Cloning of the human aspartoacylase cDNA and a common missense mutation in Canavan disease.

Canavan disease, an autosomal recessive leukodystrophy, is caused by deficiency of aspartoacylase and accumulation of N-acetylaspartic acid in brain. We have cloned the human aspartoacylase (ASP) cDNA spanning 1,435 basepairs, and show that the isolated cDNA expresses aspartoacylase activity in bacteria. Furthermore, an A to C base change, at nucleotide 854, has been found in 85% of the 34 Canavan alleles tested so far. This base change results in a missense Glu285Ala mutation that is predicted to be part of the catalytic domain of aspartoacylase. The data suggest that the catalytic centre of aspartoacylase involves a triad of Ser, His and Glu residues. Our findings have implications for diagnosis and screening of Canavan disease.

N-acetyl-beta-hexosaminidase: role in the degradation of glycosaminoglycans.

Extracts of cultured normal human skin fibroblasts released radioactivity from a (14)C-labeled heptasaccharide prepared by addition of [(14)C]N-acetylgalactosamine to the nonreducing terminus of a hexasaccharide derived from chondroitin 4-sulfate whereas fibroblast extracts from patients with Tay-Sachs and Sandhoff-Jatzkewitz diseases did not. The results suggest that N-acetyl-beta-hexosaminidase A is responsible for degradation of the oligosaccharide substrate.

Glycolipid and mucopolysaccharide abnormality in fibroblasts of fabry's disease.

Cultures of skin fiibroblasts from a patient with Fabry's disease showed an accumulation of the glycolipid, galactosyl-galactosyl-glucosyl ceramide. Such cells also showed metachromasia on staining with toluidine blue and a markedly elevated acid mucopolysaccharide content.

Sanfilippo A syndrome: sulfamidase deficiency in cultured skin fibroblasts and liver.

The Sanfilippo A syndrome is an autosomal recessive mucopolysaccharidosis characterized clinically by severe mental retardation and biochemically by storage in tissue and excretion in urine of excessive amounts of heparan sulfate. Since sulfamide groups are present in heparan sulfate, a sulfamidase deficiency could explain the impaired degradation of this polysaccharide. To investigate the enzymic basis of this disease, assays for sulfamidase were performed. Extracts of cultured fibroblasts and post-mortem liver were prepared by suspension of tissues in acetate: NaCl buffer, pH 4.5, containing Triton X-100 (Rohm and Haas Co., Philadelphia, Pa.), sonication, and centrifugation at 10,000 g. The supernatant fluid was incubated with [(35)S]-N-sulfated heparin. The release of inorganic sulfate after 18 h of incubation was determined by chromatography on Sephadex G-25. The liver and fibroblast extracts of patients with the Sanfilippo A syndrome showed a deficiency of sulfamidase. The quantity of heparan sulfate in fibroblasts derived from patients with Sanfilippo A, Hurler's and Hunter's diseases was found to be 7-10%, while it was about 1.25% of the total glycosaminoglycans in fibroblasts of normal controls.

Glycopeptide storage in skin fibroblasts cultured from a patient with alpha-mannosidase deficiency.

Patients with mannosidosis, an inherited deficiency of lysosomal alpha-mannosidase, accumulate large amounts of mannose-rich oligosaccharides (the "core" of the carbohydrate units of many glocoproteins) in brain and liver and excrete these partial degradation products in their urine. A profound alpha-mannosidase deficiency was demonstrated in fibroblasts cultured from a skin biopsy obtained from a child with mannosidosis. Further, abnormal glycopeptides rich in mannose and similar to oligosaccharides found in the patient's urine were isolated from fibroblast extracts by a variety of chromatographic procedures and by virtue of their binding to a concanavalin A-Sepharose 4B affinity column. This storage material contained mannose, N-acetylglucosamine, and asparagine in the ratio 3 : 1 : 1 together with a few toher amino acids and had a molecular weight of approximately 1,100. There was no evidence for excretion of storage material by mannosidosis fibroblasts or for any abnormality in cell surface glycoprotein composition. The glycopeptide nature of the storage material isolated from cultured skin fibroblasts may be attributed to the low level of N-aspartyl-beta-glucosamindase (EC 3.5.1.-) activity in these cells.

Double blind placebo control trial of large neutral amino acids in treatment of PKU: effect on blood phenylalanine.

Large neutral amino acids (LNAA) have been used on a limited number of patients with phenylketonuria (PKU) with the purpose of decreasing the influx of phenylalanine (Phe) to the brain. In an open-label study using LNAA, a surprising decline of blood Phe concentration was found in patients with PKU in metabolic treatment centres in Russia, the Ukraine, and the United States. To validate the data obtained from this trial, a short-term double-blind placebo control study was done using LNAA in patients with PKU, with the participation of three additional metabolic centres--Milan, Padua and Rio de Janeiro. The results of the short trial showed significant lowering of blood Phe concentration by an average of 39% from baseline. The data from the double-blind placebo control are encouraging, establishing proof of principle of the role of orally administered LNAA in lowering blood Phe concentrations in patients with PKU. Long-term studies will be needed to validate the acceptability, efficacy and safety of such treatment.

