Lifeboat Foundation: Safeguarding Humanity
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Category: genetics – Page 323

For more than two decades, I have been working to improve several staple food crops in Africa, including bananas, plantains, cassavas and yams. As principal scientist and a plant biotechnologist at the International Institute for Tropical Agriculture in Nairobi, I aim to develop varieties that are resistant to pests and diseases such as bacterial wilt, Fusarium wilt (caused by the fungus F. oxysporum) and banana streak virus.

[Editor’s note: Abdullahi Tsanni is a freelance science journalist based in Abuja, Nigeria.]

In 2011, my team and I created a set of tools, the only one of its kind in Africa, for changing DNA sequences so that we could develop genetically modified and genome-edited products in sub-Saharan Africa. In 2018, we pioneered the first application of CRISPR gene-editing technology to deactivate banana streak virus in plantains. This technology overcame a major hurdle in banana breeding on the continent, and is the first reported successful use of genome editing to improve bananas.

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The honeybee (Apis mellifera) is an important insect pollinator of wild flowers and crops, playing critical roles in the global ecosystem. Additionally, the honeybee serves as an ideal social insect model. Therefore, functional studies on honeybee genes are of great interest. However, until now, effective gene manipulation methods have not been available in honeybees. Here, we reported an improved CRISPR/Cas9 gene-editing method by microinjecting sgRNA and Cas9 protein into the region of zygote formation within 2 hr after queen oviposition, which allows one-step generation of biallelic knockout mutants in honeybee with high efficiency. We first targeted the Mrjp1 gene. Two batches of honeybee embryos were collected and injected with Mrjp1 sgRNA and Cas9 protein at the ventral cephalic side and the dorsal posterior side of the embryos, respectively. The gene-editing rate at the ventral cephalic side was 93.3%, which was much higher than that (11.8%) of the dorsal-posterior-side injection. To validate the high efficiency of our honeybee gene-editing system, we targeted another gene, Pax6, and injected Pax6 sgRNA and Cas9 protein at the ventral cephalic side in the third batch. A 100% editing rate was obtained. Sanger sequencing of the TA clones showed that 73.3% (for Mrjp1) and 76.9% (for Pax6) of the edited current-generation embryos were biallelic knockout mutants. These results suggest that the CRISPR/Cas9 method we established permits one-step biallelic knockout of target genes in honeybee embryos, thereby demonstrating an efficient application to functional studies of honeybee genes. It also provides a useful reference to gene editing in other insects with elongated eggs.

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Initially discovered in bacteria, CRISPR-based genome editing endonucleases have proven remarkably amenable for adaptation to insects. To date, these endonucleases have been utilized in a plethora of both model and non-model insects including diverse flies, bees, beetles, butterflies, moths, and grasshoppers, to name a few, thereby revolutionizing functional genomics of insects. In addition to basic genome editing, they have also been invaluable for advanced genome engineering and synthetic biology applications. Here we explore the recent genome editing advancements in insects for generating site-specific genomic mutations, insertions, deletions, as well as more advanced applications such as Homology Assisted Genome Knock-in (HACK), potential to utilize DNA base editing, generating predictable reciprocal chromosomal translocations, and development gene drives to control the fate of wild populations.

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Researchers in Australia are shining a spotlight on a safer delivery method for targeted CRISPR gene therapies—and they’re using literal illumination to pull it off.

Scientists and biomedical engineers from the University of New South Wales Sydney say they’ve developed a light-sensitive liposome that can ferry CRISPR molecules to specific sites in the body. When hit with LED light, the liposomes unleash their CRISPR payloads to hunt down faulty genes.

The CRISPR-Cas9 gene-editing tool consists of a guide RNA that homes in on a target in the DNA, and the Cas9 enzyme, which cuts the DNA much like a pair of molecular scissors. A slate of companies is exploring the technology to treat cancer and even blindness, but the therapy is traditionally delivered using viruses, which can themselves spur unwanted immune responses and other side effects.

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Senescence in cancer cells

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Sometimes, too much of a good thing can turn out to be bad. This is certainly the case for the excessive cell growth found in cancer. But when cancers try to grow too fast, this excessive speed can cause a type of cellular aging that actually results in arrested growth. Scientists at Duke-NUS Medical School have now discovered that a well-known signaling pathway helps cancers grow by blocking the pro-growth signals from a second major cancer pathway.

Inhibiting Wnt signaling with ETC-159 reactivates the hyperactive RAS-MAPK , causing cells to led undergo senescence. Many cancers are driven by activating mutations in the RAS-MAPK signaling pathway which triggers a cascade of proteins that directs cells to grow, divide and migrate. Mutations in proteins involved in this cascade can turn on genes that make this process go into overdrive, causing cells to grow out of control and aggressively invade other parts of the body. However, too much RAS-MAPK signaling causes cancer cells to prematurely age, and eventually stop growing—a process called cellular senescence.

