Non-radioactive detection of nerve growth factor receptor (NGFR) mRNA in rat brain using in situ hybridization histochemistry

Nonradioactive in situ hybridization on skeletal tissue sections

Spatial and temporal visualization of RNA transcripts in tissue is a key tool in studying both developmental and pathological processes. In situ hybridization is a highly sensitive method for RNA transcript detection. It is based on sequence complementation between a labeled RNA probe and the RNA transcript of interest. The labeled probe is then detected by immunohistochemical methods using an antibody conjugated to an enzyme that catalyzes the generation of chromogenic or fluorescent signals, which indicate the location of the transcript.

Dual fluorescence detection of protein and RNA in Drosophila tissues

Detection of RNAs by in situ hybridization (ISH) is a well-established technique that permits the study of specific RNA expression patterns in tissues; however, not all tissues are equally amenable to staining using the same procedure. Here we describe a protocol that combines whole-mount immunofluorescence (IF) and fluorescence in situ hybridization (FISH) for the simultaneous detection of specific RNA transcripts and proteins, greatly enhancing the spatial resolution of RNA expression in complex, intact fly tissues. To date, we have successfully used this protocol in adult testis, larval male gonads, adult intestine and Malpighian tubules. IF is conducted in RNase-free solutions, prior to the harsh conditions of FISH, in order to preserve protein antigenicity within dissected tissues. Separate protocols are described for mRNA and miRNA detection, which are based on robust digoxigenin (DIG) RNA and locked nucleic acid (LNA) probes, respectively. The combined IF-FISH procedure can be completed in 2 d for miRNA detection and 4 d for mRNA detection. Although optimized for Drosophila, this IF-FISH protocol should be adaptable to a wide variety of organisms, tissues, antibodies and probes, thus providing a reliable and simple means to compare RNA and protein abundance and localization.

Expression profiling of mouse placental lactogen II and its correlative genes using a cDNA microarray analysis in the developmental mouse placenta

The placenta is a highly differentiated organ essential for embryonic growth and development. In order to search for key molecules that are associated with mouse placental lactogen II (mPL-II) gene expression, we applied mouse cDNA microarray analysis to RNAs extracted from placentae on days 10, 12, 14, 16 and 18 of pregnancy. Changes in gene expression were categorized between days 10 and 12, 12 and 14, 14 and 16 and 16 and 18 of pregnancy. After microarray analysis, which had a minimum detectable fold change for differential expression of 2, we selected 10 genes, Apoa2, Apoc2, Ceacam14, Creg1, Fmo1, Igf2, Slc2a1, Spink3, Spi1-1 and Tpbpa, exhibiting a expression pattern similar to the mPL-II gene. Furthermore, we performed real-time PCR analysis and in situ hybridization (ISH) to find correlative expression genes for the mPL-II gene. From these results, we identified a resemblance in gene expression between mPL-II and Igf2 and selected these genes for performance of double-fluorescence immunohistochemical staining. We colocalized these proteins in labyrinthine trophoblast cells. These results strongly suggest that the expression of mPL-II and Igf2 is highly related to placental development in mice. This large-scale identification of genes regulated during placentogenesis assists in further elucidation of the molecular basis of extraembryonic development and function.

Cathepsin Gene Expression in Mouse Placenta during the Latter Half of Pregnancy

Gene expressions and their interaction are complex and have not been definitely clarified in the placenta. To identify interactions of gene products previously not studied, we applied cDNA subtraction analyses to the placenta between days 12 and 16, days 12 and 14, days 14 and 16 of pregnancy. Among subtracted cDNAs cathepsin M, Q and R in PECs were specifically identified on days 14 and 16 pregnancy. All of these gene expressions exhibited a similar pattern to the mPL-II gene expression determined by northern blot and RT-PCR analyses. By means of in situ hybridization, these mRNAs were localized in the basal and labyrinth zones of the placenta on day 16 of pregnancy. Double staining studies of cathepsin Q or cathepsin R mRNA by in situ hybridization followed by immunohistochemical staining of mPL-II in the same section revealed that signals for cathepsin Q and cathepsin R mRNAs were colocalized in mPL-II immunopositive trophoblast cells in the basal and labyrinth zones of the placenta on day 16 of pregnancy. Possible association of cathepsins with mPL-II may play important roles in placental functions during the latter half of pregnancy in mice.

Acute stress and dexamethasone rapidly increase hippocampal somatostatin synthesis and release from the dentate gyrus hilus

Somatostatin is a neuropeptide whose facilitatory action in the generation of long-term potentiation (LTP) in the hippocampal dentate gyrus has been associated with memory processes. Since stress and memory seem to share some neural pathways, we studied somatostatin release from dentate gyrus hilar cells of the hippocampus in unanesthetized free-moving rats subjected to stress or dexamethasone treatments. In parallel, the number of dentate gyrus hilar cells expressing somatostatin mRNA was quantified by nonradioactive in situ hybridization in these two experimental conditions. Rats were stereotaxically implanted with a push-pull cannula in the dentate gyrus hilar region. Animals were perfused 1 week later in basal or stress (30 min immobilization stress) conditions. The other group was intraperitoneally injected with the synthetic glucocorticoid dexamethasone (3 mg/kg b.w.). Samples were collected every 15 min for somatostatin radioimmunoassay. In parallel, in other groups of animals undergoing the same treatments, brains were removed for in situ hybridization studies with an oligonucleotide labeled with digoxigenin that recognizes somatostatin-14. The results showed that stress induced a significant increase in somatostatin release from dentate gyrus hilar cells 30-45 min after immobilization stress application. Dexamethasone-injected animals exhibited a similar response 45 min after drug administration. In situ hybridization analysis revealed that the two treatments significantly increased the number of cells expressing somatostatin mRNA in the hilar region. In conclusion, somatostatin interneurons of the hippocampal hilar region appear to be a novel stress stimulus target. Their rapid reactivity, expressed as modifications of both somatostatin release and number of cells expressing somatostatin mRNA, provides an interesting model of neuronal plasticity.

