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)

Lowe syndrome is a rare X-linked disease characterized by congenital cataracts, defects in renal tubule cell function, and mental retardation. Mutations in the OCRL1 gene, which encodes ocrl1, a phosphatidylinositol-4,5-bisphosphate (PtdIns(4,5)P(2)) 5-phosphatase, are the cause of Lowe syndrome. PtdIns(4,5)P(2), a substrate of ocrl1, is an important signaling molecule within the cell. OCRL1 is ubiquitously expressed and co-localizes with the trans-Golgi network (TGN) and endosomal proteins. The ocrl1 protein contains two recognizable domains, one a conserved Ptd(4,5)P(2) 5-phosphatase domain and the other with homology to Rho GTPase activating proteins (RhoGAPs). The objective of our study was to further characterize the ocrl1 RhoGAP-homology domain by analyzing the effect of two missense mutations in this domain, I751N and A780P, which were previously reported in Lowe syndrome patients. Both mutant proteins were expressed at levels similar to wild-type but their enzyme activity was reduced by 85-90%, indicating that the RhoGAP-homology domain is important for the enzymatic function of ocrl1. Study of a C-terminal region of wild-type ocrl1 containing this domain detected no GAP activity, eliminating the possibility of an effect by mutations in this domain on GTPase activation. Because members of the Arf family of small G-proteins are directly involved in (Ptd(4,5)P(2)) signaling and localize to the TGN like ocrl1, we analyzed by immunoprecipitation the interaction of ocrl1 with Arf1 and Arf6 via its RhoGAP-homology domain. Wild-type ocrl1, but not the I751N mutant protein, co-immunoprecipitated with these two Arf proteins. These results indicate that wild-type ocrl1 and Arf proteins can interact and that this interaction is disrupted by the mutation. It remains unknown whether a disrupted interaction between Arf and ocrl1 plays a role in the Lowe syndrome phenotype.
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PMID:The effect of missense mutations in the RhoGAP-homology domain on ocrl1 function. 1677 52

Three distinct OCRL1 mutations in three patients with the Dent disease phenotype are described. All the patients manifested an extremely high degree of low-molecular-weight proteinuria and showed no ocular abnormalities or apparent mental retardation. Urinalysis and blood chemistry showed no findings suggestive of Fanconi syndrome with renal tubular acidosis. Mutations in CLCN5 were ruled out. The mutations identified in OCRL1 are one frame-shift mutation (I127stop) and two missense mutations (R301C and R476W). R301C and R476W mutations might be hot spots in OCRL1, which develop very similar phenotypes as Dent-2.
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PMID:OCRL1 mutations in patients with Dent disease phenotype in Japan. 1738 68

The oculo-cerebro-renal syndrome of Lowe (OCRL) is a rare X-chromosomal disorder characterised by the triad of congenital cataracts, renal tubular dysfunction, and mental retardation. Typically complete opacification and discoid deformation of the lenses are seen, indicating a developmental defect in early embryogenesis. We report on a 35-year-old patient with a mild Lowe syndrome phenotype including incomplete lenticular opacities. Clinical findings suggest that the gene product of the mutated allele (IVS19 + 1G > A) identified in the patient exhibits some residual function.
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PMID:[Clinical findings in a patient with Lowe syndrome and a splice site mutation in the OCRL1 gene]. 1738 24

Oculocerebrorenal syndrome of Lowe is an X-linked recessive disorder localized to Xq24-26.1. The phenotypic features of this disorder are Fanconi-type renal failure, mental retardation, and various eye abnormalities. Seizures may accompany the disease, and the skin-related findings are poorly defined. This case of a 9-year-old patient, diagnosed as having and followed for oculocerebrorenal syndrome of Lowe, has been presented for his seizures, which were initially myoclonic but subsequently atonic, and for his skin findings, understood to be trichoepithelioma, cystic in nature, and stemming from mature hair follicles. In monitoring the disease, the manifestation of the seizures as atonic seizures accompanied by focally initiated secondary generalized epileptic discharges is a finding previously undefined in oculocerebrorenal syndrome of Lowe. Moreover, the presence of dermal findings of a cystic nature is reported in few cases of this syndrome. In this rare syndrome, it is necessary to be aware of the presence of atonic seizures, which have an association with the progression of the disease that has not been previously reported in the literature, and of the cystic dermal lesions as part of the syndrome.
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PMID:Different seizure types and skin lesions in oculocerebrorenal syndrome of Lowe. 1762 22

