Molecular analysis of GALT gene in Argentinian population: Correlation with enzyme activity and characterization of a novel Duarte-like allele.

BACKGROUND: Classical galactosemia is an autosomal recessive inherited metabolic disorder caused by mutations in the galactose-1-phosphate uridyltransferase (GALT) gene. GALT enzyme deficiency leads to the accumulation of galactose-1-phosphate in various organs, causing hepatic, renal and cerebral impairment. Over 300 mutations have been reported in the GALT gene. The aim of this study was to describe molecular characterization of GALT gene in Argentinian patients with decreased GALT activity, and to correlate molecular results with enzyme activity. METHODS: 37 patients with enzyme activity below 6.3 µmol/h/g Hb (35% of normal value) were included. GALT activity was measured on red blood cells. DNA was extracted from peripheral blood. p.Gln188Arg mutation was studied by PCR-RFLP and, on samples negative or heterozygous, GALT gene was sequenced. In vivo splicing analysis of the GALT gene was performed on RNA extracted from leukocytes of one patient. RESULTS: 14 different sequence variations were identified among 72 unrelated alleles. The two most common disease-causing mutations were p.Gln188Arg (24/72) and p.Lys285Asn (9/72). Three novel mutations were detected. One of them, c.688G>A, caused partial skipping of exon 9 of the GALT gene. Enzyme activity correlated with GALT genotype in 36 of the 37 patients. CONCLUSION: This is the first report of sequence variations in the GALT gene in the Argentinian population. This study highlights the contribution of the molecular analysis to the diagnosis of Galactosemia and reveals c.688G>A as a novel Duarte-like variant, with a high prevalence in our population.

Molecular diagnosis of epileptic encephalopathy of the first year of life applying a customized gene panel in a group of Argentinean patients.

OBJECTIVE: The aim of this study was to perform a molecular characterization of 17 Argentinean pediatric patients with diagnosis of having epileptic encephalopathies (EEs) of the first year of life without known etiology, applying next-generation sequencing (NGS). METHODS: We included 17 patients with EE with age of onset under 12 months without known etiology after ruling out structural abnormalities, metabolic disorders, and large chromosomal abnormalities. They presented with the following clinical phenotypes: Dravet syndrome (DS; n: 7), epilepsy of infancy with migrating focal seizures (EIMFS; n: 3), West syndrome (WS; n: 2), and undetermined epileptic encephalopathy (UEE; n: 5). Neurologic examinations, seizure semiology, brain magnetic resonance imaging, and standard electroencephalography (EEG) or video-EEG studies were performed in all cases. Using a custom amplicon strategy, we designed an NGS panel to study 47 genes associated with EEs. RESULTS: Pathogenic variants were detected in 8 cases (47%), including seven novel pathogenic variants and one previously reported as being pathogenic. The pathogenic variants were identified in 6 patients with DS (SCN1A gene), one with EIMFS (SCN2A gene), and one with UEE (SLC2A1 gene). Nonrelevant variants were identified in the patients with WS. CONCLUSION: We demonstrated the feasibility of an NGS-gene panel approach for the analysis of patients with EE in our setting. A genetic diagnosis was achieved in nearly 50% of patients, 87% of them presenting with nonpreviously reported variants. The early identification of the underlying causative genetic alteration will be a valuable tool for providing prognostic information and genetic counselling and also to improve therapeutic decisions in Argentinean patients.

Gene polymorphism profiles of drug-metabolising enzymes GSTM1, GSTT1 and GSTP1 in an Argentinian population.

