The distinct in vivo roles of the long‐form and short‐form of glutathione peroxidase 4: the short‐form is essential for somatic cell functions and the long‐form is important for male fertility

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Glutathione Peroxidase 4 (Gpx4) is an essential antioxidant enzyme that protects cells against membrane lipid peroxidation. The Gpx4 gene encodes for three isoforms: a long‐form (lGpx4), a short form (sGpx4) and a nuclear form. Genetic studies indicate that the nuclear form of Gpx4 plays a role in sperm chromatin condensation. However, the in vivo roles of lGpx4 and sGpx4, which are distinguishable by the presence or lack of a mitochondrial targeting signal peptide at the N‐terminal of the Gpx4 protein, remain unclear. In this study, we generated transgenic mice using mutated human GPX4 genes encoding either lGPX4 [Tg(lGPX4) mice] or sGPX4 [Tg(sGPX4) mice]. Tg(sGPX4) mice had increased total Gpx4 proteins in all tissues whereas Tg(lGPX4) mice had increased total Gpx4 proteins only in the testes. Tg(sGPX4) mice, but not the Tg(lGPX4) mice, were protected against diquat‐induced liver apoptosis. By cross‐breeding the Tg(sGPX4) mice with the Gpx4 knockout mice, we showed that the sGPX4 transgene was able to rescue the lethal phenotype of mouse Gpx4 null mutation. In contrast, the lGPX4 transgene failed to rescue Gpx4 null mice. Gpx4 protein expression data from the sGPX4‐rescued Gpx4 null mice indicated that sGPX4 was the major isoform in the somatic tissue subcellular fractions including mitochondria whereas lGPX4 was predominant in testes. The male sGPX4‐rescued mice were infertile and exhibited low sperm count and reduced sperm mobility, suggesting lGPX4 plays a role in male fertility. Together, our results indicate that the sGpx4 is the major isoform in somatic tissues and it is essential for survival and protection against apoptosis; the lGpx4 is predominant in the testes and it is important in regulating male fertility.