Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0025362 (mental retardation)
 15,878 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

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.
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PMID:Mutations in PIGO, a member of the GPI-anchor-synthesis pathway, cause hyperphosphatasia with mental retardation. 2268 86

Recently, mutations in genes involved in the biosynthesis of the glycosylphosphatidylinositol (GPI) anchor have been identified in a new subclass of congenital disorders of glycosylation (CDGs) with a distinct spectrum of clinical features. To date, mutations have been identified in six genes (PIGA, PIGL, PIGM, PIGN, PIGO, and PIGV) encoding proteins in the GPI-anchor-synthesis pathway in individuals with severe neurological features, including seizures, muscular hypotonia, and intellectual disability. We developed a diagnostic gene panel for targeting all known genes encoding proteins in the GPI-anchor-synthesis pathway to screen individuals matching these features, and we detected three missense mutations in PGAP2, c.46C>T, c.380T>C, and c.479C>T, in two unrelated individuals with hyperphosphatasia with mental retardation syndrome (HPMRS). The mutations cosegregated in the investigated families. PGAP2 is involved in fatty-acid GPI-anchor remodeling, which occurs in the Golgi apparatus and is required for stable association between GPI-anchored proteins and the cell-surface membrane rafts. Transfection of the altered protein constructs, p.Arg16Trp (NP_001243169.1), p.Leu127Ser, and p.Thr160Ile, into PGAP2-null cells showed only partial restoration of GPI-anchored marker proteins, CD55 and CD59, on the cell surface. In this work, we show that an impairment of GPI-anchor remodeling also causes HPMRS and conclude that targeted sequencing of the genes encoding proteins in the GPI-anchor-synthesis pathway is an effective diagnostic approach for this subclass of CDGs.
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PMID:PGAP2 mutations, affecting the GPI-anchor-synthesis pathway, cause hyperphosphatasia with mental retardation syndrome. 2356 47

Three different genes of the glycosylphosphatidylinositol anchor synthesis pathway, PIGV, PIGO, and PGAP2, have recently been implicated in hyperphosphatasia-mental retardation syndrome (HPMRS), also known as Mabry syndrome, a rare autosomal recessive form of intellectual disability. The aim of this study was to delineate the PIGV mutation spectrum as well as the associated phenotypic spectrum in a cohort of 16 individuals diagnosed with HPMRS on the basis of intellectual disability and elevated serum alkaline phosphate as minimal diagnostic criteria. All PIGV exons and intronic boundaries were sequenced in 16 individuals. Biallelic PIGV mutations were identified in 8 of 16 unrelated families with HPMRS. The most frequent mutation detected in about 80% of affected families including the cases reported here is the c.1022C>A PIGV mutation, which was found in both the homozygous as well as the heterozygous state. Four further mutations found in this study (c. 176T>G, c.53G>A, c.905T>C, and c.1405C>T) are novel. Our findings in the largest reported cohort to date significantly extend the range of reported manifestations associated with PIGV mutations and demonstrate that the severe end of the clinical spectrum presents as a multiple congenital malformation syndrome with a high frequency of Hirschsprung disease, vesicoureteral, and renal anomalies as well as anorectal malformations. PIGV mutations are the major cause of HPMRS, which displays a broad clinical variability regarding associated malformations and growth patterns. Severe developmental delays, particular facial anomalies, brachytelephalangy, and hyperphosphatasia are consistently found in PIGV-positive individuals.
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PMID:Delineation of PIGV mutation spectrum and associated phenotypes in hyperphosphatasia with mental retardation syndrome. 2412 30

