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An Intermittent Cytochemist - PubMed

An Intermittent Cytochemist

Thoru Pederson. J Histochem Cytochem. 2023 Sep.

Abstract

I wanted to be a cytochemist but encountered detours and then, in some of my work, became one of a different kind than classically defined. I recount this here to discourage young scientists from regarding cytochemistry as something that peaked in the past, but rather to be viewed as an entirely new form of the discipline, and so rich with opportunities. (J Histochem Cytochem 71: 475-480, 2023).

Keywords: career; cytochemistry then and now.

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Conflict of interest statement

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Figures

Figure 1.
Figure 1.

Rapid localization of RNase P RNA in the nucleolus. RNase P RNA was transcribed in vitro, coupled with rhodamine, microneedle injected together with fluorescein-labeled dextran into the nucleus of a normal rat kidney (NRK) cell and imaged 4 min later. This rapid localization of a known nucleolar RNA reinforced our belief that “fluorescent RNA cytochemistry” would open doors to investigating the intranuclear dynamics of various other RNAs.,,– Scale bar = 5 µm. Reproduced from Jacobson et al. by permission of the Company of Biologists.

Figure 2.
Figure 2.

Tracking nascent ribosomes in the nucleus. Rat L6 myoblasts were exposed for one hr to a set of oligodeoxynucleotides complementary to 28S ribosomal RNA, each of which was conjugated with caged fluorescein. The fluorescein was uncaged at a nucleolus (circle in second panel) and the movement of the nascent 60S ribosomes was tracked at 110 msec, 1.4 sec, 3.6 sec, and 26 sec (next four panels). The 60S ribosomes depart the nucleolus and progressively distribute throughout the nucleoplasm. That many remain in the nucleolus after 26 sec is compatible with the known overall timescale of 60S ribosome synthesis, with the observed departure representing the most mature 60S ribosomes at the time of uncaging. At later time points they began to appear in the cytoplasm (not shown).

Figure 3.
Figure 3.

“CRISPRainbow,” an iteration of our initial genome-labeling methods., The strategy here was to link the guide RNAs (targeting telomeres in this case) with 3 scaffolds consisting of pairs of aptameric RNA sequences specific for attachment of various colored proteins. This binary scheme is not the color combinations we learned as children (e.g., blue + yellow = green) but is enabled by the spectral filters in our microscope, yielding three “primary” colors (blue, green, and red, Panel A) and four “secondary” colors (cyan, yellow, magenta, and white, Panels B and C; I ask readers to forgive me for calling white a color but it was useful to have in our deployment of this system.) In these various dopings the guide RNAs retained their faithful targeting of the target telomeric sequences (Panel B). This was a far stretch from my earliest ideas of becoming a cytochemist. Reproduced from Ma et al. by permission of Nature Springer Publishing Group. Abbreviations: BFP, blue fluorescent protein; GFP, green fluorescent protein; RFP, red fluorescent protein; MCP, bacteriophage MS2 coat protein; PCP, Pseudomonas bacteriophage 7 coat protein; N22, bacteriophage N22; PP7, Pseudomonas phage 7.

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References

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