Targeted Disruption of Lats1 and Lats2 in Mice Impairs Testis Development and Alters Somatic Cell Fate

Abstract

Hippo signaling plays an essential role in the development of numerous tissues. Although it was previously shown that the transcriptional effectors of Hippo signaling Yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding motif (TAZ) can fine-tune the regulation of sex differentiation genes in the testes, the role of Hippo signaling in testis development remains largely unknown. To further explore the role of Hippo signaling in the testes, we conditionally deleted the key Hippo kinases large tumor suppressor homolog kinases 1 and -2 (Lats1 and Lats2, two kinases that antagonize YAP and TAZ transcriptional co-regulatory activity) in the somatic cells of the testes using an Nr5a1-cre strain (Lats1flox/flox;Lats2flox/flox;Nr5a1-cre). We report here that early stages of testis somatic cell differentiation were not affected in this model but progressive testis cord dysgenesis was observed starting at gestational day e14.5. Testis cord dysgenesis was further associated with the loss of polarity of the Sertoli cells and the loss of SOX9 expression but not WT1. In parallel with testis cord dysgenesis, a loss of steroidogenic gene expression associated with the appearance of myofibroblast-like cells in the interstitial space was also observed in mutant animals. Furthermore, the loss of YAP phosphorylation, the accumulation of nuclear TAZ (and YAP) in both the Sertoli and interstitial cell populations, and an increase in their transcriptional co-regulatory activity in the testes suggest that the observed phenotype could be attributed at least in part to YAP and TAZ. Taken together, our results suggest that Hippo signaling is required to maintain proper differentiation of testis somatic cells.

Lats1 and Lats2 regulate YAP and TAZ activity to control the development of mouse Sertoli cells

“…In the latter, disorganized larger tubules are also present but never become sufficiently large to fuse with each other. 30 However, inactivation of Lats1/2 is not limited to the Sertoli cells in L1;L2;Nr5a1 mice, as inactivation also occurs in the Leydig cells. Lats1/2 inactivation in Leydig cells leads to their transdifferentiation into myofibroblast-like cells and the secretion by these cells of a collagen-based extracellular matrix into the interstitial space.…”

“…The specification of Sertoli cell fate and their proper differentiation throughout testis development require the action of the transcription factors SRY and SOX9 as well as the action of autocrine factors such as FGF9, PGD2, AMH, and Activin B. [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] Although these autocrine factors and the signaling pathways they activate are essential for fetal Sertoli cell differentiation, our previous work has demonstrated that additional signaling pathways, such as Hippo signaling, 29,30 can fine-tune these processes. However, this is the first report to thoroughly evaluate the role of Hippo signaling and Lats1/2 specifically in the developing Sertoli cells.…”

“…Lats1/2 inactivation in Leydig cells leads to their transdifferentiation into myofibroblast-like cells and the secretion by these cells of a collagen-based extracellular matrix into the interstitial space. 30 This extracellular matrix could therefore more rapidly impair the proliferation of the recombined Sertoli cells. Furthermore, contrary to what is observed in L1;L2;A mice in which SOX9 expression is lost postnatally, SOX9 (but not WT1) expression was already downregulated in the Sertoli cells of L1;L2;Nr5a1 mice 30 at later stages of development, suggesting that the environment surrounding Lats1/2-null Sertoli cells could also affect their differentiation.…”

“…This latter breeding pairs were also used to maintain the colony. Genotype analyses were done on tail biopsies by PCR as previously described 29,30 …”

“…29 More recently, we also showed that inactivation of Lats1 and Lats2 in fetal Leydig and Sertoli cells of the developing testis impairs testicular development. 30 However, this model could not determine whether the abnormal phenotype observed in Sertoli cells and fetal Leydig cells resulted from a direct effect of Lats1/2 inactivation in these cells, an indirect effect of these cell populations on each other, or more likely, a combination of both.…”