Double mutation (A171T and D444H) is a common cause of profound biotinidase deficiency in children ascertained by newborn screening the the United States. Mutations in brief no. 128. Online

Biotinidase deficiency is inherited as an antosomal recessive trait that, unless treated with pharmacologic doses of biotin, can result in neurologic and cutaneous symptoms. We have identified two new mutations in exon D of the biotinidase gene of children with profound biotinidase deficiency ascertained by newborn screening. Transition 511G->A near the 5' end of exon D results in a substitution of threonine for alanine 171 (A171T) and transversion 1330G->C occurs close to the 3' end of exon D causing a substitution of histidine for aspartic acid 444 (D444H). The D444H mutation was detected in four individuals from our normal population whose mean serum biotinidase activity is 5.25 nmol/min/ml, which is significantly lower than the mean normal activity (7.1 nmol/min/ml). We calculated that this mutation causes a 52% loss of activity in the aberrant enzyme. Twenty-three individuals with the D444H mutation were found by allele specific oligonucleotide analysis of DNA from 296 randomly-selected, anonymous dried-blood spots. We estimate the frequency of this allele in the general population to be 0.039. In contrast, no individuals in 376 have the A171T mutation. Fourteen children (eleven probands and three siblings) out of the 31 enzyme-deficient children have both the A171T and D444H mutations. Both mutations are inherited from a single parent as a double mutation allele. The nine families in which this allele was identified are of mostly European ancestry, although the mutation cannot be attributed to a specific nationality or ethnic group. The serum of a child who is homozygous for the double mutation allele has very little CRM and the aberrant enzyme has very low biotinylhydrolase activity and no botinyl-transferase activity. This double mutation allele (A171T and D444H) is a common cause of profound biotinidase deficience in children ascertained by newborn screening in the United States.     

Rapid diagnosis of late-onset Pompe disease by fluorometric assay of alpha-glucosidase activities in dried blood spots

The enzymatic defect in Pompe disease is insufficient lysosomal acid alpha-glucosidase (GAA) activity which leads to lysosomal glycogen accumulation. We recently introduced a simple and reliable method to measure GAA activity in dried blood spots using Acarbose, a highly selective alpha-glucosidase inhibitor, to eliminate isoenzyme interference. Here we demonstrate that this method efficiently detects late-onset Pompe patients who are frequently misdiagnosed by conventional methods due to residual GAA activity in other tissue types.     

Oxidative stress and the pathogenesis of scleroderma: the Murrell’s hypothesis revisited

Systemic sclerosis (SSc, scleroderma) is a devastating, immune-mediated, multisystem disorder characterized by microvasculature damage, circulating autoantibodies, and fibroblast activation, leading to massive fibrosis of skin, vessels, muscles, and visceral organs. Scleroderma causes disability and death as the result of end-stage organ failure. At present, no specific diagnostic nor therapeutic tools are available to handle the disease. In spite of significant effort, the etiology and pathogenesis of SSc remain obscure and, consequently, the disease outcome is unpredictable. Several years ago, Murrell suggested a unifying hypothesis linking the pathogenesis of scleroderma to the generation of a large excess of reactive oxygen species. This hypothesis has been substantiated by several reports indicating the presence of an abnormal redox state in patients with scleroderma. This review will summarize the available evidence supporting the link between free radicals and the main pathological features of scleroderma.     

A comparison of the phenotype and genotype in adenomatous polyposis patients with and without a family history