Long-term treatment of phenylketonuria with a new medical food containing large neutral amino acids.

BACKGROUND/OBJECTIVES: Phenylketonuria (PKU) is an autosomal recessive disease caused by deficient activity of phenylalanine hydroxylase. A low phenylalanine (Phe) diet is used to treat PKU. The diet is very restrictive, and dietary adherence tends to decrease as patients get older. Methods to improve dietary adherence and blood Phe control are continuously under investigation. SUBJECTS/METHODS: A new formula Phe-neutral amino acid (PheLNAA) has been tested in this study with the purpose of improving the compliance and lowering blood phenylalanine. The formula has been tested for nitrogen balance, and it is nutritionally complete. It is fortified with more nutritional additives that can be deficient in the PKU diet, such as B12, Biotin, DHA, Lutein and increased levels of large neutral amino acids to help lower blood Phe. The new formula has been tested on 12 patients with a loading test of 4 weeks. RESULTS: Fifty-eight percent of patients had a significant decline in blood Phe concentration from baseline throughout the study. The PheLNAA was well tolerated with excellent compliance and without illnesses during the study. CONCLUSIONS: In conclusion, the new formula is suitable for life-long treatment of PKU, and it offers the PKU clinic a new choice for treatment.

Long-term treatment of phenylketonuria with a new medical food containing large neutral amino acids.

This corrects the article DOI: 10.1038/ejcn.2016.166.

Large neutral amino acids in the treatment of phenylketonuria (PKU).

Large neutral amino acids (LNAAs) have been used on a limited number of patients with phenylketonuria (PKU) with the purpose of decreasing the influx of phenylalanine (Phe) to the brain. In earlier studies on mice with PKU (ENU(2)/ENU(2)), LNAAs were given and a surprising decline in blood Phe concentrations was observed. The formula used in the mouse experiment (PreKUnil) lacked lysine. Therefore, a new formulation of LNAAs (NeoPhe) was developed, introducing changes in the concentration of some amino acids and adding lysine, so that such a mixture could be used in humans. The new formula was found to be effective in reducing blood Phe concentration in mice by about 50% of the elevated levels. Patients with PKU were given LNAAs and blood Phe concentrations were determined in an open-label study. Three centers--in Russia, the Ukraine and the USA--took part in the study. NeoPhe was given at 0.5 g/kg per day in three divided doses to eight subjects with PKU and at 1.0 g/kg per day to three patients, for one week. The NeoPhe resulted in decrease of elevated blood Phe by 50% in both groups. The preliminary data from this study are encouraging and a double blind placebo-controlled trial will be required to show long-term efficacy and tolerance of LNAAs in the treatment of PKU.

Abnormal expression of genes associated with development and inflammation in the heart of mouse maternal phenylketonuria offspring.

This study describes gene expression in the fetus hearts obtained from mouse model for phenylketonuria. These hearts have cardiovascular disease (CVD). Therefore genes involved in CVD were examined. Several genes associated with heart development and inflammation were found to be altered. In order to investigate whether the abnormal gene expression alters transcription and translation, the levels of troponin mRNA and protein were determined. One step real time RT-PCR showed a reduction in cardiac troponin I, troponin T2 and ryanodine receptor 2. Determination of troponin I and T protein levels showed reduced levels of these proteins. Our results suggest that altered gene expression affects protein production. These changes are likely involved in the cardiovascular defects seen in the mouse.

Phenylalanine metabolites, attention span and hyperactivity.

The metabolites of phenylalanine, phenylacetate, phenyllactate, phenylpyruvate and phenylethylamine, were measured in the urine of PKU patients. In general correlation was found between serum phenylalanine excretion of these metabolites. However, there were individual variations in the quantities and type of metabolites excreted that could not be explained by blood phenylalanine levels. In a PKU pregnancy large quantities of phenylalanine metabolites were found in urine despite a modest elevation of serum phenylalanine. Increase in the excretion of phenylalanine metabolites was found in patients who were considered to have good blood phenylalanine control. These preliminary studies indicate that the current practice of allowing a wide range of blood phenylalanine in the treatment of PKU may have to be reexamined. Since these metabolites are neurotoxic, they may afford a new parameter for the study of PKU not only regarding the prevention of mental retardation but also with regards to behavior and learning disabilities.

Spongy degeneration of the brain, Canavan disease: biochemical and molecular findings.

