- Wild-type estrogen receptor (ERbeta1) and the splice variant (ERbetacx/beta2) are both expressed within the human endometrium throughout the normal menstrual cycle. Critchley, H.O., Henderson, T.A., Kelly, R.W., Scobie, G.S., Evans, L.R., Groome, N.P., Saunders, P.T. J. Clin. Endocrinol. Metab. (2002)