BACKGROUND: Glutathione S-transferases (GSTs) are drug-metabolising enzymes involved in biotransformation of carcinogens, drugs, xenobiotics and oxygen free radicals. Polymorphisms of GST genes contribute to inter-individual and population variability in the susceptibility to environmental risk factors, cancer predisposition and pharmacotherapy responses. However, data about GST variability in Argentina are lacking. AIM: The purpose was to determine the prevalence of GSTM1, GSTT1 and GSTP1 polymorphisms in the general population from a central region of Argentina and to perform inter-population comparisons. SUBJECTS AND METHODS: GSTM1 and GSTT1 gene deletions and GSTP1 c.313A > G were genotyped by PCR assays in 609 healthy and unrelated Argentinians. RESULTS: The frequencies of variant genotypes in Argentinians were GSTM1-null (45%), GSTT1-null (17%) and GSTP1-GG (11%). GSTM1-present genotype was significantly associated with GSTP1-AG or GSTP1-GG variants (p = 0.037; p = 0.034, respectively). Comparison with worldwide populations demonstrated that the GST distributions in Argentina are similar to those reported for Italy and Spain, whereas significant differences were observed regarding Asian and African populations (p < 0.001). CONCLUSION: This study has determined, for the first time, the normative profile of three pharmacogenetically relevant polymorphisms (GSTM1, GSTT1 and GSTP1) in the largest Argentinian cohort described to date, providing the basis for further epidemiological and pharmacogenetic studies in this country.

Genotype-phenotype correlation of SMN locus genes in spinal muscular atrophy children from Argentina.

BACKGROUND/PURPOSE: Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disorder, considered one of the leading causes of infant mortality. It is caused by mutations in the SMN1 gene. A highly homologous copy of this gene named SMN2 and other neighbouring genes, SERF1A and NAIP, are considered phenotypic modifiers of the disease. In recent years, notable advances have been made in SMA research regarding evaluation, prognosis, and therapeutic options. Thus, genotype-phenotype studies in SMA are important to stratify patients for motor function tests and for envisaged clinical trials. The aim of this study was to provide clinical and molecular data of a series of Argentinean children with SMA to establish a comprehensive genotype-phenotype correlation. METHODS: 144 Argentinean children with SMA (56 children with type I, 58 with type II, and 30 with type III) were evaluated. The copy number of SMN2, SERF1A, and NAIP genes was established using MLPA (Multiplex Ligation-dependent Probe Amplification) and then correlated with the patients clinical subtypes. To improve clinical characterization we considered the initial symptoms that prompted the consultation, age of acquisition of motor abilities to independent walking and age at loss of gait. We also evaluated clinical and molecular features of sibling pairs in seven families. RESULTS: A strong correlation was observed between the SMN2 copy number and SMA phenotype while SERF1A and NAIP copy number showed a moderate correlation. We observed intra- and inter-family differences among the SMA types. CONCLUSION: This first genotype-phenotype correlation study in Argentinean SMA children provides data to improve patient stratification and define more adequate follow-up parameters.

Pharmacogenetic studies in children with acute lymphoblastic leukemia in Argentina.

The aim of this study was to evaluate the influence of the most common genetic variants in methylenetetrahydrofolate reductase (MTHFR), thiopurine methyltransferase (TPMT) and glutathione-S-transferases (GSTs) on the outcome of acute lymphoblastic leukemia (ALL) treatment in Argentinean children. Two hundred and eighty-six patients with ALL treated with two Berlin-Frankfurt-Münster (BFM)-based protocols were analyzed. Ten genetic variants were studied. Toxicity was evaluated during the consolidation phase. Children who received 2 g/m(2)/day of methotrexate and carried at least one 677T allele in MTHFR showed an increased risk of developing severe leukopenia (p = 0.004) and neutropenia (p = 0.003). Intermediate-risk (IR) patients with a heterozygous TPMT genotype had a higher probability of event-free survival than those with a wild-type genotype. Genotyping of MTHFR polymorphisms might be useful to optimize consolidation therapy, reducing the associated severe hematologic toxicity. Further studies are necessary to establish the usefulness of MTHFR and TPMT variants as additional markers to predict outcome in the IR group.

Mannose-binding lectin gene as a modifier of the cystic fibrosis phenotype in Argentinean pediatric patients.

