blood to the blood-brain barrier, where they activate a signaling pathway that promotes sleep during sickness. Under healthy conditions, however, the same cytokine signals help keep us awake.
Wnt signaling pathways have many important roles in cells and are highly conserved across the animal kingdom from fruit flies to humans. However, the evolutionary origins of the 19 Wnt proteins found in humans have remained mysterious. Now, as explained in this Insight article, researchers have discovered that Wnt proteins belong to a previously unknown superfamily of proteins – which they call "Lipocone" proteins on account of their shape and role in lipid binding. The Lipocones are organized into six families and three of the families – including the family that includes the 19 human Wnt proteins – are present in all three domains of the tree of life.
Many animals use a process called biomineralization to build hard structures such as shells and bones. Among the earliest animals to produce mineralized structures were sponges, but the genetic and molecular mechanisms involved in this process remain poorly understood. Now, researchers have discovered a new family of proteins – called calcarins – that have a central role in biomineralization in sponges, and have also shown that this process is similar in sponges and corals.
In the early embryo, a flat sheet of neural cells must roll up into a neural tube that will later form the brain and spinal cord. However, finding the genes that regulate this process in humans has been challenging because human early embryos cannot be studied for ethical and technical reasons. Now, as described in this Insight article, researchers have used a combination of stem cells and micropatterning techniques to generate an organoid model that resembles certain aspects of four-week-old human embryos, and then developed a genetic technique that can knock down single genes across the whole organoid. The researchers went on to use this platform to show that three genes - ZIC2, SOX11 and ZNF521 - are at the top of a hierarchy of genes that regulate the neural tube closure process.
Need a break from reading? Listen to our latest podcast and hear the authors of eLife papers discuss their research. Learn more about poison frogs and parental care, gut microbiomes and disease, queen ants and gene therapy, tapeworms and epilepsy, and the double-edged nature of trained immunity.
In February 1975, researchers gathered at Asilomar in California to discuss the threats presented by advances in biotechnology. The outcome of the meeting was a set of voluntary guidelines to ensure the safety of recombinant DNA technology. This, writes Matthew Cobb in the Los Angeles Review of Books, “led to a seismic shift in science, pharmaceutical research, and business practices, and eventually transformed the global economy.” Cobb goes on to discuss the Spirit of Asilomar, an event held to mark the 50th anniversary of the original meeting, with an agenda that included biological weapons, AI and biotechnology, and synthetic cells and the dangers of “mirror life”.
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