Genomic cloning of the Hsc71 gene in the hermaphroditic teleost Rivulus marmoratus and analysis of its expression in skeletal muscle: identification of a novel muscle-preferred regulatory element

To further our understanding of the role of stress proteins in development as well as in adaptation of fish to adverse environmental conditions, we undertook molecular analyses of stress protein encoding genes from the hermaphroditic teleost Rivulus marmoratus. We isolated a genomic clone containing the Hsc71 gene (rm-hsc71m) and its upstream sequences. rm-Hsc71m is not induced by external stress, but is enriched in a tissue-specific manner during early development. In adult, the strongest expression appeared in skeletal muscle, whereas lower expression was seen in the gill, eye and brain. To understand the regulatory basis of high muscle expression of rm-hsc71m, transfection of R.marmoratus muscle tissue was performed using 5' deletion fragments containing the rm-hsc71m promoter driving EGFP expression. An upstream region from -2.7 to -1.9 kb was identified as a muscle-specific regulatory region. Within this region, we identified at least three sites with the novel sequence TGTnACA interacting with a fish muscle factor having an M(r) of 32 000. Our data indicate that rm-hsc71m expression in skeletal muscle is controlled by a muscle-specific regulatory element containing this novel motif.

The cationic C-terminus of rat Muc2 facilitates dimer formation post translationally and is subsequently removed by furin

Earlier immunolocalization experiments showed that the extreme cationic C-terminus of the rat intestinal mucin Muc2 (RMC) was present at the base of intestinal goblet cells in the vicinity of ER and golgi compartments, but was not found with the rest of the mucin in apical storage granules. This prompted us to investigate the possibility that an early proteolytic cleavage reaction occurs post-translationally. A plasmid pRMC, encoding the C-terminal 534 amino acids of the mucin, was expressed in COS-7 cells and was shown to undergo cleavage at an R-T-R-R sequence located within the C-terminal 14 amino acids. Cleavage did not occur with the construct RMCfH, a furin site-mutated (A-T-A-A) counterpart of pRMCH (poly His6 tagged RMC). Addition of a furin inhibitor to COS-7 cell incubations also prevented cleavage of RMC and RMCH products. 35S pulse-chase kinetic experiments revealed that a truncated mutant lacking the C-terminal 14 amino acids (pRMCDeltaCT) forms faulty (doublet) dimers in the ER. These were not secreted as efficiently as the normal dimer of wild-type (pRMC) constructs. Thus the cationic C-terminus of rMuc2 apppears to facilitate the correct formation of normal Muc2 domain dimers.

Cellular distribution and clinical value of urokinase-type plasminogen activator, its receptor, and plasminogen activator inhibitor-2 in esophageal squamous cell carcinoma

To assess the participation of the plasminogen activation system in the invasiveness of esophageal squamous cell carcinoma, we performed immunohistochemistry and in situ hybridization to study the distribution of a urokinase-type plasminogen activator (u-PA), u-PA receptor (u-PAR), and plasminogen activator inhibitor-2 (PAI-2). u-PA and PAI-2 were expressed heterogeneously in cancer cells, and restricted expression was found in stromal cells, especially fibroblasts, that were located in the immediate proximity of the cancerous cells. u-PAR was found only in cancer cells located at the periphery of tumors. Compared with patients with u-PA-negative cancer cells, patients with u-PA-positive cancer cells more frequently showed a neoplastic invasion beyond the muscularis propria and lymph node metastases. They also showed a significantly shorter 5-year overall survival. Patients with PAI-2-positive fibroblasts showed significantly lower levels of local invasiveness, represented by a neoplastic invasion beyond the muscularis propria, than those who were PAI-2 negative. Our results suggest that the expression of u-PA in esophageal squamous cell carcinoma is predictive of poor survival, whereas the expression of PAI-2 in the fibroblasts surrounding them is protective. An analysis of u-PA and PAI-2 expression in cancer cells and their surrounding fibroblasts may be useful for predicting the prognosis of patients with esophageal squamous cell carcinoma.

Induction of a physiologically active brain-derived neurotrophic factor in the infant rat brain by peripheral administration of 4-methylcatechol

Effects of 4-methylcatechol (4MC), a known potent stimulator of nerve growth factor (NGF) synthesis, on expression of brain-derived neurotrophic factor (BDNF) mRNA and BDNF-like immunoreactivity (BDNF-LI) was investigated in infant rat brains. A single intraperitoneal administration of 4MC caused transient increases in the levels of BDNF mRNA and BDNF-LI in neurons of the cerebral cortex from 1 to 3 h and 3 to 12 h, respectively, after the injection. Repetitive injections of 4MC to newborn rats (12-h intervals for 10 days) caused a marked and dose-dependent elevation of the level of BDNF mRNA in the whole brain besides elevating the number of cells containing calbindin D-28 and enhancing its immunoreactive intensity in the pyriform cortex and hippocampus. These findings demonstrate that 4MC stimulates de novo synthesis of BDNF in the infant rat brain, resulting in acceleration of the developmental expression of calbindin D-28.

Hormonal regulation of glutamate receptor gene expression in the anteroventral periventricular nucleus of the hypothalamus

Glutamate plays an important role in mediating the positive feedback effects of ovarian steroids on gonadotropin secretion, and the preoptic region of the hypothalamus is a likely site of action of glutamate. The anteroventral periventricular nucleus (AVPV) of the preoptic region is an essential part of neural pathways mediating hormonal feedback on gonadotropin secretion, and it appears to provide direct inputs to gonadotropin releasing hormone (GnRH)-containing neurons. Immunohistochemistry and in situ hybridization were used in this study to define the distribution and hormonal regulation of glutamate receptor subtypes in the AVPV of juvenile female rats. Neurons that express the NMDAR1 receptor subtype are abundant in the AVPV, as are cells that express AMPA receptor subtypes (GluR1, GluR2, and GluR3 but not GluR4), and the AVPV appears to contain a dense plexus of NMDAR1-immunoreactive presynaptic terminals. However, AVPV neurons do not seem to express detectable levels of kainate receptor (GluR5, GluR6, and GluR7) or metabotropic receptor (mGluR1-6) subtypes. Treatment of ovariectomized juvenile rats with estradiol induced expression of GluR1 mRNA but did not alter levels of GluR2 or GluR3 mRNA. Treatment of estrogen-primed ovariectomized juvenile rats with progesterone caused an initial increase in GluR1 mRNA expression, followed by a small decrease 24 hr after treatment. In contrast, estrogen appears to suppress levels of NMDAR1 mRNA in the AVPV, which remained unchanged after progesterone treatment. Thus, one mechanism whereby ovarian steroids may provide positive feedback to GnRH neurons is by altering the sensitivity of AVPV neurons to glutamatergic activation.

