a, Sequencing chromatographs for four unrelated patients with CMT disorder. Nucleotide mutations are indicated on the x-axis of each chromatograph numbered from +1 for the first codon. b, Inheritance of mutant alleles in two pedigrees. Circle, female; square, male; open symbol, unaffected; filled symbol, affected. Patient BAB1079 is a compound heterozygote for protein truncation mutation F98fsX102 and missense mutation I41T. Patients BAB1372 and BAB1373 are compound heterozygotes for nonsense mutation R183X and missense mutation I41T. c, Residue isoleucine 41 is evolutionarily invariant in FIG4 from vertebrates, invertebrates and yeast. d, Location of CMT mutations in the FIG4 protein. Solid circles, protein truncation mutations. 907 amino acids are present per protein.