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R E Straub

Publications and source records attributed to R E Straub.

51 records · Page 3Linked to original sources
PubMed1994

A possible vulnerability locus for bipolar affective disorder on chromosome 21q22.3.

In a preliminary genome scan of 47 bipolar disorder families, we detected in one family a lod score of 3.41 at the PFKL locus on chromosome 21q22.3. The lod score is robust to marker allele frequencies, phenocopy rates and age-dependent penetrance, and remains strongly positive with changes in affection status. Fourteen other markers in 21q22.3 were tested on this family, with largely positive lod scores. Five of the other 46 families also show positive, but modest lod scores with PFKL. When all 47 families are analysed together, there is little support for linkage to PFKL under homogeneity or heterogeneity using lod score analysis, but the model-free affected-pedigree-member method yields statistically significant results (p < 0.0003). Our results are consistent with the presence of a gene in 21q22.3 predisposing at least one family to bipolar disorder.

Adolescent↗
PubMed1993

Linkage of Niemann-Pick disease type C to human chromosome 18.

We analyzed the involvement of chromosome 18 in Niemann-Pick disease type C (NPC), an autosomal recessive cholesterol-processing disorder. Within affected offspring, the chromosome 18 parental contributions were identified by using allele-specific microsatellite markers. Significant linkage of NPC to an 18p genomic marker, D18S40, was indicated by a two-point lod score of 3.84. Analysis of meiotic chromosomal breakpoint patterns among the affected individuals indicated that the NPC gene is pericentromerically localized on human chromosome 18.

Chromosomes, Human, Pair 18↗
PubMed1993

A microsatellite genetic linkage map of human chromosome 18.

We isolated nine new microsatellite markers from chromosome 18 and further characterized and mapped eight microsatellites developed in other laboratories. We have constructed a framework linkage map of chromosome 18 that includes 14 microsatellite markers (12 dinucleotide and 2 tetranucleotide) and 2 RFLP markers. Cytogenetic localization for the microsatellites was performed by PCR amplification of 18 somatic cell hybrids containing different deletions of chromosome 18. Twelve of the microsatellites and one of the RFLPs have heterozygosites greater than 70%. The average heterozygosity of the markers included in the map is 72%. In addition, we have made provisional placements of 3 more microsatellite markers and 2 more RFLP markers. The map lengths (in Kosambi centimorgans) are as follows: sex-averaged, 109.3 cM; male, 72.4 cM; female, 161.2 cM. The average distance between markers in the sex-averaged map is 7.3 cM, and the largest gap between markers is 16.7 cM. Analysis of the data for differences in the female:male map distance ratio revealed significant evidence for a constant difference in the ratio (chi 2 = 32.25; df = 1; P < 0.001; ratio = 2.5:1). Furthermore, there was significant evidence in favor of a variable female:male map distance ratio across the chromosome compared to a constant distance ratio (chi 2 = 27.78; df = 14; P = 0.015). To facilitate their use in genomic screening for disease genes, all of the microsatellite markers used here can be amplified under standard PCR conditions, and most can be used in duplex PCR reactions.

Base Sequence↗
PubMed1993

Diminished support for linkage between manic depressive illness and X-chromosome markers in three Israeli pedigrees.

The hypothesis that chromosomal region Xq27-28 harbours a gene for manic-depression has been a focus of interest in human genetics. X-linked inheritance of manic depressive illness has been re-examined in 3 multigeneration Israeli kindreds. Extension and re-evaluation of pedigree data, including new individuals, diagnostic follow-up, and analysis with DNA markers, shows greatly diminished support for linkage to Xq28. The peak lod scores in two of the pedigrees have dropped several lod units to clearly negative values at the RCP-F8-G6PD gene cluster. On the other hand, positive lod scores (Zmax = 2.09) are sustained in another pedigree at the same map location. None of the pedigrees show linkage to more proximal markers, including the Xq27 locus DXS98. Our analysis underscores the uncertainties in studying complex disorders.

Adult↗
PubMed1992

Identification and localization of microsatellite markers covering human chromosome 18.

To generate microsatellite markers from chromosome 18, we have cytogenetically localized a large number of lambda phage using a deletion mapping panel of somatic cell hybrids. Here we describe the identification of 65 new CA-repeat-containing phage and the localization of five markers developed in other laboratories. This approach allows the selection of a subset of markers that are well spaced across the chromosome and can be developed as genetic markers. The use of PCR-based markers should allow for the rapid genomic screening of disease genes on chromosome 18.