Colocalization of leptin receptor (OB-R) mRNA and placental lactogen-II in rat trophoblast cells: gestational profile of OB-R mRNA expression in placentae

The present study was designed to clarify the cellular localization and expression of leptin receptor(s) [OB-R(s)] mRNA including its splice variants and their correlation with the cells which secrete placental hormone, placental lactogen-II (PL-II), in rat placentae. By in situ hybridization analysis, hybridization signals for OB-Rb and the common extracellular domain of OB-R were first detectable in some cells of the labyrinth zone of the placentae on day 14 of pregnancy and then a lot of cells dispersed in the entire area of the labyrinth zone expressed OB-Rb during the latter half of pregnancy. However, no expression was observed in the decidua and the junctional zone of the placentae during pregnancy. Double staining study revealed that signals for OB-R expressing trophoblast cells showed PL-II immunoreactivity in the labyrinth zone of the placentae. In Northern blot analysis, two bands (2.8 kb and 5.1 kb) of OB-R mRNA expression were observed in the placentae from day 17 to 21 of pregnancy and the expression of both increased markedly up to day 21 of pregnancy. RT-PCR analysis revealed that OB-Rb, OB-Ra, and OB-Re are expressed in the placentae on days 19 and 21 of pregnancy. These results suggest that the OB-R may have a physiological significance in the placental function during the latter half of pregnancy.

Expression of urokinase-type plasminogen activator receptor and plasminogen activator inhibitor-1 in gastric cancer

In gastric cancer, the urokinase-type plasminogen activator (uPA) system plays important roles in invasion and metastasis, processes which entail proteolysis and adhesion. Both the urokinase-type plasminogen activator receptor (uPAR) and the plasminogen activator inhibitor-1 (PAI-1) are thought to be important factors in this system. To clarify the relationship between these two factors and gastric cancer invasiveness, we evaluated the expression of uPAR and PAI-1 in 91 cases of gastric cancer by immunohistochemistry and in situ hybridization. Urokinase-type plasminogen activator receptor-mRNA, PAI-1-mRNA, uPAR and PAI-1 protein were diffusely distributed in the cytoplasm of the cancer cells and concentrated at invasive foci. Urokinase-type plasminogen activator receptor protein expression correlated with lymphatic, venous invasion (P< 0.01) and lymph node metastasis (P< 0.05); uPAR-mRNA expression correlated with lymphatic, venous invasion and lymph node metastasis (P< 0.05). Plasminogen activator inhibitor-1 protein expression correlated with lymphatic, venous invasion, lymph node metastasis and depth of invasion (P<0.01); PAI-1-mRNA expression was linked to lymphatic, venous invasion (P< 0.01), lymph node metastasis and depth of invasion (P< 0.05). This suggests that the proteolytic activity of uPAR and the cellular motility of PAI-1 in gastric cancer cells may determine penetration of lymphatic and blood vessels, whereby lymph node metastasis may be promoted and that the promotion of cellular motility by PAI-1 may influence the depth of cancer invasion.

Expression of fibroblast growth factor 2 mRNA in early and advanced gastric cancer

We examined the expression of FGF-2 mRNA in 16 early and 14 advanced gastric cancer by in situ hybridisation to elucidate its role in cancer progression. Anti-sense RNA probes were synthesized by transcribing the subcloned vector with T7 RNA polymerase in the presence of digoxigenin-labeled UTP. FGF-2 mRNA was located mainly in the cytoplasm around the nuclei of endothelial cells, fibroblasts and carcinoma cells. The expression was more frequently in the diffuse type carcinomas (4/7, 57%) than in the intestinal type tumours (5/23, 22%). The survival rates of advanced gastric cancers with FGF-2 mRNA expression were significantly lower than those without FGF-2 mRNA expression (p < 0.01). No significant correlation was seen with other clinicopathological factors. These results suggest that FGF-2 may play an important role for the growth of diffuse type gastric cancers, particularly at their advanced stage.

Cellular localization of urokinase-type plasminogen activator, its inhibitors, and their mRNAs in breast cancer tissues

The plasminogen activation (PA) system may participate in cancer invasion and metastasis. A series of breast cancer tissue specimens was analysed using in situ hybridization and immunohistochemistry. Urokinase-type plasminogen activator (u-PA) mRNA was detected in cancer cells and fibroblasts adjacent to them and its expression was found to be more intense in invasive than in intraductal regions. In invasive but not in intraductal regions, especially those with abundant stroma, plasminogen activator inhibitor-1 (PAI-1) mRNA was observed in cancer cells, fibroblasts, macrophages, and endothelial cells, and PAI-2 mRNA was present in cancer cells, and fibroblasts, macrophages, and lymphocytes around them. These PAI-1- and PAI-2-positive cancer cells were localized at the periphery of the invasive front. Immunohistochemistry yielded basically similar results. A retrospective study of surgically resected breast cancers from 73 patients revealed significant clinical differences associated with u-PA and PAI-2 expression in cancer cells, associated with a poor and a good prognosis, respectively. These findings indicate that breast cancer cells and fibroblasts express u-PA initially and then its inhibitors, and that this process is related to invasion. Expression of u-PA and PAI-2 in cancer cells themselves may serve to up-regulate and limit PA-mediated invasion and metastasis, respectively.

