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S W Scherer

Publications and source records attributed to S W Scherer.

At least 109 records · Page 6Linked to original sources
PubMed1997

Physical mapping of the chromosome 7 breakpoint region in an SLOS patient with t(7;20) (q32.1;q13.2).

Smith-Lemli-Opitz syndrome (SLOS) is an autosomal recessive disorder characterized by multiple congenital anomalies and mental retardation. SLOS has an associated defect in cholesterol biosynthesis, but the molecular genetic basis of this condition has not yet been elucidated. Previously our group reported a patient with a de novo balanced translocation [t(7;20)(q32.1;q13.2)] fitting the clinical and biochemical profile of SLOS. Employing fluorescence in situ hybridization (FISH), a 1.8 Mb chromosome 7-specific yeast artificial chromosome (YAC) was identified which spanned the translocation breakpoint in the reported patient. The following is an update of the on-going pursuit to physically and genetically map the region further, as well as the establishment of candidate genes in the 7q32.1 breakpoint region.

Chromosome Mapping↗
PubMed1997

Maintenance of hypomethylation status and preferential expression of exogenous human MDR1/PGY1 gene in mouse L cells by YAC mediated transfer.

Selection of cells for resistance to vincristine or doxorubicin often induces overexpression of the multidrug resistance (MDR) genes, which encode the cell surface P-glycoproteins, as a result of gene amplification, transcriptional activation, or mRNA stabilization. The LMD1 and LMD4 cell lines were established after the transfer into mouse L cells of two independent yeast artificial chromosome clones containing 300 and 850 kb, respectively, of the human MDR locus. The human MDR1/PGY1 gene, but not the endogenous mouse mdr1a and mdr1b genes, was overexpressed as a result of gene amplification and transcriptional activation in various sublines of LMD1 and LMD4 cells selected for resistance to vincristine. Then we asked why human MDR1/PGY1 gene, but not mouse relevant gene, was expressed. Determination of the methylation status of cytosine residues at Msp I/Hap II cleavage sites (CCGG) in the promoter regions of human MDR1/PGY1 and mouse mdr1a revealed hypomethylation and hypermethylation of the human and mouse genes, respectively in LMD1, LMD4, and their vincristine-resistant derivatives. Various vincristine-resistant sublines were also established after exposure of LMD1 cells for 48 h to 5-aza-2'-deoxycytidine, an inhibitor of DNA methyltransferase. These sublines exhibited overexpression of mouse mdr1a and mdr1b, but not of human MDR1/PGY1, as well as hypomethylation of the mouse mdr1a promoter region. Thus, the selective expression of human or mouse MDR genes in this cell system appears to be related to the methylation status of the respective gene promoter regions.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1997

Cytogenetic rearrangements involving the loss of the Sonic Hedgehog gene at 7q36 cause holoprosencephaly.

Holoprosencephaly (HPE) is a genetically heterogeneous disorder that affects the midline development of the forebrain and midface in humans. As a step toward identifying one of the HPE genes, we have set out to refine the HPE3 critical region on human chromosome 7q36 by analyzing 34 cell lines from families with cytogenetic abnormalities involving 7q, 24 of which are associated with HPE. Genomic clones surrounding the DNA marker D7S104, which has previously been shown to be in the HPE3 critical region, have been examined by fluorescent in situ hybridization and microsatellite analysis of our panel of patient cell lines. We report the analysis of a cluster of four translocation breakpoints within a 300-kb region of 7q36 that serves to define the minimal critical region for HPE3 and that has directed the search for candidate genes. The human Sonic Hedgehog (hSHH) gene maps to this region and has been shown to be HPE3 on the basis of mutations within the coding region of the gene. We present evidence that cytogenetic deletions and/or rearrangements of this region of chromosome 7q containing Sonic Hedgehog, and translocations that may suppress Sonic Hedgehog gene expression through a position effect are common mechanisms leading to HPE.

Body Patterning↗
PubMed1997

Resources for human genetics on the World Wide Web.

A little over a century ago, the HMS Beagle sailed the Pacific Ocean bringing Charles Darwin to the perfect environment in which to piece together his observations forming the theory of evolution. Now, geneticists and laypeople alike surf the equally formidable waters of the internet in search of enlightenment. Here, we attempt to help you navigate towards resources for human genetics by providing maps to three destinations: The Human Genome Project (Box 1), education (Box 2), and human genetic diseases (Box 3). For each, we highlight a few sites that we consider are the most informative and original. A more extensive list containing other useful sites has been compiled and posted on a 'jump site' at: http:/(/)www.cgdn.generes.ca/.

