A. Dohrman et al., DISTRIBUTION OF LYSOZYME AND MUCIN (MUC2 AND MUC3) MESSENGER-RNA IN HUMAN BRONCHUS, Experimental lung research, 20(4), 1994, pp. 367-380
Immunocytochemical studies have shown that gel-forming glycoproteins (
mucins) and the bacteriolytic protein lysozyme are selectively express
ed in airway mucous and serous cells, respectively. The mechanisms med
iating this selectivity are unknown. In this study, we localized mucin
and lysozyme mRNA by in situ hybridization to investigate the possibi
lity that phenotype-specific expression of these proteins is controlle
d 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. Aut
oradiography showed that although lysozyme mRNA was strictly limited t
o cells expressing lysozyme, mucin mRNA was present both in mucin-expr
essing and mucin-non-expressing epithelial cells. This suggests that t
he restriction of lysozyme to serous cells is controlled at the level
of mRNA (synthesis and/or degradation), whereas the restriction of muc
in to mucous cells is controlled at the level of translation.