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A Baldini

Publications and source records attributed to A Baldini.

At least 55 records · Page 3Linked to original sources
PubMed1997

A genetic etiology for interruption of the aortic arch type B.

Interrupted aortic arch (IAA) type B is a congenital heart defect believed to be caused by an anomaly of bronchial arch mesenchymal development. IAA type B has been associated with DiGeorge syndrome (DGS), which includes conotruncal heart defects, T-cell immunodeficiency, hypocalcemia, and facial abnormalities. The great majority of DGS cases are associated with hemizygous deletions at the chromosome 22q11 locus. The present study was designed to establish the involvement of the 22q11 locus in the etiology of IAA type B, independently from the typical DGS phenotype. An evaluation was performed on 73 patients with conotruncal heart defects using fluorescence in situ hybridization (FISH) analysis with probes from the 22q11 DGS locus. From this group, 7 patients were deleted (including 4 of the 11 patients with IAA type B). FISH analysis was extended to a total of 22 patients with IAA type B and 11 of these (50%) were deleted. FISH and Southern blot analyses using additional markers within the DiGeorge chromosomal region were performed on patients found not to be deleted in the initial FISH screening. No small deletions or rearrangements were detected. In our patient population, a single, specific genetic defect is the basis for one half of the IAA type B cases. These data suggest that IAA type B is one of the most etiologically homogeneous congenital heart defects. A 22q11 deletion in IAA type B may or may not be associated with the typical DGS phenotype. Therefore, IAA type B, per se, should be an indication for 22q11 deletion testing.

Aorta, Thoracic↗
PubMed1997

Human acetyl-CoA carboxylase 2. Molecular cloning, characterization, chromosomal mapping, and evidence for two isoforms.

cDNA encoding the 280-kDa acetyl-CoA carboxylase 2 (ACC2) isoform was isolated from human liver using the polymerase chain reaction. Sequencing the cDNA revealed an open reading frame of 7,449 base pairs (bp) that encode 2,483 amino acids (Mr 279,380). Using 5-kilobase pair cDNA clones as probes, we localized the gene encoding the 280-kDa human carboxylase to chromosome 12q23. When the cDNA of ACC2 was compared with that of ACC1, the nucleotide sequences and the predicted amino acid sequences had about 60 and 80% identity, respectively. Ser77 and Ser79, which were found to be critical for the phosphorylation and subsequent inactivation of rat ACC1 (Ser78 and Ser80 of human ACC1), are conserved in ACC2 and are represented as Ser219 and Ser221, respectively. On the other hand, Ser1200, which is also a phosphorylation site in rat ACC1 (Ser1201 of human ACC1), is not conserved in ACC2. The homology between the amino acid sequences of the two human carboxylases, however, is primarily found downstream of residues Ser78 and Ser81 in human ACC1 and their equivalents, that is Ser219 and Ser221 in ACC2, suggesting that the sequence of the first 218 amino acids at the N terminus of ACC2 represents a unique peptide that accounts, in part, for the variance between the two carboxylases. Using a cDNA probe (400 bp) that encodes the N-terminal amino acid residues of ACC2 in Northern blot analyses of different human and mouse tissues showed that ACC2 is predominantly expressed in liver, heart, and the skeletal muscles. Polyclonal antibodies raised against the N-terminal peptide (amino acid residues 1-220) reacted specifically and equally with human and rat ACC2 carboxylases, confirming the uniqueness of this N-terminal peptide and its conservation in animal ACC2. In addition, we present evidence for the presence of an isoform of ACC2 (Mr 270,000) in human liver that differs from the 280-kDa ACC2 by the absence of 303 nucleotides that encode 101 amino acids in the region between Arg1114 and Asp1215. The regulation and physiological significance of the two ACC2 isoforms remain to be determined.

Acetyl-CoA Carboxylase↗
PubMed1997

Delineation of a duplication map of chromosome 3q: a new case confirms the exclusion of 3q25-q26.2 from the duplication 3q syndrome critical region.

We report on the clinical, cytogenetic, and molecular characterization of a propositus and his mother with a duplication of 3q25-q26, minor anomalies, and mental retardation. The duplication, detected by cytogenetic analysis, was confirmed and delineated by comparative genomic hybridization and fluorescence in situ hybridization using probes previously mapped to the region. Comparison of the mapping data obtained in these patients and those obtained in patients that present with a typical dup(3q) syndrome phenotype shows that the segment duplicated in these patients lies proximally to the reported dup(3q) syndrome critical region, thus explaining the absence in our patients of the characteristic phenotype of dup(3q) syndrome patients. Accumulation of mapping data in patients with segmental duplications of 3q will eventually allow us to build a duplication map of the region and a genotype-phenotype correlation.

