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Biomedical subjects

J Overhauser

Publications and source records attributed to J Overhauser.

At least 55 records · Page 3Linked to original sources
PubMed1995

Analysis of clinical variation seen in patients with 18q terminal deletions.

Twenty-six patients with deletions of 18q were analyzed at the clinical and molecular levels in an attempt to delineate regions of chromosome 18 important to the 18q- syndrome phenotype. Molecular cytogenetic analysis was carried out using fluorescence in situ hybridization (FISH), and deletions ranging from 18q21.1-qter to 18q22.3-qter were detected. The parental origin of the deletions was determined by the analysis of inheritance of microsatellite markers. No correlation between size, parental origin, or severity of the resulting phenotype was found. The results suggest that a critical region for 18q- syndrome lies in the most distal portion of 18q and that it confers susceptibility for the various clinical manifestations of the 18q- syndrome when present in one copy.

Abnormalities, Multiple↗
PubMed1995

Molecular cloning and characterization of the active human mitochondrial NADH:ubiquinone oxidoreductase 24-kDa gene (NDUFV2) and its pseudogene.

Two distinct loci for the 24-kDa subunit of the mitochondrial NADH:ubiquinone oxidoreductase (complex I of the respiratory chain) were detected in the human genome: a transcribed gene from chromosome 18 and an inactive locus on chromosome 19. Cosmid clones containing the functional gene (NDUFV2) and the pseudogene (NDUFV2P1) were isolated. The NDUFV2 gene spans approximately 20 kb and contains 8 exons. Refined mapping of both NDUFV2 genes by FISH resulted in an assignment of the NDUFV2 gene to 18p11.2-p11.31 and of the NDUFV2P1 gene to 19q13.3-qter. The nucleotide sequence of the NDUFV2P1 pseudogene differs from the cDNA sequence by the lack of the methionine initiator codon, an additional 165 bp of the first intron sequence, and a 1-nucleotide deletion.

Base Sequence↗
PubMed1995

Duplication 3q syndrome: molecular delineation of the critical region.

The phenotype of dup(3q) syndrome partially overlaps with Brachmann-de Lange phenotype. Convulsions and eye, palate renal, and cardiac anomalies are more frequent in dup(3q) syndrome, while limb deficiencies, hirsutism, and synophrys are more characteristic of Brachmann-de Lange syndrome. Whether the two syndromes have a biological relationship has yet to be demonstrated. Using two patient translocation cell lines, each involving distal 3q, we have narrowed the critical region of the dup(3q) syndrome to the interval 3q26.31-q27.3 and initiated its molecular characterization. We have mapped in this region 6 cosmid clones spanning approximately 3-5 Mb. The critical region appears to overlap with the region where a balanced translocation was found in a Brachmann-de Lange patient. This work provides the mapping framework for finer molecular analysis of dup(3q) syndrome.

Adult↗
PubMed1995

The structural genes, MEP1A and MEP1B, for the alpha and beta subunits of the metalloendopeptidase meprin map to human chromosomes 6p and 18q, respectively.

Meprins are cell membrane, oligomeric metalloendopeptidases composed of two distinct but evolutionarily related subunits, alpha and beta. The structural genes for the meprin subunits, Mep-1 alpha and Mep-1 beta, have been previously mapped to chromosomes 17 and 18, respectively, of the mouse genome. We now report the localization of MEP1A and MEP1B in the human genome. MEP1A mapped to the short arm of chromosome 6 by the use of radiation and somatic cell hybrids. More specifically, it is localized between the centromere and GSTA2 in 6p11-p12. MEP1B mapped to chromosome 18, by the use of somatic cell hybrids, in 18q12.2-q12.3, proximal to the TTR/PALB gene. As in the mouse genome, the two homologous human structural genes for alpha and beta (50% identical on the cDNA level) are unlinked. These new markers on human chromosomes 6 and 18 extend the region of known linkage homology with mouse chromosomes 17 and 18, respectively, and provide new molecular access to regions of the human genome.

Animals↗
PubMed1995

Five novel genes from the cri-du-chat critical region isolated by direct selection.

