Puzzling Together Muscle Structure

New research on mice shows that without an anchoring protein, called ankyrin, muscle cells would shred when used. Yikes.
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As you lift your coffee cup to your mouth, you might not think about the order in which the proteins within and between the membranes of your muscles are organized. Or how some particular proteins like to hang in a spot designated for such clustering.

But without an intricate linking pattern-a literal sidling up or binding into a cluster forming complex, the protein in your muscles would be ... I want to say, jelly-like. Not the jelly that's on your thighs (that's fat), but a soft mush that you won't find in a tough game meat.

Yes, much of the toughness in meat (muscles), we can attribute to protein. Muscular dystrophy, on the other hand, is characterized by weakness and cell damage often due to losing function of a protein called dystrophin.

Muscle cells, contract, extend, stretch, lengthen and shrink day in and day out, coffee cup after coffee cup (or for those more serious about their musculature, rep after rep). Through the entire process, they maintain their integrity. But disrupt dystrophin and things stop moving smoothly.

This new study, published in the journal Cell, shows ankyrin is responsible for grounding dystrophin.

After creating a mouse deficient in a specific ankyrin protein, the researchers noticed that the mice's shoulders pushed out of their backs in a way that resembled wings.

"I went back to my pediatric textbook and saw images of people with a form of muscular dystrophy who had splayed shoulder bones," principal investigator Vann Bennett was quoted in a release."This opened our eyes to the possibility that, in addition to defects in controlling heart rhythm that we have studied before, the mice might also suffer from muscular dystrophy."

With this in mind the researchers screened a database of human mutations and found that indeed, mutations in the regions of ankyrin/dystrophin binding resulted in muscular dystrophy.

"Without dystrophin, you lose the entire protective complex, but nobody knew why. We have found the outlines of a pathway through which dystrophin assembled this complex. The missing piece of the puzzle was the ankyrin proteins."

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