Table 1.

Brief description of select mammalian selenoproteins having implication/role in fertility, reproduction, and development.

Selenoprotein	Symbol [5]	General Description/Function [1,6,7]	Potential Implication in Reproductive Function
Glutathione peroxidase 1	GPX1	Antioxidant protection	Important role in female reproductive function; i.e., implication in determining the follicle growth, maturation, and dominance in both cows and women [8,9]. Implication in the follicular microenvironment [10]. Potential antioxidant role in follicle dominance protecting the dominant follicle from increasing levels of reactive oxygen species (ROS) [8,9].
Glutathione peroxidase 2	GPX2	Antioxidant protection	Implicated in protection of embryos and extra-embryonic tissues against ROS generated in ontogenetic periods [11].
Glutathione peroxidase 3	GPX3	Maintenance of cellular redox status Antioxidant in extracellular fluids	Gpx3 has been identified as an essential enzyme in the defense against oxidative stress during the postovulatory process of endometrial remodeling (decasualization) in preparation for implantation by reducing H2O2 in the endometrium [12]. Implicated in normal human pregnancy and birth [13]. Implicated in maternal-fetal selenium transfer mechanism [14]. Role in pre-eclampsia and pregnancy-related hypertensive conditions [15]. Implicated in preventing the oxidative stress- induced cell apoptosis during growth of large healthy follicles [16].
Glutathione peroxidase 4	GPX4	Detoxification of lipid hydroperoxides, Antioxidant role in membranes, serves as structural protein in sperm, Apoptosis. Membrane-associated. Present at high concentrations in the testis, where it is important for sperm motility and viability, male fertility	Essential for embryonic development [17,18]. Potential implication in pre-eclampsia [19,20,21]. Implication in male fertility [22].
Glutathione peroxidase 5	GPX5	Antioxidant role during sperm maturation, H2O2 scavenger [23]	Implicated in protection of sperm from oxidative damage that could compromise their integrity and, as a consequence, embryo viability [24].
Thioredoxin reductase 1	TXNRD1	Part of the thioredoxin system, Antioxidant role, redox regulation, cell signaling. Controls activity of transcription factors, cell proliferation, apoptosis	Implication in early embryonic development [25,26].
Thioredoxin reductase 2	TXNRD2	Part of the thioredoxin system, Antioxidant role, redox regulation, cell signaling	Potential role in embryogenesis [27].
Thioredoxin-glutathione reductase	TXNRD3	Part of the thioredoxin system, Antioxidant role, redox regulation, cell signaling	Role in disulfide bond formation and sperm maturation [28].
Iodothyronine deiodinase 1	DIO1	Conversion of T4 to T3 and T4 to reverse T3, Production of T3 in the thyroid and peripheral tissues	Implication in autoimmune thyroid disease and postpartum thyroid disease [29]. Dio2 and Dio3 are highly expressed at the site of implantation in pregnant rat [30]. High expression of DIO3 at utero-plecental unit and fetal epithelia has also been reported in human, Potential role in preventing the overexposure of fetus to T3 [31].
Iodothyronine deiodinase 2	DIO2	Conversion of T4 to T3, T3 production in peripheral tissues
Iodothyronine deiodinase 3	DIO3	Conversion T4 to reverse T3, Production of rT3
Selenoprotein H	SELENOH	Not fully known, potential implication in upregulation of genes relevant to glutathione synthesis	Implicated in placental oxidative stress by regulating mitochondrial biogenesis in trophoblasts (Swan-71, JEG-3 and BeWo cells) [32].
Selenoprotein P	SELENOP	By and large implicated in Se transportation and antioxidant defense, Regarded as a major contributor to plasma selenium and a good indicator of Se status, Essential for male fertility; its deficiency leads to infertility characterized by abnormal spermatozoa in mice	Implicated in maternal-fetal selenium transfer mechanism [14]. Implication in male fertility [33,34]. Involved in delivery of Se to spermatogenic cells [35]. Required for mouse sperm development [36]. Potential implication in pregnancy and pre-eclampsia [13,15,37].
Selenoprotein S	SELENOS	Cellular redox balance, Possible influence in inflammatory response	Relevant to pre-eclampsia [29,38]. Localized to the granulosa cells of large healthy and atretic follicles and also expressed in the thecal layers. Potential role in bovine follicular development [8].
Selenoprotein V	SELENOV	Unknown, possible role in redox regulation	Testis-specific expression in rodents [39], in situ hybridization experiments have shown high levels of Selenov mRNA in seminiferous tubules in mice, but its exact role in spermatogenesis remains elusive [3,39].