Synthesis of digoxigenin-labeled cRNA probes for nonisotopic in situ hybridization using reverse transcription polymerase chain reaction

Alterations in the balance of tubulin glycylation and glutamylation in photoreceptors leads to retinal degeneration

Tubulin is subject to a wide variety of posttranslational modifications, which, as part of the tubulin code, are involved in the regulation of microtubule functions. Glycylation has so far predominantly been found in motile cilia and flagella, and absence of this modification leads to ciliary disassembly. Here, we demonstrate that the correct functioning of connecting cilia of photoreceptors, which are non-motile sensory cilia, is also dependent on glycylation. In contrast to many other tissues, only one glycylase, TTLL3, is expressed in retina. Ttll3^-/- mice lack glycylation in photoreceptors, which results in shortening of connecting cilia and slow retinal degeneration. Moreover, absence of glycylation results in increased levels of tubulin glutamylation in photoreceptors, and inversely, the hyperglutamylation observed in the Purkinje cell degeneration (pcd) mouse abolishes glycylation. This suggests that both posttranslational modifications compete for modification sites, and that unbalancing the glutamylation-glycylation equilibrium on axonemes of connecting cilia, regardless of the enzymatic mechanism, invariably leads to retinal degeneration.

Endothelin-1 Immunoreactivity and its Association with Intramedullary Hemorrhage and Myelomalacia in Naturally Occurring Disk Extrusion in Dogs

Background

The pathophysiology of ascending/descending myelomalacia (ADMM) after canine intervertebral disk (IVD) extrusion remains poorly understood. Vasoactive molecules might contribute.

Hypothesis/Objectives

To investigate the immunoreactivity of endothelin‐1 (ET‐1) in the uninjured and injured spinal cord of dogs and its potential association with intramedullary hemorrhage and extension of myelomalacia.

Animals

Eleven normal control and 34 dogs with thoracolumbar IVD extrusion.

Methods

Spinal cord tissue of dogs retrospectively selected from our histopathologic database was examined histologically at the level of the extrusion (center) and in segments remote from the center. Endothelin‐1 immunoreactivity was examined immunohistochemically and by in situ hybridization. Associations between the immunoreactivity for ET‐1 and the severity of intramedullary hemorrhage or the extension of myelomalacia were examined.

Results

Endothelin‐1 was expressed by astrocytes, macrophages, and neurons and only rarely by endothelial cells in all dogs. At the center, ET‐1 immunoreactivity was significantly higher in astrocytes (median score 4.02) and lower in neurons (3.21) than in control dogs (3.0 and 4.54) (P < .001; P = .004) irrespective of the grade of hemorrhage or myelomalacia. In both astrocytes and neurons, there was a higher ET‐1 immunoreactivity in spinal cord regions remote from the center (4.58 and 4.15) than in the center itself (P = .013; P = .001). ET‐1 mRNA was present in nearly all neurons with variable intensity, but not in astrocytes.

Conclusion and Clinical Importance

Enhanced ET‐1 immunoreactivity over multiple spinal cord segments after IVD extrusion might play a role in the pathogenesis of ADMM. More effective quantitative techniques are required.

The effect of moving point of contact stimulation on chondrocyte gene expression and localization in tissue engineered constructs

Tissue engineering is a promising approach for articular cartilage repair. However, using current technologies, the developed engineered constructs generally do not possess an organized superficial layer, which contributes to the tissue's durability and unique mechanical properties. In this study, we investigated the efficacy of applying a moving point of contract-type stimulation (MPS) to stimulate the production of a superficial-like layer in the engineered constructs. MPS was applied to chondrocyte-agarose hydrogels at a frequency of 0.5, 1 or 2 Hz, under a constant compressive load of 10 mN for durations between 5 and 60 min over 3 consecutive days. Expression and localization of superficial zone constituents was conducted by qRT-PCR and in situ hybridization. Finite element modeling was also constructed to gain insight into the relationship between the applied stimulus and superficial zone constituent expression. Gene expression of superficial zone markers were affected in a frequency dependent manner with a physiologic frequency of 1 Hz producing maximal expression of PRG4, biglycan, decorin and collagen II. In situ hybridization revealed that localization of these markers predominantly occurred at 500-1000 μm below the construct surface which correlated to sub-surface strains between 10 and 25% as determined by finite element modeling. These results indicate that while mechanical stimuli can be used to enhance the expression of superficial zone constituents in engineered cartilage constructs, the resultant subsurface loading is a critical factor for localizing expression. Future studies will investigate altering the applied stimulus to further localize superficial zone constituent expression at the construct surface.

