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Genetic Linkage

Rare genetic disorder homocystinuria can cause strokes, seizures and death. A ‘genetic glitch’ in blind cavefish offers hope for a treatment

The discovery of a gene behind the absence of eyes in Mexican cavefish may suggest a new way to treat a rare but debilitating disease in humans – homocystinuria.

 

In homocystinuria, deficiency of an enzyme (cystathionine beta-synthase a, or CBS), blocks the breakdown of two protein building blocks, the amino acids methionine and serine, while a third, cysteine, diminishes. An array of signs and symptoms result.

 

To continue reading, go to Genetic Literacy Project, where this post first appeared.

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Gastruloids Stand In for Early Human Embryos

Remember human embryonic stem (hES) cells? We don't hear much about them anymore. So I was surprised to see an application of the controversial cells to grow human embryo-like structures in a recent issue of Nature.

 

Human embryonic stem cells are not, and have never been, taken from human embryos. Instead, they're grown in laboratory glassware from cells that are sampled from the inner cell mass. The "icm" is the stage when the prenatal human is a smear of cells hugging the interior of a hollow ball of cells, the blastocyst. The icm expands and contorts, layering itself into embryohood, as the blastocyst gives rise to the nurturing extra-embryonic membranes.

 

In 2009 the National Institutes of Health issued guidelines forbidding researchers from using government funds to derive new hES cells, but the agency provides nearly 500 already-existing hES cell lines. They represent dozens of inherited diseases, from cancers to neurological conditions to connective tissue disorders – quite an eclectic list.

 

To continue reading, go to my blog DNA Science, where this post first appeared.

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A Tale of Two Clinical Trials: Gene Therapy for a Rare Disease and a Vaccine for COVID-19

Encouraging preliminary findings in a phase I clinical trial for a COVID-19 vaccine were widely reported as soon as the paper appeared in The New England Journal of Medicine July 14. Coverage of the recent deaths of two boys in a clinical trial to test a gene therapy for a rare, devastating muscle disease were more under-the-radar.

Comparing the two very different scenarios illuminates the scientific rigor behind the clinical trial process.

 

The boys had X-linked myotubular myopathy. MTM affects 1 in 50,000 male births. Seventy-five percent of boys die in weeks or months of respiratory failure; average life expectancy is 29 months. Given that prognosis, taking the risk of an experimental treatment in a clinical trial makes sense. Parents of participants as well as physicians know that children can die during the trial, due to the disease or to toxicity at higher doses of a treatment.

 

In contrast, volunteers in a clinical trial to evaluate a vaccine are healthy.

 

Although comparing MTM gene therapy and a COVID-19 vaccine is a bit of apples and oranges, those fruits are in the same bin in terms of progression through the three phases of development of a new treatment or preventative:

 

To continue reading go to my blog DNA Science, where this post first appeared. 

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Two Views of Leeches, A Century Apart

Two genome sequences of the European medicinal leech Hirudo medicinalis have just been revealed in a pair of papers, and the unexpected complexity may translate into new anti-coagulant drugs.

 

Some quick leech factoids: Of the 650 species, about 20 percent live in the ocean, where they feed on fish. The longest leech known extends 18 inches. A leech has 32 distinct brains and the genome extends about 230 million base pairs of DNA. Leeches belong to the same phylum as the earthworms, Annelida.

 

A Long History

 

The animals practice "hematophagy" – literally "eating blood." A leech will gorge itself to five times its weight until, satiated, it drops off its victim. The jaws are strong enough to penetrate a hippo's hide. Leeches have been used medicinally in bloodletting for thousands of years.

 

To continue reading, go to DNA Science, where this post first appeared.

 

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How an Antibody Cocktail Against COVID-19 Channels the 3 Stooges – But is a Great Idea

"You imbecile!" bellowed Moe Howard as he stuck a finger up the nose of Curly. Moe the bully would often flick his hand across an unsuspecting face or deliver a two-pronged eye poke to distract from a simultaneous, more serious blow, elsewhere.

 

Moe, Larry, and Shemp/Curly/Joe were the various incarnations of The Three Stooges, the famed comedy team, with roots in vaudeville, who made films and TV shows from 1922 until 1970. Many of us growing up in the sixties loved them, while many of our parents didn't. The 2012 film didn't do the original three idiots justice.

 

An image of Moe poking Curly popped into my head while reading two new papers in Science that report teaming antibodies to tackle SARS-CoV-2, the virus behind COVID-19.

 

The papers describe the basis of two clinical trials that biotech company Regeneron is conducting to assess a pair of antibodies that work together, binding the viral spike protein where it contacts the human receptor (ACE2) and gains entry into our cells, but at different sites within the "receptor-binding domain." One antibody is a distractor of sorts, like Moe's finger-up-the-nose.

 

The key to the technology is in the coupling. "Our work inventing novel antibodies has shown that individual antibodies, no matter how good, are likely not enough against the devastating virus that causes COVID-19 and the ways it seeks to 'escape' being neutralized," said George D. Yancopoulos, MD, PhD, Co-Founder, President and Chief Scientific Officer at Regeneron.

 

An antibody cocktail – pitched as "antibody medicine" – provides short-term, passive immunity, as opposed to the lasting active immunity of a vaccine, in which the body learns to manufacture its own antibodies. The Chinese proverb "Give a man a fish and you feed him for a day. Teach a man to fish and you feed him for a lifetime" makes the distinction: an antibody cocktail is a fish, a vaccine the ability to fish. Both are needed desperately right now. Antibody protection would last weeks or months.

 

Viral Resistance is a Natural Consequence of Evolution

 

 

To continue reading, go to DNA Science, where this post first appeared.

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