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Biomedical subjects

G F Saunders

Publications and source records attributed to G F Saunders.

At least 19 recordsLinked to original sources
PubMed1992

RNA expression of the WT1 gene in Wilms' tumors in relation to histology.

BACKGROUND: On the basis of accumulating data, the recently isolated WT1 gene is a Wilms' tumor gene and a putative tumor suppressor gene. These findings include expression in developing fetal kidney, intragenic deletions in tumors, and germline mutations in predisposed individuals. Wilms' tumors, which exhibit a broad range of differentiation, are composed of three cell types: blastema, epithelium, and stroma. PURPOSE: The purpose of this study was to investigate the relationship between WT1 gene expression and histologic composition in Wilms' tumors in an effort to elucidate how the WT1 gene functions in proliferation of these histologic components. METHODS: We used Northern blot hybridization to study WT1 gene expression by messenger RNA (mRNA) accumulation in 20 tumors of varying histology and in adjacent uninvolved kidney tissue. In two patients, tumors were also compared before and after therapy. RESULTS: Tumors that were predominantly blastemal expressed high amounts of WT1 mRNA, whereas predominantly stromal tumors expressed either low or undetectable amounts. Blastemal tumors that were predominantly poorly differentiated expressed WT1 mRNA at higher levels than those that were more well differentiated. Although we expected that a putative tumor suppressor gene like WT1 would generally be expressed at lower levels in tumor than in normal kidney, this was true only in predominantly stromal cells. One of the two patients studied before and after therapy had a dramatic response to therapy accompanied by a decline in WT1 gene expression and disappearance of blastemal and epithelial elements. CONCLUSIONS: A correlation was observed between WT1 gene expression and histology of the tumors. Level of expression was inversely related to the degree of differentiation in blastemal tumors and in the patient with a dramatic response to therapy. These results, in conjunction with the observation that WT1 mRNA is abundant in normal fetal kidney, suggest that WT1 gene expression is related to kidney development, especially in differentiation of blastemal components. IMPLICATIONS: Further studies to search for alterations of the WT1 gene in tumors and to identify regulatory factors in gene expression will increase understanding of the role of this gene in normal development and tumorigenesis.

Gene Expression Regulation, Neoplastic↗
PubMed1992

Resolution of the two loci for autosomal dominant aniridia, AN1 and AN2, to a single locus on chromosome 11p13.

Two distinct loci have been proposed for aniridia; AN1 for autosomal dominant aniridia on chromosome 2p and AN2 for the aniridia in the WAGR contiguous gene syndrome on chromosome 11p13. In this report, the kindred segregating for autosomal dominant aniridia, which suggested linkage to acid phosphatase-1 (ACP1) and led to the assignment of the AN1 locus on chromosome 2p, has been updated and expanded. Linkage analysis between the aniridia phenotype and ACP1 does not support the original linkage results, excluding linkage up to theta = 0.17 with Z = -2. Tests for linkage to other chromosome 2p markers. APOB, D2S71, D2S5, and D2S1, also excluded linkage to aniridia. Markers that have been isolated from the chromosome 11p13 region were then analyzed in this aniridia family. Two RFLPs at the D11S323 locus give significant evidence for linkage. The PvuII polymorphism detected by probe p5S1.6 detects no recombinants, with a maximum lod score of Z = 6.97 at theta = 0.00. The HaeIII polymorphism detected by the probe p5BE1.2 gives a maximum lod score of Z = 2.57 at theta = 0.00. Locus D11S325 gives a lod score of Z = 1.53 at theta = 0.00. These data suggest that a locus for aniridia (AN1) on chromosome 2p has been misassigned and that this autosomal dominant aniridia family is segregating for an aniridia mutation linked to markers in the 11p13 region.

Alkaline Phosphatase↗
PubMed1992

Small eye (Sey): cloning and characterization of the murine homolog of the human aniridia gene.

