A single residue within the homeodomain of the Brn-3 POU family transcription factors determines whether they activate or repress the SNAP-25 promoter

The closely related POU family transcription factors Brn-3a and Brn-3b differ in their effect on a number of different neuronally expressed promoters such as that of the gene encoding the synaptic vesicle component SNAP-25. Thus Brn-3a activates these promoters whilst Brn-3b represses both their basal activity and their activation by Brn-3a. We show here that alterations of a single amino acid at position 22 in the POU-homeodomain from the isoleucine found in Brn-3b to the valine found at the equivalent position in Brn-3a converts Brn-3b from a repressor to an activator of the SNAP-25 gene promoter. The converse mutation in Brn-3a abolishes its ability to activate the SNAP-25 gene promoter and allows it to repress the basal activity of the promoter and its activation by wild type Brn-3a. This is the first time that a single amino acid change has been shown to convert an activator of a naturally occurring promoter to a repressor and vice versa. These results are discussed in terms of the critical role of position 22 in the POU homeodomain in the protein-protein interactions of POU proteins.

Efficacy of argon laser trabeculoplasty in aphakic and pseudophakic eyes

BACKGROUND AND OBJECTIVE

This study evaluated the efficacy of argon laser trabeculoplasty (ALT) in patients with aphakia or pseudophakia.

PATIENTS AND METHODS

The authors retrospectively analyzed 63 eyes of 63 patients with aphakia or pseudophakia who had uncontrolled open-angle glaucoma and were treated with 180 degrees or 360 degrees ALT.

RESULTS

The mean intraocular pressure (IOP) before ALT was 25.1 mm Hg (+/- 8.1 mm Hg). Two years after ALT, the mean IOP in the successfully treated group was 15.4 mm Hg. The mean survival time (50% success rate) for all treated eyes was 23 months, and treatment was successful in 34% of eyes at 36 months. Pseudophakic eyes had a better response than aphakic eyes (P = .06), and eyes that had extracapsular surgery did better than eyes with intracapsular surgery (P = .07).

CONCLUSION

ALT in aphakic or pseudophakic eyes with uncontrolled glaucoma is a safe, reasonably effective treatment that can delay the need for trabeculectomy.

Tissue distribution of SNAP-23 and its subcellular localization in 3T3-L1 cells

The SNARE hypothesis of vesicular traffic proposes that three proteins, VAMP/synaptobrevin, syntaxin, and SNAP-25, constitute a complex that docks the vesicle at the target membrane. VAMP and syntaxin isoforms have been identified outside the nervous system, and a cDNA to a SNAP-25 related protein, SNAP-23, was recently identified in human lymphocytes. Here we report the generation of isoform-specific antibodies to SNAP-23 cloned from human melanoma cells, and their use in detecting the expression and localization of the endogenous SNAP-23 protein in several tissues and cell lines. SNAP-23 was readily detected in liver, lung, kidney, and spleen, to a lesser extent in muscle and heart, and was almost undetectable in brain. The protein was also abundant in fibroblast, muscle, and fat cell lines, but relatively less enriched in neuroendocrine PC12 cells. SNAP-23 abundance did not change during differentiation of 3T3-L1 fibroblasts into adipocytes. In both, SNAP-23 was membrane-bound and below detectable levels in the cytosolic fraction. Subcellular fractionation of 3T3-L1 adipocytes revealed that the majority of the protein was associated with plasma membranes. These findings support the conclusion that a tripartite SNARE complex exists outside of the nervous system, and suggest that SNAP-23 may play a role in vesicle traffic in most cell types.

