GILZ-dependent modulation of mTORC1 regulates spermatogonial maintenance

Abstract

Male fertility is dependent on spermatogonial stem cells (SSCs) that self-renew and produce differentiating germ cells. Growth factors produced within the testis are essential for SSC maintenance but intrinsic factors that dictate the SSC response to these stimuli are poorly characterised. Here, we have studied the role of GILZ, a TSC22D family protein and spermatogenesis regulator, in spermatogonial function and signalling. Although broadly expressed in the germline, GILZ was prominent in undifferentiated spermatogonia and deletion in adults resulted in exhaustion of the GFRα1 SSC-containing population and germline degeneration. GILZ loss was associated with mTORC1 activation, suggesting enhanced growth factor signalling. Expression of deubiquitylase USP9X, an mTORC1 modulator required for spermatogenesis, was disrupted in mutants. Treatment with an mTOR inhibitor rescued GFRα1 spermatogonial failure, indicating that GILZ-dependent mTORC1 inhibition is crucial for SSC maintenance. Analysis of cultured undifferentiated spermatogonia lacking GILZ confirmed aberrant activation of ERK MAPK upstream mTORC1 plus USP9X downregulation and interaction of GILZ with TSC22D proteins. Our data indicate an essential role for GILZ-TSC22D complexes in ensuring the appropriate response of undifferentiated spermatogonia to growth factors via distinct inputs to mTORC1.

DAZL mediates a broad translational program regulating expansion and differentiation of spermatogonial progenitors

“…Pearson’s correlation coefficient shown. ( E ) Heatmap of sample-to-sample distances between RNA-seq datasets from (i) our 3S undifferentiated spermatogonia; (ii) Pdx1 :GFP-positive undifferentiated spermatogonia and Pdx1 :GFP-negative undifferentiated spermatogonia from 6 to 8 week old adult testes La et al, 2018a ; (iii) KIT-positive, Pou5f1 :EGFP-positive differentiating spermatogonia from P7 testes Kubo et al, 2015 ; (iv) KIT-positive differentiating spermatogonia from P7 testes ( Maezawa et al, 2017 ). RNA-seq data for protein-coding genes were quantified, normalized and transformed via DESeq prior to calculating sample distances.…”

“…We limited this list to those factors with functional evidence (knockout or knockdown data from a mouse or cell culture model). To this list, we added two factors whose functional roles in undifferentiated spermatogonia were reported after the publication of this review, Foxc2 ( Wei et al, 2018 ) and Tsc22d3 (also known as Gilz ) ( La et al, 2018a ). The complete list of factors is presented in Figure 2—source data 1 .…”

The testicular soma of Tsc22d3 knockout mice supports spermatogenesis and germline transmission from spermatogonial stem cell lines upon transplantation

“…The mechanisms of infertility of Tsc22d3‐KO mice have been studied by several groups and in several strains (Bruscoli et al, ; La et al, ; Ngo, Beaulieu, et al, ; Ngo, Cheng, et al, ; Romero et al, ; Suarez et al, ). The phenotype involves an arrest midway through the pachytene of meiosis I, massive apoptosis, SSC exhaustion, resulting in a progressive depletion of the germline, and terminating in a Sertoli cell‐only phenotype.…”

Molecular Mechanisms Controlled by mTOR in Male Reproductive System

“…Glucocorticoid-induced leucine zipper (GILZ), an essential factor for spermatogenesis [86,87], was also demonstrated to be an essential modulator of growth factor signaling in SCCs. Indeed, adult mice knockout for GILZ are characterized by SCCs exhaustion and germline degeneration [88]. GILZ knockout mice present aberrant mTORC1 activation, which was a downstream effect of aberrant activation of ERK/MAPK pathways (Figure 3) [88].…”

“…Indeed, adult mice knockout for GILZ are characterized by SCCs exhaustion and germline degeneration [88]. GILZ knockout mice present aberrant mTORC1 activation, which was a downstream effect of aberrant activation of ERK/MAPK pathways (Figure 3) [88]. Treatment of these mice with Torin1, an mTOR inhibitor, rescued SSC depletion.…”