Conventional In Situ Hybridization Research Articles

Combined method of whole mount and block-face imaging: Acquisition of 3D data of gene expression pattern from conventional in situ hybridization.

Visualization of spatiotemporal expression of a gene of interest is a fundamental technique for analyzing the involvements of genes in organ development. In situ hybridization (ISH) is one of the most popular methods for visualizing gene expression. When conventional ISH is performed on sections or whole-mount specimens, the gene expression pattern is represented in 2-dimensional (2D) microscopic images or in the surface view of the specimen. To obtain 3-dimensional (3D) data of gene expression from conventional ISH, the "serial section method" has traditionally been employed. However, this method requires an extensive amount of time and labor because it requires researchers to collect a tremendous number of sections, label all sections by ISH, and image them before 3D reconstruction. Here, we proposed a rapid and low-cost 3D imaging method that can create 3D gene expression patterns from conventional ISH-labeled specimens. Our method consists of a combination of whole-mount ISH and Correlative Microscopy and Blockface imaging (CoMBI). The whole-mount ISH-labeled specimens were sliced using a microtome or cryostat, and all block-faces were imaged and used to reconstruct 3D images by CoMBI. The 3D data acquired using our method showed sufficient quality to analyze the morphology and gene expression patterns in the developing mouse heart. In addition, 2D microscopic images of the sections can be obtained when needed. Correlating 2D microscopic images and 3D data can help annotate gene expression patterns and understand the anatomy of developing organs. These results indicated that our method can be useful in the field of developmental biology.

An Advanced Detection System for In Situ Hybridization Using a Fluorescence Resonance Energy Transfer-based Molecular Beacon Probe.

In situ hybridization (ISH) is a powerful method for detecting specific RNAs at the cellular level. Although conventional ISH using hapten-labeled probes are useful for detecting multiple RNAs, the detection procedures are still complex and required longer time. Therefore, we introduced a new application of fluorescence resonance energy transfer (FRET)-based molecular beacon (MB) probes for ISH. MCF-7 cells and C57BL/6J mouse uterus were used for ISH. MB probes for ERα mRNA and 28S rRNA were labeled with Cy3/BHQ-2 and 6-FAM/DABCYL, and conventional probes were labeled with digoxigenin. Fluorescence measurements revealed that of more-rapid hybridization kinetics compared to conventional probes. In MCF-7 cells, 28S rRNA was detected in nucleolus and cytoplasm of all cells, whereas ERα mRNA was detected in some nucleolus. In the uterus, 28S rRNA was clearly detected using complementary MB probe, but there were no signals in control slides. Moreover, 28S rRNA was detected in all cells, whereas ERα mRNA was detected mainly in the epithelium. Fluorescence intensity of 28S rRNA was decreased significantly in 1 or 2 base-mismatched sequences, that indicates highly specific detection of target RNAs. In conclusion, the FRET-based MB probes are very useful for ISH, providing rapid hybridization, high sensitivity and specificity.

Gene duplication of C-type natriuretic peptide-4 (CNP4) in teleost lineage elicits subfunctionalization of ancestral CNP.

The diversified natriuretic peptide (NP) family, consisting of four CNPs (CNP1-4), ANP, BNP, and VNP, has been identified in the eel. Here, we successfully cloned additional cnp genes from the brain of eel (a basal teleost) and zebrafish (a later branching teleost). The genes were identified as paralogues of cnp4 generated by the third round of whole genome duplication (3R) in the teleost lineage, thereby being named eel cnp4b and zebrafish cnp4-like, respectively. To examine the histological patterns of their expressions, we employed a newly developed in situ hybridization (ISH) chain reaction using short hairpin DNAs, in addition to conventional ISH. Eel cnp4b was expressed in the medulla oblongata, while mRNAs of eel cnp4a (former cnp4) were localized in the preoptic area. In the zebrafish brain, cnp4-like mRNA was undetectable, while the known cnp4 was expressed in both the preoptic area and medulla oblongata. Together with the different mRNA distribution of cnp4a and cnp4b in eel peripheral tissues determined by RT-PCR and ISH, it is suggested that subfunctionalization by duplicated cnp4s in ancestral teleosts has been retained only in basal teleosts. Intriguingly, cnp4b-expressing neurons in the glossopharyngeal-vagal motor complex of the medulla oblongata were co-localized with choline acetyltransferase, suggesting an involvement of Cnp4b in swallowing and respiration functions that are modulated by the vagus. Since teleost Cnp4 is an ortholog of mammalian CNP, the identified localization of teleost Cnp4 will contribute to future studies aimed at deciphering the physiological functions of CNP.

