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Genetic Linkage

Progress and a Setback in Treating Rare Genetic Diseases: Hemophilia A, CLN1, SMA, and DMD

In these strange days of the pandemic, it's easy to forget that people are still sick with the illnesses that we've always faced – and not just the common ones like cardiovascular disease and cancer. Times are particularly tough for the millions of people who have rare diseases.

 

Research continues into developing new treatments for rare diseases, despite the current difficulties, with some recent good news. But first, a setback.

 

Hemophilia A: Two More Years of Data Needed

 

On August 18, FDA ruled that a submission for approval of a gene therapy to treat severe hemophilia needs another two years of evidence to demonstrate that the treatment is really a "one-and-done." The agency is seeking data demonstrating "a durable effect using Annualized Bleeding Rate," a metric that the developer, Biomarin, claims had not been brought up prior to submission of the phase 3 findings.

 

Perhaps the extra scrutiny reflects the fact that treatment has been available since 1992 –recombinant clotting factor VIII. And gene therapy has been in the works for awhile. In fact, I interviewed the very first patient to receive gene therapy for hemophilia A, back in 1999. That trial used the same dangerous vector, a retrovirus, to deliver the gene that would kill Jesse Gelsinger later that year and derail the entire field.

 

 

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

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Genetics in 2016: Breakthrough, Breakdown, and Bridge

I dislike end-of-year "best of" lists, especially the "breakthroughs" that imply scientific discoveries and medical advances emerge from out of nowhere. Often they're the product of PR machines that select and then catapult certain research findings into the news releases that dictate the headlines.

WHAT MAKES SCIENCE NEWS?
Much of science news is released to journalists ahead of time (embargoed) so that we can investigate background and conduct interviews. This year, the Food and Drug Administration began offering news even earlier to select media outlets.  Read More 
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Genetic Sense and Nonsense

Genetic Linkage connects new research findings, based on the wiring of my brain after years of writing a human genetics textbook and lots of articles. Here, the linking of sense and nonsense.

The excitement of genetic research these days is when genome sweeps of people sharing a disease reveal possible responsible genes. That’s what happened when researchers at the Perelman School of Medicine at the University of Pennsylvania looked at genomic landmarks among 1,114 brains from people who had died of progressive supranuclear palsy (PSP), a form of dementia that affects movement.

PSP is a “tauopathy,” in which the dark gummy protein tau, of Alzheimer’s fame, smothers the brain. Compared to unaffected brains, the PSP brains differ in three genome neighborhoods, harboring three new
candidate genes that make sense: one impairs brain cells’ abilities to untangle misfolded proteins, another boots misfolded proteins out of cells, and a third may help wrap brain cells in insulating myelin. New drug targets!

In genetics nonsense is important too. A nonsense mutation inserts a “stop” right smack in the middle of a gene, like a period in the middle of a sentence. It shortens the encoded protein, causing some 1800 diseases. Ignoring a nonsense mutation can restore function, like saving a sentence truncated by an errant period with a stroke of white-out. The idea isn’t new – researchers discovered that bacteria can read-through nonsense mutations in the 1960s, and that certain common antibiotics, such as gentamicin, enable cells to read-through nonsense. Those drugs may provide old-fashioned (cheap) treatments for genetic diseases such as Rett syndrome. Alas, early attempts at treating cystic fibrosis, hemophilia, and Duchenne muscular dystrophy by suppressing nonsense mutations didn’t work because the antibiotic doses necessary would be toxic.

Now Yi-Tao Yu and co-workers at the University of Rochester report in Nature that they have invented a way to mimic antibiotic-mediated nonsense suppression. They’ve used a synthetic RNA to chemically tweak nonsense codons so that they are instead read as bona fide amino acids, in essence altering the genetic code. So far this approach, dubbed RNA modification, works in a test tube. But carefully-directed nonsense suppression holds enormous promise for correcting many genetic diseases. Stay tuned! Read More 
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