The expression of dnβ1 integrin shifts the axon diameter threshold for myelination toward larger diameters, shown here schematically by a shift to the right of the dose–response curve created by plotting the percentage of axons myelinated against the axon diameter. By contrast, the increased expression of Nrg1 in the PNS was previously shown to shift the myelination threshold toward lower axon sizes, i.e., to the left.