Differential sensitivity of c-Fos expression in hippocampus and other brain regions to moderate and low doses of alcohol

Alcohol consumption in humans is characterized by a wide range of behavioral effects and pathological consequences that suggest several neuroanatomical targets for this drug. To identify these targets we have mapped alcohol-induced changes in the expression of the c-Fos protein in the rat brain. Administration of a moderate dose of alcohol (1.5 g kg-1) led to a suppression of basal and novel environment-induced c-Fos expression in the hippocampus and simultaneous induction of this protein in regions important for the reinforcing as well as aversive properties of drugs. These include the extended amygdala (including the central nucleus of amygdala, bed nucleus of stria terminals and nucleus accumbens), regions processing sensory information (including the Edinger-Westphal nucleus and the paraventricular nucleus of the thalamus) and in stress-related areas (including the paraventricular nucleus of the hypothalamus, nucleus of the solitary tract and several neocortical areas). Repeated administration of the same dose of alcohol did not decrease alcohol-mediated suppression of c-Fos in the hippocampus, but decreased alcohol-induced expression of c-Fos in other areas. A lower dose of acute alcohol (0.5 g kg-1) reduced basal c-Fos expression in several areas of the neocortex, hippocampus and hypothalamus. However, while this low dose of alcohol was unable to counteract the environmental novelty-induced c-Fos expression in these areas, it increased c-Fos expression in the central nucleus of amygdala (an effect similar to the one observed previously for diazepam). Our data suggest that the effects of low doses of alcohol may be due to selective GABA-like effects of ethanol, whereas higher doses of ethanol involve effects on multiple neurotransmitter systems.

Coloboma hyperactive mutant mice exhibit regional and transmitter-specific deficits in neurotransmission

The mouse mutant coloboma (Cm/+), which exhibits profound spontaneous hyperactivity and bears a deletion mutation on chromosome 2, including the gene encoding synaptosomal protein SNAP-25, has been proposed to model aspects of attention-deficit hyperactivity disorder. Increasing evidence suggests a crucial role for SNAP-25 in the release of both classical neurotransmitters and neuropeptides. In the present study, we compared the release of specific neurotransmitters in vitro from synaptosomes and slices of selected brain regions from Cm/+ mice with that of +/+ mice. The release of dopamine (DA) and serotonin (5-HT) from striatum, and of arginine vasopressin and corticotropin-releasing factor from hypothalamus and amygdala is calcium-dependent. Glutamate release from and content in cortical synaptosomes of Cm/+ mice are greatly reduced, which might contribute to the learning deficits in these mutants. In dorsal striatum of Cm/+ mutants, but not ventral striatum, KCl-induced release of DA is completely blocked and that of 5-HT is significantly attenuated, suggesting that striatal DA and 5-HT deficiencies may be involved in hyperactivity. Further, although acetylcholine failed to induce hypothalamic corticotropin-releasing factor release from Cm/+ slices, restraint stress increased plasma corticosterone levels in Cm/+ mice to a significantly higher level than in +/+ mice, suggesting an important role for arginine vasopressin in hypothalamic-pituitary-adrenal axis activation. These results suggest that reduced SNAP-25 expression may contribute to a region-specific and neurotransmitter-specific deficiency in neurotransmitter release.

Adjustable horizontal rectus recession surgery for disparate distance-near ocular deviations

Strabismic deviations which display incomitance changing from distance fixation to near fixation are the result of many disturbances of both the supranuclear and infranuclear ocular motor system. This report details the surgical treatment and outcome of 6 patients with disparate distance-near deviations due to different etiologies. The surgical procedure involves recessing all four horizontal recti on both eyes using the adjustable suture technique. The approach to surgery consisted of operating on the vergence angle with the larger deviation with a bilateral lateral rectus recession (BLREC) or a bilateral medial rectus recession (BMREC) and simultaneously operating on the smaller vergence angle, treating the total induced deviation with the bilateral recession not used first (remaining BLREC or BMREC). All patients had a significant decrease in their distance-near disparity, increased horizontal comitance, normalization of their accommodative convergence to accommodation ratios, and resolution of diplopia. A four horizontal recti muscle, adjustable suture recession is another technique that can be added to the treatment regimens for distance-near disparity strabismic syndromes.

