Structural organization of calmodulin genes in the rat genome

In summary, we present a list of phage clones we have obtained from rat genomic libraries (from lamba SC1 to lambda SC31, lambda WC1 and lambda WC40) together with cDNA clones we have obtained from a rat brain cDNA library (PRCM1,5,3 and 4). pRCM5 corresponds to 4.0 kb mRNA species observed primarily in skeletal muscle. These clones can be classified into three groups. They belong to three bona fide calmodulin genes with five to six exons called CaM I, CaM II and CaM III and four intronless retropseudogenes, one derived from CaM I and three derived from CaM II. We have not obtained retropseudogenes for CaM III so far. These three bona fide genes are transcribed into multiple sized mRNA species in a tissue-specific manner, that is, CaM I is ubiquitous, CaM II is transcribed mainly in brain and CaM III is transcribed primarily in brain and skeletal muscle. Four retropseudogenes do not appear to be transcribed. They are probably relics of inactivated genes. The physiological meanings of multiple calmodulin mRNA species and mechanisms of transcriptional regulation of these three bona fide genes will be the main subjects of our future experiments.

Selective covalent binding of the active sulfate ester of the carcinogen 5-(hydroxymethyl)chrysene to the adenine residue of calf thymus DNA

5-(Hydroxymethyl)chrysene (5-HCR) sulfate, an active metabolite of the carcinogen 5-HCR, bound significantly in a covalent manner to the purine bases of calf thymus DNA through its 5-methylene carbon with loss of a sulfate anion when incubated at pH 7.4 and 37 degrees C. From the DNA were isolated two purine base adducts by high-pressure liquid chromatography, and they were identified as N6-[(chrysen-5-yl)methyl]adenine and N2-[(chrysen-5-yl)methyl]guanine with the corresponding synthetic specimens. The purine base adducts, appearing in the ratio 1 to 27 for guanine to adenine in the chromatogram, accounted for about 60% of the total covalent binding of 5-HCR sulfate to the DNA. 5-HCR sulfate also reacted specifically with the exocyclic amino groups of the purine bases of 2'-deoxyadenosine 5'-phosphate and 2'-deoxyguanosine 5'-phosphate at much lower rates than did with those of calf thymus DNA. Denaturing the DNA by heating followed by rapid cooling, covalent binding of 5-HCR sulfate to it markedly decreased with the increasing ratio of N2-guanine to N6-adenine adducts (1:3.6). These results strongly suggest that secondary structure of DNA has an influence on the covalent binding of 5-HCR sulfate and that intercalation of the sulfate ester into DNA base pairs plays an important role in its preferential binding to N6 of the adenine residue of native DNA.

Genes and pseudogenes for calmodulin in the spontaneously hypertensive rat

The structural organization of calmodulin genes in the spontaneously hypertensive rat (SHR) was extensively studied to search for alterations in calmodulin. We constructed genomic libraries of SHR and cloned all calmodulin-related genes in the genome. We also cloned and sequenced calmodulin complementary (c)DNA from a rat brain (Sprague-Dawley) cDNA library. We cloned three distinct calmodulin genes, naming them CaM I, II and III. Three distinct cDNA clones corresponding to these genes (pRCM1, pRCM3 and pRCM4) were also cloned. These SHR calmodulin genes all encoded normal calmodulin, and no alteration was found. Four processed pseudogenes, lambda SC9 for CaM I gene and lambda SC8, lambda SC19 and lambda SC27 genes for CaM II genes were also cloned and analysed.

Inhibition of post-decapitation convulsions in the rat by dibenzothiepin neuroleptics via alpha 1-adrenoceptor blockade

The mechanisms involved in inhibitory effects of isofloxythepin, a newly synthesized dibenzothiepin neuroleptic, on post-decapitation convulsions were studied in rats. Isofloxythepin (0.05-2.0 mg/kg s.c.) inhibited post-decapitation convulsions in a dose-dependent manner as shown by the decrease in the incidence and the shortening of the duration of convulsions. The convulsions were also inhibited by oxyprothepin, zotepine or chlorpromazine but not by haloperidol. Prazosin and bunazosin, both alpha 1-adrenoceptor antagonists, suppressed the post-decapitation convulsions but a non-selective alpha 2-adrenoceptor agonist, tolazoline, was without effect. The convulsions were inhibited dose dependently by clonidine, an alpha 2-adrenoceptor agonist, but were prolonged in duration by yohimbine, an alpha 2-adrenoceptor antagonist. Yohimbine antagonized the inhibitory effects of isofloxythepin, prazosin and clonidine. The noradrenaline-induced contraction of rat vas deferens was inhibited by isofloxythepin, prazosin or chlorpromazine. Isofloxythepin bound to alpha 1-receptors as did chlorpromazine in the rat brain cortex. The results imply that post-decapitation convulsions seem to be inhibited by a block of postsynaptic alpha 1-adrenoceptors, enhanced by a block of presynaptic alpha 2-adrenoceptors and reduced by isofloxythepin via the blocking of postsynaptic alpha 1-adrenoceptors. The convulsions thus could serve as a good model for studying the actions of drugs on the central nervous system alpha-adrenoceptors.