Abstract 5237: High-throughput slide preparation for spatially-resolved, multiplexed quantification of protein or mRNA in tumor tissues with automation of GeoMx™ DSP Assays on Leica Biosystems BOND RX

Abstract Characterization of the spatial distribution and abundance of proteins and mRNAs with morphological context within tissues enables a better understanding of biological systems in many research areas, including immunology and oncology. The GeoMxTM Digital Spatial Profiler (DSP) enables the highly-multiplexed detection of mRNA or protein targets within distinct regions of tissues, including FFPE. This assay utilizes in situ hybridization (ISH) probes or antibodies linked to indexing oligo barcodes via a photo-cleavable linker. The GeoMx DSP enables profiling of RNA or protein targets by releasing and collecting these barcodes from user-defined regions-of-interest. Manual preparation of FFPE tissue uses conventional immuno-fluorescence (IF) and ISH reagents, however it requires greater than two hours of hands-on-time over 2 days. Protocols have been developed to enable the automation of these tissue preparation protocols using the Leica Biosystems BOND RX and BOND RXm Fully Automated Research Stainers. Here we describe protocols for the semi-automated preparation of GeoMx RNA and protein assays as well as the fully-automated preparation of GeoMx RNA assays. These protocols reduce the hands-on time of performing the assay to 72 minutes and 35 minutes for the semi- and fully-automated protocols, respectively. Signal-to-noise ratios (SNR) are highly concordant between serial sections processed manually and processed on the Leica BOND RXm using the GeoMx Immune Cell Profiling Panel for protein (58-plex) and GeoMx Immune Pathways Panel for RNA (84-plex). Furthermore, automated assays show high concordance between the BOND RX and BOND RXm instruments. Lastly, we demonstrate the use of the fully automated slide preparation protocol with the GeoMx Cancer Transcriptome Atlas, a panel that targets >1,600 key cancer mRNAs that are read out by next-generation sequencing. GeoMx Assays are for RESEARCH USE ONLY. Not for use in diagnostic procedures. Citation Format: Daniel R. Zollinger, Sarah Ketting, Kristina Sorg, Oliver Appelbe, Danielle Aaker, Damian Cockfield, Chris Merritt, Joseph M. Beechem. High-throughput slide preparation for spatially-resolved, multiplexed quantification of protein or mRNA in tumor tissues with automation of GeoMx™ DSP Assays on Leica Biosystems BOND RX [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5237.

Abstract 3953: Visualization of treatment resistant subclones in colorectal cancer by mutation specific RNA in situ hybridization

