Action myoclonus-renal failure syndrome: characterization of a unique cerebro-renal disorder

Action myoclonus-renal failure syndrome (AMRF) is a distinctive form of progressive myoclonus epilepsy associated with renal dysfunction. The syndrome was not recognized prior to the advent of dialysis and renal transplantation because of its rapidly fatal course if renal failure is untreated. The first and only description of AMRF was in four French Canadian patients in three families (Andermann et al., 1986). We now describe 15 individuals with AMRF from five countries, including a follow-up of the four French Canadian patients, allowing a more complete characterization of this disease. Our 15 patients with AMRF belong to nine different families. Segregation analyses were compatible with autosomal recessive inheritance. In addition, our findings show that AMRF can present with either renal or neurological features. Tremor (onset 17-26 years, mean 19.8 years, median 19 years) and progressively disabling action myoclonus (onset 14-29 years, mean 21.7 years, median 21 years), with infrequent generalized seizures (onset 20-28 years, mean 22.7 years, median 22 years) and cerebellar features are characteristic. Proteinuria, detected between ages 9 and 30 years in all cases, progressed to renal failure in 12 out of 15 patients within 0-8 years after proteinuria detection. Brain autopsy in two patients revealed extraneuronal pigment accumulation. Renal biopsies showed collapsing glomerulopathy, a severe variant of focal glomerulosclerosis. This study extends the AMRF phenotype, and demonstrates a more extensive ethnic and geographic distribution of a syndrome originally believed to be confined to individuals of French Canadian ancestry. The independent progression of neurological and renal disorders in AMRF suggests a unitary molecular lesion with pleiotropic effects. Our results demonstrate that the renal lesion in AMRF is a recessive form of collapsing glomerulopathy. Genes identified for focal segmental glomerulosclerosis and involved with the function of the glomerular basement membrane and related proteins are thus good candidates. Treatment can improve quality of life and extend the lifespan of these patients. Dialysis and renal transplantation are effective for the renal but not the neurological features, which continue to progress even in the presence of normalized renal function; the latter can be managed with anti-myoclonic and anti-epileptic drugs.

Surveillance of individuals at intermediate risk of colorectal cancer--the impact of new guidelines

OBJECTIVE

Individuals with two first degree relatives, or one diagnosed at age < 45 years, with colorectal cancer are at sufficient risk to merit surveillance. Most undergo colonoscopy four to five yearly, starting 10 years before the youngest case. The aim of this study was to assess the impact of a proposed new surveillance protocol.

SUBJECTS AND METHODS

We identified individuals with these risk criteria seen in our clinic from 1989 to 2001 and reviewed their notes with respect to colonoscopy.

RESULTS

Colonoscopy (n = 295) was performed on 186 patients in accordance with current recommendations. Cancer was detected in three and adenoma in 21 individuals. Applying the proposed protocol, 123 (42%) fewer colonoscopies would have been performed. No cancers would have been missed, but in five cases a small adenoma would not have been detected.

CONCLUSIONS

Proposed new guidelines for surveillance of those at intermediate risk reduce the burden of colonoscopy without compromising identification of significant neoplasia.

FTIR spectroscopy demonstrates biochemical differences in mammalian cell cultures at different growth stages

We have observed differences in the infrared spectra of viable fibroblast cells depending on whether the cells were in the exponential (proliferating) or plateau (nonproliferating) phase of growth. The spectral changes were observed even after correcting for cell number and volume, ruling out these trivial explanations. Several of the changes occurred for both transformed and normal cell lines and were greater for the normal cell line. The biochemical basis of the spectral changes was estimated by fitting the cell spectra to a linear superposition of spectra for the major biochemical components of mammalian cells (DNA, RNA, protein, lipids, and glycogen). The ratios of RNA/lipid and protein/lipid increased when the cells were in the exponential phase compared to the plateau phase of growth. The fits of cell spectra to individual biochemical components also demonstrated that DNA is a relatively minor spectroscopic component as would be expected biochemically. Contrary to other reports in the literature, our data demonstrate that determining DNA content or structure using Fourier transform infrared spectroscopy data is difficult due to the relatively small amount of DNA and the overlap of DNA bands with the absorption bands of other biochemical components.

