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Biomedical subjects

W E Taylor

Publications and source records attributed to W E Taylor.

At least 19 recordsLinked to original sources
PubMed2001

Myostatin inhibits cell proliferation and protein synthesis in C2C12 muscle cells.

Myostatin mutations in mice and cattle are associated with increased muscularity, suggesting that myostatin is a negative regulator of skeletal muscle mass. To test the hypothesis that myostatin inhibits muscle cell growth, we examined the effects of recombinant myostatin in mouse skeletal muscle C2C12 cells. After verification of the expression of cDNA constructs in a cell-free system and in transfected Chinese hamster ovary cells, the human recombinant protein was expressed as the full-length (375-amino acid) myostatin in Drosophila cells (Mst375D), or the 110-amino acid carboxy-terminal protein in Escherichia coli (Mst110EC). These proteins were identified by immunoblotting and were purified. Both Mst375D and Mst110EC dose dependently inhibited cell proliferation (cell count and Formazan assay), DNA synthesis ([3H]thymidine incorporation), and protein synthesis ([1-14C]leucine incorporation) in C2C12 cells. The inhibitory effects of both proteins were greater in myotubes than in myoblasts. Neither protein had any significant effects on protein degradation or apoptosis. In conclusion, recombinant myostatin proteins inhibit cell proliferation, DNA synthesis, and protein synthesis in C2C12 muscle cells, suggesting that myostatin may control muscle mass by inhibiting muscle growth or regeneration.

Animals↗
PubMed1998

Organization of the human myostatin gene and expression in healthy men and HIV-infected men with muscle wasting.

Myostatin, a member of the transforming growth factor-beta superfamily, is a genetic determinant of skeletal muscle growth. Mice and cattle with inactivating mutations of myostatin have marked muscle hypertrophy. However, it is not known whether myostatin regulates skeletal muscle growth in adult men and whether increased myostatin expression contributes to wasting in chronic illness. We examined the hypothesis that myostatin expression correlates inversely with fat-free mass in humans and that increased expression of the myostatin gene is associated with weight loss in men with AIDS wasting syndrome. We therefore cloned the human myostatin gene and cDNA and examined the gene's expression in the skeletal muscle and serum of healthy and HIV-infected men. The myostatin gene comprises three exons and two introns, maps to chromosomal region 2q33.2, has three putative transcription initiation sites, and is transcribed as a 3.1-kb mRNA species that encodes a 375-aa precursor protein. Myostatin is expressed uniquely in the human skeletal muscle as a 26-kDa mature glycoprotein (myostatin-immunoreactive protein) and secreted into the plasma. Myostatin immunoreactivity is detectable in human skeletal muscle in both type 1 and 2 fibers. The serum and intramuscular concentrations of myostatin-immunoreactive protein are increased in HIV-infected men with weight loss compared with healthy men and correlate inversely with fat-free mass index. These data support the hypothesis that myostatin is an attenuator of skeletal muscle growth in adult men and contributes to muscle wasting in HIV-infected men.

Adult↗
PubMed1998

The genetic basis of male infertility.

Defective spermatogenesis can be the end result of a multitude of causes, such as systemic disease, malnutrition, endocrinologic disorder, genetic defects, anatomic obstruction of the passage of spermatozoa, infections, and environmental toxins. A genetic basis of infertility is thought to exist in a majority of infertile men currently classified as having idiopathic infertility. Despite advances in molecular technology, the pathophysiology of spermatogenic failure in a majority of infertile men remains unknown. Although a large number of genes and loci in experimental animals are associated with sterility, the human homologues of most of these genes have not been cloned yet. Infertility is a heterogeneous syndrome in men; therefore, it is likely that a multitude of genes and loci will be implicated in different infertility subsets.

Animals↗
PubMed1997

Chromosomal mapping of two members of the human dynein gene family to chromosome regions 7p15 and 11q13 near the deafness loci DFNA 5 and DFNA 11.

