Biomedical subjects

L Zelante

Publications and source records attributed to L Zelante.

At least 91 records · Page 5Linked to original sources

PubMed1998

Molecular basis of Fanconi anemia.

BACKGROUND AND OBJECTIVE: Fanconi anemia (FA) is an autosomal recessive disease characterized by pancytopenia, congenital malformation and high predisposition to developing malignancies. The phenotypical heterogeneity is associated with genetic heterogeneity: at least 8 complementation groups (FA-A to FA-H) have been identified, each group presumably corresponding to a separate disease gene (FAA to FAH). The FAA and FAC genes, which account for 75-80% of the patients, have been cloned. Their protein products have no significant homology to any known protein, or to each other, and may therefore represent elements of a new pathway. This review describes some of the recent contributions to the understanding of the molecular basis of FA. EVIDENCE AND INFORMATION SOURCES: The authors of the present review have been working in the field of FA for several years. In the present review they have critically examined articles published in journals covered by the Science Citation Index and Medline. STATE OF ART AND PERSPECTIVE(S): A variety of biochemical and cellular approaches have been used to determine the molecular defect of FA. Evidence for a possible role of the defective proteins in cell cycle regulation, apoptosis, or DNA stability have been reported. Recently, it has been demonstrated that FAA and FAC proteins bind each other and form a complex found in similar abundance in both cytoplasm and nucleus, suggesting a possible function in nucleus activities. Knowledge of the mutation spectrum occurring in the FA genes may contribute significantly to pathogenesis studies in FA and help to design mutation screening strategies. Further functional studies and the cloning of other FA genes will provide insights into the biological basis of FA and information for developing specific therapies for the disease.

Cell Cycle Proteins↗

PubMed1997

Exclusion of three candidate genes as determinants of congenital dyserythropoietic anemia type II (CDA-II).

Congenital dyserythropoietic anemia type II (CDA-II) is the most common form of inherited dyserythropoiesis. Previous studies have shown that the anion transporter (band 3) is narrower and it migrates faster on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE); this aspect was related to insufficient glycosylation. Biochemical data support the hypothesis that this disease is due to a deficiency of N-acetylglucosaminyltransferase II (GnT II) or alpha-Mannosidase II (alpha-Man II), which represent the key to glycosylation. In addition, a third candidate gene is alpha-Man IIx, which shows a strong homology with alpha-Man II. The knowledge of the chromosomal localization of these putative genes allowed us to perform a linkage study using three sets of microsatellite markers flanking the candidate genes. Six families with two or more affected children were enrolled in this study. The data obtained exclude linkage to all three candidate genes. In consideration of the biochemical data (reduction of enzymatic activity) of the same enzymes, our results suggest the hypothesis that a defect in an unknown transcriptional factor is involved in CDA-II.

Anemia, Dyserythropoietic, Congenital↗

PubMed1997

Hereditary hyperferritinemia-cataract syndrome caused by a 29-base pair deletion in the iron responsive element of ferritin L-subunit gene.

Iron availability regulates ferritin synthesis posttranscriptionally by the interaction between iron-regulatory proteins (IRPs) and an iron responsive element (IRE), a stem-loop sequence located on the 5' untranslated region of ferritin mRNA. IRPs recognize IREs as a sequence/structure motif, blocking ferritin translation. Recently, we and others independently described families with a combination of hyperferritinemia (serum L-ferritin > or = 1,000 microg/L, without iron overload) and congenital bilateral cataract, transmitted as an autosomal-dominant trait. The molecular basis were two distinct point mutations in the highly conserved CAGUG(X) hexaloop of L-ferritin IRE on chromosome 19. A new three-generation family with a similar phenotype and a unique genotype is here reported. DNA amplification by polymerase chain reaction and sequence analysis showed a 29-base pair deletion in the L-ferritin IRE, involving the whole 5' sequence essential to the base pairing of the IRE stem. This deletion is predicted to cause the disruption of IRE stem-loop secondary structure and the nearly complete abolition of the negative control of ferritin synthesis by IRE/IRP binding. Hereditary Hyperferritinemia-Cataract Syndrome (HHCS) appears as a new genetic disorder with a unique phenotype associated with at least four different mutations in the L-ferritin IRE. Hematologists should take into account HHCS in the differential diagnosis of unexplained hyperferritinemia.

Adult↗

PubMed1997

The genomic organization of the Fanconi anemia group A (FAA) gene.

