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Nuclear RNA is extruded from apoptotic cells
M Biggiogera1, M G Bottone, C Pellicciari
1Dipartimento di Biologia Animale, Laboratorio di Istologia, and Centro di Studio per l'Istochimica del CNR, University of Pavia, Pavia, Italy.
Summary
Apoptotic thymocytes extrude ribonucleoprotein (RNP) aggregates containing significant amounts of RNA. This suggests RNA loss during apoptosis is due to extrusion, not degradation, potentially linking to autoimmune diseases.
Area of Science:
- Cell Biology
- Molecular Biology
- Immunology
Background:
- Spontaneous apoptosis in thymocytes involves the extrusion of ribonucleoproteins (RNPs).
- The fate and composition of these extruded RNPs, particularly their RNA content, remain incompletely understood.
Purpose of the Study:
- To determine if ribonucleoprotein (RNP) aggregates extruded during thymocyte apoptosis retain a significant amount of RNA.
- To characterize the composition of these extruded RNP aggregates.
Main Methods:
- Specific cytochemical techniques were employed to detect RNA within RNP aggregates in apoptotic thymocytes.
- Analysis focused on the composition of heterogeneous ectopic RNP-derived structures (HERDS).
Main Results:
- Cytochemical analysis confirmed the presence of detectable RNA within nuclear RNP aggregates extruded into the cytoplasm of apoptotic thymocytes.
- These structures, termed HERDS, are composed of perichromatin fibrils, interchromatin granules, perichromatin granules, and nucleolar material, containing mRNA, snRNA, and rRNA.
- No DNA-containing aggregates were observed in the cytoplasm of apoptotic thymocytes.
Conclusions:
- The significant RNA content in extruded HERDS suggests that RNA loss during apoptosis is primarily due to cellular extrusion rather than RNase degradation.
- The release of RNA-containing HERDS may contribute to the presence of autoantibodies in systemic autoimmune diseases.