Use of halogenated precursors to define a transcription time window after treatment with hypometabolizing molecules

Physical Training Chronically Stimulates the Motor Neuron Cell Nucleus in the Ts65Dn Mouse, a Model of Down Syndrome

Down syndrome (DS) is a genetically-based disease based on the trisomy of chromosome 21 (Hsa21). DS is characterized by intellectual disability in association with several pathological traits among which early aging and altered motor coordination are prominent. Physical training or passive exercise were found to be useful in counteracting motor impairment in DS subjects. In this study we used the Ts65Dn mouse, a widely accepted animal model of DS, to investigate the ultrastructural architecture of the medullary motor neuron cell nucleus taken as marker of the cell functional state. Using transmission electron microscopy, ultrastructural morphometry, and immunocytochemistry we carried out a detailed investigation of possible trisomy-related alteration(s) of nuclear constituents, which are known to vary their amount and distribution as a function of nuclear activity, as well as the effect of adapted physical training upon them. Results demonstrated that trisomy per se affects nuclear constituents to a limited extent; however, adapted physical training is able to chronically stimulate pre-mRNA transcription and processing activity in motor neuron nuclei of trisomic mice, although to a lesser extent than in their euploid mates. These findings are a step towards understanding the mechanisms underlying the positive effect of physical activity in DS.

Timing of Cytosine Methylation on Newly Synthesized RNA by Electron Microscopy

Increasing evidence demonstrates that RNA nucleotides undergo epigenetic modifications, such as methylation on cytosine. Although the presence of modified bases on mRNA has been proven, their molecular significance is largely undefined. We describe here a methodology to dissect the timing of modification of cytosine to 5-methylcytosine (5mC or m⁵C) in relation to RNA elongation and processing. To do this we use chlorouridine and iodouridine, two synthetically modified nucleotide bases which can be recognized by RNA polymerase II and incorporated into nascent RNA. These modified bases are added to a cell culture for defined intervals of time, and then immunocytochemical staining using antibodies against the modified nucleotides is carried out. This procedure allows us to identify the range of time in which 5mC is produced in nascent mRNA. This method provides the ultra-resolution of electron microscopy and allows following nascent RNA molecules during their elongation.

The Histochemistry and Cell Biology pandect: the year 2014 in review

This review encompasses a brief synopsis of the articles published in 2014 in Histochemistry and Cell Biology. Out of the total of 12 issues published in 2014, two special issues were devoted to "Single-Molecule Super-Resolution Microscopy." The present review is divided into 11 categories, providing an easy format for readers to quickly peruse topics of particular interest to them.