Abstract
BackgroundMucopolysaccharidosis type I (MPS I) is caused by the deficiency of alpha-L-iduronidase (IDUA), which is involved in the degradation of glycosaminoglycans (GAGs), such as heparan sulfate and dermatan sulfate in the lysosome. It has been reported that joint symptoms are almost universal in MPS I patients, and even in the case of attenuated disease, they are the first symptom that brings a child to medical attention. However, functional tests and biological markers have not been published for the evaluation of the limitations in joint and locomotion in animal model-mimicking MPS.MethodsWe generated IDUA knockout (KO) mice to observe whether they present impairment of joint function. KO mice were characterized phenotypically and tested dual-energy X-ray absorptiometry analysis (DEXA), open-field, rotarod, and grip strength.ResultsThe IDUA KO mice, generated by disruption between exon 6 and exon 9, exhibited clinical and laboratory findings, such as high urinary GAGs excretion, GAGs accumulation in various tissues, and significantly increased bone mineral density (BMD) in both female and male mice in the DEXA of the femur and whole bone. Remarkably, we observed a decrease in grasp function, decreased performance in the rotarod test, and hypo-activity in the open-field test, which mimic the limitations of joint mobility and decreased motor performance in the 6-min walk test in patients with MPS I.ConclusionsWe generated a new IDUA KO mouse, tested open field, rotarod and grip strength and demonstrated decrease in grip strength, decreased performance and hypo-activity, which may be useful for investigating therapeutic approaches, and studying the pathogenesis of joint and locomotion symptoms in MPS I.Electronic supplementary materialThe online version of this article (doi:10.1186/s13023-015-0337-3) contains supplementary material, which is available to authorized users.
Highlights
Mucopolysaccharidosis type I (MPS I) is caused by the deficiency of alpha-L-iduronidase (IDUA), which is involved in the degradation of glycosaminoglycans (GAGs), such as heparan sulfate and dermatan sulfate in the lysosome
OSDupDel.Neo vector was used as expression vector (Open Biosystems, Alabama, USA), and the KO construct included intron 1 to a part of exon 6 of the IDUA gene (2534 bp) for the left arm, a region from a part of exon 9 to the outside of exon 14 for the right arm (7112 bp), and the neomycin resistance gene (1300 bp). pOSDupDel.Neo-IDUA construct was transfected into embryonic stem cells, and the positive cell clones were selected by Southern blotting and microinjected into C57BL/6 blastocysts
Targeting of IDUA gene and generation of IDUA KO mice For the targeting of the IDUA gene and generation of IDUA KO mice, embryonic stem (ES) cells were electroporated with linearized pOSDupDel.Neo-IDUA KO vector, and plated on fibroblast feeder layers
Summary
Mucopolysaccharidosis type I (MPS I) is caused by the deficiency of alpha-L-iduronidase (IDUA), which is involved in the degradation of glycosaminoglycans (GAGs), such as heparan sulfate and dermatan sulfate in the lysosome. It has been reported that joint symptoms are almost universal in MPS I patients, and even in the case of attenuated disease, they are the first symptom that brings a child to medical attention. Mucopolysaccharidosis type I (MPS I), known as Hurler syndrome [OMIM, #607014], is caused by a deficiency of IDUA lysosomal enzyme, and is inherited as autosomal recessive disease. This enzyme is involved in glycosaminoglycans (GAGs)’ metabolic pathway, and its deficiency causes GAGs accumulation in the lysosomes. There is no cognitive impairment, some patients may exhibit mild learning difficulties [4]
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