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Genetic Linkage

Older Siblings Made Possible Just-Approved Gene Therapy for Metachromatic Leukodystrophy

The Food and Drug Administration just announced approval of Lenmeldy (atidarsagene autotemcel), a gene therapy to treat the neurological condition metachromatic leukodystrophy (MLD). Available in Italy for three years, Lenmeldy (atidarsagene autotemcel), from Orchard Therapeutics, is groundbreaking, but comes at quite a cost – the $4.25 million price tag for the one-time infusion, and for the older siblings who contributed to developing the gene treatment, but were too sick to receive it.


An Ultrarare Neurological Condition


MLD affects the white matter in the brain, causing progressive loss of mobility and sensation, as well as intellectual decline and, ultimately, unresponsiveness.


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

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Cultivated Meat? Let Them Eat Snake

Biotechnology has solved many problems, from recombinant DNA and monoclonal antibody-derived drugs, to gene therapy and stem cell transplants, to RNA-based vaccines and genetically modified plants that resist diseases and pesticides.


In contrast, so-called cultivated meat has been, so far, a failure.


Joe Fassler's in-depth Opinion piece in the February 9 New York Times, The Revolution That Died on Its Way to Dinner, digests the unrealistic expectations, shortcuts, and glitches that have stymied what he envisions as "a high-tech factory housing steel tanks as tall as apartment buildings and conveyor belts rolling out fully formed steaks, millions of pounds a day — enough, astonishingly, to feed an entire nation."


Making Meat


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

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How the Human Lost Its Tail

In 1902's Just So Stories for Little Children, British author Rudyard Kipling famously explained curiosities of the animal kingdom: How the Leopard Got His Spots, How the Camel got his Hump, How the Rhinoceros got his Skin, to name a few.


Reading Just So Stories was one of my earliest memories of thinking like a scientist. I see them in articles on animals' oddities, such as How the Tabby Got its Stripes, in which I explored a molecular explanation for fur color patterns set in the fetus, from a report in Nature Communications.


Now new research published in Nature brings the just-so approach to the loss of tails among apes – including us.


Apes R Us


Whether or not taillessness was a liability as we evolved depends upon perspective and imagination. Would absence of a fifth appendage have made walking erect – bipedalism – easier? All mammals other than apes have tails, if only as embryos, which is the case for humans. Our tailbones are the remnants of tails.


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

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“Ordinary Soil” Revisits the Weedkiller and AgBiotech Story, While Feeding the Scientist-As-Nerd Stereotype

I love the spectacular symbiosis of my vegetable garden as harvest time approaches.


Beanstalks spiral up cornstalks, their tendrils teasing nearby tomato stems. Below, broad leaves protect ballooning squashes from the slugs that appear, seemingly from nowhere, after a rain, while providing water for passing furry creatures.


The synergism of a garden is an ancient and somewhat obvious idea. Many indigenous peoples honored the "three sisters" of corn, beans, and squash. My kids – three sisters – learned about the practice in grade school, and all recall the first meal that we grew: corn, beans, and squash.


Those memories returned as I read Alex Woodard's excellent novel Ordinary Soil.


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

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Designing a Better Probiotic. CRISPR Hubris?

Every morning I pop a Pearl probiotic. I try hard not to drop it, for the tiny, slippery yellow sphere bounces, is impossible to pick up, and cats love to bat them into unreachable domains.


A probiotic is, technically speaking, a population of live microorganisms that confers health benefits on the multicellular organism that they inhabit – such as a human. Probiotics alter the bacterial, viral, and fungal milieu within and on us – our microbiomes – in ways that ease digestion, counter inflammation, strengthen the gut lining, affect brain function, and even squelch tumors.


Each Pearl – or other variation on the probiotic theme – delivers billions of Lactobacilli to the twists and turns, nooks and crannies, of the human host's intestines, maintaining the microbial community within and keeping digestion flowing along smoothly. Other commonly used probiotics are Bifidobacterium and the yeasts Saccharomyces cerevisiae and boulardii.


Borrowed from Bacteria


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Transmissible Alzheimer’s Disease? Long-Ago Growth Hormone Treatment and a Legacy of Cannibalism and Mad Cows

A stylized slice through an Alzheimer's brain depicts amyloid-beta plaques in brown and tau tangles in blue.

Five people treated for pituitary dwarfism decades ago with human growth hormone (hGH) pooled from cadavers have shown cognitive decline reminiscent of early-onset Alzheimer's disease. Their dementia likely arose from transmission of the bits of amyloid-beta protein that lie behind Alzheimer's delivered along with the needed hormone, initiating a molecular chain reaction that led to brain effects decades later. Recombinant DNA technology has since provided a pure source of the hormone.


