Search PubMed⌕ Search

Biomedical subjects

A Ballabio

Publications and source records attributed to A Ballabio.

At least 55 records · Page 3Linked to original sources
PubMed1999

SLC7A7, encoding a putative permease-related protein, is mutated in patients with lysinuric protein intolerance.

Lysinuric protein intolerance (LPI, MIM 222700) is an autosomal recessive multisystem disorder found mainly in Finland and Italy. On a normal diet, LPI patients present poor feeding, vomiting, diarrhoea, episodes of hyperammoniaemic coma and failure to thrive. Hepatosplenomegaly, osteoporosis and a life-threatening pulmonary involvement (alveolar proteinosis) are also seen. LPI is caused by defective cationic amino acid (CAA) transport at the basolateral membrane of epithelial cells in kidney and intestine. Metabolic derangement is characterized by increased renal excretion of CAA, reduced CAA absorption from intestine and orotic aciduria. The gene causing LPI was assigned using linkage analysis to chromosome 14q11.2 near the T-cell receptor alpha/delta chains locus, and a critical region has been defined. We have identified two new transcripts (SLC7A8 and SLC7A7) homologous to amino acid transporters, highly expressed in kidney and mapping in the LPI critical region. Mutational analysis of both transcripts revealed that SLC7A7 (for solute carrier family 7, member 7) is mutated in LPI. In five Italian patients, we found either an insertion or deletion in the coding sequence, which provides evidence of a causative role of SLC7A7 in LPI. Furthermore, we detected a splice acceptor change resulting in a frameshift and premature translation termination in four unrelated Finnish patients. This mutation may represent the founder LPI allele in Finland.

Amino Acid Metabolism, Inborn Errors↗
PubMed1999

LINE-1 elements at the sites of molecular rearrangements in Alport syndrome-diffuse leiomyomatosis.

Deletions encompassing the 5' termini of the paired type IV collagen genes COL4A5 and COL4A6 on chromosome Xq22 give rise to Alport syndrome (AS) and associated diffuse leiomyomatosis (DL), a syndrome of disseminated smooth-muscle tumors involving the esophagus, large airways, and female reproductive tract. In this study, we report isolation and characterization of two deletion junctions. The first, in a patient described elsewhere, arose by a nonhomologous recombination event fusing a LINE-1 (L1) repetitive element in intron 1 of COL4A5 to intron 2 of COL4A6, resulting in a 13.4-kb deletion. The second, in a previously undescribed family, arose by unequal homologous recombination between the same L1 and a colinear L1 element in intron 2 of COL4A6, resulting in a>40-kb deletion. L1 elements have contributed to the emergence of this locus as a site of frequent recombinations by diverse mechanisms. These give rise to AS-DL by disruption of type IV collagen and perhaps other as yet unidentified genes, evidenced by deletions as small as 13.4 kb.

Adult↗
PubMed1999

X-linked late-onset sensorineural deafness caused by a deletion involving OA1 and a novel gene containing WD-40 repeats.

We have identified a novel gene, transducin (beta)-like 1 (TBL1), in the Xp22.3 genomic region, that shows high homology with members of the WD-40-repeat protein family. The gene contains 18 exons spanning approximately 150 kb of the genomic region adjacent to the ocular albinism gene (OA1) on the telomeric side. However, unlike OA1, TBL1 is transcribed from telomere to centromere. Northern analysis indicates that TBL1 is ubiquitously expressed, with two transcripts of approximately 2.1 kb and 6.0 kb. The open reading frame encodes a 526-amino acid protein, which shows the presence of six beta-transducin repeats (WD-40 motif) in the C-terminal domain. The homology with known beta-subunits of G proteins and other WD-40-repeat containing proteins is restricted to the WD-40 motif. Genomic analysis revealed that the gene is either partly or entirely deleted in patients carrying Xp22.3 terminal deletions. The complexity of the contiguous gene-syndrome phenotype shared by these patients depends on the number of known disease genes involved in the deletions. Interestingly, one patient carrying a microinterstitial deletion involving the 3' portion of both TBL1 and OA1 shows the OA1 phenotype associated with X-linked late-onset sensorineural deafness. We postulate an involvement of TBL1 in the pathogenesis of the ocular albinism with late-onset sensorineural deafness phenotype.

