Biomedical subjects

D Schlessinger

Publications and source records attributed to D Schlessinger.

At least 55 records · Page 3Linked to original sources

PubMed1997

Expressed STSs and transcription of human Xq28.

STSs, which have been used to build and format clone contigs, have been used here to assemble a transcriptional map across a cytogenetic band. Of fifty one STSs in Xq28, 20 were positive by RT-PCR. Thus, an additional 20 possible ESTs were detected among the STSs, and seven of these also identified cDNAs in at least one library. The transcripts confirm the high expression level of this region, correlated with its GC compositional map and CpG island content.

Base Sequence↗

PubMed1997

Expression and cloning of the human X-linked hypophosphatemia gene cDNA.

X-linked hypophosphatemia (XLH), which is a heritable metabolic bone disease characterized biochemically by selective renal phosphate (Pi) wasting, is associated with mutations in the PEX (Phosphate-regulating gene with homologies to Endopeptidases on the X-chromosome) gene. To further explore the physiologic role of PEX and define its effect in XLH we have determined the expression and tissue distribution. Northern analysis found abundant PEX mRNA in a restricted pattern, predominantly in adult ovary and fetal lung. In addition, PEX expression was also found in adult lung and fetal liver. A PEX cDNA of 2550 basepairs, which contains the full PEX coding region, was isolated from a human ovary cDNA library. The PEX cDNA shows high homology to other membrane-bound zinc metallopeptidases. The presence of PEX in nonosseous tissues strongly suggests features of a systemic role, rather than a unique function in bone development.

Amino Acid Sequence↗

PubMed1997

X-linked situs abnormalities result from mutations in ZIC3.

Vertebrates position unpaired organs of the chest and abdomen asymmetrically along the left-right (LR) body axis. Each structure comes to lie non-randomly with respect to the midline in an overall position designated situs solitus, exemplified in humans by placement of the heart, stomach and spleen consistently to the left. Aberrant LR axis development can lead to randomization of individual organ position (situs ambiguus) or to mirror-image reversal of all lateralized structures (situs inversus). Previously we mapped a locus for situs abnormalities in humans, HTX1, to Xq26.2 by linkage analysis in a single family (LR1) and by detection of a deletion in an unrelated situs ambiguus male (Family LR2; refs 2,3). From this chromosomal region we have positionally cloned ZIC3, a gene encoding a putative zinc-finger transcription factor. One frameshift, two missense and two nonsense mutations have been identified in familial and sporadic situs ambiguus. The frameshift allele is also associated with situs inversus among some heterozygous females, suggesting that ZIC3 functions in the earliest stages of LR-axis formation. ZIC3, which has not been previously implicated in vertebrate LR-axis development, is the first gene unequivocally associated with human situs abnormalities.

Amino Acid Sequence↗

PubMed1997

A submicroscopic deletion in Xq26 associated with familial situs ambiguus.

Abnormal left-right-axis formation results in heterotaxy, a multiple-malformation syndrome often characterized by severe heart defects, splenic abnormalities, and gastrointestinal malrotation. Previously we had studied a large family in which a gene for heterotaxy, HTX1, was mapped to a 19-cM region in Xq24-q27.1. Further analysis of this family has revealed two recombinations that place HTX1 between DXS300 and DXS1062, an interval spanning approximately 1.3 Mb in Xq26.2. In order to provide independent confirmation of HTX1 localization, a PCR-based search for submicroscopic deletions in this region was performed in unrelated males with sporadic or familial heterotaxy. A cluster of sequence-tagged sites failed to amplify in an individual who also had a deceased, affected brother. FISH identified the mother as a carrier of the deletion, which arose as a new mutation from the maternal grandfather. The deletion interval spans 600-1,100 kb and lies wholly within the 1.3-Mb region identified by recombination. Discovery of this deletion supports localization of HTX1 to Xq26.2 and reveals the first molecular-genetic abnormality associated with human left-right-asymmetry defects.

Abnormalities, Multiple↗

PubMed1997

Differential expression pattern of XqPAR-linked genes SYBL1 and IL9R correlates with the structure and evolution of the region.

The recently discovered second pseudoautosomal region (XqPAR) contains at least two genes, IL9R and SYBL1. Recent findings show that, like XpPAR genes, IL9R escapes X inactivation and its Y allele is also expressed, but SYBL1 seems to act like an X-linked gene, expressed from the active X chromosome but not from the inactive X or Y. Here we show that differences are also seen in the evolution of the sex chromosome locations of IL9R and SYBL1. IL9R is known to be autosomal in mice, and is X-linked only in primates. SYBL1, however, has been found to be on the X chromosome in all mammals tested, from marsupials to humans. Both genes were duplicated on the Y homologue of the terminal portion of the X chromosome during the evolution of Homo sapiens from other higher primates. The inactivation pattern of SYBL1 may be correlated with its longer history of X linkage, and at a more centromeric chromosomal position during evolution; the more recent X linkage and more telomeric position of the IL9R gene may explain its autosomal, 'uninactivated' transcriptional status.