The cognition decline in these people is iatrogenic – caused by a medical procedure. The pooled hGH included infectious proteins, called prions (pronounced "pree-ons"), short for "proteinaceous infectious agent." The research appears in Nature Medicine from long-time prion researcher John Collinge, director of the University College London Institute of Prion Diseases, and colleagues.


The team followed 8 patients. Two of the five with clinical signs of Alzheimer's died during the investigation, and autopsy revealed the telltale brain changes. Two other patients had mild cognitive impairment, and the eighth had no symptoms. None had mutations that cause Alzheimer's disease, ruling out genetics as a cause.


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




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Chewing Gum Reveals Stone Age Diet and Disease

Did Barney Rubble and Fred Flinstone chew gum?


We can learn about life, past and present, anywhere we find DNA and determine its sequence. DNA Science has described intriguing sources of environmental DNA, aka eDNA: DNA in Strange Places: Hippo Poop, Zoo Air, and Cave Dirt and A Glimpse of the Ocean's Twilight Zone Through Environmental DNA.  


Human remains also harbor bits of DNA that can reveal how people lived long ago.


A recent report in PLOS ONE analyzes DNA from an adenovirus and a herpes virus discovered in preserved feces – coprolites – from 5,500 to 7,000 years ago at an archaeological site in Japan. The findings suggest that those people might have suffered from similar infections to humans today.


A second recent report uncovers clues in preserved chewing gum, reminding me of Flintstones gummy vitamins. (See A Brief History of Flintstones Vitamins). 


About 9,700 years ago, a group of teens were hunting, gathering, and fishing along the western coast of Scandinavia, north of what is today Göteborg. They chewed a concoction of hardened birch tar, the preserved lumps bearing bitemarks that suggest the stuff was used as a chewing gum of sorts, perhaps also as an adhesive in construction. An international research team published their findings on the Mesolithic gum in Scientific Reports.


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

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Multi-cancer Early Detection Blood Tests (MCED) Debut

A 52-year-old woman is at her annual physical exam. The physician assistant mentions he'll need two extra vials of blood for new cancer screening tests, one just FDA-approved, the other available as part of a clinical trial.


"But I already get mammograms and colonoscopies based on family history, and my husband gets his PSA screen for prostate cancer every year. So far, so good. Why do I need these new tests?" the patient asks.


"They can catch cancers much earlier, from DNA and proteins in your blood plasma, the liquid part. Including cancers much rarer than breast, colon, and prostate."


"Sure," says the patient, rolling up a sleeve. She'd be one of the first to have "multi-cancer early detection" – MCED – blood tests that zero in on clues that cancer cells shed into the bloodstream. A treatment begun early is more likely to work. An MCED blood test could be a gamechanger for people who haven't had cancer.

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CRISPR Tackles Diverse Single-Gene Conditions

The end-of-year FDA approval of the first CRISPR-based therapy, for sickle cell disease, came a mere dozen years after Jennifer Doudna and Emmanuelle Charpentier introduced the technology. They shared the Nobel Prize in Chemistry in 2020.


CRISPR is one of the better abbreviations in genetics. It's certainly more memorable than RFLPs, GWAS, and even SNPs, so euphonious that few reports – technical or otherwise – actually use the term "clustered regularly interspaced short palindromic repeats." CRISPRs are short DNA sequences, peppered with repeats, that latch onto DNA-cutting enzymes, commandeering and directing them to snip certain parts of a chromosome.


The genomes of certain bacteria naturally harbor CRISPR sequences. The microbes deploy them to dismantle the genetic material of infecting viruses, a little like an immune response.


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

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The 500th Blog Post at DNA Science: In Celebration of Vaccines

A few weeks ago, I noticed a surprising metric when posting my weekly DNA Science blog – at year's end, I'd hit #500!


That got me thinking. Looking back, which blog post was the most important? The answer came to me quickly – but it's not what I would have expected when I began more than a decade ago.


The Birth of DNA Science


When St. Martin's Press was about to publish my book about gene therapy in 2012, my agent urged me to start blogging. I needed to widen my audience beyond college students forced to buy my textbooks and readers of the articles I'd been cranking out since the 1980s.


The book that kickstarted DNA Science was The Forever Fix: Gene Therapy and the Boy Who Saved It. It's a history of gene therapy told through the voices of the patients, families, researchers, and clinicians behind the first FDA approvals, which didn't come until 2017.


I launched a website and blog, "Genetic Linkage," through the Author's Guild. Soon, an editor at Public Library of Science asked me to post Genetic Linkage at PLoS. We renamed it DNA Science.


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

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