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)

Clinical manifestations in patients with carbonic anhydrase (CA) II deficiency include osteopetrosis, renal tubular acidosis, and cerebral calcification. Of the 39 reported cases of the carbonic anhydrase II deficiency syndrome, 72% were patients from North African and Middle Eastern countries, most, if not all, of whom were of Arabic descent. We have analyzed DNAs from members of six unrelated Arabic kindreds and found five to be homozygous and one heterozygous for a novel splice junction (donor site) mutation at the 5' end of intron 2. These findings suggest that a common "Arabic" mutation may be the predominant cause of CA II deficiency in this region. The mutation introduces a new Sau3A1 restriction site which allows polymerase chain reaction (PCR)-based diagnosis of this mutation that should be useful in diagnosis, carrier detection, and prenatal diagnosis. The presence of mental retardation and relative infrequency of skeletal fractures distinguish the clinical course of the patients with the Arabic mutation from those of the American and Belgian patients with the His 107-->Tyr mutation.
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PMID:A splice junction mutation in intron 2 of the carbonic anhydrase II gene of osteopetrosis patients from Arabic countries. 130 35

Deficiency of carbonic anhydrase II (carbonate hydro-lyase, EC 4.2.1.1) is the primary defect in the syndrome of osteopetrosis, renal tubular acidosis, and cerebral calcification. In this report we describe the molecular basis for carbonic anhydrase II deficiency in the American family in which the association of carbonic anhydrase II deficiency with this syndrome was first recognized. The three affected siblings from this family are compound heterozygotes, each having inherited two different mutations in the structural gene for carbonic anhydrase II. The paternal mutation is a splice acceptor site mutation at the 3' end of intron 5. The maternal mutation is a missense mutation in exon 3 that substitutes a tyrosine for histidine-107. We show that the mutant enzyme expressed in bacteria from the cDNA containing the His-107----Tyr mutation has detectable, though greatly reduced, activity. We suggest that residual activity of the His-107----Tyr mutant enzyme may explain the absence of mental retardation and the relatively mild phenotype of carbonic anhydrase II deficiency in affected members of this family.
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PMID:Molecular basis of human carbonic anhydrase II deficiency. 154 74

Three new cases of a syndrome including osteopetrosis, tubular acidosis, mental retardation and cerebral calcifications are reported in the same sibship. This rare syndrome has an autosomal recessive inheritance and is due to carbonic anhydrase II deficiency. Fractures and mild sensorial manifestations were noticed in 2 cases. Mental deficiency and otitis were present in the 3 cases. Blood count and phosphocalcic metabolites were normal. A proximal tubular acidosis was present in each case. The radiological features were specific: cerebral calcifications were present in all cases since the age of 2 1/2 years; osteocondensation and bone modeling were predominant in long bones metaphyses. Alcalinization improved the height growth.
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PMID:[Syndrome associating: osteopetrosis, tubular acidosis, mental retardation and cerebral calcifications due to carbonic anhydrase II deficiency. Apropos of 3 cases in the siblings]. 190 5

Four new Saudi Arabian cases of the carbonic anhydrase II deficiency syndrome from two families are described. This autosomal recessive syndrome includes osteopetrosis with renal tubular acidosis and cerebral calcification. Additional features are mental retardation, growth failure, typical facial appearance, and abnormal teeth. Two patients showed evidence of restrictive lung disease, a finding not previously described. One of the patients reported represents the first neonate reported to be affected with this syndrome. Intrauterine growth was normal, but metabolic acidosis was already evident in the neonatal period. Radiographic evidence of osteopetrosis was probably absent at birth but appeared during the late neonatal period. Carbonic anhydrase II deficiency was demonstrated in erythrocyte hemolysates from the older two siblings of this neonate, and a 50% normal level of carbonic anhydrase II was demonstrated in the erythrocyte hemolysate from their father.
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PMID:Carbonic anhydrase II deficiency syndrome: recessive osteopetrosis with renal tubular acidosis and cerebral calcification. 308 69

Three Japanese patients with carbonic anhydrase II (CAII) deficiency from three families were described. The parents of one patient were unrelated, the parents of each of the other two patients were first cousins. All the patients had renal tubular acidosis, osteopetrosis, symmetrical cerebral calcification and mental retardation. They exhibited poor activity and poor appetite in the neonatal period, and then developed psychomotor retardation. Two of them were diagnosed as having osteopetrosis at 10 months and 36 years of age, respectively, and the other as having osteomalacia at 28 years of age. All patients had recurrent episodes of muscle weakness. The CAII enzyme activity and protein levels in red blood cells in each of the three patients were deficient. Their parents exhibited approximately 50% normal levels of CAII activity and protein. This is the first report of patients with CAII deficiency in the Japanese population.
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PMID:Carbonic anhydrase II deficiency in three unrelated Japanese patients. 812 74

We describe a 16-year-old female with persistent isolated proximal renal tubular acidosis, cerebral calcification, mental retardation, band keratopathy, cataracts, glaucoma and short stature. Severe metabolic acidosis and hypokalaemia were linked to an abnormally low renal threshold for bicarbonate reabsorption (8 mmol/l). Maximal rates of urinary excretion of titratable acid and ammonium were normal; erythrocyte carbonic anhydrase II was normal. This rare case represents a systemic disease with a distinct clinical entity which may be transmitted by autosomal recessive inheritance.
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PMID:Persistent isolated proximal renal tubular acidosis--a systemic disease with a distinct clinical entity. 814 30

