Lips curve up, skin crinkles around the eyes and there it is – a smile. The facial nerve coordinates the muscles behind this gleeful expression. Damage to this peripheral nerve can cause facial paralysis. Thankfully peripheral nerves usually heal with time. However people with neurofibromatosis type II (NFII) show slower and sometimes incomplete recovery from facial paralysis – a consequence of surgery to remove the facial tumours that characterise this disease. NFII is caused by mutations in the gene encoding merlin protein. Researchers therefore investigated whether merlin is important for repairing damaged peripheral nerves. In normal mice and mice lacking merlin in their peripheral nerves (pictured), damaged nerves (green) grew back and established contacts (red) with the appropriate muscles. However despite this, mice lacking merlin didn't regain full control of their muscles. For NFII patients, getting those smiles back after surgery may therefore be hampered by the presence of mutant merlin.
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