Objectives: Adenomatous polyposis of the colon is often secondary to an inherited mutation in adenomatous polyposis coli (APC) gene, however, approximately one third of patients have no family history of the disease. We studied the phenotype and genotype of adenomatous polyposis in patients without a family history. Methods: A cohort of 57 unrelated adenomatous polyposis patients were evaluated. Seventeen patients with no family history were compared with 40 patients who had a positive family history of the disease. Family history and medical records were collected and analyzed. Germline APC and Mut Y homologue (MYH) testing was undertaken. Results: Patients without a family history were diagnosed with polyposis at an older age (41 years vs. 32 years) and presenting more frequently with symptoms (76 vs 20, P < 0.05). The number of colonic polyps and frequency of extracolonic manifestation associated with adenomatous polyposis did not differ between the two groups. APC mutations were detected less frequently among patients without a family history of the disease (4 out of 17 vs 25 out of 40, P=0.007), even among those with greater than 100 colorectal adenomas (4 out of 12 versus 21 out of 29, P=0.03). One homozygous MYH mutation carrier (G382D) was detected among the six patients without a family history and without a germline APC mutation who were tested. Conclusions: Adenomatous polyposis patients without a family history are usually diagnosed with symptoms, and at a later age. Phenotypically, they are similar to those with a family history. However, germline APC mutations are detected far less frequently in patients without a family history. A small percentage of these cases may be secondary to biallelic germline MYH mutations.     

Deletion/insertion mutation that causes biotinidase deficiency may result from the formation of a quasipalindromic structure

Biotinidase is responsible for recycling the vitamin biotin from biocytin that is formed after the proteolytic degradation of the biotin- dependent carboxylases. We have identified a deletion/insertion mutation within exon D of the human biotinidase gene in a child with biotinidase deficiency. The mutation causes a frame shift and premature termination which are predicted to result in a truncated protein. We propose that the mutation occurred during DNA replication by either of two mechanisms. Both mechanisms involve formation of a quasipalindromic hairpin loop in the template and dissociation of DNA polymerase alpha. This mutation supports the formation of palindromic structures as a possible cause of deletions in eukaryotes, and supports the proposal, derived from in vitro studies, that polymerase alpha may preferentially arrest or dissociate at specific template sequences.      

Gaucher disease in Colombia: mutation identification and comparison to other Hispanic populations

Gaucher disease is the most common of the lysosomal storage disorders, affecting all ethnic groups. The pathology of this recessively inherited disease arises from the accumulation of glucocerebroside in tissues due to deficient activity of the enzyme glucocerebrosidase (E.C. 3.2.1.45). The glucocerebrosidase (GBA) gene spans a 7.2kb fragment located on locus 1q 21, consisting of 11 exons and 10 introns. Located 16 kb downstream is a highly homologous pseudogene sequence [M. Horowitz, S. Wilder, Z. Horowitz, O. Reiner, T. Gelbart, E. Beutler, The Human Glucocerebrosidase gene and pseudogene: structure and evolution. Genomics 4 (1) (1989) 87-96.]. Fourteen fragments comprising 11 exons of the GBA gene were analyzed in DNA samples from 25 Colombian patients using denaturing High Pressure Liquid Chromatography (DHPLC). Sequencing of abnormal findings led to the discovery of three novel mutations (c.595_596 delCT, c.898 delG and c.1,255 G>C [p.D 419 H] in exons 6, 7, and 9 of the GBA gene) with high prevalence among Colombian patients. We have also found the presence of a double mutation p.L 483 P+p.E 355 K (L 444 P+E 326 K, traditional nomenclature) in two different families classified as Gaucher type 1. This mutation was previously reported in one patient with Gaucher type 2. We have found DHPLC to be a reliable and sensitive method for the detection of mutations and allelic variation in Gaucher patients.     

Analysis and enantioresolution of donepezil by capillary electrophoresis

The analysis of donepezil, a centrally acting acetylcholine esterase inhibitor, is described by a CZE method suitable for applications in pharmaceutical field. A rapid migration of the analyte was obtained under acidic conditions (pH 3.0); with detection wavelength of 320 nm a LOD of 0.8×10⁻³ mg/ml was provided. Applications on real sample (pharmaceuticals) were carried out using two different instruments with comparable results in terms of reproducibility and accuracy. The use of chiral selectors in the running buffer allowed the enantioseparation of donepezil; charged cyclodextrins (carboxymethyl-β-cyclodextrin and sulfated-β-cyclodextrin) were suitable for the chiral resolution of the analyte. Interesting results were also obtained using human serum albumin. The protein-based CE enantioseparation was carried out at pH 7.4 avoiding the partial filling technique due to the good absorptivity of donepezil at 320 nm. Interestingly, the use of bicine as BGE provided a significative improvement in the enantioresolution compared to that obtained by phosphate buffer.