We mapped expressed tagged sequences (ESTs) corresponding to two human dynein heavy chain genes: beta heavy chain of the outer dynein arm and heavy chain isotype 1B (DYH1B), by using somatic cell hybrids and radiation hybrid panels. The EST for the beta heavy chain of the outer dynein arm mapped to chromosome region 7p15, and the EST for DYH1B mapped to 11q13.5. Two loci for nonsyndromic forms of deafness, DFNA5 and DFNA11, have previously been mapped to these two chromosomal regions. Including the gene for the axonemal light chain, hp28, we have mapped three different dynein genes near loci for different forms of nonsyndromic deafness. The hypothesis that mutations in some dynein genes are associated with nonsyndromic deafness should now be tested.

Chromosome Mapping↗
PubMed1997

Complementary deoxyribonucleic acid cloning and characterization of a putative human axonemal dynein light chain gene.

Immotile Cilia Syndrome (ICS) is characterized by recurrent sinus and lung infections, bronchiectasis, and sperm immotility. Nasal cilia and sperm tails in patients with ICS exhibit a variety of ultrastructural defects, often including shortening or absence of the inner dynein arms. Immotile mutant strains of Chlamydomonas, a biflagellated algae, have ultrastructural defects similar to those seen in patients with this clinical disorder. Furthermore, splice-site mutations in the Chlamydomonas inner dynein arm gene (p28) are associated with impaired flagellar motility. We therefore hypothesized that the human homologue of the Clamydomonas dynein p28 gene would be an attractive candidate gene for patients with ICS. Accordingly, we cloned the full length complementary DNA (cDNA) and genomic clone by screening of appropriate libraries and databases, using the protein sequence of the Chlamydomonas p28 gene. The human homologue is encoded by a 921 bp transcript (accession no. AF006386) with an open reading frame of 257 amino acids. Using somatic cell and radiation hybrid panels, the hp28 gene was mapped to human chromosome 1p35.1. The hp28 cDNA probe hybridizes to sequences in all species on a zoo blot containing genomic DNA from yeast to human. Northern blot analysis reveals two hp28 gene transcripts, 0.9 and 2.5 kb, in many tissues. The 0.9 kb transcript is expressed at a 20-fold higher level than the 2.5-kb transcript in the testis. The entire gene is included in a 20-kb EcoRI genomic fragment and has 7 exons and 6 introns. Cloning of the hp28 cDNA and mapping of the intron-exon junctions should now make it possible to test whether a subset of ICS is a consequence of mutations in the human axonemal dynein light chain gene hp28.

Base Sequence↗
PubMed1996

Human stem cell factor promoter deoxyribonucleic acid sequence and regulation by cyclic 3',5'-adenosine monophosphate in a Sertoli cell line.

Stem cell factor (SCF) gene expression is regulated by FSH in testicular Sertoli cells. Many functions of FSH are mediated through the second messenger cAMP. We show that cAMP activates transcription of the human SCF promoter in a Sertoli cell line. The human SCF promoter was cloned in cosmid vector pWE15, and its DNA sequence was determined for the promoter region extending 2.3 kilobase pairs upstream from the translation start site at +184 bp. The in vivo messenger RNA (mRNA) start site, by primer-extension studies, was located in exon 1 at +109 bp in human testis mRNA, and at +99 bp in mouse SF7 Sertoli cell line or GC1 germ cell line mRNA. To test which regions of the SCF promoter are necessary for regulation by cAMP, a series of 5'-end deletions of this region were cloned onto the luciferase reporter gene in plasmid pXP1. The SCF promoter region was fused to luciferase downstream (at +120) from its +109 mRNA start site, extending upstream a variable distance to BstXI (-162), BamHI (-313), Bgl2 (-853), or XbaI (-2185). The shortest of these fragments extending only to -162 bp, contains possible SP1 and AP-2 elements. When mouse Sertoli SF7 or human JEG.3 cell lines were transfected with these plasmids, all of the mutants were regulated by 8Br-cAMP or forskolin, as expected for the SCF gene, whereas FSH and TPA had no effect. In the shortest promoter deletion -162, luciferase expression from SF7 cells in serum-free media was at a moderate basal level, but it was induced in six h about 2-fold by 8Br-cAMP, and over 7-fold by forskolin (an adenylate cyclase activator) to high levels, similar to the SV40 positive control promoter. In SCF-luc plasmids extending to -853 or -2185, luciferase expression was still inducible by 8Br-cAMP and forskolin to high levels, but basal promoter activity was repressed to levels over 15-fold lower, in both the absence or presence of testosterone in the media for SF7 cells. The distal portion of the human SCF promoter (between -313 and -853, and also -853 and -2185) inhibits the basal level of transcription, while the proximal region (5' of -162) can mediate activation by cAMP.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1995

