Mutations in HAO1 encoding glycolate oxidase cause isolated glycolic aciduria.

BACKGROUND: The primary hyperoxalurias are a group of recessive kidney diseases, characterised by extensive accumulation of calcium oxalate that progressively coalesces into kidney stones. Oxalate overproduction is facilitated by perturbations in the metabolism of glyoxylate, the product of glycolate oxidation, and the immediate precursor of oxalate. Glycolic aciduria associated with hyperoxaluria is regarded as the hallmark of type 1 primary hyperoxaluria. The genetic basis of isolated glycolic aciduria is reported here. METHODS AND RESULTS: Two brothers, born to consanguineous healthy parents of Arab descent, were evaluated for psychomotor delay associated with triple-A-like syndrome (anisocoria, alacrima and achalasia). The proband showed markedly increased urinary glycolic acid excretion with normal excretion of oxalate, citrate and glycerate. Abdominal ultrasound showed normal-sized kidneys with normal echotexture. The genetic nature of triple-A-like syndrome in this kindred was found to be unrelated to this metabolic abnormality. Direct DNA sequencing of glycolate oxidase gene (HAO1) revealed a homozygous c.814-1G>C mutation in the invariant -1 position of intron 5 splice acceptor site. Since HAO1 is a liver-specific enzyme, the effect of this novel mutation on splicing was validated by an in vitro hybrid-minigene approach. We confirmed the appearance of an abnormal splice variant in cells transfected with mutant minigene vector. CONCLUSIONS: Our results pinpoint the expression of defective splice variant of glycolate oxidase as the cause of isolated asymptomatic glycolic aciduria. This observation contributes to the development of novel approaches, namely, substrate reduction, for the treatment of primary hyperoxaluria type I.

Mutations in DDR2 gene cause SMED with short limbs and abnormal calcifications.

The spondylo-meta-epiphyseal dysplasia [SMED] short limb-hand type [SMED-SL] is a rare autosomal-recessive disease, first reported by Borochowitz et al. in 1993.(1) Since then, 14 affected patients have been reported.(2-5) We diagnosed 6 patients from 5 different consanguineous Arab Muslim families from the Jerusalem area with SMED-SL. Additionally, we studied two patients from Algerian and Pakistani ancestry and the parents of the first Jewish patients reported.(1) Using a homozygosity mapping strategy, we located a candidate region on chromosome 1q23 spanning 2.4 Mb. The position of the Discoidin Domain Receptor 2 (DDR2) gene within the candidate region and the similarity of the ddr2 knockout mouse to the SMED patients' phenotype prompted us to study this gene(6). We identified three missense mutations c.2254 C > T [R752C], c. 2177 T > G [I726R], c.2138C > T [T713I] and one splice site mutation [IVS17+1g > a] in the conserved sequence encoding the tyrosine kinase domain of the DDR2 gene. The results of this study will permit an accurate early prenatal diagnosis and carrier screening for families at risk.

Mucolipidosis II is caused by mutations in GNPTA encoding the alpha/beta GlcNAc-1-phosphotransferase.

Mucolipidosis II (ML II) is a fatal lysosomal storage disorder resulting from defects in the multimeric GlcNAc-1-phosphotransferase responsible for the initial step in the generation of the mannose 6-phosphate (M6P) recognition marker. M6P residues on oligosaccharides of newly synthesized lysosomal enzymes are essential for efficient receptor-mediated transport to lysosomes. We used the recombinant GlcNAc-1-phosphotransferase gamma subunit as an affinity matrix to purify an unknown protein identified as the product of GNPTA (encoding GNPTA, previously known as MGC4170). The cDNA encodes a protein of 1,256 amino acids with two putative transmembrane domains and a complex preserved modular structure comprising at least six domains. The N-terminal domain of GNPTA, interrupted by a long insertion, shows similarities to bacterial capsule biosynthesis proteins. We identified seven mutations in GNPTA that lead to premature translational termination in six individuals with ML II. Retroviral transduction of fibroblasts from an individual with ML II resulted in the expression and localization of GNPTA in the Golgi apparatus, accompanied by the correction of hypersecretion of lysosomal enzymes. Our results provide evidence that GNPTA encodes a subunit of GlcNAc-1-phosphotransferase defective in individuals with ML II.