Expression of epidermal growth factor-related proteins in the aged adult mouse mammary gland and their relationship to tumorigenesis

Mammary glands from female BALB/c mice of different ages and parity were screened for production of three epidermal growth factor (EGF) related transforming growth factors and their corresponding mRNAs. Glands were obtained from 2-26-month-old nulliparous, 4-26-month-old parous, and 2-8-month-old midpregnant mice. Reverse-transcribed polymerase chain reaction (RT-PCR) was used to screen for mRNA from the transforming growth factor alpha (TGF alpha), cripto-1 (CR-1), and amphiregulin (AR) genes in extracts of whole mammary glands. TGF alpha, CR-1, and AR transcripts were detected in all of the mammary glands assayed. In situ hybridization was then used to localize these mRNAs among various cell types in sections of glands. TGF alpha mRNA levels were low in the mammary epithelium from young nulliparous mice, high in the stroma of midpregnant mammary glands, and highest in luminal epithelium of the aged glands. AR mRNA levels were high and remained unchanged in all developmental stages. CR-1 mRNA level increased with age and was detected primarily in epithelium, with some scattered expression in adjacent stroma. Finally, TGF alpha, CR-1, and AR proteins were immunolocalized in histological sections of mammary glands from the various developmental stages. TGF alpha was detected sporadically in midpregnant mice, with more conspicuous reactivity seen in 18-26-month-old mice (38% of mice). CR-1 immunoreactivity was detected in 100% of the 18-26-month-old glands but not in any other age groups. Strong AR immunoreactivity was observed in in all glands, including 100% of the 18-26-month-old glands. Staining for all three of these growth factors was observed primarily in the epithelium, with some reactivity detected in the periductal fibroblasts. No significant difference was discerned between glands from nulliparous and parous animals. We also found intense CR-1 and AR mRNA expression and strong immunoreactivity in seven different carcinogen-induced and eight spontaneous mammary tumors. Our results demonstrate that these growth factors accumulate in significant amounts in the old gland of both nulliparous and parous mice. The observations suggest that these growth factors are positioned to contribute to abnormal development in the older mammary gland, predisposing them to tumorigenesis.

Co-expression of steroid hormone receptors in opioid peptide-containing neurons correlates with patterns of gene expression during the estrous cycle

The anteroventral periventricular nucleus (AVPV) of the preoptic region represents an essential component of neural pathways regulating gonadotropin secretion, and contains sexually dimorphic populations of neurons that express dynorphin or enkephalin. In the present study we used in situ hybridization to measure prodynorphin (PDYN) and proenkephalin (PENK) mRNA in the AVPV of intact animals killed on each day of the cycle. Levels of PDYN mRNA were lowest in animals killed on the afternoon of proestrus and then increased by over 60% by the morning of the following day. Expression of PENK mRNA was generally stable during the cycle, but a small yet significant reduction was detected on proestrus relative to levels of PENK mRNA in animals killed on the day of diestrus. In addition, we used double in situ hybridization to demonstrate that the majority of PDYN mRNA-containing neurons express both estrogen (50%) and progesterone receptor (85%) mRNAs. Only one quarter of the PENK-containing neurons also co-express estrogen receptor mRNA, and fewer than 10% of the PENK mRNA neurons express PR mRNA. Thus, the differential expression of PDYN and PENK during the cycle generally correlates with distinct differences in the degree of colocalization of ER and PR mRNA in PDYN and PENK mRNA-containing neurons in the AVPV.

Altered expression of bcl-2 and bax mRNA in amyotrophic lateral sclerosis spinal cord motor neurons

One of the primary neurodegenerative events occurring in amyotrophic lateral sclerosis (ALS) is the selective loss of spinal cord alpha motor neurons. To study the potential role of apoptosis in the degeneration of these motor neurons, in situ hybridization was used to measure the expression of two apoptotic cell death genes, bcl-2 and bax, in control and ALS lumbar spinal cord sections. The strongest hybridization signal for bcl-2 mRNA in neurological and nonneurological control spinal cords was found primarily in lamina IX alpha motor neurons, while a weaker hybridization signal was found in neurons of Clarke's nucleus and the proper sensory nucleus of the dorsal horn. Surviving lamina IX motor neurons in ALS spinal cord sections also expressed bcl-2 mRNA, but at levels that were significantly and selectively decreased (4.7-fold) compared with controls. bax mRNA hybridization signal was detected in several cells throughout the gray matter in control and ALS lumbar spinal cord, but was significantly and selectively increased (2.8-fold) in ALS motor neurons. Given the proposed interactive roles of these genes in apoptosis, the present findings favor a scenario in which this mode of cell death would contribute to spinal cord motor neuron degeneration in ALS.

A novel in situ double-labeling method for simultaneous detection of mRNA and expressed protein or two different mRNAs

We have developed a novel double-labeling method to investigate multiple gene expression in single cells. The method relies on the use of a radioactive probe followed by a colorimetric probe. Unique to this method, the radioactive signal is first captured on an emulsion pre-coated slide, which totally separates it from the process of color development and prevents any interference with the radiolabeled probe. We cite two applications of the new procedure: (1) to study the correlation between acetylcholine receptor (AChR) alpha-subunit mRNA and protein expression in cultured chick myoblasts and (2) to investigate the co-expression of (AChR) alpha and gamma mRNAs in nascent myotubes. In the former case, the radioactive signal is generated by incubation of live cells with 125I-alpha-bungarotoxin, in the latter, by an in situ hybridization (ISH) with 35S-labeled DNA probe. Colorimetric labeling is accomplished in a second step by ISH using digoxigenin-labeled oligos. Analysis of 203 myoblasts showed that AChR alpha-subunit protein and mRNA are co-expressed. Examination of 4-day-old myotubes suggested that most, but not all, nuclear clusters co-express alpha and gamma mRNAs. These results demonstrate that the described protocol has high sensitivity and specificity for detection of protein and message, or two different mRNAs on a single cell level.