Mutations in the inositol 5-phosphatase OCRL are responsible for Lowe syndrome, whose manifestations include mental retardation and renal Fanconi syndrome. OCRL has been implicated in membrane trafficking, but disease mechanisms remain unclear. We show that OCRL visits late-stage, endocytic clathrin-coated pits and binds the Rab5 effector APPL1 on peripheral early endosomes. The interaction with APPL1, which is mediated by the ASH-RhoGAP-like domains of OCRL and is abolished by disease mutations, provides a link to protein networks implicated in the reabsorptive function of the kidney and in the trafficking and signaling of growth factor receptors in the brain. Crystallographic studies reveal a role of the ASH-RhoGAP-like domains in positioning the phosphatase domain at the membrane interface and a clathrin box protruding from the RhoGAP-like domain. Our results support a role of OCRL in the early endocytic pathway, consistent with the predominant localization of its preferred substrates, PI(4,5)P(2) and PI(3,4,5)P(3), at the cell surface.
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PMID:A role of the Lowe syndrome protein OCRL in early steps of the endocytic pathway. 1776 81

Mutations in the inositol 5-phosphatase OCRL are responsible for Lowe syndrome, an X-linked disorder characterized by bilateral cataracts, mental retardation, neonatal hypotonia, and renal Fanconi syndrome, and for Dent disease, another X-linked condition characterized by kidney reabsorption defects. We have previously described an interaction of OCRL with the endocytic adaptor APPL1 that links OCRL to protein networks involved in the disease phenotype. Here, we provide new evidence showing that among the interactions which target OCRL to membranes of the endocytic pathway, binding to APPL1 is the only one abolished by all known disease-causing missense mutations in the ASH-RhoGAP domains of the protein. Furthermore, we demonstrate that APPL1 and rab5 independently contribute to recruit OCRL to enlarged endosomes induced by the expression of constitutively active Rab5. Thus, binding to APPL1 helps localize OCRL at specific cellular sites, and disruption of this interaction may play a role in disease.
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PMID:All known patient mutations in the ASH-RhoGAP domains of OCRL affect targeting and APPL1 binding. 1830 81

Lowe syndrome is a multisystem disorder characterized by anomalies of the eye, the nervous system, and the kidney. It is an uncommon, X-linked disease. Bilateral cataract and severe hypotonia are present at birth. Psychomotor retardation is evident in childhood, while renal complications arise in adolescence. The mutation of the gene OCRL1 localized at Xq26.1 is responsible for the disease. The authors report on a 12-year-old male with mental retardation, facial dysmorphism as prominent forehead, long and slender-shaped face, prominent eyebrows, epicanthus, microphthalmia, low-posterior set ears with prominent helix and antihelix, long philtrum, and mild prognathia. He also had history of neonatal hypotonia and congenital cataracts. His cranial magnetic resonance imaging showed increased signal intensity in white matter on T2-weighted images, and magnetic resonance spectroscopy revealed elevation of the myoinositol peak at 3.56 ppm. Molecular analysis of OCRL1 gene revealed novel N574K mutation on 17th exon.
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PMID:Magnetic resonance imaging, magnetic resonance spectroscopy, and facial dysmorphism in a case of Lowe syndrome with novel OCRL1 gene mutation. 1916 22