Hereditary motor and sensory neuropathy with agenesis of the corpus callosum

Hereditary motor and sensory neuropathy associated with agenesis of the corpus callosum (OMIM 218000) is an autosomal recessive disease of early onset characterized by a delay in developmental milestones, a severe sensory-motor polyneuropathy with areflexia, a variable degree of agenesis of the corpus callosum, amyotrophy, hypotonia, and cognitive impairment. Although this disorder has rarely been reported worldwide, it has a high prevalence in the Saguenay-Lac-St-Jean region of the province of Quebec (Canada) predominantly because of a founder effect. The gene defect responsible for this disorder recently has been identified, and it is a protein-truncating mutation in the SLC12A6 gene, which codes for a cotransporter protein known as KCC3. Herein, we provide the first extensive review of this disorder, covering epidemiological, clinical, and molecular genetic studies.

Toward the molecular flashlight: preparation, properties, and photophysics of a hypericin-luciferin tethered molecule

The synthesis of a molecule containing hypericin and luciferin moieties joined by a tether is reported. The light-induced (in vitro) antiviral activity as well as the photophysical properties of this new compound are measured and compared with those of the parent compounds, hypericin and pseudohypericin. This tethered molecule exhibits excited-state behavior that is very similar to that of its parent compounds and antiviral activity that is identical, within experimental error, to that of its more closely related parent compound, pseudohypericin. The implications for a photodynamic therapy that is independent of external light sources are discussed.

Polarized angular dependent spectroscopy of epithelial cells and epithelial cell nuclei to determine the size scale of scattering structures

An understanding of the relationship between tissue structures and light scattering from tissue will help facilitate the development and acceptance of noninvasive optical diagnostics including elastic scattering spectroscopy, diffuse reflectance, and optical coherence tomography. For example, a quantitative model of the structures that scatter light in epithelial cells would allow determination of what structures control the characteristics of in vivo light transport measurements and subsequently could provide a detailed relationship between cellular structures and optical measurements. We have determined the size distribution of refractive index structure variations in epithelial cells as well as in nuclei isolated from epithelial cells from measurements of the angular dependence of polarized light scattering. The quantitative size distributions we obtained for both whole cells and isolated nuclei include particles with effective radii of 2 microm to 10 nm or less and contain orders of magnitude more small particles than large particles. These results demonstrate that not only are biological cells very heterogeneous, but so are the nuclei within them. Light scattering is likely sensitive to structures smaller than those commonly investigated by standard pathology methods.

Prevalence of pre-cancerous lesions and cervical cancer in South Africa--a multicentre study

OBJECTIVES

To describe the age-specific prevalence rates of cancer of the cervix in South African women presenting for screening.

DESIGN

A multicentre prevalence survey in 10 geographically defined areas following a common core protocol. Services were located in existing service sites, with the exception of KwaZulu-Natal which used a mobile service. Women aged 20 years and above were eligible for inclusion.

OUTCOME MEASURES

Age-specific cervical cytologically diagnosed abnormality rates according to the Bethesda classification.

RESULTS

During the study 20,603 women participated. Eighty per cent of the sample had never had a Pap smear before and just over 91% had not had a Pap smear in the last 5 years. In this study population 468 women screened (2.42%) were found to have low-grade squamous intra-epithelial lesions (LSIL) and the average age of these women was 33.1 years; 366 (1.8%) had high-grade SIL (HSIL) and these women were statistically significantly older at 37.97 years of age; and 92 women (0.47%) were found to have cytologically diagnosed invasive cancer. These women were significantly older, with an average age of 51.3 years. A clear relationship was found between age and LSIL, with younger women having a high rate of LSIL which decreases with increasing age. A similar but inverse relationship between age and invasive cancer is described, with the rate being low in young women and increasing with increasing age. A clear relationship between HSIL and age is not described in these data. The adequacy rate (satisfactory and satisfactory but limited) of the slides was 95%, and just under 92% of the study sample received their results. Not all women were appropriately referred and it was not possible to assess if women referred for treatment received it.