Fanconi anemia (FA) is a genetically heterogenous disease involving at least five genes on the basis of complementation analysis (FAA to FAE). The FAA gene has been recently isolated by two independent approaches, positional and functional cloning. In the present study we describe the genomic structure of the FAA gene. The gene contains 43 exons spanning approximately 80 kb as determined by the alignment of four cosmids and the fine localization of the first and the last exons in restriction fragments of these clones. Exons range from 34 to 188 bp. All but three of the splice sites were consistent with the ag-gt rule. We also describe three alternative splicing events in cDNA clones that result in the loss of exon 37, a 23-bp deletion at the 5' end of exon 41, and a GCAG insertion at the 3' portion also in exon 41. Sequence analysis of the 5' region upstream of the putative transcription start site showed no obvious TATA and CAAT boxes, but did show a GC-rich region, typical of housekeeping genes. Knowledge of the structure of the FAA gene will provide an invaluable resource for the discovery of mutations in the gene that accounts for about 60-66% of FA patients.

Alternative Splicing↗

PubMed1997

Goldenhar complex: a further case with uncommon associated anomalies.

We report on a further case of Goldenhar complex with uncommon and clinically remarkable associated anomalies. This additional case increases the number of observations and descriptions of patients with "expanded Goldenhar complex." Pathogenetic aspects are discussed.

Abnormalities, Multiple↗

PubMed1997

Limb-pelvis hypoplasia/aplasia: a discrete entity in the fibuloulnar developmental field complex.

The limb-pelvis hypoplasia/aplasia (LPHA) syndrome is a rare condition of skeletal malformations affecting the ulnae, pelvic bones, fibulae and femora, sometimes associated with extraskeletal defects. Most reported patients are from the Middle East, and autosomal recessive inheritance was clearly demonstrated on the basis of multiple occurrences of affected sibs born to consanguineous matings. Here we report on a baby girl presenting with the phenotypic characteristics of LPHA. This is second observation of LPHA from Italy, and the fourth outside the Middle East. A paternal first cousin once removed had unilateral fibular hypoplasia and absence of the the 4th and 5th digital rays. The possible link between these cases is discussed in the light of the developmental field theory.

Abnormalities, Multiple↗

PubMed1997

Linkage analysis of Fanconi anaemia in Italy and mapping of the complementation group A gene.

Fanconi anaemia (FA) is an autosomal recessive disease characterised by genetic heterogeneity, with at least five complementation groups (FA-A to FA-E). The FAC gene has been cloned and localised to 9q22.3. The most frequent defective gene, FAA, was recently mapped to chromosome 16q24.3, in a region of 10 cM between D16S498 and the telomere. Eleven FA-A and 16 unclassified Italian families were analysed by microsatellite markers. To define the localisation of the FAA locus further, microsatellites were analysed at 16q24. All the families were consistent with linkage, the highest lod score being observed with D16S1320. Evidence for common haplotypes was obtained in two genetic isolates from the Brenta basin and the Naples region. Autozygosity mapping and haplotype analysis suggest that the FAA locus is distal to D16S305.

Cell Cycle Proteins↗

PubMed1997

Localization of the congenital dyserythropoietic anemia II locus to chromosome 20q11.2 by genomewide search.

Congenital dyserythropoietic anemias (CDA) are genetic disorders characterized by anemia and ineffective erythropoiesis. Three main types of CDA have been distinguished: CDA I and CDA III, whose loci have been already mapped, and CDA II (MIM 224100), the most frequent among CDAs, which is transmitted as an autosomal recessive trait and is known also as "HEMPAS" (hereditary erythroblast multinuclearity with positive acidified serum). We have recruited a panel of well-characterized CDA II families and have used them to search for the CDA II gene by linkage analysis. After the exclusion of three candidate genes, we ob-tained conclusive evidence for linkage of CDA II to microsatellite markers on the long arm of chromosome 20 (20q11.2). A maximum two-point LOD score of 5.4 at a recombination fraction of .00 was obtained with marker D20S863. Strong evidence of allelic association with the disease was detected with the same marker. Some recombinational events established a maximum candidate interval of approximately 5 cM.

Anemia, Dyserythropoietic, Congenital↗

PubMed1997

Mutations of the Fanconi anemia group A gene (FAA) in Italian patients.

Fanconi anemia (FA) is an autosomal recessive disease characterized by progressive pancytopenia, congenital malformations, and predisposition to acute myeloid leukemia. At least five complementation groups (FA-A-FA-E) have been identified. The relative prevalence of FA-A has been estimated at an average of approximately 65% but may widely vary according to ethnic background. In Italy, 11 of 12 patients analyzed by cell-fusion studies were assigned to group FA-A, suggesting an unusually high relative prevalence of this FA subtype in patients of Italian ancestry. We have screened the 43 exons of the FAA gene and their flanking intronic sequences in 38 Italian FA patients, using RNA-SSCP. Ten different mutations were detected: three nonsense and one missense substitutions, four putative splice mutations, an insertion, and a duplication. Most of the mutations are expected to cause a premature termination of the FAA protein at various sites throughout the molecule. Four protein variants were also found, three of which were polymorphisms. The missense mutation D1359Y, not found in chromosomes from healthy unrelated individuals, was responsible for a local alteration of hydrophobicity in the FAA protein, and it was likely to be pathogenic. Thus, the mutations so far encountered in the FAA gene are essentially all different. Since screening based on the analysis of single exons by genomic DNA amplification apparently detects only a minority of the mutations, methods designed to detect alterations in the genomic structure of the gene or in the FAA polypeptide may be helpful in the identification of FAA mutations.