Phenotypic parallels and genetic evidence from comparative mapping suggest that the murine Small eye (Sey) and human aniridia (AN) disorders are homologous. This report describes the isolation of a murine embryonic cDNA that is structurally homologous to the AN cDNA were recently cloned. The murine cDNA detects a 2.7-kb transcript in the adult mouse eye and cerebellum and in human glioblastomas, suggesting a neuroectodermal involvement in the etiology of Sey/AN. Sequence comparison between the murine and the human cDNAs revealed extensive homology in nucleotide sequence (greater than 92%) and virtual identity at the amino acid level. None of the differing amino acids was located within the paired box and homeobox DNA-binding domains. These results provide evidence for a common molecular basis underlying the two genetic disorders and suggest that the Sey system would be an authentic model for human AN.

Amino Acid Sequence↗
PubMed1992

Expression of the Wilms' tumor gene (WT1) in human leukemias.

Leukemic cells from seventy patients with various types of human leukemias were examined for expression of the WT1 gene, the Wilms' tumor gene located at chromosome 11p13. WT1 was expressed in 7 of 16 cases of acute lymphoblastic leukemia, 15 of 22 with acute myelogenous leukemia and 8 of 10 in blast crisis of chronic myelogenous leukemia. No detectable WT1 RNA was found in chronic leukemias, including chronic lymphocytic leukemia, plasma cell leukemia, hairy cell leukemia and chronic myelogenous leukemia in chronic phase. The expression pattern of WT1 in these human leukemia samples indicates the involvement of this gene in the early stage of hematological cell differentiation.

Adolescent↗
PubMed1991

Multiple forms of maturation-promoting factor in unfertilized Xenopus eggs.

Maturation-promoting factor (MPF), which is functionally defined by its ability to induce frog oocyte maturation independent of protein synthesis, is hypothesized to be the mitotic inducer in eukaryotic cells. Previous studies have demonstrated that the cdc2 protein kinase complex (p34cdc2-cyclin) meets the criteria for MPF. In the present study, we show that MPF activity in extracts of unfertilized Xenopus eggs can be resolved into three fractions by Q-Sepharose chromatography. Of the total MPF activity recovered, approximately 20% was in the flow-through fraction that was accounted for by the cdc2 kinase complex, approximately 40% was in the 0.2 M NaCl eluate, and the remaining approximately 40% was in the 0.5 M NaCl eluate. Neither eluate contained cdc2 kinase, but each could activate cdc2 kinase upon microinjection into Xenopus oocytes. The MPF activity in the two eluates, but not in the flow-through fraction, could be depleted by the mitosis-specific monoclonal antibody MPM-2. This antibody has been shown to inhibit Xenopus oocyte maturation and deplete MPF activity from mature oocyte extract but does not recognize the cdc2 kinase complex. The three MPFs differed in apparent molecular size, H1 kinase activity, and stability at 4 degrees C. We propose that MPF activity in unfertilized Xenopus eggs resides in at least three different molecular species, the combined activities of which may be required for autoamplification of MPF.

Amino Acid Sequence↗
PubMed1991

Interferon-gamma-inducible regulation of the human invariant chain gene.

Interferon-gamma (IFN-gamma) regulates a variety of immunoregulatory functions through the induction of a specific set of IFN-gamma response genes. This includes the invariant chain associated with the major histocompatibility complex class II molecules. To investigate the mechanism involved in the invariant chain (In) response to IFN-gamma we constructed chloramphenicol acetyltransferase (CAT) hybrid genes in which the CAT gene is under the control of the In promoter. The glioblastoma cell line, U-373 MG, transfected with a CAT construct having the In promoter sequence -790 to +1 bp showed over 3-fold increased CAT activity when treated with IFN-gamma indicating that this region confers IFN-gamma responsiveness to the CAT gene. The IFN-gamma response element in the promoter was further sublocalized to the region -120 to -61 base pairs (bp). This region contains homology to the interferon-stimulated response elements identified in other IFN responsive genes. By gel shift analyses, an IFN-gamma-induced sequence-specific DNA-binding factor was identified. This induced complex binds to an oligonucleotide corresponding to -107 to -79 bp of the In promoter. Mutations of this binding site at -94 and -92 bp drastically decreased binding of the constitutive and IFN-gamma-induced complexes. This IFN-gamma induced factor also binds to an oligonucleotide corresponding to -91 to -62 bp of the interferon-beta (IFN-beta) gene promoter, a region necessary for the induction of the IFN-beta gene by virus and double-stranded RNA. This binding specificity is characteristic of a family of DNA binding factors that bind both the interferon-stimulated response elements and the IFN-beta gene promoter.