Cri-du-chat is a well described partial aneusomy resulting from deletion of the short arm of chromosome 5. The hallmark clinical feature of cri-du-chat, a high-pitched monochromatic cry, has recently been localized to 5p15.3, separate from the remaining clinical features of the syndrome, which have been localized to 5p15.2. Five chromosome 5-specific probes from the latter region, designated the cri-du-chat critical region (CDCCR), were used to isolate 30 cosmids from the LANL chromosome 5 specific cosmid library. The 30 framework cosmids were used in a direct selection with three cDNA sources to isolate an initial set of expressed sequences. Nine unique cDNAs were found that hybridized to four discrete sets of cosmids in the CDCCR. The nine cDNAs are novel by sequence database comparisons, and conservatively represent four transcription units. More recently, we have also constructed a YAC contig of the CDCCR which spans approximately 2 Mb. As expected, ESTs derived from the nine novel cDNAs map back to the contig. Limited expression profiles of these cDNAs have been obtained. Two cDNAs that map to one discrete set of cosmids have different expression patterns, suggesting that they represent two different genes and increasing the number of putative genes to five. Further characterization of these genes and the estimated 100 additional genes deleted in cri-du-chat should lead to better diagnostic markers and an understanding of the molecular mechanisms of the disease.

Base Sequence↗
PubMed1995

Physical mapping of the holoprosencephaly critical region in 18p11.3.

Holoprosencephaly (HPE) is a common developmental defect that results in a spectrum of craniofacial malformations. HPE is genetically heterogeneous, some cases being associated with deletions of the short arm of chromosome 18. In order to map the putative HPE gene located on 18p (HPE4) more precisely, six patients with various cytogenetic 18p deletions and clinical features of HPE have been characterized by using a combination of somatic cell hybrid analysis and FISH. By using a set of 27 chromosome 18p-specific markers, the deletion in each patient was characterized. The HPE minimal critical region on 18p was defined on a molecular level, localizing the HPE4 gene to 18p11.3.

Child↗
PubMed1995

Thiopurine methyltransferase pharmacogenetics. Cloning of human liver cDNA and a processed pseudogene on human chromosome 18q21.1.

Thiopurine methyltransferase (TPMT) is a genetically polymorphic enzyme that catalyzes the S-methylation of thiopurine drugs such as 6-mercaptopurine. This genetic polymorphism is an important factor responsible for individual variation in thiopurine drug response. A cDNA for TPMT has been cloned from T84 human colon carcinoma cells. Northern blot analysis of multiple human tissues was performed with the T84 human colon carcinoma TPMT cDNA open reading frame (ORF) as a probe as one step toward understanding the molecular basis for the TPMT genetic polymorphism. Three mRNA species (approximately 1.4, 2.0, and 3.6 kb in length) were present in all tissues studied, including liver. However, none of these mRNAs matched the length of the 2.7 kb T84 TPMT cDNA. Therefore, it was important to clone a TPMT cDNA from a human drug-metabolizing organ such as the liver to determine whether its sequence matched that of the cDNA cloned from the T84 cell line. A human liver cDNA library was screened with the T84 TPMT cDNA ORF as a probe, and a 1.8 kb cDNA was isolated with a coding region sequence identical to that of the T84 TPMT cDNA. The TPMT cDNA ORF was then used to screen a human lymphocytes genomic DNA library in an attempt to clone the TPMT gene(s) in humans. Three intronless clones were isolated with identical ORF sequences that were 96% identical to that of the TPMT cDNA, but which contained multiple nucleotide substitutions and one deletion. The 3'- and 5'-flanking regions of one of the genomic DNA clones were sequenced.(ABSTRACT TRUNCATED AT 250 WORDS)

Base Sequence↗
PubMed1995

The 18q- syndrome: analysis of chromosomes by bivariate flow karyotyping and the PCR reveals a successive set of deletion breakpoints within 18q21.2-q22.2.