Designing zinc-finger ADR1 mutants with altered specificity of DNA binding to T in UAS1 sequences.

Yeast ADR1 contains two Cys2,His2 zinc fingers needed for DNA binding to the upstream activation sequence UAS1, with bases T5T6G7-G8A9G10 in the ADH2 promoter. Potential DNA-contacting amino acid residues at -1, +3, and +6 in the alpha-helical domains of ADR1's fingers one and two include RHR-RLR; however, the latter finger two residues Leu146 and Arg149 had not proved to be crucial for ADR1 binding, even though Leu146-T6 and Arg149-T5 interactions with UAS1 DNA were predicted. We altered Leu146 or Arg149 by PCR cassette mutagenesis, to study ADR1 mutant binding to 16 UAS1 variants of thymine bases T5 and T6. Mutation of Leu146 to His, making finger two (RLR) like finger one (RHR), decreased binding to wild type UAS1 having T6, but enhanced its binding strength to sequences having purines G6 or A6, similar to binding seen between finger one's His118 and base A9 of UAS1. Mutating Leu146 to Lys caused this finger two RKR mutant to bind strongly to both G6 and T6, possibly by lysine's amine H-bonding to the carbonyl of guanine or thymine. Specificity of ADR1 for UAS1 with T6 may thus be due to hydrophobic interaction between Leu146 and the T6 methyl group. ADR1 mutants with either His or Lys in the central +3 residue (146) of zinc finger two, which have Arg149 in the +6 alpha-helical position, bind with UAS1 mutant sequences having G5 very strongly, T5 strongly, A5 intermediately, and C5 weakly.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1995

Localization of glucose transporter GLUT 3 in brain: comparison of rodent and dog using species-specific carboxyl-terminal antisera.

The carboxyl-terminal amino acid sequences of the canine and gerbil glucose transporter GLUT3 were determined and compared to the published rat sequence. Eleven of 16 amino acids comprising the carboxyl terminus of GLUT3 were found to be identical in rat and dog. However, the canine sequence "ATV" substitutes for the rat sequence "PGNA" at the end of the molecule. The gerbil sequence has 12 of 16 amino acids identical to the rat, including the PGNA terminus. Based on these sequences, four peptides were synthesized, and two polyclonal antisera (one to the canine sequence and one to the rat sequence) were raised to examine the distribution of GLUT3 in canine and rodent brain. Immunoblots of brain membrane preparations showed that both antisera identified peptide-inhibitable protein bands of molecular weight 45,000-50,000. Immunocytochemical studies demonstrated that binding sites for these antisera were abundantly distributed in neuropil in all brain regions. Areas rich in synapses and areas surrounding microvessels exhibited especially high reactivity. GLUT3 reactivity was similarly distributed in canine and rodent brain, except at the blood-brain barrier. GLUT3 was not detected in the blood-brain barrier in gerbil and rat but was present in many canine cerebral endothelial cells, particularly in cerebellum and brain stem. The carboxyl-terminal antisera employed in this study exhibited high degrees of species specificity, indicating that the three or four terminal amino acids of the immunizing peptides (ATV and PGNA) are important epitopes for binding the polyclonal antibodies. These antisera exhibited only minimal binding to brain tissue of non-target species, yet yielded similar staining patterns in neuropil of rodent and canine brain. This finding provides strong evidence that the observed staining patterns accurately reflect the distribution of GLUT3 in brain. In addition, the presence of vascular GLUT3 in dog brain suggests that the canine blood-brain barrier may be preferable to that of the rat as a model for studies of glucose transport relevant to human brain.