Amino Acid Sequence↗
PubMed1999

Identification of a new locus for medullary cystic disease, on chromosome 16p12.

Autosomal dominant medullary cystic disease (ADMCKD) is an interstitial nephropathy that has morphologic and clinical features similar to autosomal recessive nephronophthisis. The typical renal dysfunction associated with ADMCKD results mainly from a defect in urinary concentration ability, although results of urinalysis are normal. Recently, a locus on chromosome 1 was associated with ADMCKD, in DNA from two large Cypriot families, and genetic heterogeneity was inferred. We describe the genomewide linkage mapping of a new locus for medullary cystic disease, ADMCKD2, on chromosome 16p12 in a four-generation Italian pedigree. The family with ADMCKD2 fulfills the typical diagnostic criteria of ADMCKD, complicated by hyperuricemia and gouty arthritis. Marker D16S3036 shows a maximum two-point LOD score of 3.68, and the defined critical region spans 10.5 cM, between D16S500 and SCNN1B1-2. Candidate genes included in the critical region are discussed.

Chromosome Mapping↗
PubMed1999

TargetFinder: searching annotated sequence databases for target genes of transcription factors.

UNLABELLED: TargetFinder is a new software tool to search a database of annotated sequences for transcription factor binding sites located in context with other important transcription regulatory signals and regions, like the TATA element, the promoter, and so on, thereby greatly reducing the background usually associated with this kind of search. AVAILABILITY: The TargetFinder Web service is available at http://hercules.tigem.it/TargetFinder.html CONTACT: giovanni.lavorgna@hsr.it

Binding Sites↗
PubMed1999

Expression of a novel human sialidase encoded by the NEU2 gene.

Sialidases (E.C.3.2.1.18) belong to a group of glycohydrolytic enzymes, widely distributed in nature, which remove sialic acid residues from glycoproteins and glycolipids. All of the sialidase so far characterized at the molecular level share an Asp block, repeated three to five times in the primary structure, and an F/YRIP sequence motif which is part of the active site. Using a sequence homology-based approach, we previously identified a human gene, named NEU2, mapping to chromosome 2q37. NEU2 encoded protein is a polypeptide of 380 amino acids with two Asp block consensuses and the YRIP sequence in the amino terminal part of the primary structure. Here we demonstrate that NEU2 encodes a functional sialidase. NEU2 was expressed in COS7 cells, giving rise to a dramatic increase in the sialidase activity measured in cell extracts with the artificial substrate 4-MU-NANA. Using a rabbit polyclonal antiserum, on Western blots a protein band with a molecular weight of about 42 kDa was detectable, and its cytosolic localization was demonstrated with cell fractionation experiments. These results were confirmed using immunohistochemical techniques. NEU2 expression in E.coli cells allowed purification of the recombinant protein. As already observed in the enzyme expressed in COS7 cells, NEU2 pH optimum corresponds to 5.6 and the polypeptide showed a K(m)for 4-MU-NANA of 0.07 mM. In addition, based on the detectable similarities between the NEU2 amino acid sequence and bacterial sialidases, a prediction of the three-dimensional structure of the enzyme was carried out using a protein homology modeling approach.

Amino Acid Sequence↗
PubMed1999

EYA4, a novel vertebrate gene related to Drosophila eyes absent.

We have isolated a family of four vertebrate genes homologous to eyes absent (eya), a key regulator of ocular development in Drosophila. Here we present the detailed characterization of the EYA4 gene in human and mouse. EYA4 encodes a 640 amino acid protein containing a highly conserved C-terminal domain of 271 amino acids which in Drosophila eya is known to mediate developmentally important protein-protein interactions. Human EYA4 maps to 6q23 and mouse Eya4 maps to the predicted homology region near the centromere of chromosome 10. In the developing mouse embryo, Eya4 is expressed primarily in the craniofacial mesenchyme, the dermamyotome and the limb. On the basis of map position and expression pattern, EYA4 is a candidate for oculo-dento-digital (ODD) syndrome, but no EYA4 mutations were found in a panel of ODD patients.