Canavan disease is a severe progressive leukodystrophy characterized by swelling and spongy degeneration of the white matter of the brain. It is an autosomal recessive disease found more frequently among Ashkenazi Jews. The clinical features are those of severe mental retardation with inability to gain developmental milestones. Hypotonia, head lag and macrocephaly are characteristic of Canavan disease and become apparent after 5-6 months of age. Massive excretion in the urine of N-acetylaspartic acid is the biochemical marker for Canavan disease, which is caused by deficiency of the enzyme aspartoacylase. This discovery allowed for accurate diagnosis of Canavan disease, while prior to that, a brain biopsy was needed. The gene for aspartoacylase has been cloned and two mutations predominate among Ashkenazi Jewish individuals with Canavan disease and account for more than 98% of the Ashkenazi Jewish patients. The mutations among other ethnic groups are more diverse. The carrier frequency for the two common mutations among Ashkenazi Jews was found to be surprisingly high, 1:37. Screening for carriers is now common practice for this population. A knock-out mouse for Canavan disease is being genetically engineered in our laboratory. The mouse model will allow for development of strategies for gene therapy.

Nonketotic hyperglycinemia: treatment with diazepam--a competitor for glycine receptors.

Two female infants with nonketotic hyperglycinemia (NKH) were treated with diazepam for the control of seizures. The first infant had seizures, lethargy, and respiratory distress in the first 24 hours of life. The diagnosis of NKH was made at 3 weeks of age and she was then placed on a regimen of strychnine and a low-protein diet. Strychnine therapy was discontinued after three months of treatment because there was no improvement in the seizure control or in the patient's condition. At 5 months of age the patient was referred to our clinic for further work-up. The second infant had seizures, hypotonia, and respiratory distress shortly after birth. She was treated with phenobarbital and diphenylhydantoin, which had no effect on her seizures. The baby was referred to our clinic at 8 months of age and diagnostic studies revealed NKH. All previous medications were stopped and both infants were placed on diazepam, a competitor for glycine receptors in the CNS. Choline and folic acid were added for one-carbon unit transfer and sodium benzoate to bind excessive glycine. Both infants responded to this treatment with cessation of seizures; they became more responsive and alert, and their EEGs showed remarkable improvement despite the persistence of elevated glycine levels in plasma, CSF, and urine. Diazepam as a competitor for the receptors of glycine may prove helpful in controlling the intractable seizures associated with NKH.

Biopterin synthesis defects: problems in diagnosis.

Hyperphenylalaninemia due to a biopterin synthesis defect was detected in an infant with decreased biopterin and increased neopterin levels in plasma and urine. Tetrahydrobiopterin (BH4) administration normalized plasma phenylalanine levels. CSF biopterin and neurotransmitter metabolite levels were normal and with the infant's normal growth and development suggest that the defect in biopterin synthesis did not affect CNS biopterin metabolism. Comparison of plasma and urine pterin levels from this patient with levels reported in patients who have neurologic complications fails to reveal differences that would distinguish patients at risk for neurologic problems. CSF pterin and neurotransmitter levels may correlate with neurologic function in these patients. CSF pterin and neurotransmitter determinations should be performed prior to initiation of neurotransmitter precursor and BH4 replacement therapies in patients who were determined to have biopterin synthesis defect(s).

Relationship among genotype, biochemical phenotype, and cognitive performance in females with phenylalanine hydroxylase deficiency: report from the Maternal Phenylketonuria Collaborative Study.

OBJECTIVE: To examine the relationship of phenylalanine hydroxylase (PAH) genotypes to biochemical phenotype and cognitive development in maternal phenylketonuria (PKU). METHODOLOGY: PAH gene mutations were examined in 222 hyperphenylalaninemic females enrolled in the Maternal PKU Collaborative Study (MPKUCS). A total of 84 different mutations were detected, and complete genotype was obtained in 199 individuals. Based on previous knowledge about mutation-phenotype associations, 78 of the mutations could be assigned to one of four classes of severity (severe PKU, moderate PKU, mild PKU, and mild hyperphenylalaninemia [MHP]). Then, 189 MPKUCS subjects were grouped according to the various combinations of mutation classifications. The sample sizes were large enough for statistical testing in four groups with at least one mutation that completely abolishes enzyme activity. These patients are considered functionally hemizygous. RESULTS: The biochemical phenotype predicted from the genotype in functionally hemizygous patients was related significantly to the assigned phenylalanine level. Cognitive performance (IQ) was also significantly related to genotype. The IQ of PAH-deficient mothers with a severe PKU mutation in combination with a MHP mutation or a mild PKU mutation was 99 and 96, respectively, whereas the IQ of PKU mothers with two severe PKU mutations or with one severe and one moderate PKU mutation was 83 and 84, respectively. Of the patients with PKU, 92% had been treated during childhood. Those who were untreated or treated late had lower than average IQ scores for their group of mutation combinations. Females with moderate or mild PKU who were treated early and treated for >6 years showed IQ scores 10 points above average for their group. CONCLUSIONS: The reproductive outcome in maternal phenylketonuria is dependent on prenatal metabolic control and postnatal environmental circumstances. Both factors depend on the intellectual resources of the mother with PKU. The significant relationship among genotype, biochemical phenotype, and cognitive performance observed in the present study is of importance for the development of an optimal strategy for future treatment of females with PKU who plan pregnancy.

