TFRC and mucopolysaccharidosis type 2: While the mechanism of these effects on the skeletal phenotype needs to be further explored, we hypothesize that the beneficial impact of ETV:IDS on the increased skeletal bone density and bone volume in our Ids-KO TfRmu/hu mouse model of MPS II may be a result of reducing GAG accumulation in bone and/or periosteal cells via TfR binding.