Alternative Splicing↗
PubMed1999

Functional characterization of the Opitz syndrome gene product (midin): evidence for homodimerization and association with microtubules throughout the cell cycle.

Opitz syndrome (OS) is a multiple congenital anomaly manifested by abnormal closure of midline structures. The gene responsible for the X-linked form of this disease, MID1, encodes a protein (midin) that contains a RING, two B-boxes, a coiled-coil (the so-called tripartite motif) and an RFP-like domain. The tripartite motif is characteristic of a family of proteins, named the B-box family, involved in cell proliferation and development. Since the subcellular compartmentalization and the ability to form multiprotein structures both appear to be crucial for the function of this family of proteins, we have studied these properties on the wild-type and mutated forms of midin. We found that endogenous midin is associated with microtubules throughout the cell cycle, co-localizing with cytoplasmic fibres in interphase and with the mitotic spindle and midbodies during mitosis and cytokinesis. Immunoprecipitation experiments demonstrated the ability of the tripartite motif to mediate midin homodimerization, consistent with the evidence, obtained by gel filtration analysis, that midin exists in the form of large protein complexes. Functional characterization of altered forms of midin, resulting from mutations found in OS patients, revealed that association with microtubules is compromised, while the ability to homodimerize and form multiprotein complexes is retained. We suggest that midin is involved in the formation of multiprotein structures acting as anchor points to microtubules and that impaired association with these cytoskeletal structures causes OS developmental defects.

Animals↗
PubMed1999

MID2, a homologue of the Opitz syndrome gene MID1: similarities in subcellular localization and differences in expression during development.

The B-box family is an expanding new family of genes encoding proteins involved in diverse cellular functions such as developmental patterning and oncogenesis. A member of this protein family, MID1, is the gene responsible for the X-linked form of Opitz G/BBB syndrome, a developmental disorder characterized by defects of the midline structures. We now report the identification of MID2, a new transcript closely related to MID1. MID2 maps to Xq22 in human and to the syntenic region on the mouse X chromosome. The two X-linked genes share the same domains, the same exon-intron organization, a high degree of similarity at the protein level and the same subcellular localization, both being confined to the cytoplasm in association to micro-tubular structures. The expression pattern studied by RNA in situ hybridization in mouse revealed that Mid2 is expressed early in development and the highest level of expression is detected in the heart, unlike Mid1 for which no expression was detected in the developing heart. Together, these data suggest that midin and MID2 have a similar biochemical function but a different physiological role during development.

Amino Acid Sequence↗
PubMed1999

Evidence for genetic heterogeneity in benign familial hematuria.

Benign familial hematuria (BFH: MIM141200) is an autosomal-dominant disease accounting for one-fifth of all hematuria of unknown cause in children. Previous observations suggest that BFH may be allelic to recessive Alport syndrome (AS: MIM 203780) with a mutation in the COL4A3/COL4A4 locus. However, it is not clear whether all cases of BFH are due to heterozygous mutation of COL4A3/COL4A4 genes. We report here the exclusion of linkage between BFH and COL4A3/COL4A4 loci at 2q35-37 in a restricted population from Sicily (Italy). Total lod score is -9.6 at theta 0. Furthermore, in some cases exclusion of linkage is evident even considering single families. We conclude that BFH is genetically heterogeneous.

Adult↗
PubMed1999

Intracellular levels of the LIS1 protein correlate with clinical and neuroradiological findings in patients with classical lissencephaly.

