A transgenic insertional inner ear mutation on mouse chromosome 1.
(57/1999)
OBJECTIVES/HYPOTHESIS: To clone and characterize the integration site of an insertional inner ear mutation, produced in one of fourteen transgenic mouse lines. The insertion of the transgene led to a mutation in a gene(s) necessary for normal development of the vestibular labyrinth. STUDY DESIGN: Molecular genetic analysis of a transgene integration site. METHODS: Molecular cloning, Southern and northern blotting, DNA sequencing and genetic database searching were the methods employed. RESULTS: The integration of the transgene resulted in a dominantly inherited waltzing phenotype and in degeneration of the pars superior. During development, inner ear fluid homeostasis was disrupted. The integration consisted of the insertion of a single copy of the transgene. Flanking DNA was cloned, and mapping indicated that the genomic DNA on either side of the transgene was not contiguous in the wild-type mouse. Localization of unique markers from the two flanks indicated that both were in the proximal region of mouse chromosome 1. However, in the wild-type mouse the markers were separated by 6.3 cM, indicating a sizable rearrangement. Analysis of the mutant DNA indicated that the entire region between the markers was neither deleted nor simply inverted. CONCLUSIONS: These results are consistent with a complex rearrangement, including at least four breakpoints and spanning at least 6.3 cM, resulting from the integration of the transgene. This genomic rearrangement disrupted the function of one or more genes critical to the maintenance of fluid homeostasis during development and the normal morphogenesis of the pars superior. (+info)
Application of cDNA microarrays in determining molecular phenotype in cardiac growth, development, and response to injury.
(58/1999)
BACKGROUND: Normal myocardial development and the tissue response to cardiac stress are accompanied by marked changes in gene expression; however, the extent of these changes and their significance remain to be fully explored. We used cDNA microarrays for gene expression profiling in rat cardiac tissue samples to study developmental transitions and the response to myocardial infarction (MI). METHODS AND RESULTS: Microarrays with rat cDNAs for 86 known genes and 989 anonymous cDNAs obtained by molecular subtraction (representational difference analysis) of mRNA from sham-operated and 6-week post-MI samples were used in 2-color hybridization experiments. Twelve known genes previously associated with myocardial development were identified together with 10 uncharacterized expressed sequence tags and 36 genes not previously associated with cardiac development. After MI, genes associated with myocardial stress and wound healing exhibited differences in magnitude and expression kinetics, and 14 genes not previously associated with MI were identified. In situ hybridization revealed mRNA localization characteristic of wound healing and vascular and cardiomyocyte reactivity. CONCLUSIONS: Tissue analysis of gene expression with cDNA microarrays provides a measure of transcriptional or posttranscriptional regulation and cellular recruitment. Our results demonstrate the complexity of gene regulation in the developing myocardium and show that cDNA microarrays can be used to monitor the evolution of the cardiac stress-inducible phenotype. (+info)
The new animal phylogeny: reliability and implications.
(59/1999)
DNA sequence analysis dictates new interpretation of phylogenic trees. Taxa that were once thought to represent successive grades of complexity at the base of the metazoan tree are being displaced to much higher positions inside the tree. This leaves no evolutionary "intermediates" and forces us to rethink the genesis of bilaterian complexity. (+info)
Quo vadis neurohypophysial hormone research?
(60/1999)
Here we highlight just a few of the outstanding questions in the field of neurohypophysial hormones that we envisage will be addressed successfully in the new millennium. To begin, we focus on the regulation of receptors. Despite intensive investigation with new drugs, molecular modelling and transgenic models, the determinants of receptor selectivity remain elusive; there may even be more vasopressin or oxytocin receptor subtypes to be discovered. We discuss the controversy over the interesting studies that indicate modulation of oxytocin receptor-binding by steroids. Oxytocin and vasopressin release and action in the brain are discussed from several aspects. Dendritically released oxytocin acting locally is important for the milk ejection reflex, and similarly released vasopressin is important in regulating patterning of vasopressin neurone activity. Such dendritically released oxytocin and vasopressin is likely to be important in paracrine modulation of neural circuitry involved in neuroendocrine control, and for a range of behaviours. Is it possible that the whole range of behaviours that comprise 'social' (or 'anti-social') or 'maternal' behaviour can be engineered by modifying the expression of just these one or two peptides and their receptors? However, whether gene expression and knockout approaches will answer all the open questions about the real functions of oxytocin and vasopressin remains to be shown. (+info)
Heterogeneous presentation in A3243G mutation in the mitochondrial tRNA(Leu(UUR)) gene.