Animals↗

PubMed1997

Linkage and physical mapping of X-linked lissencephaly/SBH (XLIS): a gene causing neuronal migration defects in human brain.

While disorders of neuronal migration are associated with as much as 25% of recurrent childhood seizures, few of the genes required to establish neuronal position in cerebral cortex are known. Subcortical band heterotopia (SBH) and lissencephaly (LIS), two distinct neuronal migration disorders producing epilepsy and variable cognitive impairment, can be inherited alone or together in a single pedigree. Here we report a new genetic locus, XLIS, mapped by linkage analysis of five families and physical mapping of a balanced X;2 translocation in a girl with LIS. Linkage places the critical region in Xq21-q24, containing the breakpoint that maps to Xq22.3-q23 by high-resolution chromosome analysis. Markers used for somatic cell hybrid and fluorescence in situ hybridization analyses place the XLIS region within a 1 cM interval. These data suggest that SBH and X-linked lissencephaly are caused by mutation of a single gene, XLIS, that the milder SBH phenotype in females results from random X-inactivation (Lyonization), and that cloning of genes from the breakpoint region on X will yield XLIS.

Cerebral Cortex↗

PubMed1997

Anhidrotic ectodermal dysplasia (EDA) protein expressed in MCF-7 cells associates with cell membrane and induces rounding.

Anhidrotic ectodermal dysplasia (EDA) is a rare X-linked recessive disorder characterized by the absence or hypoplasia of hair, teeth and sweat glands. The gene responsible for the disorder has recently been cloned. The predicted gene product is a 135 amino acid protein with no significant homology to previously known proteins. As a first step to analyze function, we have studied the subcellular localization of the EDA gene product expressed in two epithelial cell lines, COS-1 and MCF-7. Biochemical fractionation and confocal imaging analysis show that, in agreement with a single putative transmembrane domain inferred from its sequence, the EDA protein is transported to the plasma membrane. Moreover, in MCF-7 cells expression of EDA is associated with rounding and detachment of the cells. These results suggest that the EDA protein may be involved in cellular dynamics or signaling.

Animals↗

PubMed1997

4.5-Mb YAC STS contig at 50-kb resolution, spanning Xq25 deletions in two patients with lymphoproliferative syndrome.

Sequence-tagged site (STS) content mapping in yeast artificial chromosomes (YACs) was used to cover the region deleted in two patients affected with X-linked lymphoproliferative disorder. The order of markers includes, centromere to telomere, DXS8009-DXS1206-DXS8078-DXS8044-DXS982- DXS6811-DXS8093-AFM240xblO- DXS75-DXS737-DXS100-DXS6-DXS1046-DXS803 8. The order of six major markers is confirmed by fluorescent in situ hybridization, and all the markers assigned by linkage mapping fall within a 1.6-cM interval. The contig comprises 90 clones containing 89 STSs, yielding a resolution of 50 kb; DNA in a gap just telomeric to DXS8044 has not been found in > 20 equivalents of YACs or bacterial clones. The two deletions were found to have centromeric breakpoints that lie close to DXS1206 and may be identical; the telomeric breakpoints are -150 kb apart, one falling between DXS737 and DXS100, the other between DXS100 and DXS1046. Several STSs near the breakpoints show weak amplification from more than one site; one gives products from three groups of YACs, and lie, respectively, within 50 kb of the centromeric and the two telomeric deletion borders. Such partially duplicated segments of DNA are candidates for involvement in the formation of the deletions.

Chromosome Deletion↗

PubMed1997

X chromosome map at 75-kb STS resolution, revealing extremes of recombination and GC content.

A YAC/STS map of the X chromosome has reached an inter-STS resolution of 75 kb. The map density is sufficient to provide YACs or other large-insert clones that are cross-validated as sequencing substrates across the chromosome. Marker density also permits estimates of regional gene content and a detailed comparison of genetic and physical map distances. Five regions are detected with relatively high G + C, correlated with gene richness; and a 17-Mb region with very low recombination is revealed between the Xq13.3 [XIST] and Xq21.3 XY homology loci.

Base Composition↗

PubMed1997

Evolutionary features of the 4-Mb Xq21.3 XY homology region revealed by a map at 60-kb resolution.