We report on the genotype-phenotype correlation in 7 patients with classical lissencephaly carrying a heterozygous subtle mutation in the LIS1 gene. Six patients, showed a mutation predicted to encode for a truncated protein, and one mutation altered a splicing site, resulting in skipping of exon 4. Western blot analysis performed on the lymphoblastoid cell line of 2 patients bearing truncating mutations indicated that the mutated allele did not produce a detectable amount of the LIS1 protein; whereas the analysis performed on the fibroblasts from the patient with a splice-site mutation was suggestive of partial protein synthesis from the mutated allele. Although clinical and magnetic resonance imaging findings of patients with truncating mutations did not differ from those observed in patients with a heterozygous deletion, the patient bearing the exon-skipping mutation had less severe clinical and brain involvement. Our data suggest that truncating mutations in the LIS1 gene are relatively common among patients with classical lissencephaly not bearing a heterozygous deletion at 17p13.3, and strengthen the relevance of correct intracellular dosage of the LIS1 protein in the neuronal migration process.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗
PubMed1998

Identification and characterization of a novel serine-threonine kinase gene from the Xp22 region.

Eukaryotic protein kinases are part of a large and expanding family of proteins. Through our transcriptional mapping effort in the Xp22 region, we have isolated and sequenced the full-length transcript of STK9, a novel cDNA highly homologous to serine-threonine kinases. A number of human genetic disorders have been mapped to the region where STK9 has been localized including Nance-Horan (NH) syndrome, oral-facial-digital syndrome type 1 (OFD1), and a novel locus for nonsyndromic sensorineural deafness (DFN6). To evaluate the possible involvement of STK9 in any of the above-mentioned disorders, a 2416-bp full-length cDNA was assembled. The entire genomic structure of the gene, which is composed of 20 coding exons, was determined. Northern analysis revealed a transcript larger than 9.5 kb in several tissues including brain, lung, and kidney. The mouse homologue (Stk9) was identified and mapped in the mouse in the region syntenic to human Xp. This location is compatible with the location of the Xcat mutant, which shows congenital cataracts very similar to those observed in NH patients. Sequence homologies, expression pattern, and mapping information in both human and mouse make STK9 a candidate gene for the above-mentioned disorders.

Amino Acid Sequence↗
PubMed1998

Characterization of Cxorf5 (71-7A), a novel human cDNA mapping to Xp22 and encoding a protein containing coiled-coil alpha-helical domains.

The human X chromosome is known to contain several disease genes yet to be cloned. In the course of a project aimed at the construction of a transcription map of the Xp22 region, we fully characterized a novel cDNA, Cxorf5 (HGMW-approved symbol, alias 71-7A), previously mapped to this region but for which no sequence information was available. We isolated and sequenced the full-length transcript, which encodes a predicted protein of unknown function containing a large number of coiled-coild domains, typically presented in a variety of different molecules, from fibrous proteins to transcription factors. We showed that the Cxorf5 cDNA is ubiquitously expressed, undergoes alternative splicing, and escapes X inactivation. Furthermore, we precisely mapped two additional Cxorf5-related loci on the Y chromosome and on chromosome 5. By virtue of its mapping assignment to the Xp22 region, Cxorf5 represents a candidate gene for at least four human diseases, namely spondyloepiphiseal dysplasia late, oral-facial-digital syndrome type 1, craniofrontonasal syndrome, and a nonsyndromic sensorineural deafness.

Alternative Splicing↗
PubMed1998

A 5' regulatory sequence containing two Ets motifs controls the expression of the Wiskott-Aldrich syndrome protein (WASP) gene in human hematopoietic cells.