Diabetic state-induced modification of resting membrane potential and conductance in diaphragm muscle of alloxan and diabetic KK-CAy mice

The electrical properties of skeletal muscle membranes were investigated in genetically diabetic KK-CAy mice and alloxan-induced diabetic ddY mice. Using isolated phrenic nerve-diaphragm muscle or sciatic nerve-gastrocnemius muscle in situ preparations, nerve-stimulated twitch tensions (the maximal value) were obtained at lower voltage pulse in diabetic KK-CAy mice than in normal ddY mice. The diabetic state reduced resting membrane potentials (1.7-4.0 mV) and resting membrane conductance (0.37-0.44 mu siemen), decreased the amplitude (3.8-3.9 mV) and overshoot (4.5 mV) of directly induced-action potential, and prolonged action potential duration. In the diabetic state, resting membrane conductance was multiply-correlated with blood glucose level and resting membrane potential. In alloxan-induced diabetic mice, resting membrane potentials were significantly multiply-correlated with the weeks elapsed after alloxan injection and blood glucose level (p less than 0.01). Since the reduction of resting membrane potential correlated with the weeks, changes in resting membrane potential may be involved in the decrease in insulin-like growth factor action. The reduction of resting membrane conductance was correlated with the increase in blood glucose.

Transmammary transmission of Strongyloides ratti

The rate of transmammary transmission of Stronglyloides ratti was examined in albino rats in terms of the route of subcutaneous (s.c.) migration from the infection site (the skin) to the cranium. Inoculation sites nearer the cranium resulted in less frequent transmammary infection. The maximum number of adult worms was recovered from the sucklings when the mother was inoculated in her hindquarter and sucklings were allowed to feed for 30-36 h after inoculation (AI). Few worms were recovered from sucklings when they were allowed to nurse during periods of less than 24 h AI or greater than 42 h AI. In lactating mothers, larval infection of the mammary glands was commonly observed, and these larvae showed an increased esophagus length. In nonlactating mothers, most larvae completed their migration to the cranium within 36 h AI.

Primary structures of two types of alpha-subunit of rat brain Na+,K+,-ATPase deduced from cDNA sequences

A rat brain cDNA library was screened by using as a probe a fragment of cDNA encoding the alpha-subunit of human Na+,K+-ATPase. Two different cDNA clones were obtained and analyzed. One of them was concluded to be a cDNA encoding the alpha-subunit of the weakly ouabain-sensitive rat kidney-type Na+,K+-ATPase. The deduced amino acid sequence consists of 1,018 amino acids. The alpha-subunit of the rat kidney-type Na+,K+-ATPase shows 97% homology in amino acid sequence with the alpha-subunit of human, sheep, or pig enzyme and 87% with that of Torpedo. Based on a comparison of the amino acid sequence at the extracellular domain of the alpha-subunit between weakly ouabain-sensitive rat kidney-type enzyme and the ouabain-sensitive human, sheep, pig, or Torpedo enzyme, it was proposed that only two significant amino acid replacements are unique to the rat kidney-type alpha-subunit. Another cDNA clone obtained showed 72% homology in nucleotide sequence with the former cDNA coding the alpha-subunit of the rat kidney-type Na+,K+-ATPase and the deduced amino acid sequence exhibited 85% homology with that of the alpha-subunit of rat kidney-type Na+,K+-ATPase.

Molecular evolution of the calmodulin gene

On the basis of the intron/exon organization and the intramolecular homology of DNA sequences, I propose a novel model for genesis of the calmodulin gene. A primordial calmodulin gene consisting of 51 base pairs (17 amino acids) was subjected to three-fold duplication to create modern calmodulin with four calcium-binding subdomains. The model elucidates the seemingly enigmatic positions of splice junctions observed in calmodulin genes.

