Restoration of spermatogenesis and male fertility using an androgen receptor transgene.

Stefan Schlatt,William H Walker,Corey Toocheck,Rebecca S Moreci,Pancharatnam Jeyasuria,Prashanth Anamthathmakula,Evan Easton

doi:10.1371/journal.pone.0120783

Stefan Schlatt, William H Walker + Show 5 more

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https://doi.org/10.1371/journal.pone.0120783

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Abstract

Androgens signal through the androgen receptor (AR) to regulate male secondary sexual characteristics, reproductive tract development, prostate function, sperm production, bone and muscle mass as well as body hair growth among other functions. We developed a transgenic mouse model in which endogenous AR expression was replaced by a functionally modified AR transgene. A bacterial artificial chromosome (BAC) was constructed containing all AR exons and introns plus 40 kb each of 5' and 3' regulatory sequence. Insertion of an internal ribosome entry site and the EGFP gene 3’ to AR allowed co-expression of AR and EGFP. Pronuclear injection of the BAC resulted in six founder mice that displayed EGFP production in appropriate AR expressing tissues. The six founder mice were mated into a Sertoli cell specific AR knockout (SCARKO) background in which spermatogenesis is blocked at the meiosis stage of germ cell development. The AR-EGFP transgene was expressed in a cyclical manner similar to that of endogenous AR in Sertoli cells and fertility was restored as offspring were produced in the absence of Sertoli cell AR. Thus, the AR-EGFP transgene under the control of AR regulatory elements is capable of rescuing AR function in a cell selective, AR-null background. These initial studies provide proof of principle that a strategy employing the AR-EGFP transgene can be used to understand AR functions. Transgenic mice expressing selective modifications of the AR-EGFP transgene may provide crucial information needed to elicit the molecular mechanisms by which AR acts in the testis and other androgen responsive tissues.

Highlights

Androgens are a class of steroid hormones that regulate prostate function, bone density, cardiac health, muscle mass, hair growth and fertility
We found that expression of the androgen receptor (AR)-EGFP transgene from 5 of the founders was capable of restoring spermatogenesis in specific AR knockout (SCARKO) mice that lack Sertoli cell-specific endogenous AR expression
It is possible that the extent of rescued spermatogenesis may be related to the expression levels of the AR-EGFP transgene and the capability of each mouse strain to express the transgene in Sertoli cells in a stage specific manner

Summary

Introduction

Androgens are a class of steroid hormones that regulate prostate function, bone density, cardiac health, muscle mass, hair growth and fertility. Membrane and act via the intracellular androgen receptor (AR) to alter gene expression and intracellular signaling pathways in target cells. Because of the high levels of testosterone produced locally by the Leydig cells within the testis, this form of androgen is the major regulator of testis functions and the male reproductive tract. An in vivo model system in which endogenous AR expression is replaced with specific AR mutants that selectively activate either the classical or non-classical testosterone pathways would provide an essential tool for dissecting the molecular mechanisms by which AR acts. AR-EGFP transgene is able to restore complete spermatogenesis and fertility in a SCARKO mouse that lacks endogenous AR expression in Sertoli cells

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