Abstract Introduction: Tumor heterogeneity is a major underlying cause of therapy resistance and disease recurrence. Recent evidence shows that resistant clones are nearly always pre-existing in a cancer, but are present at low frequencies. Moreover, genetic analysis of clonal composition has been largely at the level of ‘bulk’ sequencing, which does not inform of the arrangement of tumor subclones in space. This spatial information contains crucial clues as to the mechanisms of subclone emergence. To address this gap in our knowledge, we have used Basescope™, a novel RNA in situ hybridization (ISH) technology to detect somatic single nucleotide variants (SNVs) within key treatment-resistance genes in sections of archival formalin fixed paraffin embedded (FFPE) colorectal cancer (CRC) and adenoma (CRA) samples. Experimental procedures: Basescope™ probes were designed against common CRC mutations in KRAS, BRAF and PIK3CA, genes that are all implicated in modulating targeted therapy response, and also for the corresponding wildtype genes. Publically available cell lines containing the mutations of interest were used to confirm the sensitivity and specificity of the Basescope™ probes. We then performed RNA-ISH on a series of FFPE colorectal tumors (n=24) using novel Basescope™ technology. The presence of detected mutations was confirmed by DNA sequencing. In additional analyses we multiplexed Basescope™ technology with conventional immunohistochemistry and DNA ISH to study concurrent DNA- and protein-level alterations. Stained sections containing subclonal mutations were digitized and used to create 2D maps depicting the precise location of mutant and wild-type subclones. These were then used to test and refine mathematical models of subclone expansion. Summary of novel results: Our data reports the application of Basescope™ technology for the in situ detection of SNVs in human CRC. We have used custom designed Basescope™ probes to visualize common mutations, and mapped the spatial arrangement of these mutant subclones. We found mutant subclones in 10 samples analyzed, and noted that these subclones appeared generally contiguous in space. Mathematical modeling of these data reveals the patterns of clonal selection and expansion within CRCs. Conclusions: This study is the first to use RNA-ISH sensitive to specific somatic SNVs to visualize the subclonal architecture of CRC, specifically of clones involved in treatment failure. Our results are suggestive of a complex clonal architecture within this common cancer type. Furthermore, we have confidently detected mutant subclones comprising less than 5% of the total lesion - these would not be reliably detected by standard methodology, and would likely be responsible for the failure of targeted therapy. More generally, we envisage that Basescope™ technology will be a useful tool in basic research, and furthermore is readily transferrable to clinical applications. Citation Format: Ann-Marie Baker, Mindy Wang, Xiao-Jun Ma, Courtney Anderson, Weini Huang, Enric Domingo, Annabelle Lewis, John Bridgewater, Marnix Jansen, Nicholas A. Wright, Manuel Rodriguez-Justo, Emily Park, Ian Tomlinson, Trevor A. Graham. Visualization of treatment resistant subclones in colorectal cancer by mutation specific RNA in situ hybridization [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3953. doi:10.1158/1538-7445.AM2017-3953

In situ DIG-labeling, loop-mediated DNA Amplification (ISDL) for highly sensitive detection of infectious hypodermal and hematopoietic necrosis virus (IHHNV)

Infectious hypodermal and hematopoietic necrosis virus (IHHNV) is also known as Penaeus stylirostris densovirus (PstDNV). Since it is listed as a reportable crustacean disease by the World Organization for Animal Health (OIE), many countries require testing for IHHNV in shrimp stocks imported for aquaculture, necessitating rapid and highly sensitive detection methods to guarantee and maintain absence of IHHNV in traded stocks. Here we describe a new, highly sensitive method for detection of IHHNV in shrimp tissues. It involves in situ loop-mediated DNA amplification (IS-LAMP) employing digoxigenin-11-dUTP (DIG-dUTP) as part of the deoxynucleotide triphosphate (dNTP) mix. This resulted in DIG-labeling of the DNA amplicons (i.e., in situ, DIG-labeling LAMP or ISDL) allowing direct in situ, immuno-histochemical detection of IHHNV using an anti-DIG antibody conjugated with alkaline phosphatase, and eliminating the lengthy hybridization step of conventional ISH. The target region for the method is at the 3'end of the IHHNV genome that has been reported least likely to give rise to endogenous viral elements (EVE) in the shrimp genome. When compared to the results for IHHN detection by conventional in situ hybridization (ISH) using a DIG-labeled oligonucleotide probe, signals from the ISDL method were stronger and also gave positive results with some tissues unreactive by the conventional ISH method. Additional comparison of the two methods revealed that the proteinase-K digestion step needed for normal ISH was unnecessary for ISDL. This further shortened the assay time and improved the tissue integrity necessary to clearly indicate the location of positive hybridization signals. The ISDL method gave no cross- reactions with tissues of shrimp infected with other common pathogens, and the total time needed to carry out ISDL was one-third of that needed for conventional ISH. Statement of relevanceThis work describes an in situ, DIG-labeling LAMP (ISDL) method, as a new, highly sensitive method for detection of IHHNV in shrimp tissues. The developed method can be used as a confirmatory test carried out with tissue sections to confirm the results from molecular assays, especially when immune-histochemical methods are not available to do so. ISDL is especially important for molecular detection from a new or unexpected location and for molecular detection in newly suspected carriers to determine whether they are actually infected or just mechanical carriers.

