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Genetic Linkage

When a Disease is Genetic but not Inherited: Bea Rienhoff's Story

Hugh and Bea Rienhoff (credit: Leah Fasten)
Genetics is the study of genes, DNA, and variation; heredity is the passing of inherited traits from parents to offspring. Families with one member, typically a child, who has a collection of unusual symptoms that don’t fit any clinical diagnosis may in fact have a genetic disease – but one that arose spontaneously in the child, rather than having been inherited from carrier parents.

Exome sequencing is helping to solve these genetics-but-not-heredity mysteries. The story of one little girl and her father’s efforts to find her mutant gene, and how the tale wove in and out and now back into my human genetics textbook, illustrates the evolution of personalized genomic medicine.

THE BEA PROJECT
When Hugh Rienhoff first saw his daughter Bea, born in December 2003, he knew something was wrong. Her long feet, clenched fingers, poor muscle tone, widely-spaced hazel eyes, and a facial birthmark might have been just peculiarities to anyone who wasn’t also a physician and a geneticist. Read More 
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Second Gene Causes Retinoblastoma

This little boy has heritable retinoblastoma. The mutation originated in him, so he didn't inherit it, but he can pass it on.
In a list of famous genes, RB1 would probably be #1. It’s the tumor suppressor gene whose “loss of function” is behind the childhood eye cancer retinoblastoma, and that Alfred Knudson investigated to deduce the 2-hit mechanism of cancer.

In 1971, the idea that the normal function of a gene could be to prevent cancer was revolutionary. Now a study in Lancet Oncology finds that an amplified oncogene can cause the eye cancer too, with just one “hit.” Read More 
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Rare Diseases: Unicorns, Not Zebras

The past and future of gene therapy: Corey Haas and Hannah Sames autograph books at the Schenectady Library.
“When you hear hoofbeats, think horses, not zebras.”

Every doctor-to-be hears this mantra. Rare Disease Day, February 28, celebrates the 7,000 or so diseases that are zebras, each affecting fewer than 200,000 people.

Giant axonal neuropathy (GAN) isn’t a zebra, but a unicorn. Eight-year-old Hannah Sames inherited one mutation from each of her parents in a gene that encodes a protein called gigaxonin. As a result, the axons of her motor neurons are slowly filling up with haphazardly-arrayed intermediate filaments. The cells bulge, blocking the messages to her muscles. She’s one of only 50 in the world known to have GAN. But if all goes according to schedule, Hannah and several other youngsters are going to have gene therapy to correct the disease. Read about it at Hannah’s Hope Fund.

Two years ago, at the annual meeting of the American Society of Gene and Cell Therapy in Washington, I had the honor of watching Hannah’s marvelous mom Lori as she watched a child helped by gene therapy – Corey Haas, whose story bookends a brief history of the technology in "The Forever Fix: Gene Therapy and the Boy Who Saved It".

Here’s an excerpt, for Rare Disease Day. Read More 
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Hidden Meanings in Our Genomes – And What To Do With Mendel

Gregor Mendel: should he stay or should he go (in textbooks)? (National Library of Medicine)
Summer reading for most people means magazines, novels, and similar escapist fare, but for me, it’s the American Journal of Human Genetics (AJHG). Perusing the table of contents of the current issue tells me what’s dominating this post-genomic era: information beyond the obvious, like a subtext hidden within the sequences of A,  Read More 
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Gavin's Story Revisited -- Childhood Blindness Mutation Discovered

Gavin's mutation (in the NMNAT1 gene), discovered 8 months ago, was announced July 29, in Nature Genetics.
I'm rerunning this blog post from November, because Gavin's mutation was announced today -- the first step towards a gene therapy! Tomorrow I'll run my blog on the discovery that is now on Scientific American blogs.


In a hotel ballroom on the campus of the University of Pennsylvania on a midsummer Saturday in 2010, an unusual roll call was under way at the Family Conference for the
Foundation for Retinal Research
. Betsy Brint, co-head of organization, was calling out what sounded like code words – CEP290,  Read More 
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Anticipation

Jordan and Hailey Kohl. Spinocerebellar ataxia type 2 affects several members of their family, including Jordan.
“Anticipation .. is keepin’ me waitin’,” sings Carly Simon in her song made famous in a ketchup commercial. But “anticipation” in the genetic sense is just the opposite of Carly’s croon – it means a disease that begins earlier with each generation.

Doctors once blamed patients for anticipation, as if people with sick older relatives could worry themselves into suffering similarly. Then, in 1991, discovery of a new type of mutation explained the curious worsening of fragile X syndrome: an expanding triplet repeat.  Read More 
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Gene Therapy Subverted in New Dystopian Novel, “When She Woke”

I don’t usually take too kindly to the evil geneticist stereotype in fiction, but I can’t resist a good dystopian novel. "When She Woke," by Hillary Jordan, is the perfect book  Read More 
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