Structural analysis of resting mouse platelets by 3D-EM reveals an unexpected variation in α-granule shape

Irina Pokrovskaya, Michael Tobin, Rohan Desai, Maria A. Aronova, Jeffrey A. Kamykowski, Guofeng Zhang, Smita Joshi, Sidney W. Whiteheart, Richard D. Leapman, Brian Storrie

Research output: Contribution to journalArticlepeer-review

4 Scopus citations

Abstract

Mice and mouse platelets are major experimental models for hemostasis and thrombosis; however, important physiological data from this model has received little to no quantitative, 3D ultrastructural analysis. We used state-of-the-art, serial block imaging scanning electron microscopy (SBF-SEM, nominal Z-step size was 35 nm) to image resting platelets from C57BL/6 mice. α-Granules were identified morphologically and rendered in 3D space. The quantitative analysis revealed that mouse α-granules typically had a variable, elongated, rod shape, different from the round/ovoid shape of human α–granules. This variation in length was confirmed qualitatively by higher-resolution, focused ion beam (FIB) SEM at a nominal 5 nm Z-step size. The unexpected α-granule shape raises novel questions regarding α-granule biogenesis and dynamics. Does the variation arise at the level of the megakaryocyte and α-granule biogenesis or from differences in α-granule dynamics and organelle fusion/fission events within circulating platelets? Further quantitative analysis revealed that the two major organelles in circulating platelets, α-granules and mitochondria, displayed a stronger linear relationship between organelle number/volume and platelet size, i.e., a scaling in number and volume to platelet size, than found in human platelets suggestive of a tighter mechanistic regulation of their inclusion during platelet biogenesis. In conclusion, the overall spatial arrangement of organelles within mouse platelets was similar to that of resting human platelets, with mouse α-granules clustered closely together with little space for interdigitation of other organelles.

Original languageEnglish
Pages (from-to)608-617
Number of pages10
JournalPlatelets
Volume32
Issue number5
DOIs
StatePublished - 2021

Bibliographical note

Funding Information:
The Storrie laboratory was supported in part by National Institutes of Health grants [R01 HL119393 and R56 HL119393]. The Whiteheart laboratory was supported in part by National Institutes of Health grants [HL56652 and HL138179], American Heart Association grant [AHA16GRNT27620001], and a Veterans Affairs Merit Award to SWW and an American Heart Association predoctoral grant [AHA15PRE25550020] to SJ. The Leapman laboratory was supported by the intramural program at NIBIB at the National Institutes of Health, Bethesda, MD The authors thank Carl Zeiss, Inc (Thornwood, NY) for performing the FIB-SEM imaging and Joel Mancusco of Zeiss for arranging this.

Publisher Copyright:
© 2020 Taylor & Francis Group, LLC.

Keywords

  • 3D SBF-SEM
  • electron microscopy
  • mouse
  • organelles
  • platelets
  • α-granules

ASJC Scopus subject areas

  • Hematology

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