CONCLUSIONS

These data indicate that cancer of the cervix is a common disease and that, similar to other countries, it is a disease of older women. These data give some positive indicators for future screening--older women will present for screening and the majority of women received their results. However, improvements in health system functioning are needed. A uniform national cytology reporting system is required as well as clear guidelines for providers on what action to take based on cytology reports. Linkage between the site of screening and treatment centre is inadequate and requires urgent attention in order to decrease cervical cancer mortality.

A pilot study of the continuous glucose monitoring system: clinical decisions and glycemic control after its use in pediatric type 1 diabetic subjects

OBJECTIVE

To determine whether the continuous glucose monitoring system (CGMS) (MiniMed, Sylmar, CA) could be used to make clinical decisions and whether it has an impact on glycemia in pediatric type 1 diabetic subjects.

RESEARCH DESIGN AND METHODS

Pediatric subjects were recruited if they had HbA(1c) >8.0% with management problems (n = 35) or episodes of severe or nocturnal hypoglycemia or hypoglycemia unawareness associated with HbA(1c) < or =8.0% (n = 12). A total of 47 patients with a mean HbA(1c) value of 8.6 +/- 1.6% (mean age 11.8 +/- 4.6 years, youngest 2.7 years, and diabetes duration 5.5 +/- 3.5 years) on three to four insulin injections/day (n = 24) or insulin pump therapy (n = 23) were followed with the CGMS for a mean of 69.5 +/- 28 h. Comparisons were made between the number of high (>150 mg/dl) and low (<70 mg/dl) glucose patterns discerned with the sensor or the logbook, and HbA(1c) levels were evaluated.

RESULTS

In patients on injection therapy, 30 high or low glucose patterns were discerned with the logbook records and 120 patterns with the CGMS. Specific alterations of the diabetes regimen were made. An overall significant change in HbA(1c), from 3 months before wearing the sensor to 6 months after (analysis of variance 0.04), was found in the subjects. Post hoc analysis showed a significant change in HbA(1c) from 8.6 +/- 1.5% at baseline to 8.4 +/- 1.3% at 3 months (paired Student's t test 0.03).

CONCLUSIONS

The CGMS can be used by pediatric patients to detect abnormal patterns of glycemia. The information that was obtained could be used to alter the diabetes regimen and impact glycemic outcome.

Molecular and functional characterization of genes encoding horse MHC class I antigens

Sequence and functional analyses were undertaken on two cDNAs and a genomic clone encoding horse major histocompatibility complex (MHC) class I molecules. All of the clones were isolated from a single horse that is homozygous for all known horse MHC class I and class II antigens. The two cDNAs (clones 8-9 and 1-29) were isolated from a lymphocyte library and encode polymorphic MHC antigens from two loci. The genomic cosmid clone, isolated from a sperm library, contains the 8-9 gene. All three genes were expressed in mouse L-cells and were recognized by alloantisera and, for the cDNAs, by alloreactive cytotoxic T lymphocytes. A total of 3815 bp of the genomic clone were sequenced, extending from 429 bp upstream (5') of the leader peptide through the 3' untranslated region. Promoter region motifs and an intron-exon structure characteristic of MHC class I genes of other species were found. A subclone containing 407 bp of the promoter region was inserted into a chloramphenicol acetyl transferase reporter plasmid, tested in transient transfection assays, and found to have promoter activity in heterologous cells. This genomic clone will enable detailed studies of MHC class I gene regulation in horse trophoblasts, and in horse retroviral infections.

Catastrophic shifts in ecosystems

All ecosystems are exposed to gradual changes in climate, nutrient loading, habitat fragmentation or biotic exploitation. Nature is usually assumed to respond to gradual change in a smooth way. However, studies on lakes, coral reefs, oceans, forests and arid lands have shown that smooth change can be interrupted by sudden drastic switches to a contrasting state. Although diverse events can trigger such shifts, recent studies show that a loss of resilience usually paves the way for a switch to an alternative state. This suggests that strategies for sustainable management of such ecosystems should focus on maintaining resilience.