Adolescent↗
PubMed1997

Comparative mapping of the DiGeorge syndrome region in mouse shows inconsistent gene order and differential degree of gene conservation.

We have constructed a comparative map in mouse of the critical region of human 22q11 deleted in DiGeorge (DGS) and Velocardiofacial (VCFS) syndromes. The map includes 11 genes potentially haploinsufficient in these deletion syndromes. We have localized all the conserved genes to mouse Chromosome (Chr) 16, bands B1-B3. The determination of gene order shows the presence of two regions (distal and proximal), containing two groups of conserved genes. The gene order in the two regions is not completely conserved; only in the proximal group is the gene order identical to human. In the distal group the gene order is inverted. These two regions are separated by a DNA segment containing at least one gene which, in the human DGS region, is the most proximal of the known deleted genes. In addition, the gene order within the distal group of genes is inverted relative to the human gene order. Furthermore, a clathrin heavy chain-like gene was not found in the mouse genome by DNA hybridization, indicating that there is an inconsistent level of gene conservation in the region. These and other independent data obtained in our laboratory clearly show a complex evolutionary history of the DGS-VCFS region. Our data provide a framework for the development of a mouse model for the 22q11 deletion with chromosome engineering technologies.

Animals↗
PubMed1997

Missense mutations abolishing DNA binding of the osteoblast-specific transcription factor OSF2/CBFA1 in cleidocranial dysplasia.

Cleidocranial dysplasia (CCD) is an autosomal dominant disorder characterized by hypoplastic or absent clavicles, large fontanelles, dental anomalies and delayed skeletal development. The phenotype is suggestive of a generalized defect in ossification and is one of the most common skeletal dysplasias not associated with disproportionate stature. To date, no genetic determinants of ossification have been identified. CCD has been mapped to chromosome 6p21, where CBFA1, a gene encoding OSF2/CBFA1, a transcriptional activator of osteoblast differentiation, has been localized. Here, we describe two de novo missense mutations, Met175Arg and Ser191Asn, in the OSF2/CBFA1 gene in two patients with CCD. These two mutations result in substitution of highly conserved amino acids in the DNA-binding domain. DNA-binding studies with the mutant polypeptides show that these amino acid substitutions abolish the DNA-binding ability of OSF2/CBFA1 to its known target sequence. Concurrent studies show that heterozygous nonsense mutations in OSF2/CBFA1 also result in CCD, while mice homozygous for the osf2/cbfa1 mull allele exhibit a more severe lethal phenotype. Thus, these results together suggest that CCD is produced by haploinsufficiency of OSF2/CBFA1 and provide direct genetic evidence that the phenotype is secondary to an alteration of osteoblast differentiation.

Amino Acid Sequence↗
PubMed1997

Interchromosomal duplications of the adrenoleukodystrophy locus: a phenomenon of pericentromeric plasticity.

A 9.7 kb segment encompassing exons 7-10 of the adrenoleukodystrophy (ALD) locus of the X chromosome has duplicated to specific locations near the pericentromeric regions of human chromosomes 2p11,10p11, 16p11 and 22q11. Comparative sequence analysis reveals 92-96% nucleotide identity, indicating that the autosomal ALD paralogs arose relatively recently during the course of higher primate evolution (5-10 million years ago). Analysis of sequences flanking the duplication region identifies the presence of an unusual GCTTTTTGC repeat which may be a sequence-specific integration site for the process of pericentromeric-directed transposition. The breakpoint sequence and phylogenetic analysis predict a two-step transposition model, in which a duplication from Xq28 to pericentromeric 2p11 occurred once, followed by a rapid distribution of a larger duplicon cassette among the pericentromeric regions. In addition to facilitating more effective mutation detection among ALD patients, these findings provide further insight into the molecular basis underlying a pericentromeric-directed mechanism for non-homologous interchromosomal exchange.

Adrenoleukodystrophy↗
PubMed1997

A mouse gene (Dgcr6) related to the Drosophila gonadal gene is expressed in early embryogenesis and is the homolog of a human gene deleted in DiGeorge syndrome.

We report the identification of a mouse gene, Dgcr6, which shows high sequence similarity to gonadal (gdl), a Drosophila gene of unknown function. Dgcr6 is the mouse homolog of human DGCR6, previously shown to be deleted in DiGeorge syndrome, a developmental field defect affecting the derivatives of the pharyngeal arches which is associated with 22q11.2 deletions. The Dgcr6 transcript has a 594 nucleotide open reading frame (ORF) encoding 198 amino acids. We previously mapped Dgcr6 to mouse chromosome 16B1-B3, a region known to contain other mouse homologs of genes deleted in DiGeorge syndrome. Expression studies were performed by Northern blotting analysis on mouse embryo and adult tissues and by RNA in situ hybridization on mouse embryo sections. Results show that Dgcr6 transcripts are abundant during mouse embryogenesis, from at least 7 days post coitum. In particular, high expression was detected in the brain, spinal cord and pharyngeal arches. On adult tissues high expression was detected in testis. The function of Dgcr6 is to be determined, but its developmental expression suggests that this gene may play a role in the developmental defects associated with 22q11.2 deletions.

