Myomixer

Where it comes from

Made in

Muscle precursor cells during development and regeneration; absent from mature fibres

Sent out by

Not secreted; it appears on the cell surface during fusion

Acts on

• The membranes of two fusing myoblasts

What it does

• Drives the final step of fusion after myomaker brings two cells together ¹
• Mice without it make muscle precursors that never join into fibres
• Found by three laboratories in 2017, each giving it a name

In medicine

• A recessive variant in it caused a myopathy resembling Carey-Fineman-Ziter syndrome, with weakness and facial features, in one family ²; further families with changes in both copies were reported in 2025, adding facial palsy and growth restriction to the picture ³
• Because changes in its partner myomaker cause the same picture, the two genes are read together when a congenital myopathy with facial weakness is being worked up

Beyond the body’s own use

• Myomaker and myomixer together make non-muscle cells fuse, and that has been turned into a delivery tool: viruses dressed in the pair home to skeletal muscle in mice, which is one answer to the oldest problem in muscle gene therapy ⁴
• Nobody takes it, nothing copies it and there is nothing to obtain; the work on it is about delivery and about repair
• What is being asked next is whether switching it back on in adult muscle helps regeneration, since mature fibres carry none of it ¹