Tumor cell toxicity of hypericin and related analogs

A series of hypericin analogs were found to differ in their cytotoxic activity induced by ambient light levels. These analogs vary in their ability to partition into cells, to generate singlet oxygen as well as in other photophysical properties. The data suggest that the biological activity of hypericin is due to a combination of factors whose roles may vary under different circumstances.

Genetic and biological variation in equine infectious anemia virus Rev correlates with variable stages of clinical disease in an experimentally infected pony

Genetic and biological variation in the regulatory protein Rev of equine infectious anemia virus (EIAV) were examined throughout a clinically dynamic disease course of an experimentally infected pony. Following infection with the virulent EIAV(Wyo), the pony underwent a variable disease course, including an acute fever episode at 12 days postinfection (DPI), multiple recurrent fever episodes until 135 DPI, a prolonged subclinical period, and two late fever episodes. Viral RNA was isolated from the inoculum and sequential sera samples, and the rev exon 2/gp45 overlapping ORFs were amplified, cloned, and sequenced. Novel variants were found throughout infection, and genetic analyses indicated that both the Rev and gp45 ORFs were under selective pressure. The Rev variant predominant in the inoculum, R1, remained predominant during the early periods following infection (until 35 DPI); however, R1 was replaced by new predominant variants during the recurrent fever period (67-135 DPI). R1 reemerged as the predominant variant during the afebrile period, but a new predominant variant, R93, was associated with the late fever episodes. Rev variants predominant during recurrent febrile and late-febrile periods had significantly higher Rev-mediated nuclear export activity than the variants predominant during the acute and afebrile periods. Statistical correlation was found between Rev activity and different stages of clinical disease. Together, these results suggest that genetic and biological variation in rev may be a contributing factor in EIAV disease progression.

Droperidol for acute psychosis

BACKGROUND

People with acute psychotic illnesses, especially when associated with agitated or violent behaviour, may require urgent pharmacological tranquillisation or sedation. Droperidol, a butyrophenone neuroleptic, is used for this purpose in several countries.

OBJECTIVES

To estimate the effects of droperidol when compared to other treatments for controlling disturbed behaviour and reducing psychotic symptoms for people with suspected acute psychotic illnesses.

SEARCH STRATEGY

The Cochrane Controlled Trials Register (Issue 2, 2000), The Cochrane Schizophrenia Group's Register (May 2000), EMBASE (1980-2000), MEDLINE (1966-2000), PASCAL (1973-2000) and PsycLIT (1970-2000) were methodically searched. Twenty-one other databases were also searched as part of a broader project and this composite database was searched for this review. This was supplemented by hand searching reference lists, contacting industry and relevant authors.

SELECTION CRITERIA

Randomised clinical trials comparing droperidol to any treatment, for people with suspected acute psychotic illnesses, such as schizophrenia, schizoaffective disorder, mixed affective disorders, manic phase of bipolar disorder or brief psychotic episode.

DATA COLLECTION AND ANALYSIS

Studies were reliably selected, quality assessed and data extracted. Data were excluded where more than 50% of participants were lost to follow up. For binary outcomes, standard estimations of risk ratio (RR) and their 95% confidence intervals (CI) were calculated. Where possible, weighted number needed to treat or harm statistics (NNT, NNH), and their 95% confidence intervals (CI), were also calculated.

MAIN RESULTS

Only two clearly relevant randomised trials with usable data were identified. One additional study was included but focused on outcomes at 30 days rather than a few hours. One small (n=41) randomised trial compared droperidol (10mg IV) with placebo IV and found that people allocated to droperidol were significantly less likely to need additional haloperidol injections in the first few minutes (n=41, RR 0.37 CI 0.2 to 0.7, NNT 2 CI 1 to 10) than those given placebo. By 90 minutes this difference was still evident but not statistically significant (RR 0.46 CI 0.2 to 1.2). When 5mg IM droperidol was compared to 5mg IM haloperidol people given droperidol were again less likely to need additional injections by 30 minutes, than those given haloperidol, but this result did not quite reach conventional levels of statistical significance (n=27, RR 0.45 CI 0.2 to 1.01). One person out of 16 given haloperidol experienced a mild dystonic reaction, and none of the 11 people allocated to droperidol were reported to have experienced adverse effects.