BACKGROUND: There is a considerable variation in the phenotype and course of the disease in cystic fibrosis (CF) even in patients with the same CFTR genotype, suggesting that other factors are important for prognosis. Mannose-binding lectin (MBL) has been proposed as one of these factors. We therefore investigated the influence of MBL2 gene variants on disease severity, age at acquisition of Pseudomonas aeruginosa, and survival in CF patients. METHODS: MBL2 variants were studied in 106 Argentinean pediatric CF patients carrying two severe CFTR mutations. Clinical phenotype was defined according to the Shwachman score and lung function tests. Age at infection with P. aeruginosa and age at death were also recorded. RESULTS: MBL insufficiency was associated with a 3.5-fold risk of having a severe phenotype (CI 95%: 1.2-10.3, p=0.03). It was also associated with an earlier onset of infection with P. aeruginosa (p=0.035). No statistically significant differences were found in FEV1 and survival. CONCLUSIONS: MBL insufficiency was associated with detrimental progression of the disease. These results together with previous findings suggest that the effect of MBL2 expression may be a major determinant of the severity of the clinical phenotype in patients with CF.

Homozygous N540K hypochondroplasia--first report: radiological and clinical features.

We describe a 16-month-old male with N540K homozygous mutation in the FGFR3 gene who showed a more severe phenotype than hypochondroplasia (HCH). To our knowledge, a homozygous state for this mutation causing HCH has not been reported before. The clinical and radiological characteristics of our patient represent an intermediate condition between achondroplasia and achondroplasia/hypochondroplasia compound heterozygosity. This case represents a new expression of FGFR3 spectrum and it is of considerable importance for the genetic counseling in cases where both parents are affected with HCH.

Mapping the differences in care for 5,000 spinal muscular atrophy patients, a survey of 24 national registries in North America, Australasia and Europe.

Spinal muscular atrophy (SMA) is an autosomal recessive genetic disorder characterised by the degeneration of motor neurons and progressive muscle weakness. It is caused by homozygous deletions in the survival motor neuron gene on chromosome 5. SMA shows a wide range of clinical severity, with SMA type I patients often dying before 2 years of age, whereas type III patients experience less severe clinical manifestations and can have a normal life span. Here, we describe the design, setup and utilisation of the TREAT-NMD national SMA patient registries characterised by a small, but fully standardised set of registry items and by genetic confirmation in all patients. We analyse a selection of clinical items from the SMA registries in order to provide a snapshot of the clinical data stratified by SMA subtype, and compare these results with published recommendations on standards of care. Our study included 5,068 SMA patients in 25 countries. A total of 615 patients were ventilated, either invasively (178) or non-invasively (437), 439 received tube feeding and 455 had had scoliosis surgery. Some of these interventions were not available to patients in all countries, but differences were also noted among high-income countries with comparable wealth and health care systems. This study provides the basis for further research, such as quality of life in ventilated SMA patients, and will inform clinical trial planning.

Influence of ß(2)-adrenergic receptor polymorphisms on asthma exacerbation in children with severe asthma regularly receiving salmeterol.

BACKGROUND: New evidence suggests that different ß(2)-adrenergic receptor (ß2AR) polymorphisms may influence asthma control in patients receiving long-acting ß(2)agonists (LABAs) as regular therapy. OBJECTIVES: To determine the influence of ß2AR polymorphisms on asthma exacerbations in children with severe asthma from Argentina receiving inhaled corticosteroid (ICS) and LABAs regularly. METHODS: Ninety-seven children with severe asthma were genotyped for polymorphisms of ß2AR at codons 16 and 27. The number of severe exacerbations, the time of first asthma exacerbation, and the number of hospitalizations during 12 months were assessed. Changes on pulmonary function from the beginning to the end of the study were also evaluated. RESULTS: The number of overall asthma exacerbations and the proportion of children with these events were similar among ß2AR genotypes at position 16 (Arg/Arg, Arg/Gly, and Gly/Gly) and at position 27 (Gln/Gln, Gln/Glu, and Glu/Glu). The time to first asthma exacerbation was similar among individuals carrying different ß2AR polymorphisms. No ß2AR genotype association was found in relation to the number of hospitalizations. Longitudinal analysis of forced expiratory volume in 1 second from baseline to the end of the study also showed no differences among ß2AR genotypes at position 16 or 27. No association was observed among the 3 most common haplotypes (Arg/Arg-Gln/Gln, Gly/Gly-Gln/Gln, and Gly/Gly-Glu/Glu) and the number of participants with asthmatic crisis or with the overall number of exacerbations. CONCLUSION: ß2AR polymorphisms were not associated with an increased risk of having asthma exacerbations or lung function decline in a population of Argentinian children with severe asthma receiving ICS and LABAs regularly.