Cell Cycle Proteins↗

PubMed1997

Connexin26 mutations associated with the most common form of non-syndromic neurosensory autosomal recessive deafness (DFNB1) in Mediterraneans.

Non-syndromic neurosensory autosomal recessive deafness (NSRD) is the most common form of genetic hearing loss. Previous studies defined at least 15 human NSRD loci. Recently we demonstrated that DFNB1, located on the long arm of chromosome 13, accounts for approximately 80% of cases in the Mediterranean area. Further analysis with additional markers now identifies several recombinants which narrow the candidate region to approximately 5 cM, encompassed by markers D13S141 and D13S232 and including several ESTs and candidate genes, including the connexin26 (GJB2) gene. Analysis of PCR products from our affected patients' DNA shows two frameshift mutations in the connexin26 gene. Deletion of a G within a stretch of six Gs at position 35 of the GJB2 cDNA (mutation 35delG) leads to premature chain termination and is present in 63% of NSRD chromosomes, demonstrating linkage to chromosome 13. Deletion of a T at position 167 of GJB2 (mutation 167delT), also resulting in premature chain termination, was detected in another patient. Four neutral sequence polymorphisms were also identified. These findings are in agreement with a recent study showing that mutations in the connexin26 gene are associated with genetic forms of deafness in three Pakistani families and that GJB2 is DFNB1. Connexin26 is a member of a large family of proteins involved in formation of gap junctions, which are involved in electrical synapses and the direct transfer of small molecules and ionic currents between neighboring cells. The identification of GJB2 as the DFNB1 gene should provide a better understanding of the biology of normal and abnormal hearing, help form the basis for diagnosis and may facilitate development of strategies for treatment of this common genetic disorder.

Connexin 26↗

PubMed1997

Two mosaic-YY males carrying asymmetric Y chromosomes.

Two patients were referred because of oligospermia and azospermia, respectively. Karyotypic analysis revealed two mosaic-YY males carrying asymmetric Y chromosomes. To our knowledge, no instance of double unequal Y chromosomes has been reported so far in human males. Results of fluorescent in situ hybridization (FISH) studies in spermatozoa from one of these patients revealed a significantly high number of hyperaploid spermatozoa.

Adult↗

PubMed1997

Detection of dystrophin deletion carriers using FISH analysis.

The detection of carrier status in female relatives of Duchenne/Becker muscular dystrophy patients is not always possible and this poses a problem in genetic counseling. We have developed a simple method that can be used in families in which affected males are characterized by the presence of a deletion within the dystrophin gene. PCR fragments, corresponding to the deleted regions are used as fluorescent probes for hybridization of peripheral lymphocytes nuclei of female relatives. The results obtained clearly demonstrate the feasibility of this method for detecting female DMD/BMD carriers.

Dystrophin↗

PubMed1997

Localization, by linkage analysis, of the cystinuria type III gene to chromosome 19q13.1.

Cystinuria is an autosomal recessive aminoaciduria in which three urinary phenotypes (I, II, and III) have been described. An amino acid transporter gene, SLC3A1 (formerly rBAT), was found to be responsible for this disorder. Mutational and linkage analysis demonstrated the presence of genetic heterogeneity in which the SLC3A1 gene is responsible for type I cystinuria but not for type II or type III. In this study, we report the identification of the cystinuria type III locus on the long arm of chromosome 19 (19q13.1), obtained after a genomewide search. Pairwise linkage analysis in a series of type III or type II families previously excluded from linkage to the cystinuria type I locus (SLC3A1 gene) revealed a significant maximum LOD score (zeta max) of 13.11 at a maximum recombination fraction (theta max) of .00, with marker D19S225. Multipoint linkage analysis performed with the use of additional markers from the region placed the cystinuria type III locus between D19S414 and D19S220. Preliminary data on type II families also seem to place the disease locus for this rare type of cystinuria at 19q13.1 (significant zeta max = 3.11 at theta max of .00, with marker D19S225).

Chromosome Mapping↗

PubMed1997

Assignment of ferritin L gene (FTL) to human chromosome band 19q13.3 by in situ hybridization.