Genetic screening for Krabbe disease: learning from the past and looking to the future.

In Israel, Krabbe disease is frequent in two Moslem Arab villages in the Jerusalem area. In this paper we present our experience of almost four decades with diagnosis of Krabbe disease, carrier screening and prenatal diagnosis. The screening program is well accepted by the community, and there is a clear trend towards premarital testing. The screening program and prenatal diagnosis have led to a decrease in the incidence of Krabbe disease from 1.6 per 1,000 live births to 0.82 per 1,000.

The clinical spectrum of fetal Niemann-Pick type C.

Niemann-Pick type C (NPC) disease is a lysosomal neurovisceral storage disease. The spectrum of the clinical presentation as well as the severity of the disease and the age of presentation may be highly variable. Fetal presentation is rarely described in the literature. Here, we report on seven new cases of fetal onset NPC of whom two were diagnosed in utero and five postnatally. The fetal clinical presentation, included, in utero splenomegaly (6/7), in utero hepatomegaly (5/7), in utero ascites (4/7), intra uterine growth retardation (IUGR) (2/7), and oligohydramnios (2/7). Placentomegaly was present in two of the three pregnancies examined. Congenital thrombocytopenia (4/4), congenital anemia (2/4), and petechial rash (2/5) were diagnosed immediately after birth. Three patients were born preterm. Pregnancy and postnatal outcome were remarkably poor with one case of intrauterine fetal death, one elective termination of pregnancy, and four patients who died within the first months of life from a rapidly fatal neonatal cholestatic disease. NPC1 gene mutation analysis identified all of the mutant alleles including three novel mutations. Splenomegaly, hepatomegaly, and ascites were the most consistent prenatal ultrasonographic findings of the NPC fetuses. We suggest that once identified these findings, should raise the suspicion of fetal NPC. Our study further expands the antenatal clinical spectrum of NPC and provides clues to its prenatal diagnosis.

P35S mutation in the NOG gene associated with Teunissen-Cremers syndrome and features of multiple NOG joint-fusion syndromes.

We report on a new family with Teunissen-Cremers syndrome. The proband presented with congenital conductive hearing loss due to stapes ankylosis and incus short process fixation with skeletal anomalies including symphalangism, broad thumbs and broad first toes, syndactyly, brachydactyly, contractures of the elbows and knees, hyperopia and lens opacities. This constellation of symptoms is compatible with the diagnosis of one of the joint-fusion syndromes namely the Teunissen-Cremers syndrome (TCS), which was first reported in 1990. Mutations in the NOG gene which encodes the noggin protein, a bone morphogenetic protein antagonist, have been identified in TCS as well as in four other autosomal dominant disorders including proximal symphalangism (SYM1), multiple synostosis (SYNS1), Tarsal-Carpal coalition syndrome and brachydactyly type B (BDB). Interestingly, we found that the mutation P35S described in this family has already been reported in patients affected with SYM1 as well as with BDB syndromes.

Angiokeratoma corporis diffusum in human beta-mannosidosis: Report of a new case and a novel mutation.

BACKGROUND: Human beta-mannosidosis, a rare disorder of oligosaccharide catabolism, results from a deficiency of beta-mannosidase activity. So far, mutational analysis has been performed in only seven families and revealed 11 mutations in the MANBA gene which encodes the enzyme beta-mannosidase. OBJECTIVES: We report here a 36-year-old Arab female with beta-mannosidosis who presented with mental retardation and multiple angiokeratomas. We describe in this patient a novel null mutation and review the previously reported MANBA gene mutations and their clinical correlations. METHODS: Histopathology, ultrastructural analysis, and enzyme assays were performed. Sequencing of cDNA and genomic DNA analysis was conducted in a search for a mutation in the MANBA gene. RESULTS: Histopathology of a skin biopsy specimen from the patient showed the characteristic findings of angiokeratoma. Electron microscopy showed cytoplasmic vacuolation. Enzymatic activity of beta-mannosidase in the patient's serum, leukocytes, and fibroblasts was less than 1% of control values. Sequencing of the MANBA cDNA revealed a G-->A transition in exon 6 at nucleotide position c.693, resulting in the formation of a stop codon (W231X). LIMITATIONS: Only one family was studied. CONCLUSIONS: A new case of human beta-mannosidosis is presented and the first MANBA gene mutation from Arab ancestry is reported. Reviewing the reported MANBA gene mutations does not reveal a clear genotype-phenotype correlation. The importance of angiokeratoma corporis diffusum as the clue to the diagnosis of beta-mannosidosis and other lysosomal storage diseases is emphasized.

