Physical analysis of murine albino deletions that disrupt liver-specific gene regulation or mesoderm development

Complementation analyses of radiation-induced deletion mutations involving the albino (c) locus in Chromosome (Chr) 7 of the mouse have identified several loci, in addition to c, that have important roles in development. The "mesoderm-deficient" (msd) and "hepatocyte-specific developmental regulation-1" (hsdr-1) loci, which are proximal and tightly linked to c, are important in the formation of mesoderm and in the regulation of liver- and kidney-specific induction of various enzymes and proteins, respectively. Cloning deletion-breakpoint-fusion fragments caused by lethal albino deletions that genetically define the extents of the msd and hsdr-1 loci is one way of generating molecular probes for studying the gene(s) involved in these phenotypes. The distal breakpoints of five such deletions were positioned on a long-range (PFGE) map of approximately 1.7 Mb of wild-type DNA surrounding the c, D7Was12, and Emv-23 loci. In addition, the distal breakpoints of two viable albino deletions, which remove part of the tyrosinase gene and extend distally, were localized in the vicinity of the lethal deletion breakpoints. Therefore, the viable deletions can be exploited to generate additional DNA probes that should facilitate the isolation of breakpoint clones from chromosomes carrying lethal deletions defining hsdr-1 and msd.

Conserved cysteine to serine mutation in tyrosinase is responsible for the classical albino mutation in laboratory mice

Albinism, due to a lack of melanin pigment, is one of the oldest known mutations in mice. Tyrosinase (monophenol oxygenase, EC 1.14.18.1) is the first enzyme in the pathway for melanin synthesis, and the gene encoding this enzyme has been mapped to the mouse albino (c) locus. We have used mouse tyrosinase cDNA clones and genomic sequencing to study the albino mutation in laboratory mice. Within the tyrosinase gene coding sequences, a G to C transversion at nucleotide 308, causing a cysteine to serine mutation at amino acid 103, is sufficient to abrogate pigment production in transgenic mice. This same base pair change is fully conserved in classical albino strains of laboratory mice. These results indicate that a conserved mutation in the tyrosinase coding sequences is responsible for the classical albino mutation in laboratory mice, and also that most albino laboratory mouse strains have been derived from a common ancestor.

Enhancing and suppressing effects of recombinant murine macrophage inflammatory proteins on colony formation in vitro by bone marrow myeloid progenitor cells

Purified recombinant (r) macrophage inflammatory proteins (MIPs) 1 alpha, 1 beta, and 2 were assessed for effects on murine (mu) and human (hu) marrow colony-forming unit-granulocyte-macrophage (CFU-GM) and burst-forming unit-erythroid (BFU-E) colonies. Recombinant MIP-1 alpha, -1 beta, and -2 enhanced muCFU-GM colonies above that stimulated with 10 to 100 U natural mu macrophage-colony-stimulating factor (M-CSF) or rmuGM-CSF, with enhancement seen on huCFU-GM colony formation stimulated with suboptimal rhuM-CSF or rhuGM-CSF; effects were neutralized by respective MIP-specific antibodies. Macrophage inflammatory proteins had no effects on mu or huBFU-E colonies stimulated with erythropoietin (Epo). However, natural MIP-1 and rMIP-1 alpha, but not rMIP-1 beta or -2, suppressed muCFU-GM stimulated with pokeweed mitogen spleen-conditioned medium (PWMSCM), huCFU-GM stimulated with optimal rhuGM-CSF plus rhu interleukin-3 (IL-3), muBFU-E and multipotential progenitors (CFU-GEMM) stimulated with Epo plus PWMSCM, and huBFU-E and CFU-GEMM stimulated with Epo plus rhuIL-3 or rhuGM-CSF. The suppressive effects of natural MIP-1 and rMIP-1 alpha were also apparent on a population of BFU-E, CFU-GEMM, and CFU-GM present in cell-sorted fractions of human bone marrow (CD34 HLA-DR+) highly enriched for progenitors with cloning efficiencies of 42% to 75%. These results, along with our previous studies, suggest that MIP-1 alpha, -1 beta, and -2 may have direct myelopoietic enhancing activity for mature progenitors, while MIP-1 alpha may have direct suppressing activity for more immature progenitors.

