Molecular cloning and hormone-dependent expression of rabbit MUC1 in the cervix and uterus

The microenvironment of the endocervix is regulated by secretory (> 10-15 x 10(6) Da) and cell-surface (less than or equal to 1 x 10(6) Da) mucins. A survey with antisense and sense (control) oligonucleotides for eight epithelial mucin genes revealed that only MUC1, an anti-adhesive protein believed to modulate immune function and the only transmembrane mucin for which molecular probes exist, is expressed in the rabbit cervix. pMUC7, a 500-base pair cDNA probe to the tandem repeat domain of human MUC1, was used to clone the cDNA for the rabbit homologue. Although the GC-rich tandem repeat of rabbit Muc1 had only 40% sequence identity with its human counterpart, its transmembrane domain and cytoplasmic tail maintained 93% sequence identity with the same regions of human MUC1. Detection of restriction length polymorphisms confirmed the Lagomorpha Muc1 gene, like the human, is polymorphic. Temporal expression of Muc1 transcripts (2.4 kilobases) correlated closely with epithelial differentiation in the cervix. However, compared with the adult cervix, uterine endometrium expressed the highest levels of Muc1. In the endometrium, Muc1 was increased (p < 0.0004) by progesterone and returned to estrous levels by treatment with estrogen. Muc1 levels in the cervix were unaffected by ovarian steroids, confirming tissue-specific regulation of Muc1 in the lower reproductive tract.