(61/1999)
AIMS: To clarify the phenotype-genotype relation associated with the A3243G mitochondrial DNA mutation. METHODS: Five unrelated probands harbouring the A3243G mutation but presenting different clinical phenotype were analysed. Probands include Leigh syndrome (LS(3243)), mitochondrial myopathy, encephalopathy, lactic acidosis and stroke like episodes (MELAS(3243)), progressive external ophthalmoplegia (PEO(3243)), and mitochondrial diabetes mellitus (MDM(3243)). Extensive clinical, histological, biochemical, and molecular genetic studies were performed on five families. RESULTS: All patients showed ragged red fibres (RRF), and focal cytochrome c oxidase (COX) deficiency except for the patient with MDM(3243). The mutation load was highest in the proband with LS(3243) (>90%), who also presented the highest proportion of RRF (68%) and COX negative fibres (10%), and severe complex I plus IV deficiency. These proportions were lower in the probands with PEO(3243) and with MDM(3243). CONCLUSION: The most severe clinical phenotype, LS(3243), was associated with the highest proportion of the A3243G mutation as well as the most prominent histological and biochemical abnormalities. (+info)
New immunofluorescence assays for detection of Human herpesvirus 8-specific antibodies.
(62/1999)
Several assays have been developed for detection of immunoglobulin G antibodies to Human herpesvirus 8 (HHV-8), including immunofluorescence assays (IFAs) and enzyme-linked immunosorbent assays (ELISAs). However, the specificity and sensitivity of these assays are not completely defined due to the lack of a "gold standard." Although IFAs based on primary effusion lymphoma (PEL) cell lines are used widely, the assays can be confounded by nonspecific reactions against cellular components and potential cross-reaction with antibodies against other herpesviruses. To provide more reliable IFAs, we established recombinant Semliki Forest viruses (rSFVs) expressing the HHV-8-specific proteins ORF73 and K8.1 and used BHK-21 cells infected with these rSFVs for IFA (ORF73-IFA and K8.1-IFA). Expression of the HHV-8-specific proteins at very high levels by the rSFV system allowed easy scoring for IFA and thereby increased specificity. The rSFV system also allowed detection of antibodies against glycosylation-dependent epitopes of K8.1. Titers measured by rSFV-based IFAs and PEL-based IFAs correlated well (correlation coefficients of >0.9), and concordances of seroreactivities between rSFV-based and PEL-based IFAs were >97% (kappa > 0.93). K8.1-IFA was more sensitive than either ORF73-IFA or peptide ELISAs. Using PEL-based lytic IFA as a reference assay, the sensitivity and specificity of K8.1-IFA were estimated to be 94 and 100%, respectively. HHV-8 prevalences determined by K8.1-IFA among the human immunodeficiency virus (HIV)-positive (HIV(+)) Kaposi's sarcoma (KS) patients, HIV(+) KS(-) patients, and healthy controls were 100, 65, and 6.7%, respectively, which were consistent with prior reports. Therefore, our rSFV-based IFAs may provide a specific and sensitive method for use in epidemiology studies. In addition, they will provide a basis for further development of diagnostic tests for HHV-8 infection. (+info)
So do we understand how enzymes work?
(63/1999)
Between 1930 and 1975 biochemical and structural analysis of enzymes led to a clear set of ideas that might form a basis for detailed understanding of enzyme action. Further development required energetic and thermodynamic analysis of enzymes in an aqueous medium, beyond the computational power then available. Structural enzymology advanced in other directions, but the fundamental questions of enzyme action must soon be re-opened. (+info)
Regulation of biological nitrogen fixation.
(64/1999)
Biological nitrogen fixation, a process found only in some prokaryotes, is catalyzed by the nitrogenase enzyme complex. Bacteria containing nitrogenase occupy an indispensable ecological niche, supplying fixed nitrogen to the global nitrogen cycle. Due to this inceptive role in the nitrogen cycle, diazotrophs are present in virtually all ecosystems, with representatives in environments as varied as aerobic soils (e.g., Azotobacter species), the ocean surface layer (Trichodesmium) and specialized nodules in legume roots (Rhizobium). In any ecosystem, diazotrophs must respond to varied environmental conditions to regulate the tremendously taxing nitrogen fixation process. All characterized diazotrophs regulate nitrogenase at the transcriptional level. A smaller set also possesses a fast-acting post-translational regulation system. Although there is little apparent variation in the sequences and structures of nitrogenases, there appear to be almost as many nitrogenase-regulating schemes as there are nitrogen-fixing species. Herein are described the paradigms of nitrogenase function, transcriptional control and post-translational regulation, as well as the variations on these schemes, described in various nitrogen-fixing bacteria. Regulation is described on a molecular basis, focusing on the functional and structural characteristics of the proteins responsible for control of nitrogen fixation. (+info)