The 18q- syndrome is one of several terminal deletion disorders that occur in humans. Previous G-banding studies suggest that the loss of a critical band, 18q21.3, results in mental retardation, craniofacial anomalies, and metabolic defects. However, it is difficult to reconcile the consistent loss of a single region with the large variability in clinical phenotype. The purpose of this study was to reassess the extent of chromosomal loss in a cohort of 17 18q- syndrome patients by using fluorescent-activated chromosome sorting, PCR, and FISH. Bivariate flow karyotypes revealed heterogeneity among the deletions; they ranged in size from 9 to 26 Mb. To confirm this heterogeneity at a molecular level, deleted and normal chromosomes 18 of six patients were collected by flow sorting, preamplified by random priming, and assayed for marker content by the PCR. This analysis defined five unique breakpoints among the six patients. We conclude that the terminal deletions in the 18q- syndrome occur over a broad region spanning the interval from 18q21.2 to 18q22.2. Our results suggest that the variability in clinical phenotype may be more representative of a contiguous-gene syndrome with a baseline deficit of 18q22.2-qter than of the loss of a single critical region within 18q21.3.

Chromosome Deletion↗
PubMed1995

Evidence for a distinct region causing a cat-like cry in patients with 5p deletions.

The cri-du-chat syndrome is a contiguous gene syndrome that results from a deletion of the short arm of chromosome 5 (5p). Patients present with a cat-like cry at birth, which is usually considered diagnostic of this syndrome. Additional features of the syndrome include failure to thrive, microcephaly, hypertelorism, epicanthal folds, hypotonia, and severe mental retardation. We report on four families in which patients with 5p deletions have only the characteristic cat-like cry, with normal to mildly delayed development. The precise locations of the deletions in each family were determined by FISH using lambda phage and cosmid clones. All of the deletion breakpoints map distal to a chromosomal region that is implicated with the facial features and severe mental and developmental delay in the cri-du-chat syndrome. DNA clones mapping in the chromosomal region associated with the cat-like cry feature will be useful diagnostic tools. They will allow for the distinction between 5p deletions that will result in the severe delay observed in most cri-du-chat syndrome patients and those deletions that result in the isolated cat-like cry feature, which is associated with a better prognosis.

Adult↗
PubMed1994

A yeast artificial chromosome contig of the critical region for cri-du-chat syndrome.

Cri-du-chat is a chromosomal deletion syndrome characterized by partial deletion of the short arm of chromosome 5. The clinical symptoms include growth and mental retardation, microcephaly, hypertelorism, epicanthal folds, hypotonia, and a high-pitched monochromatic cry that is usually considered diagnostic for the syndrome. Recently, a correlation between clinical features and the extent of the chromosome 5 deletions has identified two regions of the short arm that appear to be critical for the abnormal development manifested in this syndrome. Loss of a small region in 5p15.2 correlates with all of the clinical features of cri-du-chat with the exception of the cat-like cry, which maps to 5p15.3. Here we report the construction of a YAC contig that spans the chromosomal region in 5p15.2 that plays a major role in the etiology of the cri-du-chat syndrome. YACs that span the 2-Mb cri-du-chat critical region have been identified and characterized. This YAC contig lays the groundwork for the construction of a transcriptional map of this region and the eventual identification of genes involved in the clinical features associated with the cri-du-chat syndrome. It also provides a new diagnostic tool for cri-du-chat in the shape of a YAC clone that may span the entire critical region.

Base Sequence↗
PubMed1994

Molecular cytogenetic determination of a deletion/duplication of 1q that results in a trisomy 18 syndrome-like phenotype.

We report on an infant who presented at birth with some characteristics of trisomy 18 syndrome, including low birth weight, facial abnormalities, overlapping fingers, and congenital heart defects. On chromosome analysis, no additional chromosome 18 was observed and both chromosome 18 homologues appeared normal. However, a small piece of chromosomal material of unknown origin was detected at the tip of the long arm of chromosome 1. Fluorescence in situ hybridization (FISH) using whole chromosome 18 painting probes disclosed no additional hybridization at the telomere of 1q, suggesting that the material was derived from another chromosome. Further chromosome painting experiments suggested that the telomeric addition was of chromosome 1 origin. To identify subchromosomal regions involved in the rearrangement, additional FISH analyses were performed using single copy and repetitive DNA probes mapping to different portions of chromosome 1. The analyses showed that probes mapping to 1q34-43 were duplicated in the derivative chromosome 1. In addition, a DNA probe mapping to 1q44 was found to be deleted from the derivative chromosome 1. Our composite analysis suggests that a deletion and a duplication of chromosome 1q can result in some of the clinical findings usually associated with trisomy 18 syndrome. These results demonstrate the usefulness of FISH analysis when karyotype analysis is not consistent with the clinical description.

