Therapeutic administration of progesterone antagonist in a model of Charcot-Marie-Tooth disease (CMT-1A)

Charcot- Marie- Tooth disease (CMT) is the most common inherited neuropathy. The predominant subtype, CMT- 1A, accounts for more than 50% of all cases(1) and is associated with an interstitial chromosomal duplication of 17p12 (refs. 2,3). We have generated a model of CMT- 1A by introducing extra copies of the responsible disease gene, Pmp22 (encoding the peripheral myelin protein of 22 kDa), into transgenic rats(4). Here, we used this model to test whether progesterone, a regulator of the myelin genes Pmp22 and myelin protein zero (Mpz) in cultured Schwann cells, can modulate the progressive neuropathy caused by moderate overexpression of Pmp22. Male transgenic rats (n = 84) were randomly assigned into three treatment groups: progesterone, progesterone antagonist (onapristone) and placebo control. Daily administration of progesterone elevated the steady- state levels of Pmp22 and Mpz mRNA in the sciatic nerve, resulting in enhanced Schwann cell pathology and a more progressive clinical neuropathy. In contrast, administration of the selective progesterone receptor antagonist reduced overexpression of Pmp22 and improved the CMT phenotype, without obvious side effects, in wild- type or transgenic rats. Taken together, these data provide proof of principle that the progesterone receptor of myelin- forming Schwann cells is a promising pharmacological target for therapy of CMT- 1A.