The oculocerebrorenal syndrome of Lowe (OCRL) is a rare X-linked recessive disorder, chiefly characterized by ocular involvement, mental retardation, and kidney disease. A literature review is provided, detailing the diversity of oral anomalies associated with the OCRL syndrome. Reported abnormalities include delayed tooth eruption, odontogenic cyst formation, and constricted dental arches. In addition, we present an unusual case of an 18-year-old male affected with the OCRL syndrome and fetal alcohol syndrome. The oral radiographic examination was significant for multiple impacted permanent teeth, many with pericoronal radiolucencies, and an underdeveloped mandible.
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PMID:Oral anomalies associated with the oculocerebrorenal syndrome of Lowe: case report with multiple unerupted teeth and pericoronal radiolucencies. 1921 10

The Lowe syndrome (LS) is a life-threatening, developmental disease characterized by mental retardation, cataracts and renal failure. Although this human illness has been linked to defective function of the phosphatidylinositol 5-phosphatase, Ocrl1 (Oculo-Cerebro-Renal syndrome of Lowe protein 1), the mechanism by which this enzyme deficiency triggers the disease is not clear. Ocrl1 is known to localize mainly to the Golgi apparatus and endosomes, however it translocates to plasma membrane ruffles upon cell stimulation with growth factors. The functional implications of this inducible translocation to the plasma membrane are presently unknown. Here we show that Ocrl1 is required for proper cell migration, spreading and fluid-phase uptake in both established cell lines and human dermal fibroblasts. We found that primary fibroblasts from two patients diagnosed with LS displayed defects in these cellular processes. Importantly, these abnormalities were suppressed by expressing wild-type Ocrl1 but not by a phosphatase-deficient mutant. Interestingly, the homologous human PI-5-phosphatase, Inpp5b, was unable to complement the Ocrl1-dependent cell migration defect. Further, Ocrl1 variants that cannot bind the endocytic adaptor AP2 or clathrin, like Inpp5b, were less apt to rescue the migration phenotype. However, no defect in membrane recruitment of AP2/clathrin or in transferrin endocytosis by patient cells was detected. Collectively, our results suggest that Ocrl1, but not Inpp5b, is involved in ruffle-mediated membrane remodeling. Our results provide new elements for understanding how Ocrl1 deficiency leads to the abnormalities associated with the LS.
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PMID:Lowe syndrome patient fibroblasts display Ocrl1-specific cell migration defects that cannot be rescued by the homologous Inpp5b phosphatase. 1970 Apr 99

The oculocerebrorenal syndrome of Lowe (OCRL; MIM #309000) is an X-linked human disorder characterized by congenital cataracts, mental retardation, and renal proximal tubular dysfunction caused by loss-of-function mutations in the OCRL gene that encodes Ocrl, a type II phosphatidylinositol bisphosphate (PtdIns4,5P(2)) 5-phosphatase. In contrast, mice with complete loss-of-function of the highly homologous ortholog Ocrl have no detectable renal, ophthalmological, or central nervous system abnormalities. We inferred that the disparate phenotype between Ocrl-deficient humans and mice was likely due to differences in how the two species compensate for loss of the Ocrl enzyme. We therefore turned our attention to Inpp5b, another type II PtdIns4,5P(2) 5-phosphatase encoded by Inpp5b in mice and INPP5B in humans, as potential compensating genes in the two species, because Inpp5b/INPP5B are the most highly conserved paralogs to Ocrl/OCRL in the respective genomes of both species and Inpp5b demonstrates functional overlap with Ocrl in mice in vivo. We used in silico sequence analysis, reverse-transcription PCR, quantitative PCR, and transient transfection assays of promoter function to define splice-site usage and the function of an internal promoter in mouse Inpp5b versus human INPP5B. We found mouse Inpp5b and human INPP5B differ in their transcription, splicing, and primary amino acid sequence. These observations form the foundation for analyzing the functional basis for the difference in how Inpp5b and INPP5B compensate for loss of Ocrl function and, by providing insight into the cellular roles of Ocrl and Inpp5b, aid in the development of a model system in which to study Lowe syndrome.
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PMID:Species-specific difference in expression and splice-site choice in Inpp5b, an inositol polyphosphate 5-phosphatase paralogous to the enzyme deficient in Lowe Syndrome. 2087 66


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