Quantitation of globin mRNA in individual human erythroblasts by in situ hybridization

Chromatin texture changes related to proliferation and maturation in erythrocytes

Erythroid cell types were quantitatively assessed on the basis of the analysis of their nuclear images after Feulgen and Heidenhain blue counterstaining. An original nonsupervised classification method, developed in our laboratory, was applied to cell cycle analysis. Results obtained suggest that, in the four proliferative generation cycles, which concur with the successive morphological stages, there is a sequential flow of cells from one morphological stage to the next by cell cycling. We show that the chromatin pattern alone made it possible to set up a metric of the whole differentiation process occurring in the normal human erythroblastic lineage in which proliferating events occur.

In situ cDNA:mRNA hybridization: development of a technique to measure mRNA levels in individual cells

In this article we have described our protocol for in situ cDNA:mRNA hybridization and a variety of methodological considerations we have entertained to optimize the procedure. It should be stressed that each different system will have its own special characteristics and require optimization to obtain maximal and reproducible signals. We believe that by following a methodological logic as outlined here, researchers should be able to establish the in situ cDNA:mRNA hybridization protocol with their probes and tissue systems.

Vasopressin mRNA in situ hybridization: localization and regulation studied with oligonucleotide cDNA probes in normal and Brattleboro rat hypothalamus

Hybridizable vasopressin mRNA may be quantitatively localized in situ in sections from rat hypothalamus. Radiolabeled oligonucleotide cDNA probes, synthesized by chemical and enzymatic means, provide strong hybridization in zones known to contain vasopressin cell bodies. Multiple single-stranded 32P-, 35S-, or 3H-labeled oligonucleotides demonstrate localized hybridization that increases as probes are lengthened from 8 to 75 bases. Competition studies, RNase experiments, anatomic localization, and use of multiple probes all support hybridization specificity. An approximate doubling of hybridizable mRNA in both supraoptic and paraventricular nuclei can be detected with dehydration of the animals. Hybridizable mRNA densities are virtually normal in hypothalamic nuclei of Brattleboro rats given free access to water. These methods can provide insight into regional mRNA dynamics and may reflect functional activity of peptidergic neurons.

Correlation between protein synthesis rate and nuclear morphology of human erythroblasts as determined by quantitative autoradiography and high-resolution image analysis

Human erythropoiesis is an appropriate model for analyzing correlations between functional activity of cells during maturation and nuclear morphology as determined by high-resolution image analysis. In a previous study a relationship had been found between nuclear condensation and the proliferative activity of the cells. This present study analyzed the correlation between nuclear morphology and the protein synthesis rate. The latter was assayed by measuring the 14C-1-leucine incorporation rate utilizing the technique of quantitative 14C-autoradiography. The labeled cells were first classified according to conventional cytological criteria into four groups of increasing maturity. Following grain counting the nuclei were Feulgen-stained, and after removal of the silver grains, the local nuclear optical densities were evaluated by scanning. There was a nonlinear relationship between the protein synthesis rate and features representing the degree of chromatin condensation. This nonlinearity was explained by the mediator function of RNA, predominantly mRNA. The amount of protein produced at a given time depends on the transcriptional activity of the chromatin, the frequency of mitotic divisions partitioning the mRNA, and the half-life of the mRNA. It was concluded that the chromatin texture of erythroblasts reflects three different metabolic activities: the rate of DNA strand duplication, the transcriptional activity for structural proteins enabling a cell to grow and cycle, and for functional proteins, particularly hemoglobin. Since these three activities appear to be synchronized, it is understandable that functional as well as textural features can be used to perform a supervised classification by means of multivariate analysis. Application of the five most significant features allowed a consistent classification of the erythroblasts into the various cytological compartments in 76.7% of all cases, while the classification error of the observer amounted to 13.7%.

Identification of the messenger (m) RNA coding for the constant fragment (c mu) of the heavy chain with cloned DNA in single cells by in situ hybridization

Cells from a normal donor, a B-CLL and a T-ALL were labeled with an FITC conjugated rabbit antihuman IgM and hybridized with a rhodamine-conjugated cloned DNA coding for the c mu segment. The cells were measured simultaneously by immunofluorimetry for their surface content of IgM and their amount of m-RNA hybridizing with the cloned DNA. Thus it was possible to compare the transcription of the gene coding for the immunoglobulin mu chain and the expression of IgM in individual cells. It could be shown that besides the immunoglobulin mu containing B-cells, which were expected to contain the respective m-RNA, cells were found which did not express IgM but which were still positive for the m-RNA.