Binding preferences of the POU domain protein Brain-4: implications for autoregulation

The POU domain-containing transcription factor Brain-4 (Brn-4, RHS-2) was examined for its sites of expression and DNA binding preferences. In the rat, Brn-4 is expressed in 76 and 65% of vasopressin neurons in the paraventricular and supraoptic nuclei, respectively; but in only 10% of corticotropin-releasing factor neurons in the paraventricular nucleus of the hypothalamus. From these data we speculate that genes expressed within vasopressinergic neurons are more likely to be regulated by Brn-4 than those in corticotropin-releasing factor neurons. Random oligonucleotide site selection indicates Brn-4 prefers binding the DNA element CAATATGCTAAT and is inflexible in its spacing requirement between putative CAATAT and TAAT half sites, preferring 2 nucleotides between these elements. Electrophoretic mobility shift and DNase I footprinting analyses show five regions between nucleotides -457 and +22 of the Brn-4 promoter that are bound by Brn-4. Furthermore, Brn-4 can transactivate from this region of the Brn-4 promoter, suggesting that Brn-4 expression may be autoregulated.

Tissue distribution and developmental expression of type XVI collagen in the mouse

The expression of a recently identified collagen, alpha 1 (XVI), in adult mouse tissue and developing mouse embryo was examined by immunohistochemistry and in situ hybridization. A polyclonal antiserum was raised against a recombinant fusion protein, which contained a segment of 161 amino acids in the N-terminal noncollagenous domain of the human alpha 1 (XVI) collagen. Immunoprecipitation of metabolically labelled human or mouse fibroblast cell lysates with this antibody revealed a major, bacterial collagenase sensitive polypeptide of approximately 210 kDa. The size agrees with the prediction from the full-length cDNA. Immunofluorescence examination of adult mouse tissues using the affinity purified antibody revealed a rather broad distribution of the protein. The heart, kidney, intestine, ovary, testis, eye, arterial walls and smooth muscles all exhibited significant levels of expression, while the skeletal muscle, lung and brain showed very restricted and low signals. During development, no significant expression of the mRNA or protein was observed in embryo of day 8 of gestation, but strong signals was detected in placental trophoblasts. Expression in embryos was detectable first after day 11 of gestation with weak positive signals appearing in the heart. In later stages of development, stronger RNA hybridizations were observed in a variety of tissues, particularly in atrial and ventricular walls of the developing heart, spinal root neural fibers and skin. These data demonstrate that type XVI collagen represents another collagenous component widely distributed in the extracellular matrix and may contribute to the structural integrity of various tissues.

Developmental expression of the prion protein gene in glial cells

Replication of prions is dependent on the presence of the host protein PrPc. During the course of disease, PrPc is converted into an abnormal isoform, PrPSc, which accumulates in the brain. Attempts to identify the cell type(s) in which prion replication and PrP conversion occur have reached conflicting results. Although PrP mRNA is present in high amounts in neurons throughout the life of the animal, PrPSc initially accumulates in astrocytes and possibly other glial cells and, later in the course of the disease, spreads diffusely in the tissue, often in white matter. We report here that PrP mRNA is expressed not only in neurons but also in astrocytes and oligodendrocytes throughout the brain of postnatal hamsters and rats. The level of glial Prp mRNA expression in neonatal animals was comparable to that of neurons and increased two-fold during postnatal development. A substantial portion of brain PrP mRNA is therefore contributed by glial cells. Our results provide an explanation for the accumulation of PrPSc in white matter tissue and in the cytoplasm of glial cells and argue for a direct involvement of glia in prion propagation.

Localization of urokinase-type plasminogen activator, plasminogen activator inhibitor-1, 2 and plasminogen in colon cancer

We examined the localization of urokinase-type plasminogen activator (u-PA), plasminogen activator inhibitors (PAI-1 and PAI-2) and plasminogen (plg) in 26 cases of colon cancer by immunohistochemical staining. The u-PA antigen was detected in the cytoplasm of cancer cells (18/26) and stromal cells adjacent to cancer tissues (9/26). The localization of u-PA mRNA examined by in situ hybridization was consistent with that of u-PA antigen. The PAI-1 antigen was detected in fibroblasts and endothelial cells (22/26), while PAI-2 antigen was found in cancer cells (20/26). The plg antigen was seen in the extracellular matrix of the cancer stroma. The u-PA expression in cancer cells was significantly more frequently detected in cases with lymph node metastasis than in cases without metastasis. In either PAI-1- or PAI-2-expressing cases, lymph node metastasis seemed to be restrained. These findings indicate that cancer cells themselves produce u-PA, and suggest that u-PA converts plg into plasmin, which dissolves the extracellular matrix surrounding cancer cells, resulting in cancer invasion and metastasis. PAI-1 and PAI-2 may have inhibitory actions on cancer invasion and metastasis mediated by u-PA.

Fluorescein as a label for non-radioactive in situ hybridization

Non-radioactive techniques can be applied to many in situ hybridization (ISH) applications, and a number of non-radioactive labels for this process have been reported. However, these labels have some inherent problems in terms of both background and signal-to-noise values. We have sought to address these issues by searching for an alternative label that has the following features: efficient incorporation into probes, non-endogenous to biological systems, the availability of a high-affinity, high-specificity antibody. Fluorescein has been shown to meet these requirements. In addition, due to the fluorescent nature of the label, it has been possible to design a rapid, non-radioactive labelling assay and also to view in situ hybridization results by direct fluorescence in certain ISH applications. The hybridization kinetics have been investigated. Significant improvements have been made to the hybridization buffer leading to reduced background and increased rates of hybridization when compared to traditional hybridization buffers.