Induction of annexin-1 at transcriptional and post-transcriptional level in rat brain by methylprednisolone and the 21-aminosteroid U74389F

Brain tissue of rats pretreated with methylprednisolone or with the 21-aminosteroid U74389F, and that of untreated control rats, was assessed for the expression of annexin-1 (Anx-1) and the transcription of its mRNA. For this purpose Anx-1 cDNA was amplified and simultaneously a T7-RNA-polymerase promoter was incorporated into the cDNA using a polymerase chain reaction (PCR). Then digoxigenin-11-UTP was incorporated into the transcribed cRNA with T7-RNA-polymerase. With this probe in situ hybridization was carried out on sections of the brain. The probe was visualized by an immunoassay using an antidigoxigenin antibody conjugate. Anx-1 protein was assessed by means of immunohistochemistry using a polyclonal antibody. The various brain areas of the control animals showed an appreciable amount of Anx-1 at mRNA or protein level; on the other hand, the animals which had been pretreated with either steroid, showed a more intense Anx-1 mRNA signal than the controls in many areas. In the pretreated animals Anx-1 immunostaining was unchanged in cortex, basal ganglia, amygdala and septum, but more intense in hippocampus, hypothalamus and thalamus. In ependyma, choroid plexus, meninges, and vascular walls there was no Anx-1 mRNA transcription detectable. An opposite profile was shown by the Anx-1 immunoreactivity, the protein was present in control animals as well as the steroid-pretreated animals, suggesting that here the protein was either from systemic origin, or has diffused from adjacent structures. The results indicated that Anx-1 mRNA transcription is upregulated by either steroid, and that in the untreated animals there is a resting level of Anx-1 mRNA transcription, presumably reflecting physiological influences on Anx-1 expression.

Biosynthesis of ethyl oleate, a primer pheromone, in the honey bee (Apis mellifera L.)

Honey bees undergo a physiological transition from nursing to foraging approximately 21 days after adult emergence. This transition is delayed by ethyl oleate (EO), a primer pheromone produced by foragers when exposed to ethanol from fermented nectar. We demonstrate here that two secreted α/β-hydrolases (BeeBase ID: GB11403 and GB13365) are responsible for the reversible esterification of ethanol with oleic acid, giving EO. Expression of hydrolase GB11403 was shown to be significantly up-regulated in foragers, relative to nurses. Tissue perfusion experiments with labeled substrates consistently localized the highest level of EO production in the head, whereas in situ imaging revealed expression of relevant EO biosynthetic genes and enzymatic activity along the esophagus, the site of ethanol exposure during nectar intake. Both α/β-hydrolases were expressed in Pichia pastoris, purified and were shown produce EO in vitro. Experiments with live bees fed ethanol demonstrated that EO formed in regurgitate accumulates in the honey crop and exudes to the exoskeleton, from where it exerts its primer effect on younger bees.

In situ hybridization in the pathology laboratory: General principles, automation, and emerging research applications for tissue-based studies of gene expression

Diagnostic anatomic pathologists play an important role in the care of patients through their careful evaluation of morphological features in routinely prepared histological sections stained with Hematoxylin and Eosin. Morphological assessment of tissue sections, backed by over one hundred years of experience is powerful and allows for the accurate classification and diagnosis of the majority of disease states within pathologically altered tissues. However, the appearance of cells and their architectural arrangement within a morphologically complex tissue represents only a fraction of the information, which is contained within a histological section. These tissues also contain all of the cellular proteins and expressed genes, which help to ultimately determine the biological behavior of cells, as well as provide clues to the origins and pathogenesis of disease states. Technical and theoretical advances in our understanding of cellular biology have provided pathologists with powerful tools to probe beyond pure morphology into the abnormalities in both protein and gene expression that underlie human disease. These tools, which include immunohistochemistry and in situ hybridization, are playing an increasingly important role in diagnostic pathology, as well as in translational research. This review will focus on the emerging role of in situ hybridization within clinical and research laboratories, and will highlight a number of technical advances that have expanded the application of this technology.