A splice junction mutation at the exon 2-intron 2 boundary of the carbonic anhydrase II (CA II) gene was previously shown to be the unique mutation underlying the CA II deficiency syndrome in patients of Arab descent. Fourteen Tunisian (Maghrebian) families with a history of osteopetrosis, renal tubular acidosis, mental retardation, and CA II deficiency were studied to test the hypothesis that the mutation, found in all 24 patients, derived from a common ancestor originating in the Arabic Peninsula. A filiation study permitted us to trace these families back to a common Arabic tribe that settled in the Maghreb in the tenth century, indicating a common ethnic origin for these families. Segregation of the mutation with a TaqI biallelic restriction site polymorphism upstream of the CA II gene was studied by sequence-tagged site analysis in all the family members. These studies showed cosegregation of the Taq (-) allele with the mutation in 12 families out of 14. This observation supports a founder effect to explain the common CA II deficiency allele in this population. In the remaining two families, a genomic recombination or gene conversion occurred between the TaqI restriction marker and the mutation causing the disease. The relatively high recombination frequency suggests the presence of a hot spot for recombination or gene conversion at the CA II locus.
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PMID:Carbonic anhydrase II (CA II) deficiency in Maghrebian patients: evidence for founder effect and genomic recombination at the CA II locus. 915 Jul 31

Genetic disorders of acid-base transporters involve plasmalemmal and organellar transporters of H(+), HCO3(-), and Cl(-). Autosomal-dominant and -recessive forms of distal renal tubular acidosis (dRTA) are caused by mutations in ion transporters of the acid-secreting Type A intercalated cell of the renal collecting duct. These include the AE1 Cl(-)/HCO3(-) exchanger of the basolateral membrane and at least two subunits of the apical membrane vacuolar (v)H(+)-ATPase, the V1 subunit B1 (associated with deafness) and the V0 subunit a4. Recessive proximal RTA with ocular disease arises from mutations in the electrogenic Na(+)-bicarbonate cotransporter NBC1 of the proximal tubular cell basolateral membrane. Recessive mixed proximal-distal RTA accompanied by osteopetrosis and mental retardation is associated with mutations in cytoplasmic carbonic anhydrase II. The metabolic alkalosis of congenital chloride-losing diarrhea is caused by mutations in the DRA Cl(-)/HCO3(-) exchanger of the ileocolonic apical membrane. Recessive osteopetrosis is caused by deficient osteoclast acid secretion across the ruffled border lacunar membrane, the result of mutations in the vH(+)-ATPase V0 subunit or in the CLC-7 Cl(-) channel. X-linked nephrolithiasis and engineered deficiencies in some other CLC Cl(-) channels are thought to represent defects of organellar acidification. Study of acid-base transport disease-associated mutations should enhance our understanding of protein structure-function relationships and their impact on the physiology of cell, tissue, and organism.
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PMID:Genetic diseases of acid-base transporters. 1182 92

Proximal renal tubular acidosis (pRTA) results from an impairment of bicarbonate (HCO3-) reabsorption in the renal proximal tubules, characterized by a decreased HCO3- threshold. pRTA commonly occurs as a manifestation of a generalized functional defect in proximal tubules. In contrast, pRTA can occur without other functional defects in proximal tubules (isolated pRTA). Most of the isolated pRTA in children are hereditary. Recent progress in molecular biological analyses is unraveling the molecular basis of hereditary pRTA. Mutations in the kidney type Na+/HCO3- cotransporter gene (SLC4A4) cause permanent isolated proximal RTA with ocular abnormalities. Mutations in carbonic anhydrase II gene lead to osteopetrosis, RTA (pRTA, distal RTA or combined proximal and distal RTA), cerebral calcification, and mental retardation. SLC9A3, encoding the Na+/H+ exchanger, is a candidate gene for pRTA without other manifestations. These results help further understand the molecular basis of hereditary pRTA and characterize the clinical and genetic manifestations of the disorder.
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PMID:Molecular basis of proximal renal tubular acidosis. 1202 12

The rare bone thickening disease osteopetrosis occurs in various forms, one of which is accompanied by renal tubular acidosis (RTA), and is known as Guibaud-Vainsel syndrome or marble brain disease. Clinical manifestations of this autosomal recessive syndrome comprise increased bone density, growth failure, intracerebral calcification, facial dysmorphism, mental retardation, and conductive hearing impairment. The most common cause is carbonic anhydrase II (CAII) deficiency. Several different loss of function mutations in CA2, the gene encoding CAII, have been described. To date, there have been no exceptions to the finding of CAII deficiency in patients with coexistent osteopetrosis and RTA. Most often, the RTA is of mixed proximal and distal type, but kindreds are reported in which either distal or proximal RTA predominates. We report the molecular genetic investigation of two consanguineous kindreds where osteopetrosis and distal RTA (dRTA) were both manifest. One kindred harbours a novel homozygous frameshift alteration in CA2. In the other, CAII levels were normal despite a similar clinical picture, and we excluded defects in CA2. In this kindred, two separate recessive disorders are penetrant, each affecting a different, tissue specific subunit of the vacuolar proton pump (H(+)-ATPase), providing a highly unusual, novel genetic explanation for the coexistence of osteopetrosis and dRTA. The osteopetrosis is the result of a homozygous deletion in TCIRG1, which encodes an osteoclast specific isoform of subunit a of the H(+)-ATPase, while the dRTA is associated with a homozygous mutation in ATP6V1B1, encoding the kidney specific B1 subunit of H(+)-ATPase. This kindred is exceptional firstly because the coinheritance of two rare recessive disorders has created a phenocopy of CAII deficiency, and secondly because these disorders affect two different subunits of the H(+)-ATPase that have opposite effects on bone density, but which have only recently been determined to possess tissue specific isoforms.
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PMID:A phenocopy of CAII deficiency: a novel genetic explanation for inherited infantile osteopetrosis with distal renal tubular acidosis. 1256 20


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