Atto 465 Derivative Is a Nuclear Stain with Unique Excitation and Emission Spectra Useful for Multiplex Immunofluorescence Histochemistry

Multiplex immunofluorescence (mIF) is an effective technique for the maximal visualization of multiple target proteins in situ. This powerful tool is mainly limited by the spectral overlap of the currently available synthetic fluorescent dyes. The fluorescence excitation wavelengths ranging between 405 and 488 nm are rarely used in mIF imaging and serve as a logical additional slot for a fluorescent probe. In the present study, we demonstrate that the addition of 2,3,4,5,6-pentafluoroaniline to Atto 465 NHS ester, creating Atto 465-pentafluoroaniline (Atto 465-p), generates a bright nuclear stain in the violet-blue region of the visible spectrum. This allows the 405 nm excitation and emission, classically used for nuclear counterstains, to be used for the detection of another target protein. This increases the flexibility of the mIF panel and, with appropriate staining and microscopy, enables the quantitative analysis of at least six targets in one tissue section. (J Histochem Cytochem XX: XXX–XXX, XXXX)

Transcrptome analysis via photo-isolation chemistry

To gain insights into tissue-specific gene expression in multicellular systems, gene expression profiles are required to be precisely linked with spatial information. Here, we establish a hight-depth spatial transcriptomics method, photo-isolation chemistrty (PIC), which is able to isolate gene expression profiles only from UV-irradiatied region out of whole tissue section. This method performs reverse transcription on tissue sections using photocaged oligo DNAs. After the UV irradiation, the cDNAs in the irradiated regions are allowed to be amplified and sequenced, thereby providing gene expression profiles linked with spatial information.

Towards high spatially resolved microproteomics using expansion microscopy

Expansion microscopy is an emerging approach for morphological examination of biological specimens at nanoscale resolution using conventional optical microscopy. To achieve physical separation of cell structures, tissues are embedded in a swellable polymer and expanded several folds in an isotropic manner. This work shows the development and optimization of physical tissue expansion as a new method for spatially resolved large scale proteomics. Herein, we established a novel method to enlarge the tissue section to be compatible with manual microdissection on regions of interest and to carry out MS-based proteomic analysis. A major issue in the Expansion microscopy is the loss of proteins information during the mechanical homogenization phase due to the use of Proteinase K. For isotropic expansion, different homogenization agents are investigated, both to maximize protein identification and to minimize protein diffusion. Better results are obtained with SDS. From a tissue section enlarge more than 3-fold, we have been able to manually cut out regions of 1mm in size, equivalent to 300µm in their real size. We identified up to 655 proteins from a region corresponding to an average of 940 cells. This approach can be performed easily without any expensive sampling instrument. We demonstrated the compatibility of sample preparation for expansion microscopy and proteomic study in a spatial context.Abstract graphic

Creating virtual H&E images using samples imaged on a commercial CODEX platform

ABSTRACTMultiparametric fluorescence imaging via CODEX allows the simultaneous imaging of many biomarkers in a single tissue section. While the digital fluorescence data thus obtained can provide highly specific characterizations of individual cells and microenvironments, the images obtained are different from those usually interpreted by pathologists (i.e., H&E slides and DAB-stained immunohistochemistry slides). Having the fluorescence data plus co-registered H&E or similar data could facilitate adoption of multiparametric imaging into regular workflows, as well as facilitate the transfer of algorithms and machine learning previous developed around H&E slides. Since commercial CODEX instruments do not produce H&E-like images by themselves, we developed a staining protocol and associated image processing to make “virtual H&E” images that can be incorporated into the CODEX workflow. While there are many ways to achieve virtual H&E images, including use of a fluorescent nuclear stain and tissue autofluorescence to simulate eosin staining, we opted to combine fluorescent nuclear staining (via DAPI) with actual eosin staining. We also output images derived from fluorescent nuclear staining and autofluorescence images for additional evaluation.