Two-dimensional gel analysis of human endometrial proteins: cyclic changes in the expression of specific proteins during the normal menstrual cycle

High resolution two-dimensional (2-D) gel electrophoresis was used to compare the patterns of [35S]methionine-labelled cellular proteins in endometrial tissue from healthy, normally menstruating women. Samples of endometrial tissue were incubated with [35S]methionine for 20 h, and total cell lysates were processed for 2-D gel electrophoresis.

Using this technique it was possible to study proteins with iso-electric points (pI) ranging from 3.5 to 11 and relative molecular weights (M(r)) ranging from 10,000 to 300,000 Da. The fluorograms were compared by computer-aided analysis whereby a total of 1095 [35S]-labelled proteins were resolved on the iso-electric focusing gels (IEF, pI 3.5-7) and 488 on the non-equilibrium pH gradient electrophoresis (NEPHGE) gels (pI 6.5-11).

Of the proteins on the IEF gels, 125 showed differential expression during the menstrual cycle. Of these, 36 were maximally expressed in proliferative phase endometrium, 26 in the interval phase and 63 in secretory and/or late secretory phase endometrium. Correspondingly, on the NEPHGE gels a total of 61 proteins exhibited cyclical variation, of which 30 were more prominent in proliferative phase, 13 in interval phase and 18 in secretory phase endometrium.

This study shows that 2-D gel electrophoresis is eminently suited to the identification of proteins whose expression varies in a cyclical manner during the menstrual cycle. Further investigations should be carried out to isolate and characterize these proteins with the aim of establishing useful markers for specific endometrial phases of the menstrual cycle.