Expression of mRNAs for pore-forming protein and two serine esterases in murine primary and cloned effector lymphocytes

The cDNAs encoding several proteins present in the granules of cytolytic effector lymphocytes have now been cloned. These include the cytolytic pore-forming protein (PFP) or perforin, and at least six serine esterases (SE), also called granzymes. The cDNA probes for PFP, SE-1, and SE-2 are used here to study the expression of these proteins in murine primary effector lymphocytes. Among the stimuli effective in inducing the expression of PFP, SE-1, and SE-2 were recombinant interleukin-2, the lectin concanavalin A in the presence of phorbol esters, and allogeneic cells in mixed lymphocyte cultures. Some correlation was seen between the levels of PFP and SE mRNAs and cytotoxicity measured in a standard 51Cr release assay. We also examined a panel of 13 cloned cytotoxic T lymphocyte (CTL) lines and found that mRNAs for PFP and SE-2 were expressed in all CTL lines, including some that were previously considered not to produce PFP. Twelve of the 13 CTL lines also proved to possess the mRNA for SE-1. One thymoma cell line, TIMI.4, did not express mRNA for PFP, although it expressed mRNA for SE-1 and SE-2.

Induction of perforin and serine esterases in a murine cytotoxic T lymphocyte clone

The expression of perforin and serine esterase (SE) activities and genes was examined in a murine cytotoxic T lymphocyte line (R8i) that does not require exogenous IL-2 for proliferation. Although perforin (hemolytic) activity was detected in unstimulated R8i, it was induced 2- to 14-fold in the presence of IL-2, IL-3, IL-4, and IL-6, and to a lesser degree (less than 4-fold) by TNF and IFN-gamma. A transient induction was also observed at the mRNA level. Peak perforin protein and mRNA levels were reached within 24 h and started to decline 48 h after stimulation. A trypsinlike SE activity which cleaves the chromogenic substrate N, alpha-benzyloxycarbonyl-L-lysine thiobenzyl ester was also induced 2- to 4-fold in the presence of the various IL tested. At the mRNA level, the message for SE SE1/granzyme A/Hanukah factor was absent from R8i whereas SE2/granzyme B/CTLA-1 increased by greater than 3-fold in the presence of IL-2, IL-3, IL-4, and IL-6 and occurred with the same kinetics and pattern as perforin. The induction response occurred without any enhancement of cell proliferation, suggesting that the cytokines tested may provide a direct differentiation signal to CTL. The induction response was abrogated effectively by inhibitors of protein (cycloheximide or emetine) and RNA (actinomycin D) syntheses. These findings suggest that the various IL may provide both a growth signal and a differentiation signal to CTL, resulting in the direct activation of perforin and SE genes.

Induction of perforin and serine esterases in a murine cytotoxic T lymphocyte clone

The expression of perforin and serine esterase (SE) activities and genes was examined in a murine cytotoxic T lymphocyte line (R8i) that does not require exogenous IL-2 for proliferation. Although perforin (hemolytic) activity was detected in unstimulated R8i, it was induced 2- to 14-fold in the presence of IL-2, IL-3, IL-4, and IL-6, and to a lesser degree (less than 4-fold) by TNF and IFN-gamma. A transient induction was also observed at the mRNA level. Peak perforin protein and mRNA levels were reached within 24 h and started to decline 48 h after stimulation. A trypsinlike SE activity which cleaves the chromogenic substrate N, alpha-benzyloxycarbonyl-L-lysine thiobenzyl ester was also induced 2- to 4-fold in the presence of the various IL tested. At the mRNA level, the message for SE SE1/granzyme A/Hanukah factor was absent from R8i whereas SE2/granzyme B/CTLA-1 increased by greater than 3-fold in the presence of IL-2, IL-3, IL-4, and IL-6 and occurred with the same kinetics and pattern as perforin. The induction response occurred without any enhancement of cell proliferation, suggesting that the cytokines tested may provide a direct differentiation signal to CTL. The induction response was abrogated effectively by inhibitors of protein (cycloheximide or emetine) and RNA (actinomycin D) syntheses. These findings suggest that the various IL may provide both a growth signal and a differentiation signal to CTL, resulting in the direct activation of perforin and SE genes.