GABA-ergic interneurons of the striatum express the Shaw-like potassium channel Kv3.1

In addition to numerous GABA-ergic efferent neurons, the striatum contains a subpopulation of fast-firing GABA-ergic interneurons characterized by the presence of immunoreactivity for the calcium-binding protein, parvalbumin. Double-label in situ hybridization with digoxigenin- and radiolabelled cRNA probes was performed on striatal sections of adult rats to identify mRNAs expressed by striatal GABA-ergic interneurons. In the dorsolateral striatum, only parvalbumin mRNA-positive neurons expressed the mRNA encoding the potassium channel Kv3.1, a member of the Shaw family of potassium channels with rapid activation and inactivation kinetics, usually found in fast-firing neurons such as the basket cells of the hippocampus. Colocalization of the parvalbumin and Kv3.1 proteins was confirmed by double-label immunohistochemistry. Parvalbumin mRNA-positive neurons expressed very high levels of the mRNA encoding glutamic acid decarboxylase (Mr 67,000: GAD67) in the dorsolateral striatum. A smaller proportion of double-labelled neurons was found in the ventrolateral striatum. A small number of densely labelled neurons for GAD67 mRNA also expressed the mRNA encoding the dopamine D2 receptor, but none expressed detectable levels of the dopamine D1 receptor mRNA. This indicates major differences in the expression of dopamine receptor mRNA in a majority of GABA-ergic interneurons vs. GABA-ergic efferent neurons of the striatum. The results suggest that distinct molecular characteristics are associated with the distinct electrophysiological properties of striatal GABA-ergic neurons.

Cell-type-specific expression and regulation of a c-fos-NGF fusion gene in neurons and astrocytes of transgenic mice

A mouse line transgenic for nerve growth factor (NGF) was developed using the mouse prepro-NGF cDNA inserted within a plasmid containing the proximal region (-10 to -550 bp) of the c-fos promoter and the transcription termination and polyadenylation signals of the rabbit beta-globin gene. No significant modification of gross behavior or central nervous system anatomy was detected in adult animals as assessed by immunohistochemistry and in situ hybridization for NGF and choline acetyltransferase. The expression of the transgene and the possible regulation of its expression by agents acting on the promoter were investigated in vitro. Despite the presence of an additional pool of NGF mRNA specific to the transgene, basal levels of NGF in the supernatant of transgenic astrocytes were similar to normal ones. On the other hand, transgenic neurons spontaneously synthesized and released levels of NGF two to three times higher than normal neurons, while mRNA levels were barely detectable by conventional Northern blotting. The tissue-specificity of NGF expression was respected, with higher levels in hippocampal than neocortical neurons. Increases of NGF mRNA by agents acting on the promoter could be observed in normal and transgenic astrocytes only after inhibition of the protein synthesis by cycloheximide, suggesting a similar rapid turnover of normal and transgenic transcripts. Cyclic AMP agonists specifically increased the secretion of NGF protein by transgenic astrocytes and neurons, while activators of the protein kinase C had a similar effect on transgenic and normal cells. Differences between amounts of NGF secreted by neurons and astrocytes with regards to their respective content in mRNA suggest that transgenic transcripts are subject to normal cell- and tissue-specific post-transcriptional regulations. Agents acting on the c-fos promoter through the protein kinase C or cyclic AMP routes differentially increased the secretion of NGF by transgenic astrocytes or neurons, supporting this hypothesis.

A single protocol to detect transcripts of various types and expression levels in neural tissue and cultured cells: in situ hybridization using digoxigenin-labelled cRNA probes

We have developed a simple non-radioactive in situ hybridization procedure for tissue sections and cultured cells using digoxigenin-labelled cRNA probes. This protocol can be applied for the detection of various transcripts present at a wide range of expression levels in the central nervous system. Cerebellar hybridization signals for transcripts estimated to be expressed at high (MBP, myelin basic protein), moderate (GluR1, subunit of AMPA/kainate sensitive glutamate receptors) and low (inositol polyphosphate-5-phosphatase) levels of abundance are demonstrated as examples. The sensitivity and cellular resolution were significantly improved by avoiding any ethanol treatment commonly used in other procedures. The localization of a labelled cell with respect to its environment is shown to be more easily assessed by counterstaining of the tissue with the nuclear dye Hoechst 33258. The present protocol can be combined with immunocytochemistry as demonstrated for glial fibrillary acidic protein (GFAP). All steps of the procedure, including preparation and labelling of the cRNA probes, pretreatment of tissue, hybridization and visualization of the labelled transcripts, are described in detail.

Subcellular localization of alpha-tubulin and opsin mRNA in the goldfish retina using digoxigenin-labeled cRNA probes detected by alkaline phosphatase and HRP histochemistry

This paper describes a method for non-radioactive in situ hybridization providing subcellular localization of mRNA in 3 microns cryosections. We used two alternative colorimetric reactions to detect digoxigenin-labeled cRNA probes: alkaline phosphatase and HRP (horseradish peroxidase). With some probes the signal with the alkaline phosphatase reaction was intense, and diffusion of the reaction product was noticeable. Using HRP-conjugated antibodies improved the resolution but decreased the sensitivity of the signal. Photoamplification of the HRP reaction product increased the contrast and improved the sensitivity of the technique.

The G protein-coupled receptor BLR1 is involved in murine B cell differentiation and is also expressed in neuronal tissues

The BLR1 gene, isolated initially from Burkitt's lymphoma cells (Eur. J. Immunol. 1992. 22: 2795), encodes a G protein-coupled receptor with significant relationship to receptors for chemokines (IL-8, MIP-1 alpha) and neuropeptides. The murine homologue of human BLR1 was cloned and used to investigate its expression in vivo. blr1-specific transcripts are observed in secondary lymphatic organs and to a lesser extent in brain of adult mice but not in other tissues. RNA in situ hybridization localizes blr1 transcription to primary follicles and to the mantle zone of secondary follicles. SCID mice in which mature B cell development is severely impaired exhibit a strongly reduced level of blr1-specific RNA in the spleen. The analysis of murine lymphoid tumor cell lines representing distinct stages of the B cell lineage reveals elevated expression of blr1 in B cell lymphomas but not in pre-B lymphomas or plasmacytomas. Induction of differentiation of resting B cells by cytokines or mitogens down-regulates expression of blr1. RNA in situ hybridization using brain sections of adult mice detects blr1 transcription in the granule and Purkinje cell layer of the cerebellum. Interestingly, the blr1 gene is also expressed during late embryogenesis in fetal liver and brain. In view of the remarkable expression pattern in the B cell lineage we suggest that murine BLR1 may represent a cytokine/neuropeptide receptor exerting regulatory functions on recirculating mature B lymphocytes.