Differential regulation of genes encoding synaptic proteins by members of the Brn-3 subfamily of POU transcription factors

The three members of the Brn-3 subfamily of POU transcription factors have distinct effects on target gene expression. We show that the promoter of the gene encoding the presynaptic nerve terminal protein SNAP-25 resembles previously characterised target genes in being activated by Brn-3a and Brn-3c, but being repressed by Brn-3b. Unlike other target genes, however, the SNAP-25 promoter can be activated by either the N- or C-terminal activation domains of Brn-3a. In contrast to the SNAP-25 gene, the gene encoding the synaptic vesicle protein synapsin 1 is activated by all the Brn-3 factors, the first gene for which this activation pattern has been reported Interestingly, however, similar activation by all three Brn-3 factors can be observed if the SNAP-25 promoter is truncated by removal of sequences from -2200 to -288 relative to the transcriptional start site. Moreover, a region of the SNAP-25 promoter from -283 to -126 can render a heterologous promoter responsive to activation by all three Brn-3 factors. Differences in promoter structure may thus result in differences in the response to different Brn-3 factors, thus allowing these factors to produce diverse activation patterns of neuronally expressed genes, such as those encoding different synaptic proteins.

Long-term follow-up of ocular findings in children with Stickler's syndrome

PURPOSE

To document the longitudinal changes in eye status of children diagnosed with Stickler's syndrome in the first decade of life.

METHOD

All patients with cleft palate were referred for eye examination. Of these, patients with systemic findings of Stickler's syndrome were included in this report.

RESULTS

Thirty-four eyes in 17 patients met inclusion criteria, with median best-corrected recognition acuity of 20/30. The mean cycloplegic refraction at presentation was -5.00 diopters, and the mean refraction at last visit was -5.50 diopters.

CONCLUSIONS

Refractive errors, cataracts, and vitreoretinal abnormalities can be detected early in life in patients with Stickler's syndrome, and refractive error changed little during the follow-up period.

The effects of prenatal cocaine exposure on dopaminergic challenge and receptor binding in Wistar rats

The behavioral teratogenic effects of prenatal cocaine administration in Wistar rats were assessed in dams treated throughout gestation via oral gavage with either 0 or 80 mg/kg of cocaine. A pair-fed (PF) cohort group for the 80-mg/kg dose was used to control for an anorexic effect of cocaine. Alterations in the dopaminergic system at maturity were evaluated using pharmacological challenges with amphetamine and cocaine and by measuring D1 and D2 receptor binding in the nucleus accumbens and caudate nucleus. No significant difference among the offspring of the treatment groups was found in amphetamine-induced locomotion. A cocaine-based conditioned taste aversion was established in all offspring, but no significant effect of prenatal cocaine treatment was seen. Dopamine receptor binding was not significantly influenced by prenatal treatment, although a decreased D1 binding in the caudate nucleus of the prenatal cocaine rats approached significance.

SNAP-25 and synaptotagmin involvement in the final Ca(2+)-dependent triggering of neurotransmitter exocytosis

In neurons, depolarization induces Ca2+ influx leading to fusion of synaptic vesicles docked at the active zone for neurotransmitter release. While a number of proteins have now been identified and postulated to participate in the assembly and subsequent disengagement of a vesicle docking complex for fusion, the mechanism that ultimately triggers neuroexocytosis remains elusive. Using a cell-free, lysed synaptosomal membrane preparation, we show that Ca2+ alone is sufficient to trigger secretion of glutamate and furthermore that Ca(2+)-signaled exocytosis is effectively blocked by antibodies and peptides to SNAP-25, a key constituent of the vesicle docking complex. In addition, Ca2+ inhibits the ability of synaptotagmin, a synaptic vesicle protein proposed as a calcium sensor and triggering device, to associate with this docking complex. These results support a model in which Ca(2+)-dependent triggering of neurotransmission at central synapses acts after ATP-dependent potentiation of the docking-fusion complex for membrane fusion.