Genomic organization of the mouse pore-forming protein (perforin) gene and localization to chromosome 10. Similarities to and differences from C9

Genomic clones encompassing the entire coding region of the mouse lymphocyte pore-forming protein gene (Pfp) have been isolated and used to determine its intron-exon organization. In contrast to C9, Pfp has a simple structure, consisting of only three exons (two of which encode polypeptide), a large 5' intron, and a single, smaller intron that is situated approximately one-third of the way through the protein-coding portions of the gene. The regions encoding the homologous domains of PFP and C9 are encoded on exons 7, 8, 9, and 10 of C9, but form only approximately half of the open reading frame of exon III in Pfp. Although encoding polypeptides with related functions, the two genes possess such sharply contrasting structures as to suggest that their analogous regions may have risen independently, by a process of convergent evolution. Using a panel of somatic cell hybrid cell lines, Pfp has been mapped to chromosome 10.

Genetic and molecular analysis of chlorambucil-induced germ-line mutations in the mouse

Eighteen variants recovered from specific locus mutation rate experiments involving the mutagen chlorambucil were subjected to several genetic and molecular analyses. Most mutations were found to be homozygous lethal. Because lethality is often presumptive evidence for multilocus-deletion events, 10 mutations were analyzed by Southern blot analysis with probes at, or closely linked to, several of the specific locus test markers, namely, albino (c), brown (b), and dilute (d). All eight mutations (two c; three b; two d; and one dilute-short ear [Df(d se)]) that arose in post-spermatogonial germ cells were deleted for DNA sequences. No evidence for deletion of two d-se region probes was obtained for the remaining two d mutations that arose in stem-cell spermatogonia. Six of the primary mutants also produced low litter sizes ("semisterility"). Karyotypic analysis has, to date, confirmed the presence of reciprocal translocations in four of the six. The high frequency of deletions and translocations among the mutations induced in post-spermatogonial stages by chlorambucil, combined with its overall high efficiency in inducing mutations in these stages, should make chlorambucil mutagenesis useful for generating experimentally valuable germ-line deletions throughout the mouse genome.

Isolation, chromosomal mapping, and expression of the mouse tyrosinase gene

Using a human tyrosinase cDNA probe, we have isolated mouse tyrosinase genomic clones and used them to map the mouse tyrosinase locus and to analyze the promoter sequence of the tyrosinase gene. Southern blot analyses of DNA from somatic cell hybrids, interspecies backcross mice, and albino deletion mice have revealed that the locus for mouse tyrosinase resides at or near the albino locus on mouse chromosome 7. There were three TATA-elements, but only one CAT-element, and the CAT-element appeared to be paired with the third TATA-element, located at the position farthest upstream. Mouse tyrosinase mRNA is approximately 2.4 Kb in size. The amount of tyrosinase mRNA reflects the levels of tyrosinase activity in normal melanocytes and Cloudman S-91 melanoma cell line.

Expression characteristics of two potential T cell mediator genes

T lymphocyte subset-specific cDNA clones were recently isolated by a modified differential screening procedure. The expression patterns of two of these cDNAs, designated as 4-1BB and L2G25B, were studied in greater detail. Nucleotide sequence comparison revealed that 4-1BB was not previously recognized. Although the L2G25B sequence had been recognized recently, the function of the encoded molecule has yet to be well studied. The transcripts of the two cDNAs were inducible by concanavalin A in mouse spleen cells, cloned helper T cells (L2), cloned cytolytic T cells (L3), and cytolytic T cell hybridomas. They were also inducible with stimulation through antigen receptor (TCR), with immobilized anti-TCR antibody in cloned T cells L2, dB45, and L3. Concanavalin A inducibility was inhibited by cyclosporin A. They were not inducible by IL-2 stimulation. The expression patterns of these transcripts were similar to those of IFN-gamma, except that the level of transcripts of the two cDNAs was at least fivefold lower than that of IFN-gamma, and the peak level of expression occurred earlier. These data suggest that L2G25B and 4-1BB may represent new T cell mediators.

Establishment and partial characterization of SV40 virus-immortalized hepatocyte lines of normal and lethal mutant mice carrying a deletion on chromosome 7

