Oral Presentation Annual Meetings of the Endocrine Society of Australia and Society for Reproductive Biology and Australia and New Zealand Bone and Mineral Society 2016

Wnt signalling actions in spermatogenesis are mediated by non-coding RNAs (#165)

Manish Jhamb 1 , Pradeep Tanwar 1
  1. School of Biomedical Sciences and Pharmacy , University of Newcastle, Callaghan , NSW, Australia

Human male produces around 100 million sperm per day.  This extraordinary task of producing massive number of cells without any defect is performed by spermatogonial stem cells (SSCs).  SSCs constantly undergo proliferation and differentiation to produce daughter cells for their self-renewal and to give rise to differentiated germ cells (spermatozoa).  A key transition step in mammalian spermatogenesis is entry into spermatocyte differentiation and meiosis.  Although several genes have been proposed to regulate this transition, the mechanisms controlling it remain poorly understood.

Wnt signalling plays an important role in various cellular processes such as cell proliferation, differentiation and apoptosis.  However, role of Wnt pathway in postnatal male germ cell-biology has remained questionable.  To investigate this, we first confirmed evolutionary conserved activity of Wnt pathway in mouse, dog and human testis.  Using a well-established Wnt reporter mouse, we confirmed active Wnt signalling in SSCs.  To understand the functional importance of Wnt pathway in spermatogenesis, we developed a mouse model with germ cell-specific constitutive activation of βcatenin.  Examination of mutant testis showed defective spermatogenesis, progressive germ cell loss and flawed meiotic entry of spermatogonial cells.  Overactivation of Wnt signalling in GC1 cells, a spermatogonial cell line, also resulted in reduced cell proliferation, viability and colony formation.

To understand molecular mechanisms responsible for defective spermatogenesis, we performed RNA sequencing of testes from control and mutant mice.  Interestingly, majority of the genes altered in mutant mice were non-coding RNAs.  We found significant alterations in non-coding region of chromosome-1, loci:19037508-19037682.  This novel non-coding RNA was switched on in mutant mice with an FPKM value of 21.13 (mutant) and zero value for the control.  Functional analysis of this novel non-coding RNA is currently underway.  Collectively, this work has demonstrated that Wnt signalling plays an important role in spermatogonial self-renewal and differentiation possibly through a novel non-coding RNA.