Base Sequence↗
PubMed1991

Thyrotropin-releasing hormone (TRH) and phorbol myristate acetate decrease TRH receptor messenger RNA in rat pituitary GH3 cells: evidence that protein kinase-C mediates the TRH effect.

In a previous report we showed that TRH-induced down-regulation of the density of its receptors (TRH-Rs) on rat pituitary tumor (GH3) cells was preceded by a decrease in the activity of the mRNA for the TRH-R, as assayed in Xenopus oocytes. Here we report the effects of TRH, elevation of cytoplasmic free Ca2+ concentration, phorbol myristate acetate (PMA), and H-7 [1-(5-isoquinolinesulfonyl)2-methylpiperazine dihydrochloride], an inhibitor of protein kinases, on the levels of TRH-R mRNA, which were measured by Northern analysis and in nuclease protection assays using probes made from mouse pituitary TRH-R cDNA, in GH3 cells. These agents were studied to gain insight into the mechanism of the TRH effect, because signal transduction by TRH involves generation of inositol 1,4,5-trisphosphate and elevation of cytoplasmic free Ca2+ concentration, which leads to activation of Ca2+/calmodulin-dependent protein kinase, and of 1,2-diacylglycerol, which leads to activation of protein kinase-C. TRH (1 microM TRH, a maximally effective dose) caused a marked transient decrease in TRH-R mRNA that attained a nadir of 20-45% of control by 3-6 h, increased after 9 h, but was still below control levels after 24 h. Elevation of the cytoplasmic free Ca2+ concentration had no effect on TRH-R mRNA. A maximally effective dose of PMA (1 microM) caused decreases in TRH-R mRNA that were similar in magnitude and time course to those induced by 1 microM TRH. H-7 (20 microM) blocked the effects of TRH and PMA to lower TRH-R mRNA to similar extents.(ABSTRACT TRUNCATED AT 250 WORDS)

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1990

Expression cloning of a cDNA encoding the mouse pituitary thyrotropin-releasing hormone receptor.

Thyrotropin-releasing hormone (TRH) is an important extracellular regulatory molecule that functions as a releasing factor in the anterior pituitary gland and as a neurotransmitter/neuromodulator in the central and peripheral nervous systems. Binding sites for TRH are present in these tissues, but the TRH receptor (TRH-R) has not been purified from any source. Using Xenopus laevis oocytes in an expression cloning strategy, we have isolated a cDNA clone that encodes the mouse pituitary TRH-R. This conclusion is based on the following evidence. Injection of sense RNA transcribed in vitro from this cDNA into Xenopus oocytes leads to expression of cell-surface receptors that bind TRH and the competitive antagonist chlordiazepoxide with appropriate affinities and that elicit electrophysiological responses to TRH with the appropriate concentration dependency. Antisense RNA inhibits the TRH response in Xenopus oocytes injected with RNA isolated from normal rat anterior pituitary glands. Finally, transfection of COS-1 cells with this cDNA leads to expression of receptors that bind TRH and chlordiazepoxide with appropriate affinities and that transduce TRH stimulation of inositol phosphate formation. The 3.8-kilobase mouse TRH-R cDNA encodes a protein of 393 amino acids that shows similarities to other guanine nucleotide-binding regulatory protein-coupled receptors.

Amino Acid Sequence↗
PubMed1989

Receptor number determines latency and amplitude of the thyrotropin-releasing hormone response in Xenopus oocytes injected with pituitary RNA.

TRH evokes depolarizing membrane electrical responses in Xenopus laevis oocytes injected with RNA from pituitary cells. We have shown previously that the amplitude of this response is directly proportional to the dose of TRH and the amount of RNA injected. Herein we show that the number of TRH receptors expressed on oocytes after injection of rat pituitary (GH3) cell RNA or mouse thyrotropic (TtT) tumor RNA determines the latency as well as the amplitude of the response. In oocytes injected with a maximally effective amount of GH3 cell RNA, the latency of the response decreased from a maximal duration of 103 +/- 16 to 10 +/- 1 sec when the TRH concentration was increased from 5 to 3000 nM. When oocytes injected with different amounts of GH3 cell RNA were stimulated with 3000 nM TRH, the latency decreased from 31 +/- 4 to 11 +/- 0.5 sec when the amount of RNA injected was increased from 30 to 400 ng. Specific binding of [3H]methylhistidine-TRH increased when increasing amounts of TtT poly(A)+ RNA was injected, and binding correlated with increased response amplitude. To show that these effects were caused by mRNA for the TRH receptor and did not depend on other mRNAs, TtT poly(A)+ RNA was fractionated on a sucrose gradient. Using RNA from each fraction, there was an inverse correlation between response amplitude and latency. For size-fractionated RNA, as for unfractionated RNA, there was a direct correlation between specific [3H]methylhistidine-TRH binding and response amplitude.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Decreased TRH receptor mRNA activity precedes homologous downregulation: assay in oocytes.