Aberrations in the glycosylphosphatidylinositol (GPI)-anchor biosynthesis pathway constitute a subclass of congenital disorders of glycosylation, and mutations in seven genes involved in this pathway have been identified. Among them, mutations in PIGV and PIGO, which are involved in the late stages of GPI-anchor synthesis, and PGAP2, which is involved in fatty-acid GPI-anchor remodeling, are all causative for hyperphosphatasia with mental retardation syndrome (HPMRS). Using whole exome sequencing, we identified novel compound heterozygous PIGO mutations (c.389C>A [p.Thr130Asn] and c.1288C>T [p.Gln430*]) in two siblings, one of them having epileptic encephalopathy. GPI-anchored proteins (CD16 and CD24) on blood granulocytes were slightly decreased compared with a control and his mother. Our patients lacked the characteristic features of HPMRS, such as facial dysmorphology (showing only a tented mouth) and hypoplasia of distal phalanges, and had only a mild elevation of serum alkaline phosphatase (ALP). Our findings therefore expand the clinical spectrum of GPI-anchor deficiencies involving PIGO mutations to include epileptic encephalopathy with mild elevation of ALP.
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PMID:PIGO mutations in intractable epilepsy and severe developmental delay with mild elevation of alkaline phosphatase levels. 2441 46

Mabry syndrome, hyperphosphatasia mental retardation syndrome (HPMRS), is an autosomal recessive disease characterized by increased serum levels of alkaline phosphatase (ALP), severe developmental delay, intellectual disability, and seizures. Recent studies have revealed mutations in PIGV, PIGW, PIGO, PGAP2, and PGAP3 (genes that encode molecules of the glycosylphosphatidylinositol (GPI)-anchor biosynthesis pathway) in patients with HPMRS. We performed whole-exome sequencing of a patient with severe intellectual disability, distinctive facial appearance, fragile nails, and persistent increased serum levels of ALP. The result revealed a compound heterozygote with a 13-bp deletion in exon 1 (c.36_48del) and a two-base deletion in exon 2 (c.254_255del) in phosphatidylinositol glycan anchor, class L (PIGL) that caused frameshifts resulting in premature terminations. The 13-bp deletion was inherited from the father, and the two-base deletion was inherited from the mother. Expressing c.36_48del or c.254_255del cDNA with an HA-tag at the C- or N-terminus in PIGL-deficient CHO cells only partially restored the surface expression of GPI-anchored proteins (GPI-APs). Nonsynonymous changes or frameshift mutations in PIGL have been identified in patients with CHIME syndrome, a rare autosomal recessive disorder characterized by colobomas, congenital heart defects, early onset migratory ichthyosiform dermatosis, intellectual disability, and ear abnormalities. Our patient did not have colobomas, congenital heart defects, or early onset migratory ichthyosiform dermatosis and hence was diagnosed with HPMRS, and not CHIME syndrome. These results suggest that frameshift mutations that result in premature termination in PIGL cause a phenotype that is consistent with HPMRS.
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PMID:Mutations in PIGL in a patient with Mabry syndrome. 2570 56

Inherited GPI (glycosylphosphatidylinositol) deficiencies (IGDs), a recently defined group of diseases, show a broad spectrum of symptoms. Hyperphosphatasia mental retardation syndrome, also known as Mabry syndrome, is a type of IGDs. There are at least 26 genes involved in the biosynthesis and transport of GPI-anchored proteins; however, IGDs constitute a rare group of diseases, and correlations between the spectrum of symptoms and affected genes or the type of mutations have not been shown. Here, we report four newly identified and five previously described Japanese families with PIGO (phosphatidylinositol glycan anchor biosynthesis class O) deficiency. We show how the clinical severity of IGDs correlates with flow cytometric analysis of blood, functional analysis using a PIGO-deficient cell line, and the degree of hyperphosphatasia. The flow cytometric analysis and hyperphosphatasia are useful for IGD diagnosis, but the expression level of GPI-anchored proteins and the degree of hyperphosphatasia do not correlate, although functional studies do, with clinical severity. Compared with PIGA (phosphatidylinositol glycan anchor biosynthesis class A) deficiency, PIGO deficiency shows characteristic features, such as Hirschsprung disease, brachytelephalangy, and hyperphosphatasia. This report shows the precise spectrum of symptoms according to the severity of mutations and compares symptoms between different types of IGD.
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PMID:Phenotype-genotype correlations of PIGO deficiency with variable phenotypes from infantile lethality to mild learning difficulties. 2833 24