Forty-three yeast artificial chromosomes (YACs) from the X chromosome have been overlapped across the 4-Mb Xq21.3 region, which is homologous to a segment in Yp11.1. The region is formatted to 60-kb resolution with 57 STSs and is merged at its edges with contigs specific for X. This allows a direct comparison of marker orders and distances on X and Y. In addition to some sequence variation and possible differences in marker order, two larger evolutionary divergencies between the X and Y homologs were revealed: (1) The X homolog is interrupted by a small X-specific region detected by a 3-kb plasmid probe for locus DXS214. An STS was developed from one end of the probe, but the sequence at the other end was highly homologous to an L1 repetitive element. This suggests that the interpolation of the X-specific segment may have involved an L1-mediated event. (2) A 250-kb portion containing DXYS1 is several megabases away from the rest of the homologous DNA on the Y but is contiguous with the remainder of the homologous region on X. Marker orders are consistent with the origin of the Y-specific 250-kb region in a paracentric inversion after the initial transfer of X DNA to the Y chromosome.

Biological Evolution↗

PubMed1997

Large scale deletions in the GPC3 gene may account for a minority of cases of Simpson-Golabi-Behmel syndrome.

AIMS OF THE STUDY: To identify the proportion and type of deletions present in the glypican 3 (GPC3) gene in a group of patients with Simpson-Golabi-Behmel syndrome (SGBS). SUBJECTS AND METHODS: PCR analysis using primer pairs which amplify fragments from each of the eight exons of the GPC3 gene was carried out in a series of 18 families with SGBS (approximately half of reported cases). RESULTS: Deletions were detected in only five families (one reported previously). We found deletions in all exons of the gene except exon 3. CONCLUSIONS: Our results suggest that large scale deletions may be less common in SGBS than was originally thought. One patient, with an exon 4 and 5 deletion, lacked the characteristic facial dysmorphic features. This raises the possibility of involvement of GPC3 gene defects in a wider range of overgrowth disorders.

Abnormalities, Multiple↗

PubMed1997

mtDNA analysis shows common ancestry in two kindreds with X-linked recessive hypoparathyroidism and reveals a heteroplasmic silent mutation.

Two kindreds residing in eastern Missouri and exhibiting X-linked recessive idiopathic hypoparathyroidism have been described. Genealogical records extending back five generations revealed no common ancestor. To investigate the possibility of relatedness, the DNA sequence of the mitochondrial D-loop was compared among several individuals in both kindreds. The mtDNA D-loop was amplified from the total DNA of individuals by use of nested PCR reactions, and the resulting 430-bp fragment was sequenced. The mtDNA sequence was identical among affected males and their maternal lineage for individuals in both kindreds. Conversely, the mtDNA sequence of the fathers of the affected males differed from that of the maternal lineage at three to six positions. These results demonstrate that the two kindreds exhibiting X-linked recessive hypoparathyroidism are indeed related and that an identical gene defect is responsible for the disease. A further feature of the inheritance pattern was examined when a unique point mutation was identified in the mtDNA of one branch of one of the kindreds. This mutation appears to be de novo and segregates in subsequent generations without obscuring relatedness. In addition, the results of our study of mtDNA analysis indicate that this approach may be of importance in investigating common ancestry in other X-linked disorders.

Alleles↗

PubMed1996

Simpson-Golabi-Behmel syndrome: genotype/phenotype analysis of 18 affected males from 7 unrelated families.

Simpson-Golabi-Behmel syndrome (SGBS) is an X-linked overgrowth disorder recently shown to be caused by mutations in the heparan sulfate proteoglycan GPC3 [Pilia et al., Nat Genet; 12:241-247 1996]. We have used Southern blot analysis and polymerase chain reaction amplification of intra-exonic sequences to identify four new GPC3 mutations and further characterize three previously reported SGBS mutations. De novo GPC3 mutations were identified in 2 families. In general, the mutations were unique deletions ranging from less than 0.1 kb to more than 300 kb in length with no evidence of a mutational hot spot discerned. The lack of correlation between the phenotype of 18 affected males from these 7 families and the location and size of the GPC3 gene mutations suggest that SGBS is caused by a nonfunctional GPC3 protein.

Abnormalities, Multiple↗

PubMed1996

Ordered shotgun sequencing of a 135 kb Xq25 YAC containing ANT2 and four possible genes, including three confirmed by EST matches.

Ordered shotgun sequencing (OSS) has been successfully carried out with an Xq25 YAC substrate. yWXD703 DNA was subcloned into lambda phage and sequences of insert ends of the lambda subclones were used to generate a map to select a minimum tiling path of clones to be completely sequenced. The sequence of 135 038 nt contains the entire ANT2 cDNA as well as four other candidates suggested by computer-assisted analyses. One of the putative genes is homologous to a gene implicated in Graves' disease and it, ANT2 and two others are confirmed by EST matches. The results suggest that OSS can be applied to YACs in accord with earlier simulations and further indicate that the sequence of the YAC accurately reflects the sequence of uncloned human DNA.

