Disorders of human male reproductive health include cryptorchidism, hypospadias, infertility/subfertility, testicular germ cell cancer and primary hypogonadism. The ‘testis dysgenesis syndrome’ hypothesis proposes that ALL of these problems have a shared origin during fetal life: if testis development is perturbed during a critical window of time whilst in the womb, reproductive health and function is affected. These disorders are escalating at such high rates that it is presumed that environmental causes are to blame, and the key suspect is our increasing exposure to ‘endocrine disrupting chemicals’, particularly during fetal life.
Current toxicological testing methods are expensive and cumbersome and make little attempt to address the underlying biology. It is imperative that, in the future, chemical testing approaches focus specifically on vulnerable cell types and molecular pathways when assessing human safety. In this project Dr Spiller combined her expertise in transgenic mouse model production and knowledge of testis development to develop a new, efficient, and ethical toxicological ex vivo screening platform for EDC burden on reproductive function. The aims of the project were to:
1. Develop a novel transgenic mouse line to detect abnormal Dax1 expression; and
2. Develop an ex-vivo assay for read-out of EDC disruption to testis development
A novel mouse line was generated in which the 11kb Dax promoter drives the fluorescent reporter dsRED. Preliminary data shows that this reporter faithfully “reads out” endogenous Dax1 expression and will be useful in ongoing screening assays for disruption to its regulation (Aim 1). In parallel, a novel ex-vivo testis culture system was developed as a read-out for perturbed Retinoic acid signalling (an important signalling pathway for normal development; Aim 2). Dr Spiller used this system to evaluate the molecular effects of a common agricultural fungicide and related compounds. Most fungicides work by inhibiting specific fungal enzymes, though it is likely that it can also inhibit similar mammalian enzymes. Indeed, ther results reveal that some fungicides tested in the system can disrupt normal testis development. Results will inform future in vivo studies in mice and rats and ultimately inform a rational framework for future chemical regulatory and replacement decisions.