Amino Acid Sequence↗
PubMed1997

Molecular analysis of deletion (17)(p11.2p11.2) in a family segregating a 17p paracentric inversion: implications for carriers of paracentric inversions.

A male child with multiple congenital anomalies initially was clinically diagnosed as having Smith-Lemli-Opitz syndrome (SLOS). Subsequent cytogenetic studies revealed an interstitial deletion of 17p11.2, which is associated with Smith-Magenis syndrome (SMS). Biochemical studies were not supportive of a diagnosis of SLOS, and the child did not display the typical SMS phenotype. The father's karyotype showed a paracentric inversion of 17p, with breakpoints in p11.2 and p13.3, and the same inversion was also found in two of the father's sisters. FISH analyses of the deleted and inverted 17p chromosomes indicated that the deletion was similar to that typically seen in SMS patients and was found to bracket the proximal inversion breakpoint. Available family members were genotyped at 33 polymorphic DNA loci in 17p. These studies determined that the deletion was of paternal origin and that the inversion was of grandpaternal origin. Haplotype analysis demonstrated that the 17p11.2 deletion arose following a recombination event involving the father's normal and inverted chromosome 17 homologues. A mechanism is proposed to explain the simultaneous deletion and apparent "reinversion" of the recombinant paternal chromosome. These findings have implications for prenatal counseling of carriers of paracentric inversions, who typically are considered to bear minimal reproductive risk.

Abnormalities, Multiple↗
PubMed1996

Mosaicism for del(17)(p11.2p11.2) underlying the Smith-Magenis syndrome.

Smith-Magenis syndrome (SMS) is a multiple congenital anomalies/mental retardation syndrome associated with deletion of band p11.2 of chromosome 17. The deletion is typically detected by high-resolution cytogenetic analysis of chromosomes from peripheral lymphocytes. Fluorescence in situ hybridization (FISH) has been previously used to rule out apparent mosaicism for del(17)(p11.2p11.2) indicated by routine cytogenetics. We now report mosaicism for del(17)(p11.2p11.2) in a child with SMS. The mosaicism had gone undetected during previous routine cytogenetic analysis. FISH analysis of peripheral lymphocytes as well as immortalized lymphoblasts using markers from 17p11.2 revealed that approximately 60% of cells carried the deletion. To our knowledge, this is the first case of SMS associated with mosaicism for del(17)(p11.2p11.2).

Abnormalities, Multiple↗
PubMed1996

A transcription map in the CATCH22 critical region: identification, mapping, and ordering of four novel transcripts expressed in heart.

The acronym CATCH22 is used to indicate collectively a group of related phenotypes, namely velocardiofacial syndrome (VCFS), DiGeorge anomaly (DGA), and conotruncal anomaly face, which are associated with deletions within 22q11.2 in the great majority of patients. A deletion map has allowed us to delimit a smallest region of deletion overlap, considerably smaller than the commonly deleted region. We have mapped within this region the chromosomal breakpoint of a balanced translocation patient presenting with a DGA/VCFS phenotype, making this region the strongest candidate for the location of the gene(s) responsible for the disease phenotype. We report a systematic gene search in this region and show the presence of at least six distinct transcripts, two of which have been previously described. The region searched was approximately 270 kb; therefore, an average of one transcript every 45 kb was found. We generated eight new ESTs and mapped two ESTs present in public databases. All six transcripts are expressed in heart, an organ involved in 70%-80% of CATCH22 patients. We show that the multimethod approach to search for expressed sequences is effective and indeed necessary for a comprehensive search and provides molecular tools for further characterization of the potential genes identified.

Abnormalities, Multiple↗
PubMed1996

Cloning and comparative mapping of a gene from the commonly deleted region of DiGeorge and Velocardiofacial syndromes conserved in C. elegans.

We have identified and cloned a gene, ES2, encoding a putative 476 amino acid protein with a predicted Mr of 52,568. The gene is localized within the DiGeorge/Velocardiofacial syndrome locus on 22q11.2 and is deleted in all the patients in which a deletion within 22q11 could be demonstrated, with the exception of one patient. ES2 is expressed in all the tissues studied. Sequence comparison showed identity with five ESTs and at the amino acid level the sequence was highly similar to, and collinear with, a hypothetical C. elegans protein of unknown function. Mutation analysis was performed in 16 patients without deletion, but no mutation has been found. The cDNA sequence is conserved in mouse and is localized on MMU16B1-B3, known to contain a syntenic group in common with HSA 22q11.2.