Base Sequence↗
PubMed1991

A novel M phase-specific H1 kinase recognized by the mitosis-specific monoclonal antibody MPM-2.

At the onset of mitosis, eukaryotic cells display an abrupt increase in a Ca2(+)- and cyclic nucleotide-independent histone H1 kinase activity, referred to as growth-associated or M phase-specific H1 kinase. The molecular basis for this activity is generally attributed to a kinase complex that consists of the p34cdc2 protein and cyclin, and exhibits maturation-promoting factor (MPF) activity. In the present study, we show that more than one kinase contributes to M phase-specific H1 kinase activity. When mature Xenopus oocyte extract prepared with ATP gamma S and NaF was fractionated by gel filtration, two prominent peaks of H1 kinase activity were detected, with apparent molecular masses of 600 and 150 kDa. The 150-kDa kinase copurified with the p34cdc2 protein and was immobilized by the suc 1 gene product p13 and anti-cyclin B2, which are specific for the cdc2 kinase complex. However, the 600-kDa kinase did not satisfy any of these criteria, thus identifying it as a novel M phase-specific H1 kinase. Only the 600-kDa kinase was recognized by the mitosis-specific monoclonal antibody, MPM-2, which inhibits Xenopus oocyte maturation and immunodepletes MPF activity. Furthermore, not only did the full activation of this kinase (MPM-2 kinase) coincide with the activation of MPF during the cell cycle, but also MPM-2 kinase-positive fractions obtained by gel filtration accelerated progesterone-induced oocyte maturation. It is, therefore, likely that MPM-2 kinase is a positive regulator in the M phase induction pathway.

Animals↗
PubMed1991

Smallest region of overlap in Wilms tumor deletions uniquely implicates an 11p13 zinc finger gene as the disease locus.

The development of Wilms tumor (WT) has been associated with the inactivation of a "tumor suppressor" locus in human chromosome 11 band p13. Several WTs that exhibit homozygous deletions of an 11p13 candidate WT gene in its entirety have been reported. We report here a partial deletion of the candidate gene which, upon comparison with other documented homozygous deletions, permitted a precise definition of the critical genomic target in Wilms tumor. The smallest region of overlap between these deletions is a 16-kb segment of DNA encompassing the 5' exon(s) of an 11p13 gene coding for a zinc finger protein, together with an associated CpG island. This finding supports the notion that the candidate gene in question corresponds to the 11p13 WT1 Wilms tumor locus.

Child, Preschool↗
PubMed1991

Expression pattern of a hematopoietic proteoglycan core protein gene during human hematopoiesis.

Expression of the hematopoietic proteoglycan core protein (HpPG) gene was examined in normal peripheral blood, normal bone marrow, and leukemic peripheral blood leukocytes samples to assess the expression pattern of the HpPG gene in these cells and to ascertain points of regulation of this gene during hematopoiesis. In situ hybridization to normal bone marrow and peripheral blood leukocytes demonstrated that the gene was expressed in the promyelocytes at a approximately two fold greater level than in the segmented neutrophils and the expression decreased as the granulocytes matured. The ratio of expression in the other leukocytes to expression in the segmented neutrophils were as follows: eosinophils/basophils approximately 7; monocytes approximately 2; lymphocytes less than 1. Expression of the HpPG gene during myeloblast differentiation was assessed by Northern blot analysis of acute myelogenous leukemia (AML) RNA samples. The expression of this gene, when compared to the levels in HL-60 cells, was approximately ten fold lower in the poorly differentiated blast cells obtained from three AML patients classified M"0". Conversely, the expression in the more differentiated blast cells obtained from 10 of 11 AML patients classified as M1 and M2 were at levels similar to the levels in HL-60 cells. The expression level found in eight lymphoid leukemias was approximately ten fold or more lower than in HL-60 cells. Gene copy number determination confirmed that the HpPG gene is present in one copy per haploid genome. Thus the HpPG gene's expression pattern denotes a single copy gene being differentially expressed during hematopoiesis with initial regulation occurring very early in this developmental process and an additional up-regulatory event occurring during granule genesis.

