RESUMEN
Human ALG2 encodes an α 1,3mannosyltransferase that catalyzes the first steps in the synthesis of N-glycans in the endoplasmic reticulum. Variants in ALG2cause a congenital disorder of glycosylation (CDG) known as ALG2-CDG. Up to date, nine ALG2-CDG patients have been reported worldwide. ALG2-CDG is a rare autosomal recessive inherited disorder characterized by neurological involvement, convulsive syndrome of unknown origin, axial hypotonia, and mental and motor regression. In this study, we used MALDI-TOF MS to define both total serum protein and transferrin (Tf) N-glycan phenotypes in three ALG2-CDG patients carrying a c.752G > T, p.Arg251Leu ALG2 missense variant in homozygous state, as determined by exome sequencing. Comparing it to control samples, we have observed Tf under-occupancy of glycosylation site(s) typical of a defective N-glycan assembly and the occurrence of oligomannose and hybrid type N-glycans. Moreover, we have observed a slight oligomannose accumulation in total serum glyco-profiles. The increased heterogeneity of serum N-glycome in the studied patients suggests a marginal disarrangement of the glycan processing in ALG2-CDG. Previous studies reported on slightly increased concentrations of abnormal serum N-glycans in CDG-I due to defects in the mannosylation steps of dolichol-linked oligosaccharide biosynthesis. This preliminary work aims at considering serum N-glycan accumulation of high mannosylated glycoforms, such as oligomannose and hybrid type N-glycans, as potential diagnostic signals for ALG2-CDG patients.
Asunto(s)
Trastornos Congénitos de Glicosilación/etiología , Manosiltransferasas/genética , Polisacáridos/sangre , Argentina , Niño , Preescolar , Trastornos Congénitos de Glicosilación/genética , Femenino , Glicosilación , Homocigoto , Humanos , Focalización Isoeléctrica , Masculino , Fenotipo , Polisacáridos/análisis , Espectrometría de Masa por Láser de Matriz Asistida de Ionización Desorción , Transferrina/metabolismo , Secuenciación del ExomaRESUMEN
BACKGROUND: The incidence, prevalence, and molecular epidemiology of urea cycle disorders (UCDs) in Argentina remain underexplored. The present study is the first to thoroughly assess the clinical and molecular profiles of UCD patients examined at a single reference center in Argentina. RESULTS: Forty-nine UCD cases were collected. About half (26/49, 53%) manifested neonatally with classical presentation and had a high mortality (25/26, 96%). Ornithine transcarbamylase deficiency (OTCD) was the most common UCD (26 patients). Argininosuccinate synthetase deficiency (ASSD) was detected in 19 cases, while argininosuccinate lyase deficiency (ASLD) was diagnosed in 4 cases. Molecular genetic analysis revealed 8 private OTC mutations and two large deletion/duplication events in the OTC gene. Most mutations in the ASS1 and ASL genes were recurrent missense changes, and four alterations were novel. The clinical outcome of our UCD cohort was poor, with an overall mortality of 57% (28/49 cases), and a 28% (6/21) disability rate among the survivors. CONCLUSIONS: Most patients in our case series showed severe neonatal onset, with high morbidity/mortality. We detected in total 19 mutations, most of them recurrent and of high frequency worldwide. Noteworthy, we highlight the presence of a geographic cluster with high prevalence of a point mutation in the ASS1 gene. This study suggests that these disorders may be more frequent than commonly assumed, and stresses the need for increased awareness amongst health professionals and greater availability of diagnostic tools for accurate identification, early diagnosis, and timely treatment.
Asunto(s)
Trastornos Innatos del Ciclo de la Urea/epidemiología , Trastornos Innatos del Ciclo de la Urea/genética , Trastornos Innatos del Ciclo de la Urea/patología , Argentina/epidemiología , Aciduria Argininosuccínica/epidemiología , Aciduria Argininosuccínica/genética , Aciduria Argininosuccínica/patología , Niño , Preescolar , Citrulinemia/epidemiología , Citrulinemia/genética , Citrulinemia/patología , Femenino , Humanos , Hiperamonemia/epidemiología , Hiperamonemia/genética , Hiperamonemia/patología , Lactante , Recién Nacido , Masculino , Mutación/genética , Enfermedad por Deficiencia de Ornitina Carbamoiltransferasa/epidemiología , Enfermedad por Deficiencia de Ornitina Carbamoiltransferasa/genética , Enfermedad por Deficiencia de Ornitina Carbamoiltransferasa/patologíaRESUMEN
Classical citrullinemia type I (CTLN1) is an autosomal recessive disorder encoded by the ASS1 gene, which codes for argininosuccinate synthetase (ASS), the rate-limiting enzyme in the urea cycle. Previously, we identified the mutation p.G390R in patients with CTLN1 in the San Luis Province of Argentina. Here, we report the results of p.G390R analysis in a larger number of probands, relatives of involved families and additionally, a population study to identify carriers. Altogether, we analyzed 420 alleles, belonging to 12 probands, 26 relatives, and 172 healthy volunteers. All the probands were homozygous for the mutation, and 21 of 26 relatives were carriers. The occurrence of the disease in descendants of couples at risk was 57% showing a preferential transmission of the mutant allele compared to the normal allele. The carrier frequency in the general San Luis Province population was 4.1%, suggesting the incidence of CTLN1 to be 1:2,427, which is approximately 20 times higher than for the general population. This work suggests that there should be an increased awareness of preconceptual screening of CTNL1 among individuals/couples who are at risk in the San Luis Province in order to better inform them of their reproductive options.Cascade/family and population molecular screening for carrier identification were performed in an Argentinean province with high incidence of CTLN1, a first step to preconceptional screening.