REVIEWER'S CONCLUSIONS

This is an important and surprisingly under-researched area. Use of droperidol for the emergency situation is currently justified on experience rather than evidence from well conducted and reported randomised trials.

PAQ: Partition Analysis of Quasispecies

MOTIVATION

The complexities of genetic data may not be accurately described by any single analytical tool. Phylogenetic analysis is often used to study the genetic relationship among different sequences. Evolutionary models and assumptions are invoked to reconstruct trees that describe the phylogenetic relationship among sequences. Genetic databases are rapidly accumulating large amounts of sequences. Newly acquired sequences, which have not yet been characterized, may require preliminary genetic exploration in order to build models describing the evolutionary relationship among sequences. There are clustering techniques that rely less on models of evolution, and thus may provide nice exploratory tools for identifying genetic similarities. Some of the more commonly used clustering methods perform better when data can be grouped into mutually exclusive groups. Genetic data from viral quasispecies, which consist of closely related variants that differ by small changes, however, may best be partitioned by overlapping groups.

RESULTS

We have developed an intuitive exploratory program, Partition Analysis of Quasispecies (PAQ), which utilizes a non-hierarchical technique to partition sequences that are genetically similar. PAQ was used to analyze a data set of human immunodeficiency virus type 1 (HIV-1) envelope sequences isolated from different regions of the brain and another data set consisting of the equine infectious anemia virus (EIAV) regulatory gene rev. Analysis of the HIV-1 data set by PAQ was consistent with phylogenetic analysis of the same data, and the EIAV rev variants were partitioned into two overlapping groups. PAQ provides an additional tool which can be used to glean information from genetic data and can be used in conjunction with other tools to study genetic similarities and genetic evolution of viral quasispecies.

Clotiapine for acute psychotic illnesses

BACKGROUND

Acute psychotic illness, especially when associated with agitated or violent behaviour, requires urgent pharmacological tranquillisation or sedation. Clotiapine, a dibenzothiazepine neuroleptic, is being used for this purpose in several countries.

OBJECTIVES

To estimate the effects of clotiapine when compared to other 'standard' or 'non-standard' treatments of acute psychotic illness in controlling disturbed behaviour and reducing psychotic symptoms.

SEARCH STRATEGY

The Cochrane Controlled Trials Register (Issue 2, 2000), The Cochrane Schizophrenia Group's Register (May 2000), EMBASE (1980-2000), MEDLINE (1966-2000), PASCAL (1973-2000) and PsycLIT (1970-2000) were methodically searched. This was supplemented by hand searching reference lists, contacting industry and relevant authors.

SELECTION CRITERIA

Randomised clinical trials comparing clotiapine to any treatment, for people with acute psychotic illnesses such as in schizophrenia, schizoaffective disorder, mixed affective disorders, manic phase of bipolar disorder, brief psychotic episode or organic psychosis following substance abuse.

DATA COLLECTION AND ANALYSIS

Studies were reliably selected, quality assessed and data extracted. Data were excluded where more than 50% of participants in any group were lost to follow up. For binary outcomes a standard estimation of the risk ratio (RR) and its 95% confidence interval (CI) was calculated. Where possible, the weighted number needed to treat statistic (NNT), and its 95% confidence interval (CI), was also calculated. If heterogeneity was found, a random effects model was used. For continuous outcomes, endpoint data were preferred to change data. Non-skewed data from valid scales were summated using a weighted mean difference (WMD). Again, if heterogeneity was found a random effects model was used. A Mantel-Haenszel chi-square test was used to investigate the possibility of heterogeneity.