Hippocampal-dependent learning and experience-dependent activation of the hippocampus are preferentially disrupted by ethanol

A classical fear conditioning paradigm was used to examine the effect of acute ethanol on the acquisition of context conditioning, a hippocampal-dependent associative task, and tone conditioning, a hippocampal-independent task. Administration of ethanol before the presentation of seven tone-shock pairings severely disrupted the acquisition of context conditioning, but had only a slight effect on tone conditioning, when conditioned fear was measured 48 h later. This effect was dose dependent: a dose of 0.5 g/kg had no effect on either context or tone conditioning, while doses of 1.0 and 1.5 g/kg disrupted context conditioning by 78-86%, and tone conditioning by 9-17%. Subsequent experiments indicated that ethanol's preferential effect on context conditioning could not be attributed to the fact that context conditioning is weaker than tone conditioning, ethanol-induced changes in motivational state or state-dependent learning. The effect of ethanol on stimulus-induced increases in hippocampal and neocortical expression of c-fos mRNA, a marker for changes in metabolic neuronal activity, was also examined. Ethanol completely blocked the induction of hippocampal c-fos mRNA by exposure to the conditioning context alone or seven tone-shock pairings, but only attenuated neocortical responses to these stimuli. Together, these results suggest that ethanol disrupts hippocampal-dependent learning by preferentially impairing stimulus processing at the level of the hippocampus.

Tyrosine phosphorylation modulates the activity of clostridial neurotoxins

Clostridial neurotoxins' metalloprotease domain selectively cleaves proteins implicated in the process of synaptic vesicle fusion with the plasma membrane and, accordingly, blocks neurotransmitter release into the synaptic cleft. Here we investigate the potential modulation of these neurotoxins by intracellular cascades triggered by environmental signals, which in turn may alter its activity on target substrates. We report that the nonreceptor tyrosine kinase Src phosphorylates botulinum neurotoxins A, B, and E and tetanus neurotoxin. Protein tyrosine phosphorylation of serotypes A and E dramatically increases both their catalytic activity and thermal stability, while dephosphorylation reverses the effect. This suggests that the biologically significant form of the neurotoxins inside neurons is phosphorylated. Indeed, in PC12 cells in which tyrosine kinases such as Src and PYK2 are highly abundant, stimulation by membrane depolarization in presence of extracellular calcium induces rapid and selective tyrosine phosphorylation of internalized light chain, the metalloprotease domain, of botulinum toxin A. These findings provide a conceptual framework to connect intracellular signaling pathways involving tyrosine kinases, G-proteins, phosphoinositides, and calcium with the action of botulinum neurotoxins in abrogating vesicle fusion and neurosecretion.

The effects of cocaine and nandrolone co-administration on aggression in male rats

1. Cocaine and anabolic-androgenic steroids are among the more commonly abused substances in selected populations. These agents, when used alone or in combination, have been reported to cause aggressive tendencies in both laboratory-based animal models and in human clinical situations. This project, using a resident-intruder paradigm, examined the effects of co-administration of cocaine and a typical anabolic-androgenic steroid, nandrolone decanoate, on the development of aggression in male Sprague-Dawley rats. 2. Dose response studies demonstrated that low dose cocaine (1 mg/kg) produced more aggression in a greater percentage of animals than for either the controls or groups receiving higher doses (up to 20 mg/kg). Initially, high intermittent doses of nandrolone (20 mg twice weekly) produced more aggression; however, low daily doses of nandrolone (2 mg) produced greater levels of aggression following 4 weeks of treatment. 3. Optimal doses of cocaine and nandrolone, when administered together, resulted in aggression scores that were not significantly different from controls or either drug singly. However, a greater percentage of animals receiving both drugs exhibited aggression than did rats receiving either drug alone. 4. These results support the interpretation that the drugs interact to produce unique effects in the development of aggression. However, the complexity and extent of the interactions is great and remains to be fully elucidated.

Spatial Response of Mammals to Late Quaternary Environmental Fluctuations

Analyses of fossil mammal faunas from 2945 localities in the United States demonstrate that the geographic ranges of individual species shifted at different times, in different directions, and at different rates in response to late Quaternary environmental fluctuations. The geographic pattern of faunal provinces was similar for the late Pleistocene and late Holocene, but differing environmental gradients resulted in dissimilar species composition for these biogeographic regions. Modern community patterns emerged only in the last few thousand years, and many late Pleistocene communities do not have modern analogs. Faunal heterogeneity was greater in the late Pleistocene.

