Ncam1 may be expressed in Schwann cells,52,53 and may cause elevated serum levels in acquired and inherited demyelinating neuropathies including CMT1A,41 but may also be expressed in denervated and regenerating muscle fibres54 to promote neurite outgrowth and synapse formation.55 Muscle NCAM1 expression is high in regenerating muscle and is sustained long after denervation.56 Based on the elevation in our axonal mouse models and the lack of increase in pre-symptomatic mice (C61 het), NCAM1 seems more likely to originate from the atrophic or regenerating muscle. The gene discussed is NCAM1; the disease is Charcot-Marie-Tooth disease type 1A.