Ligand-induced decrease in cell-surface receptor number (homologous downregulation) is often due to rapid receptor internalization. Thyrotropin-releasing hormone (TRH), however, causes a slow downregulation of TRH receptors (TRH-Rs), with a half-time of approximately 12 hours, in GH3 rat pituitary cells. The mechanism of TRH-R downregulation was studied by monitoring TRH-evoked depolarizing currents in Xenopus oocytes injected with GH3 cell RNA as a bioassay for TRH-R messenger RNA (mRNA) activity. In GH3 cells, TRH caused a rapid decrease in TRH-R mRNA activity to 15 percent of control within 3 hours. Because the half-life of TRH-R mRNA activity in control cells was approximately 3 hours, the rapid decrease in mRNA activity was not due to inhibition of mRNA synthesis alone and may represent a post-transcriptional effect.

Animals↗
PubMed1987

Mechanism of membrane electrical response to thyrotropin-releasing hormone in Xenopus oocytes injected with GH3 pituitary cell messenger ribonucleic acid.

TRH evoked a complex electrical membrane response in Xenopus laevis oocytes injected with either total cytosolic or poly(A)(+)-enriched RNA from GH3 pituitary cells but not in uninjected oocytes. A typical response consisted of a transient, rapid depolarizing current followed by a prolonged depolarizing current with superimposed current fluctuations. The reversal potentials of the rapid and the slow components of the response were -23.0 and -22.6 mV, respectively, and were markedly affected by CI- concentration indicating that the TRH response was mainly an increase in Cl- conductance. The response to TRH was dose dependent and was inhibited by the TRH antagonist, chlordiazepoxide. TRH caused rapid hydrolysis of labeled phosphatidylinositol 4,5-bisphosphate and a marked, prolonged increase in 45Ca2+ efflux from injected oocytes. The depolarizing response to TRH was not diminished in oocytes incubated in a Ca2(+)-free medium, but was inhibited by microinjection of EGTA. These data suggest that TRH evokes an electrophysiological response in oocytes injected with RNA from GH3 cells via activation of the same biochemical pathway that mediates its actions in GH3 cells. This pathway involves hydrolysis of phosphatidylinositol 4,5-bisphosphate, forming inositol trisphosphate that causes mobilization of cellular Ca2+. We suggest that oocytes injected with GH3 cell RNA, because of their large size and easy access to their intracellular milieu, will be a useful intact cell model in which to define the molecular details of signal transduction by TRH.

Animals↗
PubMed1986

Thyrotropin-releasing hormone and GTP activate inositol trisphosphate formation in membranes isolated from rat pituitary cells.

Stimulation of the hydrolysis of phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2) by a phospholipase C to produce inositol trisphosphate (InsP3) and 1,2-diacylglycerol appears to be the initial step in signal transduction for a number of cell-surface interacting stimuli, including thyrotropin-releasing hormone (TRH). In suspensions of membranes isolated from rat pituitary (GH3) cells that were prelabeled to isotopic steady state with [3H]inositol and incubated with ATP, [3H] PtdIns(4,5)P2, and [3H]phosphatidylinositol 4-phosphate, the polyphosphoinositides, and [3H]InsP3 and [3H]inositol bisphosphate, the inositol polyphosphates, accumulated. TRH and GTP stimulated the accumulation of [3H]inositol polyphosphates in time- and concentration-dependent manners; half-maximal effects occurred with 10-30 nM TRH and with 3 microM GTP. A nonhydrolyzable analog of GTP also stimulated [3H] inositol polyphosphate accumulation. Moreover, when TRH and GTP were added together their effects were more than additive. Fixing the free Ca2+ concentration in the incubation buffer at 20 nM, a value below that present in the cytoplasm in vivo did not inhibit stimulation by TRH and GTP of [3H]inositol polyphosphate accumulation. ATP was necessary for basal and stimulated accumulation of [3H]inositol polyphosphates, and a nonhydrolyzable analog of ATP could not substitute for ATP. These data demonstrate that TRH and GTP act synergistically to stimulate the accumulation of InsP3 in suspensions of pituitary membranes and that ATP, most likely acting as substrate for polyphosphoinositide synthesis, was necessary for this effect. These findings suggest that a guanine nucleotide-binding regulatory protein is involved in coupling the TRH receptor to a phospholipase C that hydrolyzes PtdIns(4,5)P2.

Adenosine Triphosphate↗