EXPRESSION OF ESTROGEN RECEPTOR-ALPHA SPLICING VARIANTS AND ESTROGEN RECEPTOR-BETA IN ENDOMETRIUM OF INFERTILE PATIENTS

Endometrium is one of the main target tissues of oestrogens. Although homozygous inactivation of oestrogen receptor-alpha leads to infertili ty in transgenic mice, oestrogen receptor-alpha is detected in endomet rium of patients with unexplained infertility. Oestrogen receptor-alph a splicing variants and oestrogen receptor-beta have been studied in o estrogen target tissues, but their expression in endometrium throughou t the menstrual cycle and in unexplained infertility is unknown. Using reverse transcription-polymerase chain reaction (RT-PCR), we studied the expression of oestrogen receptor-alpha splicing variants and oestr ogen receptor-beta in uterine biopsies from 12 patients with endometri osis and 15 patients with unexplained infertility. A control group inc luded 19 women who had had a previous pregnancy. Our study gave eviden ce of exon 2, 3, 4 or 7 deleted oestrogen receptor-alpha variants co-e xisting with the wild-type receptor. We did not find any exon 5 or 6-d eleted variants. Exon 4 or 7-deleted variants were detected in all sam ples. Exon 2 or 3-deleted variants were detected at a similar frequenc y in fertile women (58 and 68% respectively), endometriotic patients ( 67 and 83% respectively) and infertile patients (73 and 80% respective ly). During the follicular phase, there was a non-significant trend to wards a lower frequency of exon-2 deleted variants in the fertile grou p when compared with the hypofertile group. Oestrogen receptor-beta wa s detected in all samples. Our preliminary study showed that altered e xpression of oestrogen receptor-alpha variants and oestrogen receptor- beta may not explain the hypofertility state.