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)

The Lowe oculocerebrorenal syndrome (OCRL; McKusick 309000) is an X-linked disorder characterized by congenital cataracts, muscular hypotonia, mental retardation, and Fanconi syndrome of the renal tubules. A pair of yeast artificial chromosomes (YACs) that span the Xq25-q26 translocation breakpoint in a female with OCRL were used as probes to screen cDNA libraries made from bovine lens and human kidney. The methods used to prepare the YACs as probes and to screen the libraries are presented in detail. Two different transcripts were found that map to the region around the Xq25-q26 breakpoint. These transcripts are now being studied to determine whether one or the other is a candidate gene for OCRL.
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PMID:Isolation of cDNA sequences around the chromosomal breakpoint in a female with Lowe syndrome by direct screening of cDNA libraries with yeast artificial chromosomes. 152 13

We describe three patients with Lowe (oculocerebrorenal) syndrome, emphasizing primarily the central nervous system and renal pathology. Using magnetic resonance imaging, we noted diffuse high T2 signals periventricularly, indicating significant white matter destruction, which may be responsible in part for the mental retardation, seizure disorder, hypotonia, and areflexia observed in the patients. In contrast to previously published reports, there was minimal renal tubular dysfunction; however, proteinuria was significantly increased in all patients. We believe that the observed proteinuria is primarily the result of glomerular pathology rather than renal tubular dysfunction and may represent a net loss of negative charges within the glomerular filter. This loss of charge may be linked to the increased excretion of glycosaminoglycans in the urine.
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PMID:Central nervous system and renal investigations in patients with Lowe syndrome. 157 8

A Hispanic girl with Lowe oculocerebrorenal syndrome (OCRL), an X-linked recessive condition characterized by cataracts, glaucoma, mental retardation, and proteinuria, is reported. A balanced X;20 chromosomal translocation with the X chromosome breakpoint at q26.1 was found with high-resolution trypsin-Giemsa banding. Somatic cell hybridization was used to separate the X chromosome derivative and the chromosome 20 derivative in order to position, with respect to the translocation breakpoint, several DNA loci that are linked to the Lowe syndrome locus (Xq24-q26). DXS10 and DXS53 were found to be distal to the breakpoint, whereas DXS37 and DXS42 were located proximal to it. These studies suggest that the OCRL locus lies in the region between these probes. The translocation chromosome originated from an unaffected male without a visible translocation, indicating that the most likely cause of OCRL in this patient is the de novo translocation that disrupted the OCRL locus.
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PMID:Lowe oculocerebrorenal syndrome in a female with a balanced X;20 translocation: mapping of the X chromosome breakpoint. 189 26

The Lowe oculocerebrorenal syndrome (OCRL) is characterized by congenital cataract, mental retardation, and renal tubular dysfunction. We are using the approaches of linkage analysis, mapping with somatic cell hybrids, and long-range restriction mapping to determine the order of Xq24-q26 markers with respect to each other and to the OCRL locus. DXS42 and DXS100 are proximal to the translocation breakpoint in a female patient with OCRL and a de novo translocation t(X;3)(q25;q27). DXS10, DXS86, HPRT, and DXS177 are distal to the breakpoint. These flanking markers show tight linkage to the disease locus in 11 families segregating for OCRL. Results from field inversion gel analysis show that DXS86 and DXS10 share a 460-kb BssHII fragment. Multipoint analysis to determine the position of HPRT with respect to (DXS10,DXS86) suggests that HPRT is proximal to (DXS10,DXS86). We propose the following order for markers in Xq24-q26: Xcen-(DXS42,DXS37,DXS100)-OCRL-DXS53 -HPRT-[(DXS10,DXS86),DXS177]-Xqter. The identification of additional tightly linked flanking markers extends the number of markers available for use in genetic counseling and begins to define the physical map of the region containing the gene for OCRL.
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PMID:Genetic and physical mapping of Xq24-q26 markers flanking the Lowe oculocerebrorenal syndrome. 208 1