A new genetic disorder (Hyperferritinemia and Cataract Syndrome) characterized by a combination of high serum ferritin level and congenital bilateral nuclear cataract has been recently described. This disease is transmitted as autosomal dominant trait and is due to mutations in the ferritin L gene (FTL). FTL gene has been localized to 19q13.3-qter by somatic cell hybrids. In this work we present the precise mapping of FTL gene on chromosome 19q13.3 using in situ fluorescence hybridization.

Apoferritins↗

PubMed1996

Genomic structure and organization of the human rBAT gene (SLC3A1).

Cystinuria is an autosomal recessive disorder of amino acid transport, manifesting as three phenotypes (I, II, and III). An amino acid transport gene, rBAT, is responsible for cystinuria. Mutation and linkage analyses have demonstrated the disease to be heterogeneous, with rBAT being the defective gene in type I cystinuria. The genomic structure of the human rBAT gene (HGMW-approved symbol SLC 3A1) has been established via two strategies: (i) construction of two different genomic libraries by subcloning the Mega-YAC921B6 (CEPH), containing rBAT, in Lambda ZAP and screening using rBAT cDNA and different PCR products; and (ii) generation and sequencing of genomic fragments by long PCR using rBAT cDNA-derived primers. The rBAT gene spans approximately 45 kb and consists of 10 exons. The introns range from 500 to 13,000 bp. All splice sites conform to the GT/AG rule. The promoter region has been further analyzed, and a predicted TATA box 98 bp upstream of the first coding ATG was identified. In addition an Alu repeat has been detected 72 bp upstream of the predicted TATA box.

Amino Acid Transport Systems, Basic↗

PubMed1996

Molecular and cytogenetic analysis of the fragile X syndrome in a series of 453 mentally retarded subjects: a study of 87 families.

We report on a series of 453 mentally retarded subjects investigated for fragile X syndrome from 1982 to July 1995. The 22% rate of efficiency of FRAX positivity indicated a significant preselection by the clinicians. However, this rate dropped to 11% in the last year. Since 1992, Southern blot analysis was extended to include family members of the 87 positive subjects, for a total of 442 individuals examined with the probe StB12.3. In addition to premutated (118), fully mutated (148), and pre/full mutation mosaic subjects (27), 14 atypical cases were found. Some of these cases are described in more detail. In particular, we report on the hybridization and polymerase chain reaction data of 2 fragile X subjects with full mutation and a 2.8-kb allele and 1 with full mutation and a 2.4-kb allele. An intellectually normal male with 18% of fraXq27.3 and an unmethylated full mutation is also described. Finally, a mentally retarded child with only a lower allele of 2.7 kb is presented.

Chromosome Aberrations↗

PubMed1996

Molecular characterization of Fanconi anaemia group C (FAC) gene polymorphisms.

Fanconi anaemia (FA) is a genetically heterogeneous disease with defects in at least five genes. The gene for complementation group C (FAC) has been cloned and mapped to chromosome 9q22.3 in the interval between D9S280 and D9S287. Linkage analysis is a rapid tool for the exclusion of FA families from complementation group C. The currently available markers are informative microsatellites flanking FAC and an intragenic restriction fragment length polymorphism (RFLP). In this paper, the identification of three CA polymorphic repeats localized in introns-1a, 2 and 3 and one rare variant in exon 2 are reported. The new microsatellites will enable more accurate analysis not only of FA but also in families affected by multiple self-healing squamous epitheliomata (ESS1) and nevoid basal cell carcinoma (NBCCS), since the genes of both syndromes have been mapped in the same interval as FAC.

Base Sequence↗

PubMed1996

Identification of three novel mutations in the PIG-A gene in paroxysmal nocturnal haemoglobinuria (PNH) patients.

Paroxysmal nocturnal haemoglobinuria (PNH) is an acquired haemolytic disorder caused by the absence of glycosyl phosphatidylinositol (GPI)-anchored surface proteins resulting from a defect in one step of GPI-anchor biosynthesis. Recent analysis has shown that mutations at the PIG-A (phosphatidylinositoglycan-class A) gene are responsible for GPI-anchor deficiency in all PNH patients. In the current study, we describe three new mutations of the PIG-A gene in Italian patients with PNH. The analysis has been performed by RNA/single-strand conformation polymorphism using genomic DNA purified from nucleated peripheral blood cells. An abnormal pattern of migration of polymerase chain reaction amplified fragments containing exons 2 and 5 was observed. Sequencing analysis led to the identification of three mutations: a transversion C-to-A creating a stop codon (Y98X), an A insertion at position 460 (460insA), and a C deletion (1114delC). All the mutations cause a premature termination of the translation of the PIG-A protein.

Base Sequence↗