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Mutations in PIGO, a Member of the GPI-Anchor-Synthesis Pathway, Cause Hyperphosphatasia with Mental Retardation

2012; Elsevier BV; Volume: 91; Issue: 1 Linguagem: Inglês

10.1016/j.ajhg.2012.05.004

1537-6605

Peter Krawitz, Yoshiko Murakami, Jochen Hecht, Ulrike Krüger, Susan Holder, Geert Mortier, Barbara Delle Chiaie, Elfride De Baere, Miles D. Thompson, Tony Roscioli, Szymon M. Kiełbasa, Taroh Kinoshita, Stefan Mundlos, Peter N. Robinson, Denise Horn,

Lysosomal Storage Disorders Research

Hyperphosphatasia with mental retardation syndrome (HPMRS), an autosomal-recessive form of intellectual disability characterized by facial dysmorphism, seizures, brachytelephalangy, and persistent elevated serum alkaline phosphatase (hyperphosphatasia), was recently shown to be caused by mutations in PIGV, a member of the glycosylphosphatidylinositol (GPI)-anchor-synthesis pathway. However, not all individuals with HPMRS harbor mutations in this gene. By exome sequencing, we detected compound-heterozygous mutations in PIGO, a gene coding for a membrane protein of the same molecular pathway, in two siblings with HPMRS, and we then found by Sanger sequencing further mutations in another affected individual; these mutations cosegregated in the investigated families. The mutant transcripts are aberrantly spliced, decrease the membrane stability of the protein, or impair enzyme function such that GPI-anchor synthesis is affected and the level of GPI-anchored substrates localized at the cell surface is reduced. Our data identify PIGO as the second gene associated with HPMRS and suggest that a deficiency in GPI-anchor synthesis is the underlying molecular pathomechanism of HPMRS.