Amino Acid Sequence↗
PubMed1995

An avirulent ICP34.5 deletion mutant of herpes simplex virus type 1 is capable of in vivo spontaneous reactivation.

The herpes simplex virus type 1 (HSV-1) ICP34.5 gene is a neurovirulence gene in mice. In addition, some ICP34.5 mutants have been reported to have a reduced efficiency of induced reactivation as measured by in vitro explantation of latently infected mouse ganglia. However, since spontaneous reactivation is almost nonexistent in mice, nothing has been reported on the effect of ICP34.5 mutants on spontaneous reactivation in vivo. To examine this, we have deleted both copies of the ICP34.5 neurovirulence gene from a strain of HSV-1 (McKrae) that has a high spontaneous reactivation rate in rabbits and used this mutant to infect rabbit eyes. All rabbits infected with the ICP34.5 mutant virus (d34.5) survived, even at challenge doses greater than 4 x 10(7) PFU per eye. In contrast, a 200-fold-lower challenge dose of 2 x 10(5) PFU per eye was lethal for approximately 50% of rabbits infected with either the wild-type McKrae parental virus or a rescued ICP34.5 mutant in which both copies of the ICP34.5 gene were restored. In mice, the 50% lethal dose of the ICP34.5 mutant was over 10(6) PFU, compared with a value of less than 10 PFU for the rescued virus. The ICP34.5 mutant was restricted for replication in rabbit and mouse eyes and mouse trigeminal ganglia in vivo. The spontaneous reactivation rate in rabbits for the mutant was 1.4% as determined by culturing tear films for the presence of reactivated virus. This was more than 10-fold lower than the spontaneous reactivation rate determined for the rescued virus (19.6%) and was highly significant (P < 0.0001, Fisher exact test). Southern analysis confirmed that the reactivated virus retained both copies of the ICP34.5 deletion. Thus, this report demonstrates that (i) the ICP34.5 gene, known to be a neurovirulence gene in mice, is also important for virulence in rabbits and (ii) in vivo spontaneous reactivation of HSV-1 in the rabbit ocular model, although reduced, can occur in the absence of the ICP34.5 gene.

Animals↗
PubMed1994

GLUT1 and GLUT3 gene expression in gerbil brain following brief ischemia: an in situ hybridization study.

GLUT1 and GLUT3 mRNAs in normal and post-ischemic gerbil brains were examined qualitatively and semi-quantitatively using in situ hybridization in conjunction with image analysis. Coronal brain sections at the level of the anterior hippocampus were prepared three hours, one day, and three days after animals were subjected to six min of ischemia. The sections were hybridized with vector- and PCR-generated RNA probes labeled with 35S. Microscopic evaluation of hybridized brain sections coated with autoradiographic emulsion indicated that GLUT1 mRNA was associated with brain microvessels, choroid plexus, and some ependymal cells. GLUT1 mRNA was not observed in neurons, except that one day following ischemia, this mRNA was induced in neurons of the dentate gyrus. GLUT3 mRNA was detected only in neurons. Image analysis of film autoradiograms revealed that both the GLUT1 and GLUT3 messages increased following ischemia but returned nearly to control levels by day three. In the CA1 region of the hippocampus the increase in GLUT3 mRNA was not statistically significant, and by day three the level had fallen significantly below the control, coinciding with the degeneration of the CA1 neurons. Our results suggest that the brain possesses mechanisms for induction and up-regulation of glucose transporter gene expression.