Abnormalities, Multiple↗
PubMed1996

Quantification by flow cytometry of chromosome-17 deletions in Smith-Magenis syndrome patients.

We have used bivariate flow karyotyping to quantify the deletions involving chromosome 17 in sixteen patients with Smith-Magenis syndrome (SMS). The fluorescence intensities of mitotic chromosomes stained with Hoechst 33258 and chromomycin were quantified in a dual-beam flow cytometer. For each patient, the position of the peak representing the deleted chromosome 17 was compared to those of the normal homologs of an unaffected parent. The patients could be classified into four groups based on the size of their deletions. The deletions ranged from approximately 9-10 Mb (approximately 10-11% of the chromosome) to below the detection limit of the technique (2 Mb). Different deletion sizes were detected among patients whose high-resolution banding results were similar. Some deletions detected by banding were not detected by flow analyses. Deletion estimates are largely consistent with the results of molecular analyses. Patients with larger deletions that extend into band 17p 12 have abnormal electrophysiologic studies of peripheral nerves. Deletion size does not appear to correlate with the degree of mental retardation, presence of behavioral abnormalities, craniofacial anomalies or common skeletal findings in SMS. By identifying patients with varying deletion sizes, these data will aid the construction of a long-range deletion-based map of 17p11.2 and identification of the genes involved in this syndrome.

Abnormalities, Multiple↗
PubMed1996

Duplication of a gene-rich cluster between 16p11.1 and Xq28: a novel pericentromeric-directed mechanism for paralogous genome evolution.

We have identified a 26.5 kb gene-rich duplication shared by human Xq28 and 16p11.1. Complete comparative sequence analysis of cosmids from both loci has revealed identical Xq28 and 16p11.1 genomic structures for both the human creatine transporter gene (SLC6A8) and five exons of the CDM gene (DXS1357E). Overall nucleotide similarity within the duplication was found to be 94.6%, suggesting that this interchromosomal duplication occurred within recent evolutionary time (7-10 mya). Based on comparisons between genomic and cDNA sequence, both the Xq28 creatine transporter and DXS1357E genes are transcriptionally active. Predicted translation of exons and RT-PCR analysis reveal that chromosome 16 paralogs likely represent pseudogenes. Comparative fluorescent in situ hybridization (FISH) analyses of chromosomes from various primates indicate that this gene-rich segment has undergone several duplications. In gorilla and chimpanzee, multiple pericentromeric localizations on a variety of chromosomes were found using probes from the duplicated region. In other species, such as the orangutan and gibbon, FISH signals were only identified at the distal end of the X chromosome, suggesting that the Xq28 locus represents the ancestral copy. Sequencing of the 16p 11.1/Xq28 duplication breakpoints has revealed the presence of repetitive immunoglobulin-like CAGGG pentamer sequences at or near the paralogy boundaries. The mobilization and dispersal of this gene-rich 27 kb element to the pericentromeric regions of primate chromosomes defines an unprecedented form of recent genome evolution and a novel mechanism for the generation of genetic diversity among closely related species.

Animals↗
PubMed1996

Molecular analyses of 17p11.2 deletions in 62 Smith-Magenis syndrome patients.

Smith-Magenis syndrome (SMS) is a clinically recognizable, multiple congenital anomalies/mental retardation syndrome caused by an interstitial deletion involving band p11.2 of chromosome 17. Toward the molecular definition of the interval defining this microdeletion syndrome, 62 unrelated SMS patients in conjunction with 70 available unaffected parents were molecularly analyzed with respect to the presence or absence of 14 loci in the proximal region of the short arm of chromosome 17. A multifaceted approach was used to determine deletion status at the various loci that combined (i) FISH analysis, (ii)PCR and Southern analysis of somatic cell hybrids retaining the deleted chromosome 17 from selected patients, and (iii) genotype determination of patients for whom a parent(s) was available at four microsatellite marker loci and at four loci with associated RFLPs. The relative order of two novel anonymous markers and a new microsatellite marker was determined in 17p11.2. The results confirmed that the proximal deletion breakpoint in the majority of SMS patients is located between markers D17S58 (EW301) and D17S446 (FG1) within the 17p11.1-17p11.2 region. The common distal breakpoint was mapped between markers cCI17-638, which lies distal to D17S71, and cCI17-498, which lies proximal to the Charcot Marie-Tooth disease type 1A locus. The locus D17S258 was found to be deleted in all 62 patients, and probes from this region can be used for diagnosis of the SMS deletion by FISH. Ten patients demonstrated molecularly distinct deletions; of these, two patients had smaller deletions and will enable the definition of the critical interval for SMS.

Abnormalities, Multiple↗