Evidence for channeled diffusion of pre-mRNAs during nuclear RNA transport in metazoans

We report studies using an enhanced experimental system to investigate organization of nuclear pre-mRNA metabolism. It is based on the powerful genetic system and polytene nuclei of Drosophila. We observe (at steady state) movement of a specific pre-mRNA between its gene and the nuclear surface. This movement is isotropic, at rates consistent with diffusion and is restricted to a small nuclear subcompartment defined by exclusion from chromosome axes and the nucleolus. Bulk polyadenylated nuclear pre-mRNA precisely localizes in this same subcompartment indicating that most or all pre-mRNAs use the same route of intranuclear movement. In addition to association with nascent transcripts, snRNPs are coconcentrated with pre-mRNA in this subcompartment. In contrast to constitutive splices, at least one regulated splice occurs slowly and may undergo execution remotely from the site of pre-mRNA synthesis. Details of our results suggest that retention of incompletely spliced pre-mRNA is a function of the nuclear surface. We propose a simple model--based on channeled diffusion--for organization of intranuclear transport and metabolism of pre-mRNAs in polytene nuclei. We argue that this model can be generalized to all metazoan nuclei.

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

Nonisotopic methods of mRNA in situ hybridization have distinct advantages over isotopic techniques. Nonisotopically labeled probes are stable and nontoxic, have short detection times, demonstrate excellent spatial resolution of their signals and have sensitivities comparable to radiolabeled probes. We developed a simple method of generating nonisotopically labeled cRNA probes which is based on the reverse transcription polymerase chain reaction (RT-PCR) and used it to synthesize a panel of probes for various murine extracellular matrix genes. Engelbreth-Holm-Swarm (EHS) tumor RNA was reverse transcribed and PCR was used to amplify defined regions of multiple extracellular matrix protein genes from the resulting first strand cDNAs. Bacteriophage promoters which had been incorporated into the PCR products were then used to generate digoxigenin-conjugated antisense and sense cRNAs. The antisense probes were employed to detect the specific extracellular matrix protein mRNAs in the EHS tumor by in situ hybridization. This technique provides a rapid and efficient alternative to conventional transcription systems which use plasmid vectors for the synthesis of digoxigenin-labeled cRNA probes.

Differential distribution of the alternative forms of the sarcoplasmic/endoplasmic reticulum Ca(2+)-ATPase, SERCA2b and SERCA2a, in the avian brain

Cellular distribution of the two forms of SERCA2 was examined in adult chicken brain. Four regions of the brain were analyzed with three immunological reagents: a monoclonal antibody that recognizes both forms of SERCA2, and two antisera which are specific for the two alternative forms, SERCA2b or SERCA2a. Cerebellar Purkinje cells express predominantly SERCA2b but also low levels of SERCA2a, as has been reported for mammals. The nucleus isthmo-opticus, nucleus magnocellularis cochlearis, and nucleus laminaris all express high levels of SERCA2 but with different ratios of SERCA2b and SERCA2a. These immunohistochemical results were supported by in situ hybridization analysis. Therefore, it appears that regions within the brain have specific requirements for the two forms of SERCA2. This suggests functional significance for the alternative forms SERCA2b and SERCA2a, and possible functions are discussed.

HMG-CoA reductase mRNA in the post-implantation rat embryo studied by in situ hybridization

3-Hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase (EC 1.1.1.34) is the rate limiting step in the mevalonate pathway that produces isoprenoids and cholesterol. Inhibitors of HMG-CoA reductase are teratogenic in vivo and induce neural tube defects in rat embryo culture, effects which appear unrelated to cholesterol deficiency. This study is the first to localize HMG-CoA reductase mRNA by in situ hybridization (ISH). Expression of reductase mRNA was examined in post-implantation rat embryos, and for control purposes in rat liver and UT-1 cells, using a digoxigenin-11 (dig-11) labelled cRNA probe. Eighteen-day fetal liver showed heavy but patchy hybridization, and adult rat liver showed strong hybridization only on some periportal hepatocytes, which was absent in livers of fasted animals. UT-1 cells stimulated to overexpress HMG-CoA reductase mRNA were strongly positive with the same probe. Control hybridizations with sense strand RNA probe, or with cRNA probe on pre-RNased tissue were negative. Strong hybridization signal for HMG-CoA reductase mRNA was observed in all tissues of the post-implantation rat embryo, from egg cylinder to 30 somite stages (7 to 12 days). Heavy signal was noted in primitive ectoderm and neural tube. The wide embryonic and extraembryonic distribution and abundance of HMG-CoA reductase mRNA may reflect developmental requirements for products of the mevalonate pathway, e.g., isoprenoids for post-translational farnesylation of p21ras.

Photoreceptors of mouse retinas possess D4 receptors coupled to adenylate cyclase

In the mouse, the light-sensitive pool of cAMP can be eliminated in the dark by application of the dopamine D2-like receptor agonists LY 171555 (quinpirole), (+)-N0437 (2-[N-(n-propyl)-N-2-(thienylethylamino)-5-hydroxytetralin]) , or (+)-3-PPP [3-(3-hydroxyphenyl)-N-propylpiperidine hydrochloride]. The rank-order affinity of the ability of the D2-like antagonists to block the action of LY 171555 matched that of the rat D4 receptor. Reverse transcription of retina mRNA followed by DNA amplification using D4-specific nucleotides demonstrates the presence of D4 mRNA in retina. In situ hybridization studies using D4-specific digoxygenin-labeled oligonucleotides or 35S-labeled UTP RNA probes demonstrate the presence of D4 mRNA in the photoreceptor cell layer and in the inner nuclear and ganglion cell layers. The modulation by D4 ligands of the dark level of light-sensitive cAMP in photoreceptors demonstrates the physiological coupling of the D4 receptor subtype.