Computer Communication Networks↗
PubMed1997

Germline and somatic mutations in the tyrosine kinase domain of the MET proto-oncogene in papillary renal carcinomas.

Hereditary papillary renal carcinoma (HPRC) is a recently recognized form of inherited kidney cancer characterized by a predisposition to develop multiple, bilateral papillary renal tumours. The pattern of inheritance of HPRC is consistent with autosomal dominant transmission with reduced penetrance. HPRC is histologically and genetically distinct from two other causes of inherited renal carcinoma, von Hippel-Lindau disease (VHL) and the chromosome translocation (3;8). Malignant papillary renal carcinomas are characterized by trisomy of chromosomes 7, 16 and 17, and in men, by loss of the Y chromosome. Inherited and sporadic clear cell renal carcinomas are characterized by inactivation of both copies of the VHL gene by mutation, and/or by hypermethylation. We found that the HPRC gene was located at chromosome 7q31.1-34 in a 27-centimorgan (cM) interval between D7S496 and D7S1837. We identified missense mutations located in the tyrosine kinase domain of the MET gene in the germline of affected members of HPRC families and in a subset of sporadic papillary renal carcinomas. Three mutations in the MET gene are located in codons that are homologous to those in c-kit and RET, proto-oncogenes that are targets of naturally-occurring mutations. The results suggest that missense mutations located in the MET proto-oncogene lead to constitutive activation of the MET protein and papillary renal carcinomas.

Adult↗
PubMed1997

Mutations in the C-terminal domain of Sonic Hedgehog cause holoprosencephaly.

Holoprosencephaly (HPE) is the most common brain anomaly in humans, involving abnormal formation and septation of the developing central nervous system. Among the heterogeneous causes of HPE, mutations in the Sonic Hedgehog (SHH) gene have been shown to result in an autosomal dominant form of the disorder. Here we describe a total of five different mutations in the processing domain encoded by exon 3 of SHH in familial and sporadic HPE. This is the first instance in humans where SHH mutations in the domain responsible for autocatalytic cleavage and cholesterol modification of the N-terminal signaling domain of the protein have been observed.

Alanine↗
PubMed1997

Translocation breakpoint maps 5 kb 3' from TWIST in a patient affected with Saethre-Chotzen syndrome.

Saethre-Chotzen syndrome, a common autosomal dominant craniosynostosis in humans, is characterized by brachydactyly, soft tissue syndactyly and facial dysmorphism including ptosis, facial asymmetry, and prominent ear crura. Previously, we identified a yeast artificial chromosome that encompassed the breakpoint of an apparently balanced t(6;7) (q16.2;p15.3) translocation associated with a mild form of Saethre-Chotzen syndrome. We now describe, at the DNA sequence level, the region on chromosome 7 affected by this translocation event. The rearrangement occurred approximately 5 kb 3' of the human TWIST locus and deleted 518 bp of chromosome 7. The TWIST gene codes for a transcription factor containing a basic helix-loop-helix (b-HLH) motif and has recently been described as a candidate gene for Saethre-Chotzen syndrome, based on the detection of mutations within the coding region. Potential exon sequences flanking the chromosome 7 translocation breakpoint did not hit known genes in database searches. The chromosome rearrangement downstream of TWIST is compatible with the notion that this is a Saethre-Chotzen syndrome gene and implies loss of function of one allele by a positional effect as a possible mechanism of mutation to evoke the syndrome.

Acrocephalosyndactylia↗
PubMed1997

Paraoxonase-2 gene (PON2) G148 variant associated with elevated fasting plasma glucose in noninsulin-dependent diabetes mellitus.