Bacteriophage lambda↗

PubMed1996

Refinement of the background genetic map of Xq26-q27 and gene localisation for Börjeson-Forssman-Lehmann Syndrome.

A detailed map of genetic markers was constructed around the gene for the X-linked mental retardation syndrome of Börjeson-Forssman-Lehmann (BFLS). A multipoint linkage map of framework markers across Xq26-27, based on CEPH families, was integrated with the physical map, based on a YAC contig, to confirm marker order. The remaining genetic markers, which could not be ordered by linkage, were added to create the comprehensive genetic back-ground map, in the order determined by physical mapping, to determine genetic distances between adjacent markers. This background genetic map is applicable to the refinement of the regional localisation for any disease gene mapping to this region. The BFLS gene was localised using this background map in an extended version of the family described by Turner et al. [1989]. The regional localisation for BFLS extends between recombination events at DXS425 and DXS105, an interval of 24.6 cM on the background genetic map. The phenotypic findings commonly seen in the feet of affected males and obligate carrier females may represent a useful clinical indicator of carrier status in potential female carriers in the family. Recombination between DXS425 and DXS105 in a female with such characteristic feet suggests that the distal limit of the regional localisation for the BFLS gene might reasonably be reduced to DXS294 for the purpose of selecting candidate genes, reducing the interval for the BFLS gene to 15.5 cM. Positional candidate genes from the interval between DXS425 and DXS105 include the SOX3 gene, mapped between DXS51(52A) and DXS98(4D-8). SOX3 may have a role in regulating the development of the nervous system. The HMG-box region of this single exon gene was examined by PCR for a deletion and then sequenced. No deviation from normal was observed, excluding mutations in the conserved HMG-box region as the cause of BFLS in this family.

Chromosome Mapping↗

PubMed1996

YAC/STS map across 12 Mb of Xq27 at 25-kb resolution, merging Xq26-qter.

A 12-Mb YAC contig has been assembled spanning the Xq27 cytogenetic band with 203 YACs, 121 STSs, and >300 hybridization probes to a resolution of 25 kb. At its centromeric end, the contig is merged with a 9-Mb contig covering Xq26.1-q26.3 at a point 1 Mb telomeric to the factor IX gene; at its telomeric end, it is merged to 7.5 Mb of contigs from the IDS gene to the Xq28 telomere. Thus, the distal 29 Mb of the Xq arm is available cloned in long-range contiguity. The physical map has been integrated with current genetic data by the localization of 18 markers that detect polymorphism. Apparent recombination levels reach >4.5 cM/Mb near the centromeric border of Xq27. The ratio of cM/Mb correspondingly delimits the location of several disease genes-including, for example, X-linked hypoparathyroidism in 3 Mb (6 cM) telomeric to Factor IX.

Base Sequence↗

PubMed1996

YAC/STS map of 9 Mb of Xq26 at 100-kb resolution, localizing 6 ESTs, 6 genes, and 32 genetic markers.

To facilitate functional analysis of the Xq26 region, the physical map has been extended across 9 Mb with 192 YACs and markers including 90 STSs (sequence-tagged sites) and 50 hybridization probes. Six genes and six ESTs are localized. In addition, 32 markers that detect polymorphism permit an integration of physical with genetic linkage data. The localizations of eight uncloned disease genes are thereby delimited on the physical map. The data also suggest a possible gradient of recombination across the cytogenetic band, with little or no recombination reported in the centromeric 3.5-4 Mb.

Base Sequence↗

PubMed1996

A 2-megabase physical contig incorporating 43 DNA markers on the human X chromosome at p11.23-p11.22 from ZNF21 to DXS255.

A comprehensive physical contig of yeast artificial chromosomes (YACs) and cosmid clones between ZNF21 and DXS255 has been constructed, spanning 2 Mb within the region Xp11.23-p11.22. As a portion of the region was found to be particularly unstable in yeast, the integrity of the contig is dependent on additional information provided by the sequence-tagged site (STS) content of cosmid clones and DNA marker retention in conventional and radiation hybrids. The contig was formatted with 43 DNA markers, including 19 new STSs from YAC insert ends and an internal Alu-PCR product. The density of STSs across the contig ranges from one marker every 20 kb to one every 60 kb, with an average density of one marker every 50 kb. The relative order of previously known genes and expressed sequence tags in this region is predicted to be Xpter-ZNF21-DXS7465E (MG66)-DXS7927E (MG81)-WASP, DXS1011E, DXS7467E (MG21)-DXS- 7466E (MG44)-GATA1-DXS7469E (Xp664)-TFE3-SYP (DXS1007E)-Xcen. This contig extends the coverage in Xp11 and provides a framework for the future identification and mapping of new genes, as well as the resources for developing DNA sequencing templates.

Animals↗