RESUMEN
Congenital disorders of glycosylation (CDG) are genetic diseases caused by abnormal protein and lipid glycosylation. In this chapter, we report the clinical, biochemical, and molecular findings in two siblings with an unidentified CDG (CDG-Ix). They are the first and the third child of healthy consanguineous Argentinean parents. Patient 1 is now a 11-year-old girl, and patient 2 died at the age of 4 months. Their clinical picture involved liver dysfunction in the neonatal period, psychomotor retardation, microcephaly, seizures, axial hypotonia, feeding difficulties, and hepatomegaly. Patient 1 also developed strabismus and cataract. They showed a type 1 pattern of serum sialotransferrin. Enzymatic analysis for phosphomannomutase and phosphomannose isomerase in leukocytes and fibroblasts excluded PMM2-CDG and MPI-CDG. Lipid-linked oligosaccharide (LLO) analysis showed a normal profile. Therefore, this result could point to a deficiency in the dolichol metabolism. In this context, ALG8-CDG, DPAGT1-CDG, and SRD5A3-CDG were analyzed and no defects were identified. In conclusion, we could not identify the genetic deficiency in these patients yet. Further studies are underway to identify the basic defect in them, taking into account the new CDG types that have been recently described.
RESUMEN
OBJECTIVE: Citrullinemia type I (CTLN1) is an urea cycle defect caused by mutations in the argininosuccinate synthetase gene. We report the first identification in Argentina of patients with CTLN1 in a limited geographic area. DESIGN AND METHODS: Molecular analysis in patient/relatives included PCR, sequencing and restriction enzyme assay. RESULTS: The studied families showed the same mutation: ASS~p.G390R, associated with the early-onset/severe phenotype. CONCLUSION: We postulate a possible population cluster. A program to know the carrier frequency in that population is in progress.
Asunto(s)
Sustitución de Aminoácidos/genética , Argininosuccinato Sintasa/genética , Citrulinemia/enzimología , Citrulinemia/genética , Genética de Población , Mutación/genética , Argentina , Familia , Femenino , Genotipo , Geografía , Humanos , Recién Nacido , Masculino , LinajeRESUMEN
Classical homocystinuria is due to cystathionine beta-synthase (CBS) deficiency. More than 130 mutations, which differ in prevalence and severity, have been described at the CBS gene. Mutation p.I278T is very prevalent, has been found in all European countries where it has been looked for with the exception of the Iberian peninsula, and is known to respond to vitamin B6. On the other hand, mutation p.T191M is prevalent in Spain and Portugal and does not respond to B6. We analysed 30 pedigrees from Spain, Portugal, Colombia and Argentina, segregating for homocystinuria. The p.T191M mutation was detected in patients from all four countries and was particularly prevalent in Colombia. The number of p.T191M alleles described in this study, together with those previously published, is 71. The prevalence of p.T191M among CBS mutant alleles in the different countries was: 0.75 in Colombia, 0.52 in Spain, 0.33 in Portugal, 0.25 in Venezuela, 0.20 in Argentina and 0.14 in Brazil. Haplotype analyses suggested a double origin for this mutation. No genotype-phenotype correlation other than the B6-nonresponsiveness could be established for the p.T191M mutation. Additionally, three new mutations, p.M173V, p.I429del and c.69_70+8del10, were found. The p.M173V was associated with a mild, B6-responsive, phenotype.