MAIN RESULTS

Five trials were included. None compared clotiapine with placebo, but control drugs were either antipsychotics (chlorpromazine, perphenazine, trifluoperazine and zuclopenthixol acetate) or benzodiazepines (lorazepam). Versus antipsychotics: results for global clinical outcome were heterogeneous (p=0.09) but did not suggest clotiapine to be superior, or inferior, to chlorpromazine, perphenazine, or trifluoperazine (total randomised = 83). Use of clotiapine did change the proportion of people ready for hospital discharge by the end of the study in one small trial (n=49, RR 1.04 95%CI 0.96 to 2.12). Overall, attrition rates were low. No significant difference was found for those allocated to clotiapine compared with people randomised to other antipsychotics (n=121, RR 2.26 95%CI 0.40 to 13). Weak data suggests that clotiapine may result in less need for antiparkinsonian treatment compared with zuclopenthixol acetate (n=38, RR 0.43 95%CI 0.02 to 0.98). Versus lorazepam: when used to control aggressive/violent outbursts for people already treated with haloperidol, clotiapine did not significantly improve mental state compared to lorazepam (WMD -3.36 95%CI -8.09 to 1.37). Much data could not be pooled due to skew or inadequate presentation of results. Economic outcomes and satisfaction with care were not addressed.

REVIEWER'S CONCLUSIONS

We found no significant evidence to support the use of clotiapine rather than other 'standard' or 'non-standard' treatments for the management of acute psychotic illness. The trials included in this review all present important methodological flaws. We do not wish to discourage clinicians from using clotiapine in the psychiatric emergency, we would just like to point out the fact that good quality controlled trials are needed on this subject.

Image-guided sinus surgery: navigation without road maps

Many otorhinolaryngologists have recognized the necessity of developing new methods to increase the safety of endoscopic sinus surgery and improve patient outcomes. Despite the rapid advances made in the field, serious iatrogenic complications still occur. To counteract these complications, one recent advancement has been the development of a computed tomographic image-guided surgery (IGS) system, which can enhance the ability to treat the crippling effects of sinus disease. These systems have gained a degree of accuracy, making them suitable for difficult surgical procedures, and they may soon become standard of care. The perioperative nurse must understand and be able to work with IGS.

Endoscopic ultrasound is highly accurate and directs management in patients with neuroendocrine tumors of the pancreas

Preoperative localization of pancreatic neuroendocrine tumors with traditional imaging fails in 40-60% of patients. Endoscopic ultrasound (EUS) is highly sensitive in the detection of these tumors. Previous reports included relatively few patients or required the collaboration of multiple centers. We report the results of EUS evaluation of 82 patients with pancreatic neuroendocrine tumors.

METHODS

We prospectively used EUS early in the diagnostic evaluation of patients with biochemical or clinical evidence of neuroendocrine tumors. Patients had surgical confirmation of tumor localization or clinical follow-up of >1 yr.

RESULTS

Eighty-two patients underwent 91 examinations (cases). Thirty patients had multiple endocrine neoplasia syndrome type 1. One hundred pancreatic tumors were visualized by EUS in 54 different patients. The remaining 28 patients had no pancreatic tumor or an extrapancreatic tumor. Surgical/pathological confirmation was obtained in 75 patients. The mean tumor diameter was 1.51 cm and 71% of the tumors were < or =2.0 cm in diameter. Of the 54 explorations with surgical confirmation of a pancreatic tumor, EUS correctly localized the tumor in 50 patients (93%). Twenty-nine insulinomas, 18 gastrinomas, as well as one glucagonoma, one carcinoid tumor, and one somatostatinoma were localized. The most common site for tumor localization was the pancreatic head (46 patients). Most tumors were hypoechoic, homogenous, and had distinct margins. EUS of the pancreas was correctly negative in 20 of 21 patients (specificity, 95%). EUS was more accurate than angiography with or without stimulation testing (secretin for gastrinoma, calcium for insulinoma), transcutaneous ultrasound, and CT in those patients undergoing further imaging procedures. EUS was not reliable in localizing extrapancreatic tumors.