The Clinical Significance of Detecting Bacterial DNA by in situ Hybridization Method in Patients With Decompensated Liver Cirrhosis

Introduction: Patients with decompensated cirrhosis often suffer from various complications such as spontaneous bacterial peritonitis (SBP). However, it is difficult to diagnose SBP or bacteremia because bacteria in ascites or blood cannot be detected accurately by conventional culture method. It has been showed that the method using in situ hybridization (ISH) for detecting the gene of bacteria phagocytized by neutrophil in ascites is possibly useful to diagnose SBP within one day (Enomoto et al. J Hepatology 2012). It is thought that SBP is developed following bacteremia after bacterial translocation from the intestinal tract. Therefore we used the ISH method for blood samples taken from patients with decompensated liver cirrhosis and evaluated the significance of bacterial detection. Methods: Samples of peripheral blood and ascites were collected from 35 patients with ascites caused by liver cirrhosis. Blood samples were examined for bacteria using both conventional blood culture and ISH method. Samples of ascites were also evaluated by conventional culture simultaneously. The ISH method we used was the kit from Fuso Pharmaceuticals (Tokyo, Japan). Results: Eight of 35 patients were diagnosed with SBP. Six of the 8 patients showed positive results using the ISH method while bacteria were detected inonly one case byblood culture and one case by ascites culture. In 27 patients without SBP, 15 patients showed positive results using the ISH method while bacteria were detected in 4 cases by blood culture. The differences between 21 positive and 14 negative results by the ISH method were significant in presence of fever (16 / 5, p < 0.05) and decreased serum albumin levels (2.3 / 2.7, p < 0.05). However, there was no significant difference between administration of antibiotics, C-reaction protein level, and the presence of hepatocellular carcinoma. Notably, no patient who had a positive blood culture had a negative ISH result. Conclusion: The ISH method resulted in a higher positive rate of bacterial detection than culture in patients with decompensated cirrhosis. These results might implicate that “bacterial translocation,” which cannot be proved by conventional culture methods, really occurs. Therefore, it would be better for these patients with positive ISH results to be treated immediately. In patients with decompensated cirrhosis, the ISH method can be helpful for rapid diagnosis and early management of bacteremia and SBP.

In Situ Hybridization in Human and Rodent Tissue by the Use of a New and Simplified Method

In situ hybridization (ISH) is a method that detects and localizes DNA or RNA in morphologically preserved tissue and cell preparations. The method is based on the principle that DNA or RNA will undergo hydrogen binding to complimentary sequences. Selective probes are labeled and used in order to detect specific sequences in tissues or cell preparations. Even though the method has improved over the past decades, there are still issues with sensitivity and specificity. The protocols are nonstandardized, and often time consuming due to multiple steps. In this paper, we have used a new and commercially available ISH kit for the detection of mRNA in formalin-fixed paraffin-embedded tissue. We have used both human and Mongolian gerbil tissue, and we evaluated mRNA expression of the neuroendocrine markers chromogranin A and histidine decarboxylase in both normal tissue and poorly differentiated tumor. In our experience, this method offers excellent sensitivity and specificity. The protocol is more standardized, and our results have been consistent. It is also less time consuming than conventional ISH protocols.