Dominant inheritance of a syndrome similar to Rubinstein-Taybi.

Two sibs and their mother were affected with a syndrome like the Rubinstein-Taybi syndrome. All three individuals had broad terminal phalanges of the thumbs and great toes, antimongoloid slant of the palpebral fissures, and characteristic facial appearance with beaked noses. Four sibs of the mother had broad thumbs, suggesting a familial pattern. So far there has been no report of dominant transmission of the Rubinstein-Taybi syndrome. This family bears close resemblance to the Rubinstein-Taybi syndrome, which is transmitted as an autosomal or X-linked dominant trait. Inasmuch as the expressivity of the syndrome may be variable, we propose that a thorough family investigation is indicated in all apparently sporadic cases of Rubinstein-Taybi syndrome. Familial cases may be more common than realized and require appropriate genetic counseling.

Transmission of ring 14 chromosome from mother to two sons.

We report on a family with transmission of a ring chromosome 14 from an affected mother to her 2 sons. The mother was mosaic, 46,XX,r(14)/45,XX,t(14q21q). Both of her sons, affected by seizures and mental retardation, have the karyotype 46,XY,r(14). In considering the association of translocation 14:21 in the mother with ring 14, we postulate that either the ring chromosome was formed first and then opened with translocation of the partially deleted chromosome 14 to chromosome 21, or the 14:21 translocation was present first, then the chromosomes 14 and 21 broke apart, and the partially deleted 14 formed the ring. The published literature of cases of ring 14 is reviewed.

Simpson-Golabi-Behmel syndrome: follow-up of the Michigan family.

Here we report a follow-up on a boy born in 1983 into a family with presumed Simpson-Golabi-Behmel syndrome and first reported as patient 3 by Opitz [1984] under the designation "Golabi-Rosen" syndrome. The patient died at 25 months without having attained any measure of psychomotor development or maturation and with a neurologic picture of irritability, increased muscle tone, seizures, deafness and possible cortical blindness. He had a striking facial appearance similar to that of severely affected individuals in the family reported by Golabi and Rosen [1984], with mild hepatosplenomegaly, unusual skin, normal growth, decelerating OFC, and on autopsy a spongiform degeneration of brain stem and cerebrum. Results of all biochemical studies, including those pertaining to GM3 gangliosidosis, were normal.

Aspartoacylase deficiency and N-acetylaspartic aciduria in patients with Canavan disease.

An increased amount of N-acetylaspartic acid was found in urine and plasma of three patients, from two families, with the diagnosis of cerebral spongy degeneration (Canavan disease). Aspartoacylase was assayed in cultured skin fibroblasts from one patient of each family and a profound deficiency of this enzyme was found. Although the function of N-acetylaspartic acid is not understood, it is known to occur in high concentration in human brain. The finding of a defect in the metabolism of N-acetylaspartic acid causing progressive spongy degeneration of the brain may lead to a better understanding of the function of this amino acid derivative. The aspartoacylase assay affords a new tool for determining the diagnosis of Canavan disease. Since aspartoacylase activity was present in cultured amniotic cells and chorionic villi, it is likely that the assay for this enzyme can be used for the prenatal diagnosis of Canavan disease.

A therapeutic trial of amniotic epithelial cell implantation in patients with lysosomal storage diseases.

To determine whether allografts of normal amniotic epithelium might provide a nonimmunogenic cellular source of exogenous lysosomal enzymes, subcutaneous implants of amniotic epithelium were performed in six children with clinically advanced storage diseases. The clinical and the biochemical status of each patient was observed for several weeks after amniotic epithelial cell implantation (AECI). Serial studies of blood samples from each patient in the post-AECI period did not demonstrate any increase in levels of deficient lysosomal hydrolase. In two patients, quantitative urinary excretion of substrate was also studied and did not show consistent alterations after AECI. No patient had objective improvement in clinical or neurodevelopmental status following AECI. Two patients died with progressive disease at 2 1/2 and 3 1/2 mo after AECI; no residual amniotic epithelium was found at postmortem examination. Four patients are alive with progressive disease at 6-14 mo after AECI. We conclude that allografts of normal human amnion do not provide sufficient replacement hydrolases for clinical or biochemical improvement in lysosomal storage diseases.