Mutations in ISPD cause Walker-Warburg syndrome and defective glycosylation of α-dystroglycan

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Walker-Warburg syndrome (WWS) is an autosomal recessive multisystem disorder characterized by complex eye and brain abnormalities with congenital muscular dystrophy (CMD) and aberrant α-dystroglycan glycosylation. Here we report mutations in the ISPD gene (encoding isoprenoid synthase domain containing) as the second most common cause of WWS. Bacterial IspD is a nucleotidyl transferase belonging to a large glycosyltransferase family, but the role of the orthologous protein in chordates is obscure to date, as this phylum does not have the corresponding non-mevalonate isoprenoid biosynthesis pathway. Knockdown of ispd in zebrafish recapitulates the human WWS phenotype with hydrocephalus, reduced eye size, muscle degeneration and hypoglycosylated α-dystroglycan. These results implicate ISPD in α-dystroglycan glycosylation in maintaining sarcolemma integrity in vertebrates.

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Figure 1: Overview of genetic data in the cohort of individuals with WWS.
Figure 2: Magnetic resonance images and muscle staining of subject WWS-160.
Figure 3: Knockdown of zebrafish ispd recapitulates pathological defects of human WWS.
Figure 4: Hypoglycosylation of α-dystroglycan and disrupted sarcolemma integrity in ispd MO1–injected zebrafish embryos.


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We thank all family members who participated in this study. We would also like to thank A. Charon for referring an affected individual, G. Powell and S. Gerety for critical comments on the manuscript and R. Schot for study of the deletion in family WWS-161. This project was supported by the Large-Scale Integrating Project GENCODYS-Genetic and Epigenetic Networks in COgnitive DYSfunction (241995), which is funded by the European Union Framework Programme 7 (FP7) Health program (to H.v.B.), the Australian National Health and Medical Research Council (NHMRC) with an overseas postdoctoral fellowship (to T.R.), The Prinses Beatrix Fund (grant W.OR09-15 to D.L. and H.v.B.), the Hersenstichting Nederland (to H.v.B.) and a European Molecular Biology Organization (EMBO) Long-Term Fellowship (ALTF 805-2009 to K.B.). All zebrafish work was sponsored by the Wellcome Trust (grant WT 077047/Z/05/Z and WT 077037/Z/05/Z). Next-generation sequencing experiments were financially supported by the Department of Human Genetics at Nijmegen, as well as by the Netherlands Organisation for Health Research and Development (ZonMW; grant 916-86-016 to L.E.L.M.V.).

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The study was designed and results were interpreted by T.R., K.B., D.L.S., Y.-Y.L., H.G.B., D.J.L. and H.v.B. Subject ascertainment and recruitment were carried out by I.M., U.A., B.G., G.M.S.M., P.D., M.A.W., D.P.R., D.C., C.B., E.S., E.A.J.P., G.M.B.T.-S., C.E.d.D.-S., K.D., H.K., O.A.E.-F.E.-H. and H.v.B. Sequencing, CNV analysis and genotyping were carried out and interpreted by T.R., E.-J.K., K.B., I.M., J.v.R., C.v.d.E., E.v.B., M.R., R.P., L.E.L.M.V., M.S., M.F.B., H.Z., J.A.V., C.G., G.M.S.M. and H.v.B. Zebrafish studies were designed and carried out by K.B., D.L.S. and Y.-Y.L. Bioinformatic data analysis and protein modeling were performed by T.R., J.v.R., C.G. and D.J.L. The manuscript was drafted by T.R., K.B., D.J.L., Y.-Y.L. and H.v.B. All authors contributed to the final version of the paper.

Correspondence to Yung-Yao Lin or Hans van Bokhoven.

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