Multiple calmodulin mRNA species are derived from two distinct genes

We have observed three calmodulin mRNA species in rat tissues. In order to know from how many expressed genes they are derived, we have investigated the genomic organization of calmodulin genes in the rat genome. From a rat brain cDNA library, we obtained two kinds of cDNAs (pRCM1 and pRCM3) encoding authentic calmodulin. DNA sequence analysis of these cDNA clones revealed substitutions of nucleotides at 73 positions of 450 nucleotides in the coding region, although the amino acid sequences of these calmodulins are exactly the same. DNA sequences in the 5' and 3' noncoding regions are quite different between these two cDNAs. From these results, we conclude that they are derived from two distinct bona fide calmodulin genes, CaMI (pRCM1) and CaMII (pRCM3). Total genomic Southern hybridization suggested four distinct calmodulin-related genes in the rat genome. By cloning and sequencing the calmodulin-related genes from rat genomic libraries, we demonstrated that the other two genes are processed pseudogenes generated from the CaMI (lambda SC9) and CaMII (lambda SC8) genes, respectively, through an mRNA-mediated process of insertions. Northern blotting showed that the CaMI gene is transcribed in liver, muscle, and brain in similar amounts, whereas the CaMII gene is transcribed mainly in brain. S1 nuclease mapping indicated that the CaMI gene produced two mRNA species (1.7 and 4 kilobases), whereas the CaMII gene expressed a single mRNA species (1.4 kilobases).

Structure of a gene for rat calmodulin

The structural organization of the entire rat calmodulin gene was determined by cloning and sequencing overlapping genomic and cDNA clones from rat genomic and brain cDNA libraries. The intron/exon organization was determined by direct comparison of these sequences. Rat calmodulin gene is 9000 bases long and consisted of six exons interrupted by introns of variable sizes. The first intron separates the initiation codon (ATG) from the coding region of the protein. Three out of four intron/exon junctions in the coding region reside in the middle of calcium binding subdomains and do not correlate with the quarterly divided intramolecular homology of the protein. Their positions exactly coincide with those of the corrected version of chicken calmodulin gene. The rat calmodulin gene harbors a stretch of sequences homologous to a rat middle repetitive "identifier sequence" in the middle of the third intron. Analysis of the immediate 5' upstream region detected a TATA box (TATATATAT) and three C-G boxes (CCGCCC) but not a CAT box (CCAAT). A conserved sequence (GCGCCGCGYCYYGGGGGC) was found at -125 for rat and at -204 for chicken calmodulin genes.

Dependence of hatching of Schistosoma haematobium miracidia on physical and biological factors

The effects of light, agitation, and salinity on the hatching pattern of Schistosoma haematobium eggs were examined. Whereas all three factors influenced the hatching pattern, only salinity affected the hatching rate. Eggs began to hatch 5 min after dilution and reached a peak 10-15 min after dilution when urination, dilution of urine, and observation of hatching were conducted under ordinary laboratory conditions (25 degrees C in diffuse sunlight). Complete darkness delayed hatching. Agitation of urine by aspiration into a syringe accelerated egg hatching, the miracidia reaching peak numbers 5 min earlier.

A peculiar repetitive sequence in the rat genome

We report here a new type of peculiar repetitive sequence, A15T(TC)9T12, which was detected at 750 base pairs (bp) upstream of a rat calmodulin processed pseudogene by DNA sequencing of cloned DNA fragments. This sequence element could possibly form a cruciform structure with a 12-AT-pair stem, exposing (CT)9 sequences as a loop. S1 nuclease protection experiments failed to identify this element as a cruciform structure but instead detected an alternating purine pyrimidine tract at 50 bp downstream of this element. Total genomic Southern blotting showed that the rat genome contains only a few of these elements.

Structure of rat calmodulin processed genes with implications for a mRNA-mediated process of insertion