Defining the genetic determinants of NIDDM requires evidence from several complementary approaches, including both linkage and association analyses using both discrete phenotypes and intermediate quantitative traits. We tested for association between common genomic variation in three genes that map to chromosome 7q21-q22 and quantitative traits related to NIDDM in a sample of Oji-Cree. We found that a common genomic variation in codon 148 (alanine or glycine) of the paraoxonase-2 gene (PON2) demonstrated a significant association with a variation in fasting plasma glucose (P < 0.0001). Furthermore, we found a significant association between a variation in fasting plasma glucose and the interaction term comprised of a PON2 codon 148 genetic variation and the presence of noninsulin-dependent diabetes mellitus (NIDDM; P < 0.0001). We then analyzed subjects according to PON2 genotype and NIDDM status. In subjects with NIDDM, the PON2 codon 148 G/G homozygotes had significantly higher mean fasting plasma glucose than subjects with the other two genotypes (P < 0.0001). However, in non-NIDDM subjects, there was no difference in mean fasting plasma glucose among any of the genotypes. There was no association of the PON2 genotype with NIDDM itself, with impaired glucose tolerance, or with other quantitative traits related to NIDDM in this sample. These findings suggest that 1) the PON2 G148 gene variant worsens glycemia in subjects with NIDDM; 2) defining the physiological role of the PON2 gene product would be worthwhile; and 3) genetic factors can modify the severity of clinical phenotypes in subjects with NIDDM.

Adolescent↗
PubMed1996

Structure and mapping of the human lanosterol 14alpha-demethylase gene (CYP51) encoding the cytochrome P450 involved in cholesterol biosynthesis; comparison of exon/intron organization with other mammalian and fungal CYP genes.

Sterol 14alpha-demethylase (P45014DM) encoded by CYP51 is a member of the cytochrome P450 (CYP) gene superfamily involved in sterol biosynthesis in fungi, plants, and animals. Constraints imposed by the specific function of CYP51 have severely limited sequence divergence in this family. Consequently, CYP51 is the only P450 family recognizable across all eukaryotic phyla. We have determined the structure of the functional human CYP51 gene, which spans 22 kb, is divided into 10 exons, and maps to 7q21.2-q21.3. The 5' portion of intron 1 is GC-rich and contains potential binding sites for several transcription factors. Primer extension studies reveal predominant transcription initiation sites in liver, kidney, lung, and placenta 250 and 249 bp upstream from the translation start site and a second major site at -100 bp. Ubiquitous expression of human CYP51 (Strömstedt et al., Arch. Biochem. Biophys. 329: 73-81, 1996), the absence of TATA and CAAT patterns, a GC-rich sequence in the promoter region, and initiation of CYP51 transcription at more than one site indicate that CYP51 is a housekeeping gene. The 5'-flanking region, exon 1, and a portion of intron 1 show the characteristics of a CpG island, with the observed/expected CpG ratio of 0.79. Sterol responsive element-like motifs were present in this region, suggesting regulation by oxysterols via a mechanism similar to that associated with other genes involved in cholesterol homeostasis. Comparison of the human CYP51 gene structure with structures of other mammalian and fungal CYP gene families shows that 7 of the 9 CYP51 introns are located at unique positions. More than 80 intron locations exist in mammalian and fungal CYP gene families, and it seems very unlikely that all these introns could have been present in the primordial CYP gene.

Amino Acid Sequence↗
PubMed1996

Genomic organization and transcript analysis of ICAp69, a target antigen in diabetic autoimmunity.

Islet cell antigen p69 (ICAp69) is a target self-antigen in autoimmune (insulin-dependent) diabetes mellitus. Distributed over more than 100 kb on chromosome 6 (6{A1-A2}), the single murine genomic locus contains 14 coding exons, 39-271 bp in length. The identified human and mouse intron-exon junctions are identical, with intron sizes ranging from 94 bp to 24 kb and with conserved flanking region intron sequences. cDNA cloning identified alternatively spliced ICAp69 mRNA transcripts. The predominating alpha-transcripts lack exon 4, while beta-transcripts include this exon, which codes translation termination in all reading frames and a truncated molecule following in vitro expression. gamma-Transcripts show splice removal of exons 8-12, while delta-transcripts exclude exon 11. Transcripts use alternative polyadenylation signals including a less frequent ATTAAA sequence. 5'-Untranslated cDNA and genomic sequencing and long PCR analysis suggest the presence of more noncoding exons. All splice variants encode the conserved T-cell epitope (in exon 2) recognized by autoreactive T cells in diabetic children and diabetes-prone NOD mice.

Amino Acid Sequence↗
PubMed1996

Detailed deletion mapping with a refined physical map of 7q31 localizes a putative tumor suppressor gene for breast cancer in the region of MET.