Aggrecans↗
PubMed1991

The human placental lactogen genes: structure, function, evolution and transcriptional regulation.

hPL is a member of an evolutionarily related gene family including hGH and hPRL. Expression of hPL is limited to the placenta but its physiological actions are far reaching. hPL has a direct somatotropic effect on fetal tissues, it alters maternal carbohydrate and lipid metabolism to provide for fetal nutrient requirements, and aids in stimulation of mammary cell proliferation. Two hPL genes (hPL3 and hPL4) encoding identical proteins are responsible for the production of up to 1-3 g PL hormone/day. Recent studies have characterized the regulatory controls of hPL expression. At the post transcriptional level, RNA stability may contribute to variable levels of hPL3 vs. hPL4 production. In addition, non-tissue-specific protein-promoter interactions involving the Sp1 transcription factor are necessary for hPL transcription initiation. A transcriptional enhancer located 3' to the hPL3 gene is responsible for the placenta-specific expression of this gene, while an additional enhancer may be located 3' to the hPl4 gene. The hPL enhancer is bound by multiple proteins including at least one placental specific protein that interacts with a TEF-1 motif. Therefore, enhancer-protein interactions most likely play a large part in the high levels of placenta-specific hPL expression.

Amino Acid Sequence↗
PubMed1991

DNA diagnosis in a family with autosomal dominant aniridia.

A large family with autosomal dominant aniridia is described. One of the family members presented with reduced visual acuity, nystagmus, slightly distorted macular reflex, but normal irides and clear media. Because of the high variability in expression of aniridia, even within family, a diagnosis of aniridia could not be excluded. However linkage analysis using tightly linked chromosome 11p13 markers flanking the aniridia locus (catalase, D11S151, and D11S325) made it highly unlikely that this patient inherited the aniridia gene from his affected mother.

Adolescent↗
PubMed1991

Evidence for WT1 as a Wilms tumor (WT) gene: intragenic germinal deletion in bilateral WT.

The inactivation of two alleles at a locus on the short arm of chromosome 11 (band 11p13) has been suggested to be critical steps in the development of Wilms tumor (WT), a childhood kidney tumor. Two similar candidate WT cDNA clones (WT33 and LK15) have recently been identified on the basis of both their expression in fetal kidney and their location within the smallest region of overlap of somatic 11p13 deletions in some tumors. These homozygous deletions, however, are large and potentially affect more than one gene. Using a cDNA probe to the candidate gene, we have analyzed DNA from both normal and tumor tissue from WT patients, in an effort to detect rearrangements at this locus. We report here a patient with bilateral WT who is heterozygous for a small (less than 11 kb) germinal deletion within this candidate gene. DNA from both tumors is homozygous for this intragenic deletion allele, which, by RNA-PRC sequence analysis, is predicted to encode a protein truncated by 180 amino acids. These data support the identification of this locus as an 11p13 WT gene (WT1) and provide direct molecular data supporting the two-hit mutational model for WT.

Chromosome Deletion↗
PubMed1991

Genomic changes on the short arm of human chromosome 1 in breast cancer.

A total of 38 DNA sample pairs from normal and cancerous breasts were specifically examined for alterations on the short arm of chromosome 1 using probe pYNZ2. Of the pairs, 24 (63%) displayed changes at this locus including amplifications, deletions, gene rearrangements, and altered band intensities between heterozygous alleles. Due to technical considerations, this number is likely to be a conservative estimate of the frequency of alterations in this region. When data using a different probe from the short arm of chromosome 1 was added, the overall involvement of this region increased to 73%. The combined data indicate we have localized a region, likely to be less than 85 cm in size, that is involved in the development of breast cancer.

Breast Neoplasms↗