Mouse model of hyperkinesis implicates SNAP-25 in behavioral regulation

Although hyperkinesis is expressed in several neurological disorders, the biological basis of this phenotype is unknown. The mouse mutant coloboma (Cml+) exhibits profound spontaneous locomotor hyperactivity resulting from a deletion mutation. This deletion encompasses several genes including Snap, which encodes SNAP-25, a nerve terminal protein involved in neurotransmitter release. Administration of amphetamine, a drug that acts presynaptically, markedly reduced the locomotor activity in coloboma mice but increased the activity of control mice implicating presynaptic function in the behavioral abnormality. In contrast, the psychostimulant methylphenidate increased locomotor activity in both coloboma and control mice. When a transgene encoding SNAP-25 was bred into the coloboma strain to complement the Snap deletion, the hyperactivity expressed by these mice was rescued, returning these corrected mice to normal levels of locomotor activity. These results demonstrate that the hyperactivity exhibited by these mice is the result of abnormalities in presynaptic function specifically attributable to deficits in SNAP-25 expression.

Characterization and ontogeny of synapse-associated proteins in the developing facial and hypoglossal motor nuclei of the Brazilian opossum

The characterization and ontogeny of synapse-associated proteins in the developing facial and hypoglossal motor nuclei were examined in the Brazilian opossum (Monodelphis domestica). Immunohistochemical markers utilized in this study were the synaptic vesicle-associated proteins synaptophysin and synaptotagmin; a synaptic membrane protein, plasma membrane-associated protein of 25 kDa (SNAP-25); a growth cone protein, growth-associated phosphoprotein-43 (GAP-43); and the microtubule-associated proteins axonal marker tau and dendritic marker microtubule-associated protein-2 (MAP-2). In this study, we have found that, during the first 10 postnatal days (1-10 PN), the facial motor nucleus lacked immunoreactivity for synaptophysin, synaptotagmin, GAP-43, tau, and SNAP-25. After 10 PN, immunoreactivity increased in the facial motor nucleus for synaptophysin, synaptotagmin, GAP-43, and tau, whereas immunoreactivity for SNAP-25 was not evident until between 15 and 25 PN. Conversely, immunoreactivity for MAP-2, was present in the facial motor nucleus from the day of birth. In contrast, the hypoglossal motor nucleus displayed immunoreactivity from 1 PN for synaptophysin, synaptotagmin, SNAP-25, GAP-43, tau, and MAP-2. These results suggest that the facial motor nucleus of the opossum may not receive afferent innervation as defined by classical synaptic markers until 15 PN and, further, that characteristic mature synapses are not present until between 15 and 25 PN. These results indicate that there may be a delay in synaptogenesis in the facial motor nucleus compared to synaptogenetic events in the hypoglossal motor nucleus. Because the facial motor nucleus is active prior to completion of synaptogenesis, we suggest that the facial motoneurons are regulated in a novel or distinct manner during this time period.

Coloboma contiguous gene deletion encompassing Snap alters hippocampal plasticity

Mice heterozygous for the semidominant mutation coloboma (Cm/+) display several distinct pathologies including head bobbing, ophthalmic deformation, and locomotor hyperactivity. The Cm/+ mutation comprises a contiguous gene defect which encompasses deletion of the gene Snap encoding the presynaptic nerve terminal protein SNAP-25 that is an integral component of the synaptic vesicle docking and fusion complex. Indeed, SNAP-25 is required for axonal growth and for the regulated release of neurotransmitters at the synaptic cleft. As an extension of our studies on the behavioral deficits exhibited by these mutants, including evaluation of the hyperkinesis and dopamine-related behavioral pharmacology that might be related to attention-deficit hyperactivity disorder in humans, we have studied spontaneous electroencephalographic and evoked potential recordings in the dentate gyrus of halothane-anesthetized Cm/+ and normal (+/+) littermates to evaluate potential physiological abnormalities of synaptic function in these mice. While sensory activation elicited by brief (10 sec) tail-pinch produced 1-2 min of theta rhythmic activity in +/+ mice, theta induction was markedly reduced in Cm/+ mice. There were no significant differences in dentate afferent-evoked population excitatory postsynaptic potential (pEPSP) slopes, pEPSP facilitation, or population spike (PS) amplitudes; however, paired-pulse inhibition of dentate PS amplitudes was significantly increased in Cm/+ mice. Furthermore, although brief high-frequency stimulation of the perforant path produced robust long-term potentiation (LTP) of synaptic responses in the dentate gyrus of +/+ mice, LTP was attenuated in Cm /+ mice. It has been previously demonstrated that dopamine (DA) neurotransmission is essential for induction of one type of hippocampal theta rhythm and also may modulate hippocampal LTP, suggesting that alterations in DA synaptic transmission may underlie the behavioral abnormalities, in particular the hyperactivity, associated with Cm/+ mutant mice.

