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 wasused to compare the patterns of [³⁵S]methionine-labelled cellularproteins in endometrial tissue from healthy, normally menstruatingwomen. Samples of endometrial tissue were incubated with [³⁵S]methioninefor 20 h, and total cell lysates were processed for 2-D gelelectrophoresis. Using this technique it was possible to studyproteins with iso-electric points (pI) ranging from 3.5 to 11and relative molecular weights (M_r) ranging from 10 000 to 300000 Da. The fluorograms were compared by computer-aided analysiswhereby a total of 1095 [³⁵S]-labelled proteins were resolvedon the iso-electric focusing gels (IEF, pI 3.5–7) and488 on the non-equilibrium pH gradient electrophoresis (NEPHGE)gels (pI 6.5–11). Of the proteins on the IEF gels, 125showed differential expression during the menstrual cycle. Ofthese, 36 were maximally expressed in proliferative phase endometrium,26 in the interval phase and 63 in secretory and/or late secretoryphase endometrium. Correspondingly, on the NEPHGE gels a totalof 61 proteins exhibited cyclical variation, of which 30 weremore prominent in proliferative phase, 13 in interval phaseand 18 in secretory phase endometrium. This study shows that2-D gel electrophoresis is eminently suited to the identificationof proteins whose expression varies in a cyclical manner duringthe menstrual cycle. Further investigations should be carriedout to isolate and characterize these proteins with the aimof establishing useful markers for specific endometrial phasesof the menstrual cycle.