In breast cancer, loss of heterozygosity (LOH) has been described on the long arm of chromosome 7 at band q31, suggesting the presence of a tumor suppressor gene in this region. To define the deleted region, we analysed 73 cases of breast cancer and matched normal DNAs with 17 polymorphic markers. A minimal area of LOH was identified as the chromosomal interval flanked by markers D7S687 and metH, spanning a segment of 2 Mb on chromosome 7q31. Of the 73 breast cancer patients studied, all were informative for at least one marker in this region and nine patients showed LOH at one or more loci (12.3%). To define the physical size of the deletion and to ensure the correct interpretation of the LOH deletion studies, we redefined the physical map of markers within this region of 7q31. We present a new physical order for markers at 7q31. More significantly, we have mapped the minimum deletion of 7q31 in the breast cancers studied to date to a physical distance of 1000 kb, contained on a single YAC clone, which includes the MET receptor tyrosine kinase but no other known genes.

Breast Neoplasms↗
PubMed1996

Cloning and characterization of PDK4 on 7q21.3 encoding a fourth pyruvate dehydrogenase kinase isoenzyme in human.

Different isoenzymes of pyruvate dehydrogenase kinase (PDK) inhibit the mitochondrial pyruvate dehydrogenase complex by phosphorylation of the E1alpha subunit, thus contributing to the regulation of glucose metabolism. By positional cloning in the 7q21.3-q22.1 region linked with insulin resistance and non-insulin-dependent diabetes mellitus in the Pima Indians, we identified a gene encoding an additional human PDK isoform, as evidenced by its amino acid sequence identity (>65%) with other mammalian PDKs, and confirmed by biochemical analyses of the recombinant protein. We performed detailed comparative analyses of the gene, termed PDK4, in insulin-resistant and insulin-sensitive Pima Indians, and detected five DNA variants with comparable frequencies in both subject groups. Using quantitative reverse transcription polymerase chain reaction, we found that the variants identified in the promoter and 5'-untranslated region did not correlate with differences in mRNA level in skeletal muscle and adipose tissue. We conclude that alterations in PDK4 are unlikely to be the molecular basis underlying the observed linkage at 7q21.3-q22.1 in the Pima Indians. Information about the genomic organization and promoter sequences of PDK4 will be useful in studies of other members of this family of mitochondrial protein kinases that are important for the regulation of glucose metabolism.

Adipose Tissue↗
PubMed1996

Identification of genes from a 500-kb region at 7q11.23 that is commonly deleted in Williams syndrome patients.

Williams syndrome (WS) is a multisystem developmental disorder caused by the deletion of contiguous genes at 7q11.23. Hemizygosity of the elastin (ELN) gene can account for the vascular and connective tissue abnormalities observed in WS patients, but the genes that contribute to features such as infantile hypercalcemia, dysmorphic facies, and mental retardation remain to be identified. In addition, the size of the genomic interval commonly deleted in WS patients has not been established. In this study we report the characterization of a 500-kb region that was determined to be deleted in our collection of WS patients. A detailed physical map consisting of cosmid, P1 artificial chromosomes, and yeast artificial chromosomes was constructed and used for gene isolation experiments. Using the techniques of direct cDNA selection and genomic DNA sequencing, three known genes (ELN, LIMK1, and RFC2), a novel gene (WSCR1) with homology to RNA-binding proteins, a gene with homology to restin, and four other putative transcription units were identified. LIMK1 is a protein kinase with two repeats of the LIM/double zinc finger motif, and it is highly expressed in brain. RFC2 is the 40-kDa ATP-binding subunit of replication factor C, which is known to play a role in the elongation of DNA catalyzed by DNA polymerase delta and epsilon. LIMK1 and WSCR1 may be particularly relevant when explaining cognitive defects observed in WS patients.

Amino Acid Sequence↗
PubMed1996

MADR2 maps to 18q21 and encodes a TGFbeta-regulated MAD-related protein that is functionally mutated in colorectal carcinoma.

The MAD-related (MADR) family of proteins are essential components in the signaling pathways of serine/threonine kinase receptors for the transforming growth factor beta (TGFbeta) superfamily. We demonstrate that MADR2 is specifically regulated by TGFbeta and not bone morphogenetic proteins. The gene for MADR2 was found to reside on chromosome 18q21, near DPC4, another MADR protein implicated in pancreatic cancer. Mutational analysis of MADR2 in sporadic tumors identified four missense mutations in colorectal carcinomas, two of which display a loss of heterozygosity. Biochemical and functional analysis of three of these demonstrates that the mutations are inactivating. These findings suggest that MADR2 is a tumor suppressor and that mutations acquired in colorectal carcinomas may function to disrupt TGFbeta signaling.

Amino Acid Sequence↗