Hypospadias is a common developmental defect characterised by failure of urethral closure in the developing phallus, but its aetiology remains largely unknown. The tammar wallaby is a useful model because sexual differentiation takes place after birth over a relatively long time period, so it is amenable to hormonal manipulation. The phallus does not become sexually dimorphic until after day 50pp, but there is a short window of androgen sensitivity between day 20-30pp (Chew, et al. 2014, Leihy, et al. 2004). At day 50pp, the urethra has not yet closed, but by day 90pp urethral closure is well underway (Leihy, et al. 2011). This project investigates the effects of treatment of females with exogenous androstanediol (adiol) and males with oestrogen on the coding and non-coding genes in the developing phallus of the tammar.
The urethra of treated males failed to close by day 150pp and expression of AR and ESR1 were significantly upregulated by day 50pp after treatment with oestrogen. After treatment with adiol, the phallus of females was masculinised by day 150pp and expression of AR, ATF3 and CYR61 were significantly upregulated by day 50pp There were numerous long non-coding RNAs (lncRNAs) affected by oestrogen or adiol treatment. One, BMP5 and its neighbouring lncRNA, were significantly reduced by treatment with oestrogen. We characterised the expression pattern of FGF10, FGFR2IIIB, DLX5, EFNB2 and MAFB in the normal day 90pp phallus and all were significantly higher in male phalluses. The mRNA of EFNB2, FGF10 and FGFR2IIIB co-localised in the distal part urethral epithelium of the phallus. EFNB2 was also found in the mesenchyme. MAFB was localised in the urethral epithelium at the beginning of urethral closure. Thus the closure of the urethra appears to be induced via specific effects of androgens or oestrogens on the lncRNAs associated with their respective coding genes.