Deletions in chromosome 7 of the mouse have been shown to cause failure of expression of various hepatocyte-specific genes in newborn deletion homozygotes, including the gene encoding tyrosine amino transferase (TAT) (EC 2.6.1.5) (Gluecksohn-Waelsch, 1979). Primary liver cultures of newborn albino deletion mutant mice (c14CoS/c14CoS) and of phenotypically normal mice (c14CoS/cch or cch/cch) were infected with SV40 virus and multiplying hepatocytes selected in arginine-deficient medium containing epidermal growth factor (EGF), insulin, and hydrocortisone (HC). Resulting normal (NMH-ch) and mutant (NMH-m14) hepatocyte lines expressing integrated viral transforming sequences did not senesce, they multiplied autonomously of EGF in medium with insulin plus HC, and they retained hepatocyte-specific functions. Both lines synthesized arginine and contained albumin and alpha-fetoprotein (AFP) mRNAs. TAT-specific mRNA was detected in normal but not in mutant hepatocyte lines. A fragment of the mouse tyrosinase gene, known to map at the albino locus (c) within the region deleted in the c14CoS mutant, hybridized with a 2.5 kb EcoRI fragment of normal NMH-ch DNA, whereas this fragment was undetectable in mutant NMH-m14 DNA. These immortalized hepatocyte lines reflect important properties of normal and mutant liver tissues from which they were derived. The deletion mutant mouse cell lines may be useful for complementation studies involving sequences corresponding to the deletions that encode regulatory gene(s) involved in the control of inducible expression of certain hepatocyte-specific genes such as TAT.

Molecular basis of mouse Himalayan mutation

Many different coat-colors result from the c-locus mutation in the mouse. One of these interesting mutants is a Himalayan, which produces temperature sensitive tyrosinase, and the basis of this sensitivity remains unknown. We cultured Himalayan mouse melanocytes from the skin and constructed a cDNA library; then, we isolated the Himalayan tyrosinase cDNAs and determined the nucleotide sequence. The tyrosinase gene in the Himalayan mouse contains an A----G change at nucleotide 1259 that alters a histidine residue to an arginine residue at amino acid 420. This histidine residue and the surrounding amino acids are conserved in their evolution from mouse to human. Interestingly, the residue with its surrounding eight amino acids are aligned between mouse b-protein and human tyrosinase. These results indicate the possibility that the altered residue at amino acid 420 of mouse tyrosinase may be important in stabilization of the tyrosinase molecule, or in interaction with other molecules, such as tyrosinase inhibitors.

cDNA sequences of two inducible T-cell genes

We have previously described a set of human T-lymphocyte-specific cDNA clones isolated by a modified differential screening procedure. Apparent full-length cDNAs containing the sequences of 14 of the 16 initial isolates were sequenced and were found to represent five different species of mRNA; three of the five species were identical to previously reported cDNA sequences of preproenkephalin, T-cell-replacing factor, and a serine esterase, respectively. The other two species, 4-1BB and L2G25B, were inducible sequences found in mRNA from both a cytolytic T-lymphocyte and a helper T-lymphocyte clone and were not previously described in T-cell mRNA; these mRNA sequences encode peptides of 256 and 92 amino acids, respectively. Both peptides contain putative leader sequences. The protein encoded by 4-1BB also has a potential membrane anchor segment and other features also seen in known receptor proteins.

The structure of the mouse lymphocyte pore-forming protein perforin

Purified murine lymphocyte pore-forming protein (PFP or perforin) was partially sequenced. Oligonucleotides synthesized on the basis of this sequence information were used to screen a murine cytotoxic T lymphocyte (CTL) cDNA library. Seven clones were obtained, two of which were sequenced, providing full-length sequence information on PFP. Murine PFP (534 a.a.) is 68% identical to human PFP. Hydropathic analysis revealed a predominantly hydrophilic protein with some hydrophobic domains, including a region (a.a. 191-251) that could contain putative membrane-spanning domains. PFP is approx. 20% identical to human C7, C8 and C9 within a region encompassing 270 a.a., confirming previous immunological cross-reactivity studies. Northern blot analysis showed that expression of PFP but not of a serine esterase transcript is enhanced in a CTL line by antigen receptor-stimulation. Southern blot analysis of mouse genomic DNA indicated that PFP is encoded as a single-copy gene with the coding region contained within 10 kilobases of genomic DNA.