Influencia del número de copias del gen smn2 y de la deleción del gen naip en el desarrollo y evolución de la atrofia muscular espinal / Influence of smn2 gene copy number and deletion of naip gene in the development and evolution of spinal muscular atrophy

INTRODUCCIÓN La atrofia muscular espinal (AME) se clasifica en tres subtipos pediátricos. El 95% de los niños con AME presenta deleción homocigota del gen SMN1. La variabilidad fenotípica se relaciona con genes modificadores como SMN2 y NAIP. OBJETIVOS Correlacionar el número de copias del gen SMN2 y la deleción del gen NAIP con la severidad de la enfermedad en niños con AME, diagnosticados y en seguimiento. MÉTODOS En el Hospital de Pediatría Juan P. Garrahan se estudió a 98 niños con diagnóstico de AME, categorizados de acuerdo con criterios establecidos a nivel internacional (Consensus Statement for Standard of Care in Spinal Muscular Atrophy 2007). El número de copias del gen SMN2 se determinó mediante Multiplex Ligation-dependent Probe Amplification (MLPA) y PCR en tiempo real. La ausencia de NAIP se determinó por MLPA. RESULTADOS Mediante MLPA se pudo determinar el número de copias de SMN2 en todos los pacientes, con la PCR en tiempo real en 96/98 pacientes. Los resultados de ambas técnicas fueron equivalentes en 95/96 casos. Todos los AME tipo I presentaron 2 copias, mientras que más del 95% de los AME tipo II y III mostraron entre 3 y 4 copias de SMN2. Sólo en el grupo AME tipo III se observaron 4 copias de SMN2. El gen NAIP estuvo ausente en el 76% de los AME tipo I y presente en más del 89% de los AME tipo II y III. DISCUSIÓN El número de copias del gen SMN2 se correlacionó con el fenotipo de AME (más leve a mayor número de copias de SMN2). La ausencia del gen NAIP se asoció con el fenotipo más severo. La metodología MLPA resultó ser más robusta que la PCR en tiempo real y proporcionó mayor información acerca de la región AME.

Thyroid axis dysfunction in patients with Prader-Willi syndrome during the first 2 years of life.

INTRODUCTION: Prader-Willi syndrome (PWS) is a genetic disorder caused by the loss of expression of paternally transcribed genes in a highly imprinted region of chromosome 15q11-13. The clinical phenotype has been well characterized, mostly related to hypothalamic dysfunction. Even though central hypothyroidism has been documented in 20-30% of patients with PWS, thyroid function during the first 2 years of life has not been clearly defined. OBJECTIVE: To evaluate hypothalamic-pituitary-thyroid function in infant PWS patients. STUDY DESIGN: Eighteen patients with PWS, aged 0.16-2 years, were included in a prospective study. PWS diagnosis was based on clinical features and molecular analysis. Serum total (T) T4, free (F) T4, T3 and thyroid-stimulating hormone (TSH) were evaluated in the patients with PWS included in the study. Serum hormone values were compared to those of a large reference population of the same age. RESULTS: In 13 of 18 patients with PWS (72.2%), serum TT4 and/or FT4 levels were below the 2.5th percentile of the reference population, while in only one PWS patient serum T3 was below this cut-off. CONCLUSION: The results of this study suggest that transient or definitive thyrotropin-releasing hormone (TRH)-TSH thyroid axis dysfunction may frequently be present in infant PWS patients. Paediatricians should be aware of this dysfunction in this critical period of thyroid hormone action on neurological development.

Prevalence of DFNB1 mutations in Argentinean children with non-syndromic deafness. Report of a novel mutation in GJB2.

