In silico cloning of mouse Muc5b gene and upregulation of its expression in mouse asthma model.

Using a BLAST-searching approach, we identified a mouse expressed sequence tag (EST) clone (AA038672) showing great similarity to the 3' end of the human MUC5B gene. The clone was named "3pmmuc5b-1" after complete nucleotide sequencing (Genbank Accession, AF369933). A subsequent search of the mouse genome database with the 3pmmuc5b-1 sequence identified two overlapping genomic clones (AC020817 and AC020794) that contained the sequence of both 3pmmuc5b-1 and the mouse Muc5ac gene. Like their human homologs, the genomic order of the mouse Muc genes is 5'-Muc5ac-Muc5b-3'. These results suggest that the newly identified EST clone, 3pmmuc5b-1, is part of the 3' portion of the mouse Muc5b gene. In situ hybridization demonstrated that this putative mouse Muc5b message was expressed in a restricted manner in the sublingual gland region of the tongue and the submucosal gland region of the mouse trachea in a normal animal. However, the gene expression was greatly enhanced in airway surface epithelium and the submucosal gland region in ovalbumin-induced asthmatic mice. These results were consistent with previous studies of human airway tissues. We therefore conclude that this newly cloned mouse Muc5b gene could be used as a marker for studying aberrant mucin gene expression in mouse models of various airway diseases.