Alk4:actriib heteromultimers and uses thereof

A method for treating a patient having a disorder associated with muscle loss or insufficient muscle growth, comprising administering to a patient in need thereof an effective amount of a soluble recombinant heteromultimer comprising an ALK4 polypeptide and an ActRIIB polypeptide, wherein the ALK4 polypeptide comprises an amino acid sequence that is at least 90% identical to amino acids 34-101 of SEQ ID NO:

• 9, and wherein the ActRIIB polypeptide comprises an amino acid sequence that is at least 90% identical to amino acids 29-109 of SEQ ID NO:
• 1, wherein the ActRIIB polypeptide does not comprise an aspartic acid (D) at the amino acid position corresponding to L79 of SEQ ID NO:
• 1, wherein the ALK4 and/or ActRIIB polypeptide is a fusion protein further comprising a heterologous domain, and wherein the heteromultimer binds to activin B.

(canceled)

(canceled)

A method for treating a patient having a disorder associated with neurodegeneration, comprising administering to the patient in need thereof an effective amount of a soluble recombinant heteromultimer comprising an ALK4 polypeptide and an ActRIIB polypeptide, wherein the ALK4 polypeptide comprises an amino acid sequence that is at least 90% identical to amino acids 34-101 of SEQ ID NO:

• 9, and wherein the ActRIIB polypeptide comprises an amino acid sequence that is at least 90% identical to amino acids 29-109 of SEQ ID NO:
• 1, wherein the ActRIIB polypeptide does not comprise an aspartic acid (D) at the amino acid position corresponding to L79 of SEQ ID NO:
• 1, wherein the ALK4 and/or ActRIIB polypeptide is a fusion protein further comprising a heterologous domain, and wherein the heteromultimer binds to activin B.

150-214. (canceled)