OBJECTIVE: Mutations in DFNB1 locus, containing GJB2 (connexin 26) and GJB6 (connexin 30) genes, are the most common cause of autosomal recessive non-syndromic hearing loss. More than 100 mutations in GJB2 have been reported worldwide. Two deletions in GJB6, del(GJB6-D13S1830) and del(GJB6-D13S1854), have been found to be frequent in the Spanish population. The aim of this study was to determine the prevalence of GJB2 mutations and both GJB6 deletions in Argentinean children with non-syndromic deafness. METHODS: This study included 94 unrelated children with moderate to profound non-syndromic sensorineural hearing impairment. Molecular analysis was performed using a tiered approach. All DNA samples were screened for c.35delG mutation by PCR/RFLP. Samples from patients who were not homozygous for c.35delG were analysed for the presence of GJB6 deletions by PCR multiplex. The samples that remained unresolved after screening were further analysed by direct sequencing of GJB2 coding region. Finally, the splice site mutation IVS1+1G-->A was analysed by PCR/RFLP. RESULTS: Sequence variations in the GJB2 and GJB6 genes were found in 49 of the 94 unrelated patients. The most prevalent GJB2 mutation, c.35delG, was found in 40 of the 68 pathogenic alleles with the second most common allele being p.R143W (4/68). Fourteen sequence variations other than c.35delG were identified. Seven already described mutations were present in more than one allele; among them, IVS1+1G-->A, the rare splice site mutation flanking exon 1. In addition to known disease-related alterations, a novel GJB2 mutation, c.262G>C (p.A88P), was also identified. Six alleles were identified carrying GJB6 deletions; the most prevalent was del(GJB6-D13S1830). The frequency of the latter was found to be as high as that found in Spain from where Argentina has received one of its major immigration waves. CONCLUSIONS: The overall frequency of GJB2/GJB6 mutations in the present sample is in agreement with other Caucasian populations. As expected, c.35delG was the most prevalent mutation. The deletion del(GJB6-D13S1830) was the second most common mutation. These findings reinforce the importance of the study of GJB2/GJB6 genes in diagnosis to provide early treatment and genetic counselling.

Beta 2-adrenergic polymorphisms and total serum IgE levels in children with asthma from Argentina.

BACKGROUND: Beta 2-Adrenergic receptor polymorphisms occurring at amino acid positions 16 (arginine/glycine) and 27 (glutamine/glutamic acid) are known to be functionally relevant. Associations with several asthma-related phenotypes, such as total serum IgE, have been investigated with different results. OBJECTIVE: To determine the contribution of polymorphisms and haplotypes of beta 2-adrenergic receptor with serum IgE levels in children from Argentina with mild, moderate, and severe asthma. METHODS: Beta 2-Adrenergic receptor polymorphisms were analyzed in 124 white asthmatic children using polymerase chain reaction during a 3-year period (January 1, 2005, through December 31, 2007). Total serum IgE level was measured by standard methods in all study participants, and age-adjusted values were determined for each individual. RESULTS: Serum levels of IgE were 4.3-fold higher than age-adjusted normal values in the study population. No association was found in regard to asthma severity. A significant difference of IgE serum levels was observed among polymorphisms at position 16, with the highest IgE level in the arginine/arginine group (P = .04). At position 27, even though median levels of IgE in homozygous glutamine were 2.2 times higher than homozygous glutamic acid, this increase did not reach statistical significance. When the population was stratified according to the most common homozygous haplotypes (arginine-arginine 16/glutamine-glutamine 27, glycine-glycine 16/glutamine-glutamine 27, and glycine-glycine 16/glutamic acid-glutamic acid 27), no association was found in relation to the serum levels of IgE. CONCLUSIONS: Beta 2-Adrenergic receptor polymorphisms, especially homozygous arginine 16, were associated with higher serum IgE levels in children with asthma. These genetic variants appear to contribute to the IgE level in asthmatic children from Argentina.

Influence of beta2-adrenoceptor polymorphisms on the response to chronic use of albuterol in asthmatic children.