Use of quantum dots to detect human papillomavirus in oral squamous cell carcinoma

To examine the association of oral squamous cell carcinoma with human papillomavirus (HPV) using quantum dots (QD) in situ hybridization (ISH). Expression of HPV16/18 was analyzed in a representative collection of 21 oral squamous cell carcinomas by tissue microarrays. The presence of HPV16/18 high risk was detected by applying QDISH which is compared with conventional ISH. Seven cases out of 21 (33.3%) were positive for QDISH while 1 out of 21 (4.8%) was positive for ISH, although all of HPV DNA were localized in the nuclei in the spinous and basal cell layer of the epithelium. The difference between these two methods was significant (P < 0.05). These results demonstrate that the QD might be an efficient method for determination of HPV infection and HPV-associated oral squamous cell carcinoma.

EnVision+, a new dextran polymer-based signal enhancement technique for in situ hybridization (ISH).

Seventy paraffin-embedded cervical biopsy specimens and condylomata were tested for the presence of human papillomavirus (HPV) by conventional in situ hybridization (ISH) and ISH with subsequent signal amplification. Signal amplification was performed either by a commercial biotinyl-tyramide-based detection system [GenPoint (GP)] or by the novel two-layer dextran polymer visualization system EnVision+ (EV), in which both EV-horseradish peroxidase (EV-HRP) and EV-alkaline phosphatase (EV-AP) were applied. We could demonstrate for the first time, that EV in combination with preceding ISH results in a considerable increase in signal intensity and sensitivity without loss of specificity compared to conventional ISH. Compared to GP, EV revealed a somewhat lower sensitivity, as measured by determination of the integrated optical density (IOD) of the positively stained cells. However, EV is easier to perform, requires a shorter assay time, and does not raise the background problems that may be encountered with biotinyl-tyramide-based amplification systems. (J Histochem Cytochem 49:1067-1071, 2001)

Sensitive nonradioactive detection of mRNA in tissue sections: novel application of the whole-mount in situ hybridization protocol.

The relative insensitivity of nonradioactive mRNA detection in tissue sections compared to the sensitive nonradioactive detection of single-copy DNA sequences in chromosome spreads, or of mRNA sequences in whole-mount samples, has remained a puzzling issue. Because of the biological significance of sensitive in situ mRNA detection in conjunction with high spatial resolution, we developed a nonradioactive in situ hybridization (ISH) protocol for detection of mRNA sequences in sections. The procedure is essentially based on the whole-mount ISH procedure and is at least equally sensitive. Increase of the hybridization temperature to 70C while maintaining stringency of hybridization by adaptation of the salt concentration significantly improved the sensitivity and made the procedure more sensitive than the conventional radioactive procedure. Thicker sections, which were no improvement using conventional radioactive ISH protocols, further enhanced signal. Higher hybridization temperatures apparently permit better tissue penetration of the probe. Application of this highly reliable protocol permitted the identification and localization of the cells in the developing heart that express low-abundance mRNAs of different members of the Iroquois homeobox gene family that are supposedly involved in cardiac patterning. The radioactive ISH procedure scarcely permitted detection of these sequences, underscoring the value of this novel method.

Qualitative and Quantitative Assessment of Modified In Situ Reverse Transcription-Polymerase Chain Reaction (In Situ RT-PCR) Method.

The in situ reverse transcription-polymerase chain reaction (in situ RT-PCR) method has been used to detect low levels of expression of mRNA in cells and tissues. We applied a newly developed in situ RT-PCR to cells and quantitatively compared the sensitivity of the in situ RT-PCR with that of conventional in situ hybridization (ISH). Human tumor cell lines with either high, moderate, low or no expression of IL-6 mRNA as determined by in vitro competitive RT-PCR were used. In situ RT-PCR was performed using Thermus thermophilus DNA polymerase, special primer sets to form high molecular weight concatemers and an in situ digoxigenin (DIG) direct labeling technique. Conventional ISH was performed using DIG-labeled cRNA probe. Specific signals of IL-6 mRNA were observed in the cytoplasm of positive cells by both in situ RT-PCR and ISH. In situ RT-PCR was more than 100-fold more sensitive than ISH. The specificity of in situ RT-PCR was confirmed by appropriate control tests. The data indicated that the sensitivity of our in situ RT-PCR applied to culture cells was significantly higher than that of ISH, and that the technique retained high specificity.

