Brain mosaics and neurodegeneration

“You are a slightly different genetic version of yourself today from yesterday, and will be different yet again tomorrow.”—Roxanne Khamsi

“Each neuron really is a beautiful and unique snowflake”—Ed Yong

Roxanne Khamsi is one of the leading life science journalists, a contributing writer at The Atlantic, recognized with multiple awards for notable publications. Her new book is entitled BEYOND INHERITANCE. It tells the story about us all being genetic mosaics, chock full of somatic (acquired) mutations, and the implications of those mutations for our health. The myth of a single genome, carbon copy, master blueprint, but instead a dynamic, shifting mosaic in constant internal evolution.

And here’s the back cover. I was delighted to endorse this book, and reread it to prepare for our podcast. It’s extraordinary and mind-bending.

Here are the topics we covered:

—The Math. 330 billion cells of our ~37 trillion turnover each day, which yields trillions of mutations per day.

—Cellular competition. Winners and losers of an “endoevolution,” Darwinian selection inside us whereby healthy or super-fit mutated cells can crowd out the unfit ones.

This was theorized in 1881 in a book THE STRUGGLE OF PARTS, by Wilhelm Roux

which led to Friedrich Nietzsche’s famous quote “Uniformity is pure delirium.”

—Single-cell sequencing. How this field catapulted forward owing to the ability to zoom in on genomic mutations at the cellular level.

—Cancer chemotherapy overkill. The routine scorched earth, carpet bombing approach can promote resistance and deleterious mutations, leading to an adaptive strategy of leaving some cancer cells behind, as has been shown to be effective in prostate cancer for improving survival.

—The immune system somatic hypermutation. B cells have the theoretical capacity to produce 1 quintillion unique antibodies (a million trillion). If this weren’t possible, we could die from a common cold. In the Covid pandemic, even before the Omicron variant appeared, Covid booster shots induced hundreds of unique antibodies with neutralization capacity against Omicron. The anticipatory “Red Queen” effect.

—Autocorrection of mutations. They can revert, cure a rare genetic disease from within. It can be considered “Natural Gene Therapy.” Example below of a skin condition Epidermolysis Bullosa with revertant mutations (→ normal skin appearance)

—Different role of acquired mutations through the lifespan. Examples: At embryonic stage, Lines of Blaschko (Image below). In mid-life endometriosis, and in older adults Loss of the Y chromosome (LOY) and Clonal Hematopoiesis of Indeterminate Potential (CHIP). Note these 2 somatic mutation clone conditions are associated with risk of diseases; CHIP-cardiovascular and cancer; LOY-heart failure and Alzheimer’s. I’ve written about CHIP extensively here and here.

—Phenocopy. How a somatic mutation can look the same as a germ-line, inherited mutation, with respect to a disease, and how that is determined.

—Environmental effects inducing somatic mutations: UV light, air pollution, plastics

—and 3 new papers in the past week!

* Somatic mutations in the microglia cells of the brain, same as cancer mutations, drive inflammation and are enriched in the Alzheimer’s brain

2.. The potential of “promolytic drugs” to be used to prevent cancer in people who exhibit precancerous somatic mutations

3. How somatic mutations can be the basis of autoimmune diseases

We also spoke about the role of somatic mutations in aging and super aging

A related excerpt at The Atlantic

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One more thing:

SUPER AGERS was featured on the CBS Morning Show this week in a segment with Dr. Jonathan LaPook, Chief Medical Correspondent, on the meaning and measurement of biological aging.