Two distinct processed calmodulin genes of rat (lambda SC8 and lambda SC9) were identified, cloned and their DNA sequences determined. The existence of direct repeats of 19 base-pairs for lambda SC8 or 9 base-pairs for lambda SC9 at both ends of the coding plus non-coding regions suggested a possible involvement of a mRNA-mediated process of insertion. Total genomic Southern hybridization suggested the existence of at least three different calmodulin-related genes in the rat genome. The other gene was the bona fide calmodulin gene (lambda SC4) which was split into at least five exons. lambda SC9 contained insertions of one nucleotide and two 17 base-pair direct repeats in the coding region. These insertions cause frameshift mutations probably preventing it from encoding a functional calmodulin. It also carried an insertion of a rat middle repetitive sequence, identifier sequence (IDS: Sutcliffe et al., 1982) in the 3'-non-coding region. Otherwise, it consisted of an almost identical DNA sequence to that of the bona fide calmodulin gene (lambda SC4), including the 3'-non-coding region down to the poly(A) recognition signal, A-A-T-A-A-A. On the other hand, lambda SC8 did not possess frameshift mutations in the coding region, and hence was capable of encoding a functional protein. In fact, a probe specific to the lambda SC8 sequence identified a band in Northern blotting whose size was 300 nucleotides smaller than that of authentic calmodulin mRNA. Comparison of the nucleotide sequences showed that only the coding regions of these two processed genes were homologous, indicating that the divergence of these two processed genes from the common ancestor calmodulin was an ancient event.

Primary structure of the alpha-subunit of human Na,K-ATPase deduced from cDNA sequence

Clones carrying cDNA sequences for the alpha-subunit of the Na,K-ATPase from HeLa cells have been isolated. Nucleotide sequence analysis of the cloned cDNA has revealed the primary structure of this polypeptide, which consists of 1,023 amino acids. The alpha-subunit of the human Na,K-ATPase exhibited 87% homology with its Torpedo counterpart and 98% homology with its sheep counterpart. The six putative transmembrane segments M1-M6 showed higher conservation than the total segments. Total genomic Southern hybridization indicated the existence of at most two copies, possibly only one, of the gene encoding the Na,K-ATPase alpha-subunit in the human genome.

Stability of structures of the epsilon subunit and terminator of thermophilic ATPase

F1-type ATPase is the central enzyme for ATP synthesis in most organisms. Because of the extreme reconstitutability of thermophilic ATPase (TF1) and diversity of the minor subunits of F1 type ATPase, an operon coding for TF1 was isolated from DNA of thermophilic bacterium PS3, and its terminal region containing the epsilon subunit (TF1 epsilon) and terminator was sequenced. The primary structure of the epsilon subunit (Mr = 14 333) was deduced from the nucleotide sequence (396 base-pairs) and amino-acid sequence of its amino terminus. The conclusions drawn from the results are as follows. Homologies: TF1 epsilon shows only 6% homology with the epsilon subunits of eight species reported, but 50% homology with Escherichia coli epsilon and 41% with chloroplast. The residues having a tendency to form reverse turns (Gly, Pro and Tyr) and His are relatively well conserved. Unlike some F1 epsilon types TF1 epsilon has no ATPase inhibitor activity and is not homologous with ATPase inhibitor. TF1 epsilon is essential to connect F1 to F0, like the b subunit, and is weakly homologous with the b subunit of F0F1. The cause of 3 beta: 1 epsilon subunit stoichiometry: The ribosome binding sequence of TF1 epsilon is TAGGN7, which is incomplete compared with that of TF1 beta. The codon usage for TF1 epsilon is similar to that for TF1 epsilon. The cause of stability of TF1 epsilon and its gene: There are 18 ionic groups at the putative reverse turns and the N- and C-termini of TF1 epsilon, but only 10 ionic groups in the corresponding sites of E. coli epsilon subunit. These ionic groups enhance the external polarity of TF1 epsilon and may intensify subunit-subunit interaction. There is a terminator at the 3' end of the TF1 epsilon gene, which is stabilized by a long (13 base-pairs) stem.

Molecular cloning and sequence analysis of human Na,K-ATPase beta-subunit

We have isolated a cDNA clone for the beta-subunit of HeLa cell Na,K-ATPase, containing a 2208-base-pair cDNA insert covering the whole coding region of the beta-subunit. Nucleotide sequence analysis revealed that the amino acid sequence of human Na,K-ATPase exhibited 61% homology with that of Torpedo counterpart (Noguchi et al. (1986) FEBS Lett. in press). A remarkable conservation in the nucleotide sequence of the 3' non-coding region was detected between the human and Torpedo cDNAs. RNA blot hybridization analysis revealed the presence of two mRNA species in HeLa cells. S1 nuclease mapping indicated that they were derived from utilization of two distinct polyadenylation signals in vivo. Total genomic Southern hybridization indicated the existence of only a few, possibly one set of gene encoding the Na,K-ATPase beta-subunit in the human genome.