Isolation and sequence analysis of serine protease cDNAs from mouse cytolytic T lymphocytes

Three new cDNA clones (designated MCSP-1, MCSP-2, and MCSP-3) encoding mouse serine proteases were isolated from cloned cytolytic T lymphocytes (CTL) by a modified differential screening procedure. The putative mature proteins of MCSP-2 and MCSP-3 are each composed of 228 amino acids with molecular weights of 25,477 and 25,360, respectively. NH2-terminal amino acids of MCSP-2- and MCSP-3-predicted proteins were identical to those reported for granzyme E and F, respectively. The third species, MCSP-1, was closely related to the two other cDNA species but approximately 30 amino acids equivalents of the NH2-terminal portion of the cDNA were not cloned. The amino acids forming the active sites of serine proteases were well conserved among the three predicted proteins. The active site pocket residue positioned six residues before the active-site Ser184 is alanine in MCSP-1, threonine in MCSP-2, and serine in MCSP-3, indicating that both MCSP-2 and MCSP-3 may have chymotrypsin-like specificity. There are three potential asparagine-linked glycosylation sites in MCSP-1 and MCSP-3, and four in MCSP-2-deduced amino acid sequences. Amino acid comparison of MCSP-1 with four other reported serine proteases whose active site pocket residue is alanine revealed that MCSP-1 was substantially different from the other molecules, indicating that MCSP-1 may be a new member of mouse T cell serine protease family. Antibodies made against a MCSP-1 lacZ gene fusion protein stain granules of CTL and react on immunoblots with two distinct granule protein bands of 29 and 35-40 kD. Only the 35-kD species labels with [3H]DFP. Since a protease cascade may play a key role in cytolytic lymphocyte activation, our isolation of cDNAs representative of unique serine esterases should help to investigate such a cascade process.

Tyrosinases of murine melanocytes with mutations at the albino locus

Tyrosinase (monophenol monooxygenase; monophenol, L-dopa:oxygen oxidoreductase, EC 1.14.18.1) is a key enzyme in the synthesis of melanin. Reduced levels of tyrosinase play an important role in albinism. The data described here show differences in the expression and characteristics of tyrosinase in cutaneous murine melanocytes grown in culture from normal wild-type strains (C/C); from three albino locus mutants: himalayan (ch/ch), chinchilla (cch/cch), and albino (c/c); and from the double-mutant heterozygous pink-eyed chinchilla (cchp/cp). Our results suggest that the diminished pigmentation in all mutants is due to abnormal posttranslational modification of the enzyme: the levels of mRNA for tyrosinase in wild-type, himalayan, and pink-eyed chinchilla melanocytes are similar; the himalayan mutation confers a deficiency in N-linked glycosylation, which results in an extremely unstable enzyme that is also temperature sensitive; the chinchilla and albino mutations confer susceptibility to proteolytic cleavage; the pink-eye dilution confers a reduction in the levels of immunoprecipitable tyrosinase, and what little enzyme there is fails to be translocated from the trans-Golgi network to melanosomes. The kinetics of activation and inhibition of the enzyme by the cofactor dopa are unique for the mutants tested and differ from those of tyrosinase from wild-type melanocytes. The findings support the conclusion that the albino locus in mice encodes the structural gene of tyrosinase.

bFGF as an autocrine growth factor for human melanomas

Normal human melanocytes in culture require specific additives such as basic fibroblast growth factor (bFGF) and dibutyryl cyclic adenosine monophosphate (dbcAMP) in order to proliferate in defined or serum-containing medium (Halaban et al., 1987). This stringent requirement is absent in cells derived from metastatic melanomas which not only proliferate in regular culture medium, but also produce a substance immunologically related to bFGF (Halaban et al., 1987). We show here that the mitogenic activity necessary for normal human melanocytes is constitutively present in several lines of human metastatic melanomas and that this activity is inactivated by anti-bFGF antibodies. Melanoma cells, but not normal melanocytes, express bFGF gene transcripts. Although the molecular mechanism underlying the abnormal expression of bFGF in melanomas is not known, the results suggest that bFGF acts as an autocrine growth factor in melanomas.

Human tyrosinase gene, mapped to chromosome 11 (q14----q21), defines second region of homology with mouse chromosome 7

The enzyme tyrosinase (monophenol,L-dopa:oxygen oxidoreductase; EC 1.14.18.1) catalyzes the first two steps in the conversion of tyrosine to melanin, the major pigment found in melanocytes. Some forms of oculocutaneous albinism, characterized by the absence of melanin in skin and eyes and by a deficiency of tyrosinase activity, may result from mutations in the tyrosinase structural gene. A recently isolated human tyrosinase cDNA was used to map the human tyrosinase locus (TYR) to chromosome 11, region q14----q21, by Southern blot analysis of somatic cell hybrid DNA and by in situ chromosomal hybridization. A second site of tyrosinase-related sequences was detected on the short arm of chromosome 11 near the centromere (p11.2----cen). Furthermore, we have confirmed the localization of the tyrosinase gene in the mouse at or near the c locus on chromosome 7. Comparison of the genetic maps of human chromosome 11 and mouse chromosome 7 leads to hypotheses regarding the evolution of human chromosome 11.