BACKGROUND: Several studies have suggested that after regular use of short acting beta2-agonists the bronchodilator effect of the drug may decline and this condition would be related to polymorphisms of the beta2-adrenergic receptor (beta2-AR). OBJECTIVE: To assess the frequency of beta2-AR polymorphisms in asthmatic children from Argentina, and to evaluate their influence on bronchodilator desensitization to albuterol over a 4-week treatment. METHODS: beta2-AR genotypes were determined in 117 children with asthma and 101 of them were under 4 weeks treatment with albuterol. Spirometric changes in FEV(1) were recorded at the beginning (day 1) and at the end of the study (day 30) and compared to genotypes at position 16 and 27 of the receptor. The frequency of the polymorphisms was calculated in all population. RESULTS: The presence of glutamine at position 27 (Gln27) was significantly more frequent in this Argentinean study population than in other Caucasian populations. The homozygosity for Gln27 polymorphism was associated to a desensitization of the receptor with a decline in the bronchodilator response to albuterol after chronic use. CONCLUSION: Gln27 polymorphism might be a marker for adverse clinical outcomes with chronic beta2-agonist exposure in children with asthma from Argentina.

Carrier frequency of the 35delG and A1555G deafness mutations in the Argentinean population. Impact on the newborn hearing screening.

OBJECTIVE: Hearing loss is a complex multifactorial disorder caused by genetic and environmental factors. The 35delG mutation in the GJB2 gene is the most prevalent mutation in Caucasian patients with genetic sensorineural deafness. The A1555G mutation in the mitochondrial 12S rRNA is the main genetic alteration associated with aminoglycoside-induced deafness. The aim of this study was to evaluate the prevalence of both mutations in general population of Argentina. METHODS: A total of 712 samples of unrelated healthy blood donors and 330 newborn dried blood spots were studied by PCR-RFLP. RESULTS: The 35delG mutation was detected in 11/ 712 unrelated blood donors. The carrier frequency found in this sample (1/65) proved to be lower than that found in Southern European countries, mainly Spain and Italy, from where Argentina originally received its major immigration waves. When the populations of Southern Europe were considered altogether, this difference reached statistical significance. The A1555G mutation was not found in any of the 1042 samples tested. CONCLUSIONS: Taking into account the 35delG carrier frequency found in this study, it could be estimated that 130-160 children with congenital deafness due to mutations in the connexin genes would be born per year in Argentina. In contrast, the mitochondrial mutation A1555G appears to be infrequent in general Argentinean population.

Clinical-etiologic correlation in children with Prader-Willi syndrome (PWS): an interdisciplinary study.

Prader-Willi syndrome (PWS) is a multisystemic disorder caused by the loss of expression of paternally transcribed genes within chromosome 15q11-q13. Most cases are due to paternal deletion of this region; the remaining cases result from maternal uniparental disomy (UPD) and imprinting defects. To better understand the phenotypic variability of PWS, a genotype-phenotype correlation study was performed in 91 children with PWS. Patients were diagnosed by Southern Blot Methylation assay and genetic subtypes were established using FISH and microsatellite analyses. Fifty-nine subjects with deletion (31/28 males/females; mean age 3.86 years), 30 with UPD (14/16 males/females; mean age 3.89 years) and 2 girls with a presumed imprinting defect (mean age 0.43 yrs) were identified. For correlation purposes patients were grouped as "deleted" and "non-deleted." An increased maternal age was found in the UPD group. Four of Holm's criteria were more frequently present in the deleted group: need for special feeding techniques, sleep disturbance, hypopigmentation, and speech articulation defects. Concerning cognitive assessments, only 9.52% of subjects with deletion had Full-Scale IQ (FSIQ) > or =70, while 61.53% of subjects without deletion had FSIQ > or =70. Similar results were found in behavioral measures. Sleep disorders and carbohydrate metabolism were systematically assessed. Polysomnoghaphic studies revealed a higher frequency of central events with desaturations > or =10% in the deleted group (P = 0.020). In summary, the phenotype was significantly different between both groups in certain parameters related to the CNS. These results might be related to the differences in brain gene expression of the genetic subtypes.

Characterization of alterations in carbohydrate metabolism in children with Prader-Willi syndrome.