Quantitation of the mRNA levels of Epo and EpoR in various tissues in the ovine fetus

A partial cDNA of the sheep erythropoietin receptor (EpoR) was obtained and used in real-time PCR to quantitate mRNA levels in placenta, liver and kidney throughout development (term=150 days). This was compared with Epo mRNA levels in the same tissues. Both Epo and EpoR mRNA were present in the placenta throughout gestation at low levels from 66 days onwards and these did not vary throughout gestation. Compared with the expression levels in the placenta, the levels of EpoR gene expression in the liver at 66, 99 and 140 days were, median (range)-288 (120-343), 278 (63-541) and 7 (3-15), respectively, reflecting the disappearance of erythropoiesis after 130 days. Low levels of EpoR gene expression were seen in the kidney at 3 (2-5), 5 (2-7), and 7 (2-10) times that in the placenta at 66, 99, and 140 days, respectively. By hybridization histochemistry the EpoR mRNA was located in the proximal tubular cells of the mesonephros and metanephros at 42 days. Epo mRNA levels in the kidney were 215 (116-867), 528 (113-765) and 46 (15-204) times those in the placenta at 69, 99, and 140 days, respectively. In the liver at the same ages the concentrations of mRNA were lower than in the kidney, the liver/placenta ratios being 50 (11-90), 17 (3-39), 9 (5-14). At 130 days Epo/EpoR levels in the hippocampus were 6+/-3 and 8+/-3 times that in the term placenta, respectively. These studies demonstrate that the ovine placenta expresses the Epo gene from at least 66 days of gestation. However, gene expression levels are very low compared with those in the liver and kidney, and even the hippocampus.

Endothelin-1 and monocyte chemoattractant protein-1 modulation in ischemia and human brain-derived endothelial cell cultures

Brain tissue damage due to ischemia/reperfusion has been shown to be caused, in part, by activated macrophages infiltrating into the post-ischemic brain. Using the Middle Cerebral Artery Occlusion (MCAO) mouse model, this study demonstrated that, in vivo, both endothelin-1 (Et-1), a potent vasoconstrictor, and the macrophage chemokine, monocyte chemoattractant factor-1 (MCP-1) are induced in ischemia. Further studies, using human brain-derived endothelial cells (CNS-EC), showed that in vitro, Et-1 can directly stimulate MCP-1 mRNA expression and MCP-1 protein; and this Et-1-induced MCP-1 production is mediated by the ET(A) receptor. Inflammatory cytokines, tumor necrosis factor alpha and interleukin-1beta, functioned additively and synergistically, respectively, with Et-1 to increase this MCP-1 production. Partial elucidation of the signal transduction pathways involved in Et-1-induced MCP-1 production demonstrated that protein kinase C-, but not cAMP-dependent pathways are involved. These data demonstrate that Et-1, functioning as an inflammatory peptide, increased levels of MCP-1, suggesting a mechanism for chemokine regulation during ischemia/reperfusion injury.

Impaired endochondral ossification and angiogenesis in mice deficient in membrane-type matrix metalloproteinase I

Membrane-type matrix metalloproteinase I (MT1-MMP)-deficient mice were found to have severe defects in skeletal development and angiogenesis. The craniofacial, axial, and appendicular skeletons were severely affected, leading to a short and domed skull, marked deceleration of postnatal growth, and death by 3 wk of age. Shortening of bones is a consequence of decreased chondrocyte proliferation in the proliferative zone of the growth plates. Defective vascular invasion of cartilage leads to enlargement of hypertrophic zones of growth plates and delayed formation of secondary ossification centers in long bones. In an in vivo corneal angiogenesis assay, null mice did not have angiogenic response to implanted FGF-2, suggesting that the defect in angiogenesis is not restricted to cartilage alone. In tissues from null mice, activation of latent matrix metalloproteinase 2 was deficient, suggesting that MT1-MMP is essential for its activation in vivo.

Intracellular localization of poliovirus plus- and minus-strand RNA visualized by strand-specific fluorescent In situ hybridization

The time courses of poliovirus plus- and minus-strand RNA synthesis in infected HEp-2 cells were monitored separately, using a quantitative RNase assay. In parallel, viral RNA and proteins were located in situ by confocal microscopy within cells fixed by a protocol determined to retain their native size and shape. Plus- and minus-strand RNAs were visualized by fluorescent in situ hybridization (FISH) with strand-specific riboprobes. The probes were labelled with different fluorochromes to allow for the simultaneous detection of plus- and minus-strand RNA. The FISH experiments showed minus-strand RNA to be present in distinct, regularly sized, round structures throughout the viral replication cycle. Plus-strand RNA was found in the same structures and also in smaller clusters of vesicles. Association of viral RNA with membranes was demonstrated by combining FISH with immunofluorescence (IF) detection of the viral 2B- and 2C-containing P2 proteins, which are known to be markers for virus-induced membranes. At early times postinfection, the virus-induced membranous structures were distributed through most of the cytoplasm, whereas around peak RNA synthesis, both RNA-associated membranous structures migrated to the center of the cell. During this process, the plus- and minus-strand-containing larger structures stayed as recognizable entities, whereas the plus-strand-containing granules coalesced into a juxtanuclear area of membranous vesicles. An involvement of Golgi-derived membranes in the formation of virus-induced vesicles and RNA synthesis early in infection was investigated by IF with 2C- and Golgi-specific antibodies.