Abnormalities, Multiple↗
PubMed1994

Targeted insertions of two exogenous collagen genes into both alleles of their endogenous loci in cultured human cells: the insertions are directed by relatively short fragments containing the promoters and the 5' ends of the genes.

Previous studies demonstrated that type II procollagen is synthesized by HT-1080 cells that are stably transfected with constructs of the human COL2A1 gene that contain the promoter and 5' end of either the COL2A1 gene or the human COL1A1 gene. Since the host HT-1080 cells were from a human tumor line that synthesizes type IV collagen but not type II or type I procollagen, the results suggested that the constructs were integrated near active enhancers or promoters. Here, however, we demonstrate that a 33-kb construct of the COL2A1 gene containing a 5' fragment from the same gene was inserted into both alleles of the endogenous COL2A1 gene on chromosome 12, apparently by homologous recombination by a nonconservative pathway. In contrast, a similar construct of the COL2A1 gene in which the 5' end was replaced with a 1.9-kb fragment from the 5' end of the COL1A1 gene was inserted into both alleles of the locus for the COL1A1 gene on chromosome 17. Therefore, targeted insertion of the gene construct was not directed by the degree of sequence homology. Instead, it was directed by the relatively short 5' fragment from the COL1A1 gene that contained the promoter and the initially transcribed sequences of the gene. After insertion, both gene constructs were expressed from previously inactive loci.

3T3 Cells↗
PubMed1994

Regional localization of 188 sequence tagged sites on a somatic cell hybrid mapping panel for human chromosome 3.

Chromosome 3 comprises 7% of the genome and contains at least 210 Mb of DNA. To expedite the analysis of this chromosome, we have assembled a somatic cell hybrid mapping panel that subdivides human chromosome 3 into 23 intervals using a total of 19 hybrids. Hybrids were constructed from 16 patients' cells containing chromosome 3 translocations. All of these hybrids selectively retained the derivative 3 chromosome. In addition, we utilized 2 radiation-reduced hybrids and 3 hybrids carrying spontaneous translocations between human chromosome 3 and rodent chromosomes. The entire panel has 9 short arm breakpoints that involve bands p24.2, p22, p21, p14, and p12 plus a total of 11 long arm breakpoints that involve bands q13, q21, q25, q26, and q27. In addition, two cell lines appear to have breakpoints at or near the centromere. To date, we have used this panel to localize 92 sequences regionally on the short arm, 89 sequences on the long arm, and 7 sequences near the centromere. These hybrids are useful tools that allow the rapid localization of markers on chromosome 3 and greatly assist other mapping efforts.

Animals↗
PubMed1994

Physical mapping of genetic markers on the short arm of chromosome 5.

The deletion of the short arm of chromosome 5 is associated with the cri-du-chat syndrome. In addition, loss of this portion of a chromosome is a common cytogenetic marker in a number of malignancies. However, to date, no genes associated with these disorders have been identified. Physical maps are the first step in isolating causative genes, and genes involved in autosomal recessive disorders are now routinely mapped through the identification of linked markers. Extensive genetic maps based upon polymorphic short tandem repeats (STRs) have provided researchers with a large number of markers to which such disorders can be genetically mapped. However, the physical locations of many of these STRs have not been determined. Toward the goal of integrating the human genetic maps with the physical maps, a 5p somatic cell hybrid deletion mapping panel that was derived from patients with 5p deletions or translocations was used to physically map 47 STRs that have been used to construct genetic maps of 5p. These data will be useful in the localization of disease genes that map to 5p and may be involved in the etiology of the cri-du-chat syndrome.

Animals↗