 "sla" mice harbor a partial deletion mutation of the "HEPH" gene, resulting in the expression of a hephaestin protein that is truncated by 194 amino acids.Studies suggest that this truncated hephaestin protein still retains a minimal, yet detectable and quantifiable level of ferroxidase activity.This raises the possibility that alternative factors may contribute to the decreased efflux of iron seen in the "sla" phenotype.