Asunto(s)
Cistationina betasintasa/genética , Homocistinuria/epidemiología , Homocistinuria/genética , Mutación , Prevalencia , Alelos , Distribución de Chi-Cuadrado , Colombia/epidemiología , Frecuencia de los Genes , Haplotipos , Humanos , Desequilibrio de Ligamiento , Linaje , Portugal/epidemiología , España/epidemiologíaRESUMEN
Cystic Fibrosis (CF) is an autosomal recessive disorder affecting 1/2000-4000 newborns in Caucasian populations. This lethal disease mainly affects respiratory and digestive organs as well as fertility in man. So far, the CF prevalence and mutational spectrum have showed specificity among populations and regions, making it necessary to establish them in each one. In this study, we present the spectrum and frequency of CFTR gene mutations in CF patients from Córdoba (a province with 3.1 millions inhabitants in the middle of Argentina) and its zone of influence, to offer an accurate genetic testing. The study includes 78 families in which 98 patients fulfilled clinical criteria to CF diagnosis. The strategy for the molecular diagnosis comprised analysis of 21 common mutations, microsatellite haplotypes and the complete CFTR gene analysis using scanning techniques followed by sequencing of the abnormal migration patterns. Our first step led us to the identification of 10 mutations that represented 76% of alleles. Another four mutations (p.R1066C, c.1811 + 1.6 kbA > G, c.711 + 1G > T, and p.G85E) were found based on the microsatellite haplotype-mutation association. Finally, 14 mutations were characterized after the CFTR gene scanning, three of them are not previously described (p.G27R, c.622-2A > G, and p.W277R). In summary, we have identified 27 mutations accounting for 94.23% of CF alleles. This characteristic mutational spectrum highlights the 14 most frequent mutations (>1%) in the Córdoba region.
Asunto(s)
Regulador de Conductancia de Transmembrana de Fibrosis Quística/genética , Fibrosis Quística/genética , Adulto , Argentina , Niño , Preescolar , Fibrosis Quística/diagnóstico , Análisis Mutacional de ADN , Femenino , Pruebas Genéticas , Haplotipos , Humanos , Lactante , Recién Nacido , Masculino , Repeticiones de Microsatélite , MutaciónAsunto(s)
Endopeptidasas/biosíntesis , Proteínas de la Membrana/biosíntesis , Lipofuscinosis Ceroideas Neuronales/diagnóstico , Saliva/enzimología , Adolescente , Adulto , Aminopeptidasas , Argentina , Niño , Preescolar , Dipeptidil-Peptidasas y Tripeptidil-Peptidasas , Salud de la Familia , Femenino , Humanos , Lactante , Persona de Mediana Edad , Valores de Referencia , Serina Proteasas , Tioléster Hidrolasas , Tripeptidil Peptidasa 1RESUMEN
Glycogen storage disease type Ia (GSD-Ia) is caused by deleterious mutations in the glucose-6-phosphatase gene (G6PC). A molecular study of this gene was carried out in 11 Argentinean patients from 8 unrelated families. Four missense (p.Gln54Pro, p.Arg83Cys, p.Thr16Arg, and p.Tyr209Cys) and one deletion (c.79delC) mutations have been identified. Two novel mutations, p.Thr16Arg (c.47C>G) located within the amino-terminal domain and p.Tyr209Cys (c.626A>G) situated in the sixth transmembrane helix, were uncovered in this study. Site-directed mutagenesis and transient expression assays demonstrated that both p.Thr16Arg and p.Tyr209Cys mutations abolished enzymatic activity as well as reduced G6Pase stability.
Asunto(s)
Eliminación de Gen , Expresión Génica , Glucosa-6-Fosfatasa/genética , Enfermedad del Almacenamiento de Glucógeno Tipo I/genética , Mutación Missense/genética , Animales , Argentina , Western Blotting , Células COS , Cricetinae , Cricetulus , Análisis Mutacional de ADN , Cartilla de ADN , Femenino , Glucosa-6-Fosfatasa/metabolismo , Enfermedad del Almacenamiento de Glucógeno Tipo I/metabolismo , Humanos , Masculino , Mutagénesis Sitio-Dirigida , Monoéster Fosfórico Hidrolasas/metabolismoRESUMEN
We report the first case of isolated biotin resistant 3-methylcrotonyl-CoA carboxylase (MCC) deficiency in Argentina. The diagnosis was established at 14 months of age by urinary organic-acid analysis and confirmed by enzyme assay in fibroblasts. The patient suffered from severe psychomotor retardation, hypotonia, areflexia, and failure to thrive, and died unexpectedly at 3 years 4 months of life. Brain MRI at 14 months showed signals of the white matter on cerebral T2-weighted, which were indicative of confluent and multiple foci of leukodystrophy, a pattern not previously described in this entity. In addition, high levels of oxypurines were detected in cerebrospinal fluid. This might be related to energetic consequences of the enzyme deficiency in the brain. This case extends the phenotype of isolated MCC deficiency in infancy and suggests this entity should be considered to be one of the possible causes of "metabolic leukodystrophies."