Dna encoding polypeptide capable of modulating muscle-specific tyrosine kinase activity

A DNA encoding a polypeptide that activates a muscle-specific tyrosine kinase, the DNA being selected from the following members (a) to (c):

• (a) a DNA including a nucleotide sequence capable of hybridizing with the nucleotide sequence set out in SEQ ID NO:
• 2 under stringent conditions;
• (b) a DNA including a nucleotide sequence encoding an amino acid sequence having at least one of the substitution, deletion and addition of at least one amino acid residues in the amino acid sequence set out in SEQ ID NO:
• 1;
• and
• (c) a DNA including a nucleotide sequence having at least 90% homology to the nucleotide sequence set out in SEQ ID NO:
• 2.

A test method for a disease derived from an abnormality in a neuromuscular junction, comprising the steps of:

• extracting a DNA from a cell of a subject;
• amplifying the extracted DNA as a template by performing a polymerase chain reaction using a primer capable of specifically amplifying at least one of a DNA including the nucleotide sequence set out in SEQ ID NO:
• 2, and a part or all of the DNA of the expression control region thereof;
• reading the nucleotide sequence of the amplified DNA;
• and
• comparing the read nucleotide sequence with the nucleotide sequence set out in SEQ ID NO:
• 2.

A test method for a disease derived from an abnormality in a neuromuscular junction, comprising the steps of:

• determining the amount of expression of a DNA having the nucleotide sequence set out in SEQ ID NO:
• 2 in a cell of a subject;
• and
• comparing the determined amount of expression of the DNA with the amount of expression of the DNA set out in SEQ ID NO:
• 2 in a cell of healthy individual.

A screening method for a compound candidate for a therapeutic drug for a disease derived from an abnormality in the neuromuscular junction, comprising the steps of:

• bringing a muscle-specific tyrosine kinase into contact with at least one of a polypeptide having the amino acid sequence set out in SEQ ID NO:
• 1 and a fragment thereof having a binding activity with a muscle-specific tyrosine kinase, in the presence and absence of a test substance;
• and
• comparing the binding activity in the presence of the test substance with the binding activity in the absence of the test substance.

A screening method for a compound candidate for a therapeutic drug for a disease derived from an abnormality in the neuromuscular junction, comprising the steps of:

• bringing a test substance into contact with a cell expressing a DNA having the nucleotide sequence set out in SEQ ID NO:
• 2;
• and
• detecting alteration of the amount of expression of the DNA.