MUC4 and MUC5B transcripts are the prevalent mucin messenger ribonucleic acids of the human endocervix

Mucins secreted by the endocervical epithelium protect the surfaces of the reproductive tract epithelium from pathogen penetrance and modulate sperm e ntry into the uterus. Three large gel-forming mucins, MUCs 5AC, 5B, and 6, are expressed by the endocervical epithelium, as is MUC4, a relatively unch aracterized mucin for which only tandem repeat sequence has been reported. We sought to determine the relative abundance of each of these mucin gene t ranscripts and to relate their expression to blood progesterone and estradi ol. Samples were obtained from six subjects at successive stages in the men strual cycle. Primers to nontandem repeat sequences of MUCs 4, 5AC, 5B, and 6 were used in semiquantitative reverse transcription-polymerase chain rea ction to determine relative abundance of each mucin gene in relation to bet a(2)-microglobulin message control. in order to design primers from a nonta ndem repeat region of MUC4 so that MUC4 message levels could be quantitated , we obtained approximately 2.7-kilobase nontandem repeat sequence 5' to th e tandem repeat sequence of a MUC4 genomic clone. The sequence showed lack of cysteine-rich D-domains and was rich in serine and threonine. Semiquanti tative polymerase chain reaction analyses indicated that the principal muci n transcripts of human endocervix are MUC4 and MUC5B, with MUC4 predominant in 15 of 21 samples. When correlated with plasma steroid levels, message l evels of both MUC4 and MUC5B were inversely related to progesterone levels.