The frequency of mucolipidosis type IV in the Ashkenazi Jewish population and the identification of 3 novel MCOLN1 mutations.

Mucolipidosis type IV (MLIV) is a neurodegenerative lysosomal storage disorder that occurs in an increased frequency in the Ashkenazi Jewish (AJ) population. The frequency of the disease in this population has been established by the testing of 66,749 AJ subjects in the Dor Yeshorim program, a unique premarital population-screening program designed for the Orthodox Jewish community. A carrier rate of 0.0104 (95% C.I 0.0097-0.011) was found. The distribution of the 2 AJ founder mutations, namely, c.416-2A>G and c.1_788del, was determined to be 78.15% and 21.85%, respectively. Three novel mutations were identified in non-Jewish MLIV patients, a missense mutation c.1207C>T, p.Arg403Cys; a 2bp deletion, c.302_303delTC; and a nonsense, c.235C>T, Gln79X.

A novel SCARB2 mutation in progressive myoclonus epilepsy indicated by reduced ß-glucocerebrosidase activity.

Action myoclonus renal failure (AMRF) syndrome is a rare form of progressive myoclonus epilepsy with renal dysfunction related to mutations in the SCARB2 gene. This gene is involved in lysosomal mannose-6-phosphate-independent trafficking of ß-glucocerebrosidase (GC), an enzyme deficient in Gaucher disease. We report a family with myoclonic epilepsy, ataxia and skeletal muscle atrophy but without cognitive impairment or overt renal disease. A novel SCARB2 mutation was indicated by a striking discrepancy between lymphocyte and fibroblast GC activity in the proband evaluated for possible Gaucher disease. Our findings expand the genetic and phenotypic diversity of AMRF and suggest that low GC activity may present an important biochemical clue to the diagnosis of AMRF.

When Mucolipidosis III meets Mucolipidosis II: GNPTA gene mutations in 24 patients.

Mucolipidosis II (ML II) and Mucolipidosis type III (ML III) are autosomal recessive disorders of lysosomal hydrolases trafficking due to the deficiency of the multimeric enzyme, UDP-N-acetylglucosamine-1-phosphotransferase. The alpha/beta subunits encoded by the GNPTA gene is the catalytic subunit of the enzyme while the gamma recognition subunit is encoded by the GNPTAG gene. We report the molecular analysis of GNPTA in 21 families with ML II and 3 families with ML III. The ML II mutant genotypes included three splice-site mutations [IVS1-2A>G; IVS17+1G>A; IVS18+1G>A] in seven Palestinian, Israeli Arab-Muslims, and Turkish patients; a two base pair deletion [c.3503_4delTC] [corrected] in 11 patients from Israel, Turkey, and Ireland; two nonsense mutations [c.2533C>T (Q845X); c.3613C>T (R1205X)], in a Turkish and an Arab-Muslim patient from the Nablus area, respectively, and an insertion mutation [c.2916insT] in a patient from Nablus. The ML III mutant genotypes included a splice-site mutation [IVS17+6T>G] in two patients from Irish/Scottish origin who were compound heterozygous for a nonsense mutation [c.3565C>T (R1189X)] and the deletion mutation [c.3503_4delTC] [corrected] respectively. The third ML III patient from France was compound heterozygous for a missense mutation [c.1196C>T] and the same deletion [c.3503_4delTC] [corrected] found homozygous in 11 ML II patients. The 21 ML II patients were homozygous while the three ML III patients were compound heterozygous for mutations in GNPTA. The results of this study confirm that ML II or ML III phenotype is not due to the localization of the mutations, but rather to the severity of the mutations, ML II and ML III might be allelic, and ML III is genetically heterogeneous. We suggest that the diseases due to mutations in GNPTA represent a clinical continuum between ML III and ML II, and the classification of these diseases should be based on the age of onset, clinical symptoms, and severity.