Neurologic features of oculocerebrorenal (Lowe) syndrome include mental retardation, hypotonia, and areflexia. We performed a sural nerve biopsy, computerized tomography (CT) scan, and magnetic resonance imaging (MRI) scan on a 14-year-old boy with oculocerebrorenal syndrome with very mild renal disease. The nerve biopsy exhibited decreased number of myelinated fibers, normal myelination on remaining axons without redundant basal lamina, and no evidence of active degeneration or regeneration. MRI scan revealed diffuse and irregular foci of increased T2 signal with sparing of commissural fibers, pyramidal tracts, and cerebellar white matter. We conclude that both a peripheral axonopathy and a central demyelinating or gliotic process occurs in oculocerebrorenal syndrome in the absence of the severe renal disease that often complicates this disorder.
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PMID:MRI findings and peripheral neuropathy in Lowe's syndrome. 283 62

The Lowe oculocerebrorenal syndrome (OCRL) is characterized by congenital cataract, mental retardation, and defective renal tubular function. A map assignment of OCRL to Xq24-q26 has been made previously by linkage analysis with DXS42 at Xq24-q26 (theta = 0, z = 5.09) and with DXS10 at Xq26 (theta = 0, z = 6.45). Two additional families were studied and three additional polymorphisms were identified at DXS42 by using a 35-kb sequence isolated with the probe detecting the original polymorphism at DXS42. With additional OCRL families made informative for DXS42, theta remained 0 with z = 6.63; and for DXS10 theta = 0.03 and z = 7.07. Evidence for placing OCRL at Xq25 also comes from a female with Lowe syndrome and an X;3 translocation. We have used the Xq25 breakpoint in this patient to determine the position of OCRL relative to the two linked markers. Each derivative chromosome was isolated away from its normal counterpart in somatic cell hybrids. DXS42 was mapped to the derivative chromosome X containing Xpterq25, and DXS10 was mapped to the derivative chromosome 3 containing Xq25-qter. The markers DXS10 and DXS42 therefore show tight linkage with OCRL in six families and flank the Xq25 breakpoint in a female patient with an X;3 translocation. Linkage analysis with flanking markers was used to assess OCRL carrier status in women at risk. Results, when compared with carrier determination by ophthalmologic examination, indicated that the slit-lamp exam can be a sensitive and specific method of carrier determination in many cases.
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PMID:Tightly linked flanking markers for the Lowe oculocerebrorenal syndrome, with application to carrier assessment. 289 82

Lowe (oculocerebrorenal) syndrome (LS) is an X-linked disorder characterized by congenital cataracts, generalized hypotonia, mental retardation, and renal Fanconi syndrome. The basic defect remains unknown, but the possibility that fibroblasts express reduced sulfation of glycosaminoglycans has been studied in several laboratories. A mechanism involving overproduction of an enzyme (nucleotide pyrophosphatase) active against adenosine 3'-phosphate, 5'-phosphosulfate (PAPS) has been postulated. Decreased synthesis of normally sulfated glycosaminoglycans was also reported. We measured the synthesis of proteoglycans and glycosaminoglycans by incorporation of [3H]glucosamine and Na2(35)SO4 into cultured fibroblasts from four LS patients and related it directly to the synthesis in six normal fibroblast cultures. We found that the rate of synthesis varied greatly among the normal cultures (cv, 30%), but not significantly between LS and the normal. The LS fibroblasts' ability to sulfate glycosaminoglycans was assayed as the amount of 3H-glycosaminoglycan eluting at low ionic strength on anion exchange chromatography, the amount of non-sulfated disaccharide present in chondroitinase digests of labeled proteoglycans, and the ratio of 35S to 3H incorporation into proteoglycans. Each parameter suggested that the LS cells were synthesizing normally sulfated glycosaminoglycans (e.g. % delta Di-0S, 21 +/- 6 in normal; 27 +/- 6 in LS). The cells' ability to sulfate glycosaminoglycans was tested under conditions of markedly stimulated glycosaminoglycan synthesis, by treating the cultures with a beta-D-xyloside. LS and normal cells responded to the treatment by elevating the rate of synthesis of normally sulfated glycosaminoglycans (3.5-6-fold in normal, 3-7-fold in LS). Nucleotide pyrophosphatase activities were found to be elevated in each of our four LS cell strains as in the previous studies, excluding genetic heterogeneity as an explanation for our findings. We conclude that LS fibroblasts do not express defects in sulfation of glycosaminoglycans or in synthesis of proteoglycans.
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PMID:Proteoglycan synthesis in normal and Lowe syndrome fibroblasts. 357 Dec 27