Sequence analysis of mouse tyrosinase cDNA and the effect of melanotropin on its gene expression

Using human tyrosinase cDNA as a probe, a mouse tyrosinase cDNA clone representing approximately 75% of the tyrosinase coding region and a mouse genomic clone which includes the tyrosinase 5' coding sequences were isolated: nucleotide and deduced amino acid sequence of the mouse tyrosinase gene were determined from these clones. The predicted amino acid sequence revealed that the mouse tyrosinase is composed of 533 amino acids with a molecular weight of 60,536. The deduced protein contains 6 potential N-glycosylation sites, two cysteine- and two histidine-rich regions which may serve as copper-binding sites, a potential signal and transmembrane sequences. The mouse and human tyrosinase nucleotide and deduced amino acid sequences are approximately 81% homologous. The level of mouse tyrosinase mRNA was elevated after stimulation of Cloudman S-91 melanoma cells with melanotropin and isobutylmethylxanthine and the level of transcript reflected that of tyrosinase activity and melanin content in the cells.

A melanocyte-specific complementary DNA clone whose expression is inducible by melanotropin and isobutylmethyl xanthine

Two groups of cDNA clones were isolated by screening a lambda gt11 cDNA library of normal human melanocytes with antityrosinase antibodies: one group of 13 was related to the human tyrosinase gene. The properties of the other group of three cDNA clones was investigated by the use of a representative clone, Pmel 17-1. The cDNA hybridized to an mRNA species of approximately 2600 bases from human and murine melanocytes. The transcript of Pmel 17-1 (17-1 mRNA) was expressed preferentially in melanocytes and its abundance paralleled the melanin content. The expression of Pmel 17-1 mRNA increased after stimulation of human and murine melanoma cells with agents that increase the levels of melanization. Immunocompetition assays with monoclonal antibodies to gp75, a known pigmentation-associated antigen of melanocytes, suggested that Pmel 17-1 encodes a 75,000 Mr glycoprotein that is highly abundant in melanotic cells and shares some immunological homology with tyrosinase. The gene for Pmel 17-1 did not map at or near the c-albino locus in mice. The cDNA of Pmel 17-1 detected a single hybridizing restriction fragment in both human and murine DNA, indicating that the gene has been conserved between these two species and exists as a single gene in each.

Isolation and sequence of a cDNA clone for human tyrosinase that maps at the mouse c-albino locus

Screening of a lambda gt11 human melanocyte cDNA library with antibodies against hamster tyrosinase (monophenol, L-dopa:oxygen oxidoreductase, EC 1.14.18.1) resulted in the isolation of 16 clones. The cDNA inserts from 13 of the 16 clones cross-hybridized with each other, indicating that they were from related mRNA species. One of the cDNA clones, Pmel34, detected one mRNA species with an approximate length of 2.4 kilobases that was expressed preferentially in normal and malignant melanocytes but not in other cell types. The amino acid sequence deduced from the nucleotide sequence showed that the putative human tyrosinase is composed of 548 amino acids with a molecular weight of 62,610. The deduced protein contains glycosylation sites and histidine-rich sites that could be used for copper binding. Southern blot analysis of DNA derived from newborn mice carrying lethal albino deletion mutations revealed that Pmel34 maps near or at the c-albino locus, the position of the structural gene for tyrosinase.

Isolation and initial characterization of multiple species of T-lymphocyte subset cDNA clones

A modified differential screening procedure was applied to analyze cDNA libraries of cloned helper T lymphocytes (Th) and cytolytic T lymphocytes (CTL). Negative and positive differential screening and RNA blot analysis were used to identify cDNA clones that were expressed preferentially in Th or CTL. Seven clones corresponded to previously described T-cell genes, and 16 additional types of cDNA clones were isolated, 9 from Th and 7 from CTL. Of these, 3 were expressed in both Th and CTL, 7 were expressed in only Th, and 6 only in CTL. These clones were analyzed for induction after stimulation by interleukin 2 or Con A or after stimulation of the T-cell antigen receptor (TCR). Three different patterns of expression were seen: induction only by Con A, induction by Con A and interleukin 2, and induction by Con A and TCR stimulation. The approach is potentially useful for analyzing paths of T-cell differentiation and detecting cDNA clones encoding unrecognized cytokines.