RHS2, a POU domain-containing gene, and its expression in developing and adult rat

Gene expression within the central nervous system is regulated by complex interactions of DNA-binding proteins, among which are the POU domain-containing proteins, which are distantly related to homeobox proteins. These POU domain-containing proteins have been implicated in control of transcription and replication within the central nervous system. We used degenerate primers with the PCR to isolate another POU domain-containing cDNA, RHS2, from hypothalamic RNA. Isolation of a putative full-length cDNA was accomplished by using serial dilutions of a hypothalamic cDNA library grown on solid medium. This member of the class III POU family is expressed in rats from embryonic day 11.5 into adulthood, being especially prominent in the brain. We performed double-labeling hybridization histochemistry and determined that RHS2 is coexpressed with a variety of neuropeptides in medium-sized neurons in the caudate putamen and with dynorphin in the paraventricular and supraoptic nuclei of the hypothalamus. Expression of RHS2 in the caudate putamen was increased by elimination of its nigrostriatal dopaminergic innervation.

Cholinergic neurons in the rat central nervous system demonstrated by in situ hybridization of choline acetyltransferase mRNA

Digoxigenin-labeled RNA probes and in situ hybridization histochemistry were used to examine choline acetyltransferase gene expression in the rat central nervous system. Hybridization signal was present only in brain sections processed with the antisense riboprobe. The sense probe did not yield labeling, further validating the specificity of tissue reactivity. Telencephalic neurons containing the mRNA for the cholinergic synthetic enzyme were found in the caudate-putamen nucleus, nucleus accumbens, olfactory tubercule, islands of Calleja complex, medial septal nucleus, vertical and horizontal limbs of the diagonal band, substantia innominata, nucleus basalis, and nucleus of the ansa lenticularis. Some somata evincing hybridization signal were observed in the anterior amygdalar area, and an occasional such cell was seen in the basolateral and central amygdalar nuclei. Neurons in the cerebral cortex, hippocampus, and primary olfactory structures did not demonstrate hybridocytochemically detectable amounts of choline acetyltransferase mRNA. Thalamic cells were devoid of reactivity, with the exception of several neurons located primarily in the ventral two-thirds of the medial habenula. A few somata labeled with riboprobe were found in the lateral hypothalamus, caudal extension of the internal capsule, and zona incerta. Neurons in the pedunculopontine and laterodorsal tegmental nuclei were moderately reactive, whereas cells of the parabigeminal nucleus exhibited a very weak hybridization signal. No somata in the brainstem raphe nuclei, including raphe obscurus and raphe magnus, were observed to bind riboprobe. In contrast, motor neurons of the cranial nerve nuclei demonstrated relatively large amounts of choline acetyltransferase mRNA. Putative cholinergic somata in the ventral horns and intermediolateral cell columns of the spinal cord were also labeled with riboprobe, as were a few cells around the central canal. We conclude that hybridocytochemistry with digoxigenin-labeled riboprobes confirms the existence of cholinergic neurons (i.e. those that synthesize and use acetylcholine as a neurotransmitter) in most of the neural regions deduced to contain them on the basis of previous histochemical and immunocytochemical data. Notable exceptions are the cerebral cortex and hippocampus, which do not possess neurons expressing detectable levels of choline acetyltransferase mRNA.

Detection of rabies virus mRNA in mouse brain by using in situ hybridization with digoxigenin-labelled RNA probes

A non-isotopic method of in situ hybridization (ISH) was developed for the detection of rabies virus RNA in paraffin-embedded tissues. Digoxigenin-labelled RNA probes for rabies virus glycoprotein mRNA were used. The method had good sensitivity and low backgrounds, and there was excellent cellular localization of signals. ISH wih digoxigenin-labelled probes was compared with ISH with 3H-labelled probes. This non-isotopic method of ISH is more convenient than the radiolabelled method, and it is quicker because a long autoradiographic exposure is not required.

Quantitative non-radioactive in situ hybridization of preproenkephalin mRNA with digoxigenin-labeled cRNA probes

Non-radioactive detection of mRNA with in situ hybridization histochemistry has emerged as an important new technology for the study of gene expression. Quantitative in situ hybridization studies have generally relied upon counting of autoradiographic grains in the emulsion overlying cells containing hybridized, radioactively labeled probe. However, such high resolution studies require tedious grain counting over individual cells, frequently in addition to weeks of exposure to nuclear emulsion. The present report describes a quantitative, non-radioactive approach to the detection of a specific mRNA in the brain with the advantages of comparatively rapid tissue processing and computerized image analysis. The validity of this approach was tested by measuring the haloperidol-induced increase in the level of preproenkephalin mRNA in striatal sections of the rat brain using an RNA probe labeled with digoxigenin-11-UTP. Detection of probe hybridized to tissue sections was carried out enzymatically following complex formation with an antidigoxigenin-alkaline phosphatase conjugate. Using computerized image analysis, it was found that chronic treatment of rats with haloperidol resulted in a 50 +/- 6% increase in striatal neuronal optical density, a value in good agreement with previous studies using low-resolution radioactive methods, showing a 30-80% increase in striatal preproenkephalin mRNA hybridization signal.

Cellular retinoic acid-binding protein type 2 mRNA is overexpressed in human psoriatic skin as shown by in situ hybridization

In situ hybridization with full length mouse cellular retinoic acid-binding protein type 1 and cellular retinoic acid-binding protein type 2 cDNA derived RNA probes showed overexpression of cellular retinoic acid-binding protein type 2 mRNA in lesional hyperplastic psoriatic skin whereas cellular retinoic acid-binding protein type 1 mRNA was undetectable. This suggests that the previously reported increase of cellular retinoic acid-binding protein in psoriatic epidermis corresponds to increased translation of cellular retinoic acid-binding protein type 2 gene. Cellular retinoic acid-binding protein types 1 and 2 mRNAs were not detectable in normal epidermis; however, type 2 message was detected in non-hyperplastic, non-lesional skin of psoriatic patients thus before altered epidermal differentiation and hyperplasia are morphologically detectable.