The recently-identified Wiskott-Aldrich syndrome protein gene (WASP) is responsible for the Wiskott-Aldrich X-linked immunodeficiency as well as for isolated X-linked thrombocytopenia (XLT). To characterize the regulatory sequences of the WASP gene, we have isolated, sequenced and functionally analyzed a 1.6-Kb DNA fragment upstream of the WASP coding sequence. Transfection experiments showed that this fragment is capable of directing efficient expression of the reporter chloramphenicol acetyltransferase (CAT) gene in all human hematopoietic cell lines tested. Progressive 5' deletions showed that the minimal sequence required for hematopoietic-specific expression consists of 137 bp upstream of the transcription start site. This contains potential binding sites for several hematopoietic transcription factors and, in particular, two Ets-1 consensus that proved able to specifically bind to proteins present in nuclear extracts of Jurkat cells. Overexpression of Ets-1 in HeLa resulted in transactivation of the CAT reporter gene under the control of WASP regulatory sequences. Disruption of the Ets-binding sequences by side-directed mutagenesis abolished CAT expression in Jurkat cells, indicating that transcription factors of the Ets family play a key role in the control of WASP transcription.

Base Sequence↗
PubMed1998

Spastic paraplegia and OXPHOS impairment caused by mutations in paraplegin, a nuclear-encoded mitochondrial metalloprotease.

Hereditary spastic paraplegia (HSP) is characterized by progressive weakness and spasticity of the lower limbs due to degeneration of corticospinal axons. We found that patients from a chromosome 16q24.3-linked HSP family are homozygous for a 9.5 kb deletion involving a gene encoding a novel protein, named Paraplegin. Two additional Paraplegin mutations, both resulting in a frameshift, were found in a complicated and in a pure form of HSP. Paraplegin is highly homologous to the yeast mitochondrial ATPases, AFG3, RCA1, and YME1, which have both proteolytic and chaperon-like activities at the inner mitochondrial membrane. Immunofluorescence analysis and import experiments showed that Paraplegin localizes to mitochondria. Analysis of muscle biopsies from two patients carrying Paraplegin mutations showed typical signs of mitochondrial OXPHOS defects, thus suggesting a mechanism for neurodegeneration in HSP-type disorders.

ATPases Associated with Diverse Cellular Activitie↗
PubMed1998

The human ROX gene: genomic structure and mutation analysis in human breast tumors.

We have recently isolated a human gene, ROX, encoding a new member of the basic helix-loop-helix leucine zipper protein family. ROX is capable of heterodimerizing with Max and acts as a transcriptional repressor in an E-box-driven reporter gene system, while it was found to activate transcription in HeLa cells. ROX expression levels vary during the cell cycle, being down-regulated in proliferating cells. These biological properties of ROX suggest a possible involvement of this gene in cell proliferation and differentiation. The ROX gene maps to chromosome 17p13.3, a region frequently deleted in human malignancies. Here we report the genomic structure of the human ROX gene, which is composed of six exons and spans a genomic region of less than 40 kb. In an attempt to identify possible inactivating mutations in the ROX gene in human breast cancer, we performed a single-strand conformation polymorphism analysis of its coding region in 16 sporadic breast carcinomas showing loss of heterozygosity in the 17p13.3 region. No mutations were found in this analysis. Five nucleotide polymorphisms were identified in the ROX gene, three of which caused an amino acid substitution. These nucleotide changes were present in the peripheral blood DNAs of both the patients and the control individuals. In vitro translated assays did not show a significant decrease in the ability of the ROX mutant proteins to bind DNA or to repress transcription of a driven reporter gene in HEK293 cells. Despite experimental evidence that ROX might act as a tumor suppressor gene, our data suggest that mutations in the coding region of ROX are uncommon in human breast tumorigenesis.

Basic Helix-Loop-Helix Leucine Zipper Transcriptio↗
PubMed1998

Identification and characterization of a novel member of the dystrobrevin gene family.

A new member of the dystrobrevin gene family was identified using a bioinformatics approach. Sequence analysis indicates that this gene, named DTN-B, is highly homologous to the rabbit A0, the previously described dystrobrevin (DTN), Torpedo 87 kDa and to the C-terminus of dystrophin. The coiled-coil domain, shown to be the site of interaction between dystrobrevins and dystrophin, is highly conserved. Immunostaining studies indicate that DTN-B and DTN expression is absent in affected muscle fibers from DMD patients and carriers.

Amino Acid Sequence↗