Publishing in Cancer Research, the Duke-NUS research team found that another important and well-known biochemical pathway, the Wnt (pronounced “wint”) signaling pathway, allows some cancers to grow by dampening RAS-MAPK signaling.

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Scientists at the University of Liverpool have sequenced the genome of the bowhead whale, estimated to live for more than 200 years with low incidence of disease.

Published in the journal Cell Reports, the research could offer new insight into how animals and humans could achieve a long and healthy life.

Scientists compared the genome with those from other shorter-lived mammals to discover unique to the bowhead whale.

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In Project Apollo, life support was based on carrying pretty much everything that astronauts needed from launch to splashdown. That meant all of the food, air, and fuel. Fuel in particular took up most of the mass that was launched. The enormous three-stage Saturn-V rocket was basically a gigantic container for fuel, and even the Apollo spacecraft that the Saturn carried into space was mostly fuel, because fuel was needed also to return from the Moon. If NASA’s new Orion spacecraft takes astronauts back to the Moon, they’ll also use massive amounts of fuel going back and forth; and the same is true if they journey to a near-Earth asteroid. However, once a lunar base is set up, astronauts will be able use microorganisms carried from Earth to process lunar rock into fuel, along with oxygen. The latter is needed not just for breathing, but also in rocket engines where it mixes with the fuel.

Currently, there are microorganisms available naturally that draw energy from rock and in the process release chemical products that can be used as fuel. However, as with agricultural plants like corn and soy, modifying such organisms can potentially make a biologically-based lunar rock processing much more efficient. Synthetic biology refers to engineering organisms to pump out specific products under specific conditions. For spaceflight applications, organisms can be engineered specifically to live on the Moon, or for that matter on an asteroid, or on Mars, and to synthesize the consumables that humans will need in those environments.

In the case of Mars, a major resource that can be processed by synthetic biology is the atmosphere. While the Martian air is extremely thin, it can be concentrated in a biological reactor. The principal component of the Martian air is carbon dioxide, which can be turned into oxygen, food, and rocket fuel by a variety of organisms that are native to Earth. As with the Moon rocks, however, genetic techniques can make targeted changes to organisms’ capabilities to allow them to do more than simply survive on Mars. They could be made to thrive there.

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Viruses are tiny invaders that cause a wide range of diseases, from rabies to tomato spotted wilt virus and, most recently, COVID-19 in humans. But viruses can do more than elicit sickness — and not all viruses are tiny.

Large viruses, especially those in the nucleo-cytoplasmic large DNA virus family, can integrate their genome into that of their host — dramatically changing the genetic makeup of that organism. This family of DNA viruses, otherwise known as “giant” viruses, has been known within scientific circles for quite some time, but the extent to which they affect eukaryotic organisms has been shrouded in mystery — until now.

“Viruses play a central role in the evolution of life on Earth. One way that they shape the evolution of cellular life is through a process called endogenization, where they introduce new genomic material into their hosts. When a giant virus endogenizes into the genome of a host algae, it creates an enormous amount of raw material for evolution to work with,” said Frank Aylward, an assistant professor in the Department of Biological Sciences in the Virginia Tech College of Science and an affiliate of the Global Change Center housed in the Fralin Life Sciences Institute.

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Circa 2013

The Book of Genesis puts Adam and Eve together in the Garden of Eden, but geneticists’ version of the duo — the ancestors to whom the Y chromosomes and mitochondrial DNA of today’s humans can be traced — were thought to have lived tens of thousands of years apart. Now, two major studies of modern humans’ Y chromosomes suggest that ‘Y-chromosome Adam’ and ‘mitochondrial Eve’ may have lived around the same time after all1, 2.

When the overall population size does not change (as is likely to have happened for long periods of human history), men have, on average, just one son. In this case, evolutionary theory predicts that for any given man there is a high probability that his paternal line will eventually come to an end. All of his male descendants will then have inherited Y chromosomes from other men. In fact, it is highly probable that at some point in the past, all men except one possessed Y chromosomes that by now are extinct. All men living now, then, would have a Y chromosome descended from that one man — identified as Y-chromosome Adam. (The biblical reference is a bit of a misnomer because this Adam was by no means the only man alive at his time.)

Similarly, the theory predicts that all mitochondrial genomes today should be traceable to a single woman, a ‘mitochondrial Eve’. Whereas the Y chromosome is passed from father to son, mitochondrial DNA (mtDNA) is passed from mother to daughter and son.

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