OBJECTIVE: To study carbohydrate metabolism and insulin sensitivity and secretion in children and adolescents with Prader-Willi syndrome (PWS) compared with multifactorial obesity (MO) controls. PATIENTS AND METHODS: Seventy-five patients with PWS and 395 controls with MO were studied by oral glucose tolerance test. Insulin resistance (IR) and beta-cell function were assessed by homeostasis model assessment (HOMA), insulin glucose index, fasting insulin and insulin sensitivity index. RESULTS: The incidence of diabetes mellitus was 0% in PWS and 1.5% in MO, while carbohydrate intolerance was 9.3% in the former group and 7.6% in the latter (NS); basal insulin level (12 +/- 8.2 vs 22.3 +/- 25 mU/ml) and HOMA-IR (2.47 +/- 1.6 vs 4.18 +/- 5.05) were lower in PWS (p = 0.004 and 0.04, respectively), whereas HOMA beta-cell index was lower in PWS than in MO (59 +/- 42 vs 102 +/- 119, p = 0.03). ISI Composite was higher in PWS compared to MO (6 +/- 5.7 vs 4.18 +/- 5.05, p = 0.04). CONCLUSION: Patients with PWS presented lower insulin resistance and a dissociation between beta-cell secretion and the degree of obesity.

High specificity of head circumference to recognize N540K mutation in hypochondroplasia.

Hypochondroplasia (HCH) is a skeletal dysplasia characterized by short stature with disproportionately short arms and legs. Anthopometrics and skeletal features are very similar to achondroplasia but milder. Seventy per cent of affected individuals are heterozygous for a mutation of the FGFR3 gene. Differences in some anthropometric measurements in affected patients with and without N540K mutation were analysed. Diagnosis of the disease was made on the presence of previously standardized criteria: short stature, short limbs and three or more X-ray features. Genomic DNA was extracted from peripheral blood leukocytes by standard procedures. PCR amplification of exons 10, 13 and 15 of FGFR3 was performed. Twenty-six patients were studied (median age was 7.31, range 0.27-20.0 years). Sitting height, body proportions and head circumference (HC) were statistically different in the mutated group. Receiver Operating Characteristic (ROC) analysis was carried out in order to estimate the discriminating power of different cut-off points of HC for recognizing patients with and without the mutation. A figure of 1.86 SD for HC was found to have a sensitivity of 73.3% and specificity of 100% for detecting HCH patients with the mutation. All of them had a HC greater than 1.86?SD. These results contribute to a better characterization of the clinical-molecular relationships in HCH.

Caracterización de tres microsatelites del gen de fibrosis quistica en familias argentinas / Characterization of 3 microsatellites of the cystic fibrosis gene in Argentine families

La población de Argantina es altamente Heterogénea para las mutaciones del gen regulador de la conductancia de transmembrana de la fibrosis quística (CFTR). El estudio de 14 mutaciones reportadas entre las más frecuentes, detectó ambos alelos mutados (genotipo completo) en sólo el 51 porciento de los pacientes. Este estudio confirmó el diagnóstico de Fibrosis Quística de estos pacientes y posibilitó detectar entres sus familiares, individuos portadores asintomáticos. Sin embargo, en el resto de los pacientes, el análisis molecular directo, no aportó la información necesaria para el asesoriamento familiar. Con el objetivo de estabelecer la transmisióan de microsatélite (IVS17bTA, IVS8CA y IVS17bCA) localizados en regiones intrónicas del gan CFTR. En las 40 familias FQ analizadas, se detectaron diferentes variantes alélicas, 15 para IVS17TA, 10 para IVS8CA y 4 para IVS17CA . El contenido de información polimórfica y de heterocigosis de estos marcadores fue elevado, a exepción de IVS17bCA que resultó poco polimórfico. A través del análisis simultáneo de estos tres microsatélite se pudo asesorar al 100 porciento de las familias. Nuestros resultados demuestran que estos microsatélites, constituyen un excelente gru[po de marcadores, útiles para realizar estudios de ligamiento de población Argentina.