Related Experiment Videos
Distribution of lysozyme and mucin (MUC2 and MUC3) mRNA in human bronchus
A Dohrman1, T Tsuda, E Escudier
1Department of Anatomy, University of California, San Francisco.
Abstract:
Immunocytochemical studies have shown that gel-forming glycoproteins (mucins) and the bacteriolytic protein lysozyme are selectively expressed in airway mucous and serous cells, respectively. The mechanisms mediating this selectivity are unknown. In this study, we localized mucin and lysozyme mRNA by in situ hybridization to investigate the possibility that phenotype-specific expression of these proteins is controlled at the level of mRNA. Radiolabelled sense and antisense probes were constructed from the human tracheal mucin cDNA, HAM1 (MUC2 gene), the human small intestinal mucin cDNA, SIB139 (MUC3 gene), and the bovine tracheal lysozyme cDNA, Lys 7a. Frozen sections of human bronchus were hybridized with these probes and washed under routine conditions. Autoradiography showed that although lysozyme mRNA was strictly limited to cells expressing lysozyme, mucin mRNA was present both in mucin-expressing and mucin-non-expressing epithelial cells. This suggests that the restriction of lysozyme to serous cells is controlled at the level of mRNA (synthesis and/or degradation), whereas the restriction of mucin to mucous cells is controlled at the level of translation.
Insights
This study investigated the control of mucin and lysozyme expression in airway cells. Lysozyme expression is regulated at the mRNA level, while mucin expression is controlled post-transcriptionally.
Area of Science:
- Cell Biology
- Molecular Biology
- Respiratory System
Background:
- Airway mucous and serous cells selectively express gel-forming glycoproteins (mucins) and the bacteriolytic protein lysozyme.
- The mechanisms underlying this selective protein expression remain unknown.
Purpose of the Study:
- To investigate if phenotype-specific expression of mucins and lysozyme is controlled at the mRNA level.
- To differentiate between transcriptional and post-transcriptional regulation of these proteins.
Main Methods:
- In situ hybridization was used to localize mucin and lysozyme mRNA in human bronchus sections.
- Radiolabelled probes derived from human mucin cDNA (HAM1, SIB139) and bovine lysozyme cDNA (Lys 7a) were employed.
- Autoradiography was used to visualize mRNA distribution.
Main Results:
- Lysozyme mRNA was exclusively found in cells expressing lysozyme.
- Mucin mRNA was detected in both mucin-expressing and mucin-non-expressing epithelial cells.
- This indicates differential mRNA localization and regulation.
Conclusions:
- Lysozyme restriction to serous cells is regulated at the mRNA level (synthesis/degradation).
- Mucin restriction to mucous cells is regulated at the translational level.
- These findings elucidate the distinct regulatory mechanisms for key airway proteins.