In situ hybridization detection of low copy nucleic acid sequences using catalyzed reporter deposition and its usefulness in clinical human papillomavirus typing.

In situ hybridization (ISH) detection of low copy DNA and RNA sequences using nonisotopic probes has been difficult in the past because of a lack of sensitivity. Several techniques, such as ISH with radioisotopic-labeled probes, in situ polymerase chain reaction, in situ reverse transcription polymerase chain reaction, self-sustained sequence replication, and chemiluminescence, have allowed increased sensitivity but have required specialized and often expensive equipment, lengthy protocols, and in the case of radioactive probes, there has been an associated increased health risk. Catalyzed reporter deposition (CARD) combined with ISH (CARD-ISH) increases the signal-generating potential of labeled hybridized probes and allows the detection of low copy sequences of nucleic acids in formalin-fixed, paraffin-embedded tissue sections. To determine the sensitivity of CARD-ISH to detect nucleic acids in routinely processed specimens, we analyzed the detection of HPV 16 and 18 infection in formalin-fixed, paraffin-embedded sections of cultured cell lines, including CaSki cells with 400-600 copies of HPV 16, HeLa 229 cells with 10-50 copies of HPV 18, and SiHa cells with 1-2 copies of HPV 16 using a conventional ISH method and by CARD-ISH. In addition, 20 cases of clinical specimens previously analyzed for HPV 6, 11, 16, 18, 31, 33, and 51 with the Enzo PathoGene kit (Enzo Diagnostics, Inc., Farmingdale, NY, U.S.A.) were reexamined with the CARD-ISH method. The CARD-ISH system detected one to two copies of HPV 16 in the SiHa cells whereas the conventional ISH method did not. Both methods detected HPV 16 and 18 in CaSki and HeLa 229 cells, respectively. Three clinical cases that were previously negative and two weakly positive cases of HPV infection were all strongly positive with the CARD-ISH system, a 25% increase in the detection of positive cases by CARD-ISH. We also showed for the first time that a cocktail of six biotinylated oligonucleotide probes was capable of detecting one to two copies of HPV 16 in SiHa cells. These results show that the CARD-ISH method increases the sensitivity of nonisotopic ISH to the level of detecting one to two copies of HPV DNA in formalin-fixed, paraffin-embedded tissue sections using biotinylated cDNA or oligonucleotide probes.

Detection of Human Papillomavirus in Warty Carcinoma of the Uterine Cervix: Comparison of Immunohistochemistry,In Situ Hybridization and In Situ Polymerase Chain Reaction Methods

Warty carcinoma of the uterine cervix is a very rare specific variant of invasive squamous cell carcinoma, usually described as a hybrid feature of condyloma with invasive squamous cell carcinoma. Besides having the koilocytes and maturation of squamous epithelium, there is unequivocal stromal invasion. The feathery surface seems to be characteristic of warty carcinoma, differentiating it from condylomata acuminata or verrucous carcinoma. Using in situ polymerase chain reaction (IS-PCR) and in situ hybridization (ISH) as well as an immunohistochemical technique (IHC), we determined the amplification and expression of several human papilloma virus (HPV) types (6, 11, 33, 16 and 18) in nine warty carcinomas of the uterine cervix. We found amplified HPV predominantly in the nuclei of the feathery surface in all cases only when IS-PCR was applied, while it was detected only in five (55.6%) or six cases (66.7%) by conventional IHC or ISH, respectively. We found multiple types in the same lesion in six cases (66.7%) by IS-PCR, in comparison with ISH which detected a lower incidence (22.2%). This finding of coinfection is more consistent with that seen in low-grade squamous intraepithelial lesions (LSILs) of the uterine cervix than in high SIL. It is important to be aware of these distinct lesions in postmenopausal women with their characteristic feathery and thin surface, as well as a hybrid form of exophytic condyloma and stromal invasion, and frequent coinfection of multiple different HPVs as a type of LSILs.

