Knockout of Cyclin-Dependent Kinases 8 and 19 Leads to Infertility in Male Mice by Disrupting Spermatogenesis and Testosterone Synthesis

Grunnleggende konsepter

Knockout of cyclin-dependent kinases 8 and 19 (CDK8/19) in mice causes infertility by disrupting spermatogenesis and testosterone synthesis in Leydig cells.

Sammendrag

The study generated mice with a conditional double knockout (DKO) of Cdk8 and constitutive knockout of Cdk19, and investigated the effects on the male reproductive system.

Key findings:

• DKO males were infertile, with an atrophic reproductive system and lack of postmeiotic spermatids and spermatocytes.
• Testosterone levels were decreased in DKO mice, while luteinizing hormone levels were unchanged, indicating a direct effect of CDK8/19 on Leydig cell function.
• Single-cell RNA sequencing revealed significant downregulation of key steroidogenic genes (Cyp17a1, Star, Fads) in Leydig cells of DKO mice.
• Sertoli cells in DKO mice showed disruption of cytoskeleton organization and cell-cell contacts, likely due to the lack of testosterone.
• Spermatocytes in DKO mice were blocked at the pachytene stage of meiosis I, with upregulation of stress response and apoptosis pathways.
• The phenotype was not recapitulated by pharmacological inhibition of CDK8/19 kinase activity, suggesting a kinase-independent role of CDK8/19, potentially through stabilization of their binding partner Cyclin C.
• Over time, a partial recovery of spermatogenesis was observed in DKO mice, but without restoration of testosterone production or fertility.

Statistikk

Testosterone levels were significantly decreased in DKO mice compared to controls.
Luteinizing hormone levels were unchanged across all genotypes.
The number of round and elongated spermatids was dramatically reduced in DKO mice.

Sitater

"DKO males, but not single Cdk8 and Cdk19 KO, had an atrophic reproductive system and were infertile."
"The DKO males lacked postmeiotic spermatids and spermatocytes after meiosis I pachytene."
"Testosterone levels were decreased whereas the amounts of the luteinizing hormone were unchanged."

Viktige innsikter hentet fra

Knockout of cyclin dependent kinases 8 and 19 leads to depletion of cyclin C and suppresses spermatogenesis and male fertility in mice

by Bruter,A. V.... klokken www.biorxiv.org 11-05-2023

https://www.biorxiv.org/content/10.1101/2023.11.04.564913v3

Dypere Spørsmål

How do the kinase-independent functions of CDK8/19, such as Cyclin C stabilization, contribute to the observed phenotype in DKO mice?

The kinase-independent functions of CDK8/19, particularly the stabilization of Cyclin C, play a crucial role in the observed phenotype in DKO mice. Cyclin C is a binding partner of CDK8/19 and has been implicated in CDK8/19-independent functions. In the DKO mice, the depletion of Cyclin C leads to significant changes in gene expression and cellular processes.
One key aspect is the impact on steroidogenesis in Leydig cells. The downregulation of key steroidogenic genes, such as Cyp17a1, Star, and Fads, is observed in Leydig cells of DKO mice. These genes are essential for testosterone production and lipid metabolism, both critical for spermatogenesis. The absence of Cyclin C destabilizes the CDK8/19-Cyclin C complex, leading to disruptions in steroid biosynthesis and hormonal activity in Leydig cells. This disruption ultimately affects spermatogenesis and male fertility in DKO mice.
Furthermore, the kinase-independent functions of CDK8/19 may also influence other cellular processes beyond steroidogenesis. The stabilization of Cyclin C by CDK8/19 is known to have implications for lipid metabolism, stress response pathways, and cell cycle regulation. These functions can impact the overall cellular environment in the testes, contributing to the observed phenotype of spermatogenesis blockage and infertility in DKO mice.

How do the potential compensatory mechanisms lead to partial recovery of spermatogenesis in DKO mice over time?

The partial recovery of spermatogenesis in DKO mice over time can be attributed to potential compensatory mechanisms triggered in response to the initial disruption caused by the loss of CDK8/19 and Cyclin C. Several factors may contribute to this partial recovery:

Compensatory gene expression: In response to the disruption of key genes involved in spermatogenesis and steroidogenesis, the cells may activate compensatory pathways to restore some level of functionality. Upregulation of certain genes or activation of alternative pathways could help in partially overcoming the initial blockage in spermatogenesis.

Cellular adaptation: The cells in the testes, including spermatogonia, Sertoli cells, and Leydig cells, may undergo adaptive changes to cope with the loss of CDK8/19 and Cyclin C. This adaptation could involve alterations in gene expression, cellular processes, and signaling pathways to maintain essential functions for spermatogenesis.

Reprogramming of cell fate: In some cases, cells may undergo reprogramming or differentiation changes to compensate for the loss of critical regulatory factors. This reprogramming could lead to the restoration of certain cell types or functions necessary for spermatogenesis.

Feedback mechanisms: The disruption caused by the loss of CDK8/19 and Cyclin C may trigger feedback mechanisms within the testicular microenvironment. These feedback loops could involve hormonal signaling, cell-cell interactions, and signaling cascades that help in restoring some level of spermatogenesis.

Overall, the partial recovery of spermatogenesis in DKO mice over time is likely a result of complex interplay between compensatory mechanisms, cellular adaptation, and feedback responses within the testicular environment.

Could the disruption of CDK8/19-mediated regulation of other transcription factors and signaling pathways contribute to the infertility phenotype beyond the effects on steroidogenesis?

The disruption of CDK8/19-mediated regulation of other transcription factors and signaling pathways could indeed contribute to the infertility phenotype observed in DKO mice beyond the effects on steroidogenesis. CDK8/19 are known to regulate the transcriptional activity of various signaling pathways and transcription factors, impacting multiple cellular processes beyond steroidogenesis. Here are some ways in which the disruption of CDK8/19-mediated regulation could contribute to infertility:

Transcriptional regulation: CDK8/19 are involved in the regulation of transcription factors that control key genes essential for spermatogenesis. Disruption of this regulatory function could lead to dysregulation of gene expression patterns critical for germ cell development, meiosis progression, and sperm maturation.

Cell cycle control: CDK8/19 play a role in cell cycle regulation and progression. The loss of CDK8/19 could affect the cell cycle dynamics in spermatogenic cells, leading to cell cycle arrest, apoptosis, or aberrant differentiation, all of which can impact fertility.

Signaling pathways: CDK8/19 are implicated in various signaling pathways that are crucial for male reproductive function. Disruption of these pathways could affect hormone signaling, cell-cell communication, and developmental processes necessary for spermatogenesis and male fertility.

Epigenetic regulation: CDK8/19 have been linked to epigenetic modifications and chromatin remodeling, which are essential for proper gene expression during spermatogenesis. Alterations in epigenetic regulation due to the loss of CDK8/19 could impact the differentiation and maturation of germ cells.

In conclusion, the disruption of CDK8/19-mediated regulation of transcription factors and signaling pathways can have broad implications for male fertility beyond steroidogenesis. The multifaceted roles of CDK8/19 in gene expression, cell cycle control, signaling, and epigenetic regulation highlight the complexity of their contribution to spermatogenesis and reproductive function.