CONCLUSIONS

In this series, the largest single center experience reported to date, EUS had an overall sensitivity and accuracy of 93% for pancreatic neuroendocrine tumors. Our results support the use of EUS as a primary diagnostic modality in the evaluation and management of patients with neuroendocrine tumors of the pancreas.

Antigenic and genetic stability of bovine immunodeficiency virus during long-term persistence in cattle experimentally infected with the BIV(R29) isolate

Experimental infection of cattle with bovine immunodeficiency virus (BIV) is characterized by persistent, low levels of virus replication in the absence of clinical disease. A virus neutralization (VN) assay was developed to examine the role of VN antibodies in controlling virus replication in cattle experimentally infected with the BIV(R29) isolate of BIV. All animals developed VN antibody, but there was no correlation between VN titres and restriction of virus replication in vivo. BIV infection did not induce high-titred, cross-neutralizing antibody and there was no evidence for antigenic variation through more than 4 years in vivo. Genetic comparisons among the BIV(R29) inoculum virus and viruses isolated from infected animals identified only limited genetic variation during 4 years in vivo. Moreover, there was no evidence that the observed variation was due to selection. Analyses of genetic diversity in the virus stock used for inoculation indicated a fairly homogeneous population. In the absence of high levels of virus replication and overt clinical disease, there appeared to be little selection of virus variants, resulting in antigenic and genetic stability of BIV(R29) during long-term, persistent infection.

Binding of equine infectious anemia virus rev to an exon splicing enhancer mediates alternative splicing and nuclear export of viral mRNAs

In addition to facilitating the nuclear export of incompletely spliced viral mRNAs, equine infectious anemia virus (EIAV) Rev regulates alternative splicing of the third exon of the tat/rev mRNA. In the presence of Rev, this exon of the bicistronic RNA is skipped in a fraction of the spliced mRNAs. In this report, the cis-acting requirements for exon 3 usage were correlated with sequences necessary for Rev binding and transport of incompletely spliced RNA. The presence of a purine-rich exon splicing enhancer (ESE) was required for exon 3 recognition, and the addition of Rev inhibited exon 3 splicing. Glutathione-S-transferase (GST)-Rev bound to probes containing the ESE, and mutation of GAA repeats to GCA within the ESE inhibited both exon 3 recognition in RNA splicing experiments and GST-Rev binding in vitro. These results suggest that Rev regulates alternative splicing by binding at or near the ESE to block SR protein-ESE interactions. A 57-nucleotide sequence containing the ESE was sufficient to mediate Rev-dependent nuclear export of incompletely spliced RNAs. Rev export activity was significantly inhibited by mutation of the ESE or by trans-complementation with SF2/ASF. These results indicate that the ESE functions as a Rev-responsive element and demonstrate that EIAV Rev mediates exon 3 exclusion through protein-RNA interactions required for efficient export of incompletely spliced viral RNAs.

Identification and genomic cloning of CMHC1. A unique myosin heavy chain expressed exclusively in the developing chicken heart

We report the identification and cloning of a unique chick myosin heavy chain (CMHC1) that is expressed exclusively in the heart during embryogenesis. Using primers specific to myosin heavy chains, we used reverse transcriptase-polymerase chain reaction to clone and isolate CMHC1 from embryonic day 10 chicken heart RNA. Sequence analysis indicated that CMHC1 was a novel member of the myosin heavy chain family. Expression of the CMHC1 transcripts was detected in Hamburger Hamilton stage 10 chick embryos in the fusing myocardium. Expression of CMHC1 was maintained at high levels throughout the tubular heart of later stage embryos. Reverse transcriptase-polymerase chain reaction and in situ hybridizations failed to detect CMHC1 transcripts in the developing somites, limb buds, or skeletal musculature at any stage of chick development. Genomic CMHC1 clones have been isolated that contain sequences approximately 5.2 kilobase upstream of the presumptive CMHC1 transcription start site. Portions of the upstream regulatory region induced a 21-fold increase in reporter gene expression in primary cardiomyocytes. Because of its unique cardiac-restricted expression, CMHC1 will provide an excellent model system to study the molecular mechanisms required for the early developmental regulation of heart-specific genes.