Detection and typing of human papillomavirus in biopsy and cytological specimens by polymerase chain reaction and restriction enzyme analysis: a method suitable for semiautomation.

Screening for high-risk human papillomavirus (HPV) types allows the detection of women at a high risk of cervical squamous carcinomas, thereby defining a subset of patients targeted for more intensive screening and follow-up. Thirty-four cervical biopsy specimens and isolated cells from cervical smears of normal women or women diagnosed with high-grade intraepithelial lesion (HGSIL) were screened for the presence of HPV by in situ hybridization (ISH) and/or by polymerase chain reaction (PCR). The exact HPV type was determined using a novel restriction typing method. The detection of HPV was facilitated greatly by the use of a PCR-enzyme-linked immunosorbent assay (ELISA)-based method. HPV was detected by PCR in 32% of the biopsy specimens, whereas only 23% had a positive staining by ISH. In one case, a double infection was detected by ISH as well as by PCR. In two cases, the presence of HPV was detected by both methods but the exact type was different. Analyzing cells isolated from cervical smears by the PCR-ELISA technique or by PCR followed by agarose gel electrophoresis, HPV was detected only in patients with HGSIL and not in the control group. The PCR system is more sensitive than conventional ISH, and the PCR-ELISA system presented in this study is efficient in screening large series of cytological samples. Furthermore, this system allows exact HPV typing on the microtiter plate. These innovations may allow the application of HPV detection and typing as a routine screening method to identify patients with a high risk of developing cervical neoplasia.

Detection of human papillomavirus by in situ polymerase chain reaction in paraffin-embedded cervical biopsies

The efficiency of the in situ polymerase chain reaction (PCR) for the detection of human papillomavirus (HPV) DNA sequences in 20 cervical biopsies fixed with buffered formalin, paraffin-embedded and revealed negative by conventional in situ hybridization (ISH) has been investigated. The biopsies were classified histologically into condylomata acuminata without dysplasia, cervical intraepithelial neoplasia and carcinoma in situ. Amplified HPV DNA was performed after an optimal proteolytic digestion using one pair of consensus oligonucleotide primers located in the L1 ORF of HPV 6 and ISH was carried out after the PCR assay with a cocktail of biotinylated HPV probes. Viral DNA was detected in 100% of high grade squamous intraepithelial lesions (SIL) and in 50 to 60% of low grade SIL. The high sensitivity of the in situ PCR applicable to paraffin-embedded archival biopsies facilitated the detection of cells poorly reactive by conventional ISH. In situ PCR appeared clearly an efficient tool to investigate HPV infection in tissue sections.

Ontogeny of glucocorticoid and D2 receptors in the rat pituitary: an in situ hybridization study

The expression of glucocorticoid and D2 dopamine receptors (GR and D2R) during rat pituitary ontogenesis was studied by in situ hybridization (ISH). On early stages, E13–E14, a weak specific signal for GR mRNA was obvious in the whole Rathke's pouch (RP) whereas subsequently, from E17–E18, strong labelling was restricted to the anterior lobe (AL) and the neural lobe (NL). At the same time, D2R mRNAs appeared in the intermediate lobe (IL) and the long isoform of the D2R (D2R 444) was detectable with specific probes. On the postnatal stages, until adult, GR mRNA, if present, was always undetectable in the IL using the conventional ISH technique. These data indicate a possible early regulation of POMC gene expression by glucocorticoid in corticotrophic cells of the AL and by dopamine in the melanotrophic cells of the IL. The possibility of a negative regulation of GR mRNA by dopamine (DA) in the IL as soon as E17 is discussed.