Lowe oculocerebrorenal syndrome (OCRL) (MIM 309000) is a rare X-linked multisystem disorder characterized by congenital cataracts, muscular hypotonia, areflexia, mental retardation, maladaptive behavior, renal tubular dysfunction, vitamin-D-resistant rickets, and scoliosis. The underlying gene OCRL1 is located on chromosome Xq25-q26 and contains 24 exons. It encodes a 105-kDa phosphatidylinositol 4,5-bisphosphate (PtdIns[4,5]P(2)) 5-phosphatase that is localized to the Golgi complex. To confirm the clinical diagnosis and to assess the carrier state of female relatives for genetic counseling we examined 6 independent patients and their families (a total of 23 individuals) using an improved mutation screening strategy for the OCRL1 gene by sequencing of large PCR amplicons. Four novel and two known mutations were identified: three premature terminations caused by either frameshift mutations (1899insT in exon 17 and 2104-2105delGT in exon 18) or a nonsense mutation (1399C > T in exon 12), two missense mutations (1676G > A and 1754C > T in exon 15), and a 6-bp deletion (1609-1614delAAGTAT in exon 14). An ophthalmological examination was performed in all patients and 14 female relatives. All genotypically proven carrier females showed characteristic lenticular opacities, while all proven noncarriers were lacking this phenotypic finding. The results confirm that ophthalmological evaluation is an apparently reliable first-line method to ascertain the carrier state in Lowe oculocerebrorenal syndrome. The high expressivity of lenticular symptoms in OCRL1 gene carriers is consistent with the hypothesis that (PtdIns[4,5]P(2)) 5-phosphatase activity has low functional reserve capacity for maintaining a balanced homeostasis of lenticular metabolism.
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PMID:Carrier assessment in families with lowe oculocerebrorenal syndrome: novel mutations in the OCRL1 gene and correlation of direct DNA diagnosis with ocular examination. 1076 76

Lowe syndrome is a rare X-linked disorder characterized by bilateral congenital cataracts, renal Fanconi syndrome, and mental retardation. Lowe syndrome results from mutations in the OCRL1 gene, which encodes a phosphatidylinositol 4,5 bisphosphate 5-phosphatase located in the trans-Golgi network. As a first step in identifying the link between ocrl1 deficiency and the clinical disorder, we have identified a reproducible cellular abnormality of the actin cytoskeleton in fibroblasts from patients with Lowe syndrome. The cellular abnormality is characterized by a decrease in long actin stress fibers, enhanced sensitivity to actin depolymerizing agents, and an increase in punctate F-actin staining in a distinctly anomalous distribution in the center of the cell. We also demonstrate an abnormal distribution of two actin-binding proteins, gelsolin and alpha-actinin, proteins regulated by both PIP(2) and Ca(+2) that would be expected to be altered in Lowe cells. Actin polymerization plays a key role in the formation, maintenance, and proper function of tight junctions and adherens junctions, which have been demonstrated to be critical in renal proximal tubule function, and in the differentiation of the lens. These findings point to a general mechanism to explain how this PIP(2) 5-phosphatase deficiency might produce the Lowe syndrome phenotype.
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PMID:The deficiency of PIP2 5-phosphatase in Lowe syndrome affects actin polymerization. 1242 11

We present a 20-year-old patient with Lowe syndrome and eruptive vellus hair cysts. Also known as oculocerebrorenal syndrome, it 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. The causative gene, oculocerebrorenal-Lowe 1 (OCRL1), encodes a phosphatase whose function is to regulate the phosphatidylinositol pool of intracellular signaling molecules that regulate the release of lysosomal enzymes in tissues. Low levels of this phosphatase lead to the extracellular release of lysosomal enzymes in organs such as the eye, brain, and kidney, with the resulting tissue damage most likely accounting for the characteristic phenotype. Our patient with Lowe syndrome had several discrete, dome-shaped papules on his midchest. They clinically resembled either eruptive vellus hair cysts or steatocystoma multiplex. Histologically they were most diagnostic of eruptive vellus hair cysts, which are not a known feature of Lowe syndrome. We present a hypothesis based on the known biochemical deficiencies resulting from the mutations in the OCRL1 gene, which may account for the cyst formation. To our knowledge, this is the first reported case of skin findings associated with this disorder.
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PMID:Eruptive vellus hair cysts in a patient with Lowe syndrome. 1487 28


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