Vertebrate Reproduction

Abstract

Vertebrate reproduction requires a myriad of precisely orchestrated events-in particular, the maternal production of oocytes, the paternal production of sperm, successful fertilization, and initiation of early embryonic cell divisions. These processes are governed by a host of signaling pathways. Protein kinase and phosphatase signaling pathways involving Mos, CDK1, RSK, and PP2A regulate meiosis during maturation of the oocyte. Steroid signals-specifically testosterone-regulate spermatogenesis, as does signaling by G-protein-coupled hormone receptors. Finally, calcium signaling is essential for both sperm motility and fertilization. Altogether, this signaling symphony ensures the production of viable offspring, offering a chance of genetic immortality.

Vitamin K in Vertebrates’ Reproduction: Further Puzzling Pieces of Evidence from Teleost Fish Species

“…Reproduction is a tightly regulated biological process that guarantees species perpetuation and increases intra-specific genetic variability, allowing for offspring to increase its fitness and adaptation to the environmental changes and avoiding the extinction. Although vertebrates exhibit a diverse set of modes of sexual reproduction (including hermaphroditism), with oviparous, ovoviviparous, or viviparous offspring production, semelparity or iteroparity (with single (seasonal), or multiple reproductive cycles along the year), as well as with synchronous, group-synchronous, and asynchronous gonadal development; it requires a myriad of precisely orchestrated events, governed by host signaling pathways that are considerably conserved along its evolution [ 81 ]. A great research effort has been paid to understand the physiological changes and the related underpinning molecular pathways in order to warrant successful reproduction and solve reproductive disorders.…”

The Calcium-Sensing Receptor and the Reproductive System

“…For transition of the unfertilized egg to a developing embryo, egg activation is initiated by alterations in Ca${}_{\text{i}}^{2+}$, which is triggered by fusion of the sperm with the egg involving a sperm-derived factor. The type of Ca 2+ -signal is species dependent, a prolonged series of Ca${}_{\text{i}}^{2+}$ oscillations in the egg cytoplasm is characteristic in e.g., mammals, while other species (e.g., fish) exhibit a single increase in Ca${}_{\text{i}}^{2+}$ concentration (Kornbluth and Fissore, 2015). Egg activation comprises a series of events including cortical granule exocytosis, modifications of the zona pellucida and plasma membrane to prevent polyspermy, completion of meiosis II in the egg, recruitment of maternal mRNAs into polysomes for translation, and formation of male and female pronuclei (Schultz and Kopf, 1995; Wang and Machaty, 2013; Swann and Lai, 2016).…”

“…The mass production of the male gamets starts with puberty, when the hypothalamic-pituitary-gonadal axis is established, and is a continuous, life-long process. Spermatogenesis consists of three major phases (1) the proliferation of the stem cells (spermatogonia) resulting in spermatocytes, (2) two meiotic divisions that give rise to haploid spermatids, and (3) spermiogenesis, the differentiation into mature sperms (for details see Kornbluth and Fissore, 2015 ). Spermatogenesis occurs in the seminiferous tubulus of the testes and is supported by testicular non-germ line cells, such as Sertoli and Leydig cells, which nourish the sperms and/or produce factors required for proper spermatogenesis.…”

“…Calcium (Ca 2+ ) is indispensable in the context of mammalian reproduction (Baczyk et al, 2011 ; Correia et al, 2015 ; Kornbluth and Fissore, 2015 ). Firstly, Ca 2+ contributes to crucial developmental processes such as skeletal formation and mineralization (Riccardi et al, 2013 ; Kovacs, 2014 , 2015 ), lung (Riccardi et al, 2013 ) and kidney development (Gilbert et al, 2011 ) or formation and maturation of neuronal circuits and long-term memory (Leclerc et al, 2011 ).…”

Zinc: A small molecule with a big impact on sperm function

“…This study indicates that roles for zinc and zinc transporters in signaling may be important to investigate in human sperm development and function. Though calcium has long been known to function as a signaling component important for fertility [ 25 ], other reports are surfacing of zinc playing signaling roles in various contexts. For example, a release of zinc from oocytes into the extracellular space, referred to as a zinc spark, has been shown to occur upon fertilization as eggs activate [ 26 ].…”