Animals↗
PubMed1990

cAMP-dependent phosphorylation and inactivation of yeast transcription factor ADR1 does not affect DNA binding.

Transcription factor ADR1 increases the level of ADH2 gene expression 200-fold by binding to a palindromic upstream activation sequence (UAS1) in the glucose-repressible ADH2 promoter in Saccharomyces cerevisiae. cAMP-dependent protein kinase (cAPK) phosphorylates ADR1 in vitro and a yeast strain with elevated cAPK activity inhibits the ability of ADR1 to activate ADH2 transcription in vivo [Cherry, J. R., Johnson, T. R., Dollard, C., Schuster, J. R. & Denis, C. L. (1988) Cell 56, 409-419]. Intact ADR1 protein was detected at comparable levels in extracts made from repressed or derepressed yeast cells, indicating that glucose repression is not due to absence of ADR1. ADR1 in extracts made from glucose-repressed and -derepressed cells bound UAS1 DNA with similar affinities despite having greatly different abilities to activate ADH2 gene expression in vivo. A mutant form of ADR1 encoded by ADR1-5c, which has an altered consensus sequence for phosphorylation by cAPK conferred constitutive expression on ADH2 but bound DNA to the same extent as wild-type ADR1 protein. Similarly, normal DNA binding was seen for ADR1 produced in mutants with altered levels of cAPK activity. Because inactivation of ADR1 by phosphorylation has no detectable effect on either DNA binding or ADR1 levels, ADR1 probably binds to UAS1 constitutively and phosphorylation prevents it from promoting transcription.

Alcohol Dehydrogenase↗
PubMed1988

Zinc-dependent structure of a single-finger domain of yeast ADR1.

In the proposed "zinc finger" DNA-binding motif, each repeat unit binds a zinc metal ion through invariant Cys and His residues and this drives the folding of each 30-residue unit into an independent nucleic acid-binding domain. To obtain structural information, we synthesized single and double zinc finger peptides from the yeast transcription activator ADR1, and assessed the metal-binding and DNA-binding properties of these peptides, as well as the solution structure of the metal-stabilized domains, with the use of a variety of spectroscopic techniques. A single zinc finger can exist as an independent structure sufficient for zinc-dependent DNA binding. An experimentally determined model of the single finger is proposed that is consistent with circular dichroism, one- and two-dimensional nuclear magnetic resonance, and visual spectroscopy of the single-finger peptide reconstituted in the presence of zinc.

Circular Dichroism↗
PubMed1988

The yeast regulatory protein ADR1 binds in a zinc-dependent manner to the upstream activating sequence of ADH2.

The yeast ADR1 protein contains two zinc finger domains that are essential for its role in transcriptional activation of alcohol dehydrogenase (ADH2). These domains are thought to function as DNA-binding structures. An ADR1-beta-galactosidase fusion protein made in Escherichia coli and containing the finger domains of ADR1 binds in vitro in a zinc-dependent manner to DNA fragments containing the two ADH2 upstream activation sequences. The strongest binding is to upstream activation sequence 1, a 22-base-pair palindrome.

Alcohol Dehydrogenase↗
PubMed1987

Transcription of the ADH2 gene in Saccharomyces cerevisiae is limited by positive factors that bind competitively to its intact promoter region on multicopy plasmids.

Transcription of the ADH2 gene in the yeast Saccharomyces cerevisiae was inhibited by excess copies of its own promoter region. This competition effect was promoter specific and required the upstream activation sequence of ADH2 as well as sequences 3' to the TATA box. Introducing excess copies of ADR1, an ADH2-specific regulatory gene, did not alleviate the competition that was observed in these circumstances during both constitutive and derepressed ADH2 expression. Excess copies of the upstream region did not release ADH2 from glucose repression, consistent with the view that ADH2 is regulated by positive trans-acting factors.

Alcohol Dehydrogenase↗