Effects of acyclovir therapy during simultaneous reactivation of latent HSV-1 in rabbits

Acyclovir (ACV) therapy with a simultaneous reactivation of latent HSV-1 was evaluated in HSV-1 infected rabbit eyes. When the latently infected rabbits received epinephrine iontophoresis into corneas without ACV therapy 100% of eyes shed virus into tear film. The shedding was initiated on the second day of the epinephrine iontophoresis and lasted for an average of 4.6 days. When the rabbits received ACV (60 mg/kg body weight) intravenously once daily and topically (5% ACV ointment) twice daily for 6 consecutive days while a 0.01% epinephrine solution was iontophoresed into cornea for the first 3 consecutive days, 33% (2/6) of eyes showed detectable HSV-1 in the tear film only after terminating the ACV therapy, and the duration of shedding was for only one day. The average quantity of virus detectable in the tear film was decreased 14-fold in the latter group compared to the epinephrine iontophoresis group without ACV therapy. Four days after the last ACV therapy the titer of HSV-1 in the cell-free homogenates of the trigeminal and superior cervical ganglia was determined. For the epinephrine iontophoresed group, 67% of ganglia (8/12) were HSV-1 positive, while only 33% (4/12) of the ganglia from the combined treatment group were HSV-1 positive. The difference was statistically significant (p = 0.034). Furthermore, the titer of virus detectable in the cell-free homogenates of the virus-positive ganglia from the combined treatment group was less than that from the ganglia of the epinephrine iontophoresed group or untreated group. This suggests a reduction in the total number of latent foci for the combined treatment group.

Timolol induces HSV-1 ocular shedding in the latently infected rabbit

Timolol iontophoresis into the eye can induce herpes simplex virus type 1 (HSV-1) shedding in rabbits latently infected with HSV-1 strain McKrae. Anodal iontophoresis of 0.01% timolol was done at 0.8 mAmp for 8 min once a day for 3 consecutive days. Viral shedding was determined by the presence of HSV-1 in the preocular tear film obtained by eye swabs. In two experiments, iontophoresis of 0.01% timolol resulted in all eyes (18/18) shedding HSV-1 for an average duration of 4.3 days. When 5.0% timolol was applied topically to rabbit eyes supersensitized by iontophoresis of 6-hydroxydopamine (6-HD), all eyes (10/10) shed virus for an average duration of 2.9 days. All eyes (12/12) receiving iontophoresis of 6-HD, pre- and posttreatment with topical application of 5.0% timolol, and posttreatment with topical application of 1.0% epinephrine shed virus for an average duration of 3.6 days. Eyes treated with topical application of 5.0% timolol alone showed no difference in HSV-1 ocular shedding, compared with untreated eyes. We concluded that both iontophoresis of 0.01% timolol and topical application of 5.0% timolol to adrenergically supersensitized eyes induced HSV-1 shedding reliably and with a high frequency, and that topically applied timolol does not block the HSV-1 ocular shedding induced by epinephrine in adrenergically supersensitized eyes.

Mouse mammary tumor virus-related sequences in mouse lymphocytes are inducible by 12-O-tetradecanoyl phorbol-13-acetate

cDNA libraries from EL-4 cells treated with 12-O-tetradecanoyl phorbol-13-acetate (TPA) were screened for TPA-inducible sequences by differential hybridization. The most abundant inducible species was a sequence similar to that of mouse mammary tumor virus (MMTV). Induction of the mRNA corresponding to the MMTV-related sequences was already evident 30 min after TPA treatment, whereas the maximum accumulation occurred after 20 h of exposure to TPA. TPA also increased levels of MMTV-related RNA in the normal spleen cells of BALB/c and C57BL/6 mice. The level of RNA expression corresponding to MMTV-related sequences, however, was markedly elevated in EL-4 cells as compared with normal spleen cells. Southern blots of EL-4 cell DNA showed that the MMTV-related sequences were inserted into multiple locations of the EL-4 genome. Sequence analysis revealed that the MMTV-related cDNA clones included a part of the env gene and the right long terminal repeat of MMTV. However, the cDNA sequences were substantially different from published MMTV proviral sequences, most notably because of a contiguous deletion of 491 base pairs in the open reading frame within the U3 region.