Disrupted human fetal testis development may lead to testicular germ cell tumours and other testicular pathologies, particularly during the masculinisation programming window (MPW) which falls between gestational weeks (GW) 8 and 14. During this interval, germ cells undergo epigenetic remodelling and heterogeneously enter quiescence. High levels of transcripts encoding several TGFβ superfamily members (activin A, activin B, NODAL and LEFTY) are present between GW 10-12. Because fetal exposure to abnormally high activin A levels may occur during pregnancy (e.g. in preeclampsia), we hypothesised that disruptions to TGFβ superfamily signalling in utero during the MPW contribute to adult testicular pathologies.
Human fetal gonads were obtained from elective first trimester terminations. Gonads with mesonephros were bisected for 72h hanging-drop cultures, with one half placed in media (MEM-α/10% FBS/1% ITS/1% Pen-Strep) containing 50 ng/mL activin A or 10 µM SB431542 (inhibits activins/Nodal/TGFβ), and one half in media with vehicle. Samples were snap-frozen for qRT-PCR or fixed for histology.
Preliminary results indicate that acute exposure of GW 9 testes to activin A (n=1) or SB431542 (n=2) inversely affected the somatic activin A target transcript SERPINA5 (activin A, 1.3-fold increase; SB431542, 0.6-fold decrease), and altered the germ cell transcripts KIT and SOX17. Limited analysis of GW 8 (n=1) and GW 11 (n=1) testes to date suggests responses are age-dependent. In ovaries, SB431542 increased KIT at GW 9-10 (n=4), while activin A reduced KIT at GW 9 (n=2), indicating the female gonad is also sensitive to TGFβ signalling disruption.
Ongoing experiments are informed by evaluation of normal human fetal testis transcriptomes from RNA-Seq/scRNA-Seq, and our own datasets from activin A transgenic mouse testes. This will expand knowledge of activin A target genes in human fetal gonads, and ultimately reveal how altered activin A signalling in utero may influence adult fertility and gonadal pathologies.