Diabetes mellitus-induced hypersensitivity of mouse skeletal muscles to acetylcholine and succinylcholine

The myopathy in skeletal muscles of genetically diabetic male KK-CAy mice or alloxan-induced diabetic mice was investigated. In these diabetic mice, nerve-stimulated twitch tensions of in situ sciatic nerve-gastrocnemius muscle preparations were inhibited by intraarterially administered succinylcholine (SuCh) to a greater extent than in normal (non-diabetic) ones. Despite the high blood glucose level, at one week after alloxan administration, no hypersensitivity to SuCh was induced in mice, but mice at 2 weeks and 4 weeks after alloxan showed greater sensitivities. In isolated diaphragm muscles of diabetic KK-CAy mice, the acetylcholine (ACh, iontophoretically applied) potential amplitude was greater than in KK-CAy prediabetic muscles. SuCh in diabetic KK-CAy muscles inhibited ACh potentials to a greater extent than in normal ddY muscles. Hill coefficients obtained from the inhibition curve by SuCh of the nerve-stimulation response were decreased by the diabetic state. The sensitivities to d-tubocurarine and alpha-bungarotoxin were the same in both kinds of muscles. Both extrajunctional ACh receptors in denervated muscles of normal ddY and diabetic KK-CAy mice revealed the lower sensitivity to SuCh than junctional receptors in non-denervated normal muscles. In conclusion, diabetic muscles showed the hypersensitivity restricted to SuCh. These phenomena are neither due to glycosylation nor to denervation supersensitivity.

Hypersensitivity of acetylcholine receptor in diabetic skeletal muscle to neuromuscular blockers: the effect of myotubes cultured with spinal cord or its extract

The hypersensitivity of the neuromuscular junctions of diabetic mice to succinylcholine (SuCh), but not to d-tubocurarine (d-TC), was investigated using a cross culture preparation of diabetic skeletal muscle or spinal cord extract with normal tissues. Whether the hypersensitivity is due to the muscle cells themselves was examined using adult muscle of diabetic KK-CAy, prediabetic KK-CAy and normal ddY mice cocultured with embryonic spinal cord of normal ddY mice. The cultured neuromuscular junctions between diabetic KK-CAy muscle and normal ddY spinal cord was hypersensitive to SuCh, but not to d-TC. In contrast, such junctions between prediabetic KK-CAy muscle and normal ddY spinal cord were not hypersensitive to either drug. The involvement of neuronal factors in hypersensitivity to SuCh in diabetic KK-CAy neuromuscular junctions was examined using adult spinal cord extract (SCE) from diabetic KK-CAy and from normal ddY mice. We followed the time course of change in sensitivity of the acetylcholine (ACh) receptors in normal ddY embryonic myotubes to SuCh and d-TC. Both diabetic SCE and normal SCE reduced the sensitivity of myotubes to ACh; the reduction of ACh potential amplitudes by the former was less than that by the latter. Myotubes cultured with diabetic SCE was hypersensitive to both 1.51 microM SuCh and 0.134 microM d-TC. These results suggest that the hypersensitivity of the neuromuscular junctions in diabetic KK-CAy mice to SuCh but not to d-TC is mainly attributable to the diabetic muscle cells themselves.

Acetylcholine sensitivity in myotubes of nerve-muscle co-culture cultured with anti-muscle antibodies, alpha-bungarotoxin and D-tubocurarine

The effects of alpha-bungarotoxin (alpha-BuTX), D-tubocurarine (D-TC) and antibodies against muscle extract on acetylcholine (ACh) sensitivity were investigated in developing mouse myotubes in a nerve-muscle co-culture. Antibodies clearly suppressed the ACh potential amplitude in adult mouse diaphragm muscle, but antibodies in muscle pre-treated with D-TC (1 microgram/ml) weakly suppressed it. The addition of D-TC to muscle extract dose-dependently inhibited the formation of the immunoprecipitation lines. The exposure of developing myotubes to antibodies for 10 days in culture suppressed both resting potential and ACh potential, whereas co-existence of alpha-BuTX (1 microgram/ml) or D-TC (0.1 mg/ml) with antibodies suppressed ACh potential but did not affect resting potential compared with antibodies alone. The ACh potentials in myotubes cultured with alpha-BuTX and D-TC alone were also suppressed. The appearance (day 8 in culture) of this suppressive effect by alpha-BuTX was faster than that (day 11 in culture) of D-TC. These different effects depending on the time in culture may account for the conformational change of developing ACh receptors to alpha-BuTX and D-TC.