Practice guidelines. What are internists looking for?

To determine features of the presentation of clinical practice guidelines that may enhance their use by internists, we conducted a cross-sectional survey to which 1,513 (60%) of 2,513 eligible internists responded. Endorsements by respected colleagues and by major organizations were identified as very important by 72% and 69% of respondents, respectively. Respondents preferred short pamphlets and manuals summarizing a number of guidelines and felt that concise recommendations (86%), synopsis of supporting evidence (85%), and quantification of benefit (77%) were important in guideline presentation. We conclude that guideline developers should gain the endorsement of major organizations and present key aspects in brief, easily assimilated formats.

Coloboma hyperactive mutant exhibits delayed neurobehavioral developmental milestones

The coloboma mutation (Cm) is a neutron-irradiation induced gene deletion located on the distal portion of mouse chromosome 2. This deletion region includes a gene encoding the synaptic vesicle docking fusion protein, synaptosomal-associated protein of 25 kDa (SNAP-25). The resulting mutation is semi-dominant with heterozygote mice exhibiting a triad of phenotypic abnormalities that comprise profound spontaneous hyperactivity, head bobbing and a prominent eye dysmorphology. Because the expression pattern of two SNAP-25 isoforms begins to change during the first postnatal week, neurobehavioral developmental milestones were examined in order to determine if the expression of the coloboma behavioral phenotype could be detected during this period of postnatal development. The early classification of coloboma mutant offspring may help to further describe the penetrance of this mutation as well as the contribution of developmental changes to the adult behavioral phenotype. The coloboma mutation resulted in delays in some tests of complex motor skills including righting reflex and bar holding. In addition, coloboma mutants were characterized by body weight differences (first appearance day 7) and hyperreactivity to touch (day 11) and head bobbing (day 14). These data demonstrate disruptions in the time course of attaining developmental milestones in coloboma mutants and provide further evidence supporting the hypotheses that alterations in Snap gene expression are associated with functional behavioral consequences in developing offspring.

Immediate upstream promoter regions required for neurospecific expression of SNAP-25

The promoter structure and regulation of Snap, a gene encoding the presynaptic t-SNARE SNAP-25 implicated in synaptic vesicle docking and fusion, was studied. Transcription start-site analysis revealed two major start sites located 42 nucleotides apart. Nucleotide sequence of a promoter region 2073 nucleotides upstream of the first transcription site contains three AP-1, one CRE sequence, and three Sp1-like sites close to the TATA box. Further upstream of these sites two TG repeats were found. The ability of regions within the 5' upstream sequence to promote basal neural-specific expression in tissue culture cells was evaluated using a series of constructs containing both Snap gene start sites with progressively restricted 5' sequence linked to the chloramphenicol acetyl transferase (CAT) reporter gene. CAT expression was maximal in neuron-like undifferentiated ND7 and PC12 cells transfected with constructs containing Snap sequences up to 127 bp from the start site. In contrast, nonneuronal fibroblast cell lines did not express significant amounts of CAT, suggesting that this short 127-bp sequence is sufficient to drive neural specific expression of SNAP-25. Band shift analysis of oligonucleotides spanning from -127 to -41 bp of the Snap promoter revealed three distinct DNA-protein complexes generated by brain nuclear extracts and one by liver nuclear extracts, indicating that transcription factors that bind to this 86-bp sequence located just upstream of the TATA box are involved in regulation of basal neurospecific expression of this gene.