Methods for treatment of charcot-marie-tooth disease with follistatin polypeptides

1. A method of treating a patient having Charcot-Marie-Tooth disease, the method comprising administering an effective amount of a follistatin fusion protein by an intramuscular route of administration to a targeted muscle of a patient in need thereof, wherein the follistatin fusion protein comprises a first amino acid sequence and a second amino acid sequence, wherein the first amino acid sequence comprises an amino acid sequence that is at least 90% identical to SEQ ID NO: 15 or 16, wherein the first amino acid sequence ends at the amino acid corresponding to any one of amino acids 291-302 of SEQ ID NO: 4; wherein the second amino acid sequence comprises a constant domain of an immunoglobulin G (IgG); and wherein the follistatin fusion protein inhibits signaling by myostatin in a cell-based assay.

2. The method of claim 1 , wherein the first amino acid sequence comprises an amino acid sequence that is at least 95% identical to SEQ ID NO: 15 or 16.

3. The method of claim 1 , wherein the first amino acid sequence ends at the amino acid corresponding to position 291 of SEQ ID NO: 4.

4. The method of claim 2 , wherein the first amino acid sequence ends at the amino acid corresponding to position 291 of SEQ ID NO: 4.

5. The method of claim 1 , wherein an increase in muscle size or strength occurs in the targeted muscle.

6. The method of claim 1 , wherein the follistatin fusion protein does not have a substantial systemic effect on muscle size or strength.

7. The method of claim 1 , wherein the follistatin fusion protein is administered to only one targeted muscle.

8. The method of claim 1 , wherein the follistatin fusion protein is administered to more than one targeted muscle.

9. The method of claim 1 , wherein a muscle that is contralateral to a targeted muscle does not substantially increase in size or strength.

10. The method of claim 1 , wherein the follistatin fusion protein binds to one or more ligands selected from the group consisting of: myostatin, growth differentiation factor 11 (GDF-11), activin A and activin B with a dissociation constant (K D ) less than 1 nM, 100 pM, 50 pM or 10 pM.

11. The method of claim 1 , wherein the follistatin fusion protein forms a dimer.

12. The method of claim 1 , wherein the follistatin fusion protein comprises an Fc portion of an IgG.

13. The method of claim 1 , wherein the follistatin fusion protein does not mediate substantial antibody-dependent cell-mediated toxicity (ADCC).

14. The method of claim 1 , wherein the follistatin fusion protein does not mediate substantial complement-dependent cytotoxicity (CDC).

15. The method of claim 1 , wherein the constant domain of the IgG is selected so as to mediate no substantial antibody-dependent cell-mediated cytotoxicity (ADCC) and/or no substantial complement dependent cytotoxicity (CDC).

16. The method of claim 1 , wherein the method causes no substantial effect in the patient on a measure selected from the group consisting of: serum follicle stimulating hormone (FSH) levels, liver size, hematocrit and reticulocyte levels.

17. The method of claim 1 , wherein the constant domain of the IgG is a constant domain of an IgG1.

18. The method of claim 17 , wherein the constant domain of the IgG1 comprises the amino acid sequence of SEQ ID NO: 17.

19. The method of claim 1 , wherein the constant domain of the IgG is a constant domain of an IgG2.

20. The method of claim 18 , wherein the constant domain of the IgG2 comprises the amino acid sequence of SEQ ID NO: 18.

21. The method of claim 1 , wherein a linker directly connects the C-terminal portion of the first amino acid sequence to the N-terminal portion of the second amino acid sequence.

22. The method of claim 21 , wherein the linker is 1-10 amino acids in length.

23. The method of claim 21 , wherein the linker comprises the sequence of SEQ ID NO: 46.

24. The method of claim 21 , wherein the linker consists of the sequence of SEQ ID NO: 46.

25. The method of claim 1 , wherein the first amino acid sequence comprises an amino acid sequence that is at least 95% identical to SEQ ID NO: 15 or 16; wherein a linker directly connects the C-terminal portion of the first amino acid sequence to the N-terminal portion of the second amino acid sequence; wherein the linker is 1-10 amino acids in length; wherein the constant domain of the IgG is a constant domain of an IgG2 comprising the amino acid sequence of SEQ ID NO: 18.

26. The method of claim 1 , wherein the follistatin fusion protein comprises the amino acid sequence of SEQ ID NO: 43, but wherein the final (carboxy-terminal) lysine (K) of SEQ ID NO: 43 is optionally absent.

27. The method of claim 26 , wherein the final (carboxy-terminal) lysine (K) of SEQ ID NO: 43 is absent.