The key role of vitamin A in spermatogenesis
Cathryn A. Hogarth, Michael D. Griswold
Cathryn A. Hogarth, Michael D. Griswold
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The key role of vitamin A in spermatogenesis

Abstract

Spermatogenesis in adult mammals is highly organized, with the goal being continual sperm production. Vertebrate testes are arranged into recurring cellular associations that vary with time and distance along the tubule. These changes over time and distance are designated the cycle of the seminiferous epithelium and the spermatogenic wave, respectively. In this Review, we briefly outline the roles that follicle-stimulating hormone (FSH) and testosterone play in regulating spermatogenesis and describe our current understanding of how vitamin A regulates germ cell differentiation and how it may lead to the generation of both the cycle of the seminiferous epithelium and the spermatogenic wave.

Authors

Cathryn A. Hogarth, Michael D. Griswold

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Figure 4

The fate of vitamin A in the spermatogonia.

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The fate of vitamin A in the spermatogonia. Retinol is delivered to germ...
Retinol is delivered to germinal cells on the retinol-binding protein (RBP) and is internalized via the membrane receptor STRA6. It is also plausible that RA is delivered directly to spermatogonia either by Sertoli cells or from the serum. Inside the cell, retinol is converted to RA in a two-step process and can interact with RARs such as RARγ. The RA is bound up by an excess of cellular retinoic acid–binding protein (CRABP). The activated receptor can stimulate transcription of a number of genes including Stra8, which has been shown to be necessary for progression through meiosis. Excess RA can be metabolized by the enzyme CYP26B1 into 4-oxo and 4-hydroxy forms. These forms are then secreted from the cell.