Expression of annexin and annexin-mRNA in rat brain under influence of steroid drugs

Brain tissue of rats pretreated with methylprednisolone or with the 21-aminosteroid U74389F, and that of untreated control rats, was assessed for the expression of Annexin-1 (Anx-1) and the transcription of its mRNA. For this purpose Anx-1 cDNA was amplified and simultaneously a T7-RNA-polymerase promotor was incorporated into the cDNA using Polymerase Chain Reaction (PCR). Then digoxigenin-11-UTP was incorporated into the transcribed cRNA with T7-RNA-polymerase. With this probe in situ hybridization was carried out in sections of the brain. The probe was visualized by an immunoassay using an anti-digoxigenin antibody conjugate. Anx-1 protein was assessed by means of immunohistochemistry using a polyclonal antibody. The various brain areas of the control animals showed an appreciable amount of Anx-1 at mRNA or protein level; on the other hand, the animals which had been pretreated with either steroid, showed a more intense Anx-1 mRNA signal than the controls in many areas. In the pretreated animals Anx-1 immunostaining was unchanged in cortex, basal ganglia, amygdala and septum, but more intense in hippocampus, hypothalamus and thalamus. In ependyma, choroid plexus, meninges, and vascular walls there was no Anx-1 mRNA transcription detectable. An opposite profile was shown by the Anx-1 immunoreactivity, the protein was present in control animals as well as the steroid-pretreated animals, suggesting that here the protein was either from systemic origin, or has diffused from adjacent structures. The results indicate that Anx-1 mRNA transcription is upregulated by either steroid, and that in the untreated animals there is a resting level of Anx-1 mRNA transcription, presumably reflecting physiological influences on Anx-1 expression.

Reversible dissociation of the poliovirus replication complex: functions and interactions of its components in viral RNA synthesis

Membrane-bound replication complexes containing transcriptionally active replicative intermediates (RI) can be isolated from poliovirus-infected HEp-2 cells and consist of rosette-like structures of virus-induced vesicles surrounding the replicating viral RNA. At low ionic strength and low temperature, the rosettes reversibly dissociate into individual tubulated vesicles. As determined by immunoelectron microscopy and immunoprecipitation, the vesicles carry a set of viral structural and nonstructural proteins as well as RI RNA. At 30 degrees C, the vesicles reassociate into rosettes synthesizing plus-strand RNA in the RI. The in vitro transcriptional activities of rosettes and vesicles kept separated by high dilution were assessed by an RNase protection assay. The synthesis of the first 178 nucleotides at the 5' end of the plus strand was considered to reflect initiation, and the detection of a 530-nucleotide fragment in the P2 genomic region was considered to reflect elongation. It could be shown that the initiation and elongation of plus strands on individual vesicles are comparable to those in rosettes, with initiation proceeding in de novo-assembled initiation complexes. By use of detergent treatment it was found that initiation, but not elongation, is dependent on vesicular membranes.

Immunocytochemistry and in situ hybridization in the electron microscope: combined application in the study of virus-infected cells

The present review evaluates methods for electron microscopic immunocytochemistry and in situ hybridization, using post-embedding techniques and colloidal gold as a label. Special emphasis is given to double labeling immunocytochemistry and double in situ hybridization and to their combined application on the same specimen. Brief guidelines are presented for fixation, embedding media, the use of polyclonal and monoclonal antibodies and nucleic acid probes. Conditions for labeling and binding of antibody and nucleic acid probes to the target and protocols for direct and indirect immunodetection are discussed. Combinations of direct and indirect immunodetections in multiple labeling experiments are summarized.

The polymerase chain reaction in histopathology

Thanks to the advent of the polymerase chain reaction (PCR) molecular genetic study of histological samples is now a relatively straightforward task and the vast histopathology archives are now open to molecular analysis. In this review we outline technical aspects of PCR analysis of histological material and evaluate its application to the diagnosis and study of genetic, infectious and neoplastic disease. In addition, we describe a number of newly developed methods for the correlation of PCR analysis with histology, which will aid the understanding of the molecular basis of pathological processes.