Abortive Spontaneous Egg Activation: An Emerging Biological Threat for the Existence of Mammals

Abstract

Mammals are important for balancing the natural ecosystem, but in the past few decades, several species have rapidly been entered under threatened category worldwide. The environmental changes, loss of natural habitats, human activities, and thereby stress are responsible for a gradual decline in reproductive outcome. Stress induces generation of reactive oxygen species (ROS). High physiological level of ROS drives abortive spontaneous egg activation (SEA), while beyond the physiological level causes oxidative stress (OS). The OS induces apoptosis and deteriorates egg quality that limits reproductive outcome. The reduced reproductive outcome is one of the major causes for gradual decline in population size of several mammalian species. Despite having several conservation programs, a gradual decline in species reproductive outcome and their population size is the serious concern for the existence of threatened mammalian species. Thus, it is important to identify and prevent the underlying causes responsible for abortive SEA, which could be an emerging problem for several mammalian species that are threatened or at the verge of extinction.

Maturation promoting factor destabilization mediates human chorionic gonadotropin induced meiotic resumption in rat oocytes

“…; Prasad et al . , , ). In addition, involvement of MAPK and its interaction with MPF have been reported to trigger meiotic maturation and spontaneous exit from M‐II arrest (Cui et al .…”

“…, ; Premkumar & Chaube , ; Prasad et al . , , ). However, it remains unclear whether hCG‐mediated decrease of Cdc25B and increase of Wee1 kinase activity could destabilize MPF during meiotic exit from diplotene as well as MII arrest.…”

“…Finally, MPF destabilization triggers meiotic exit from M‐II arrest in ovulated oocytes (Brunet & Maro ; Premkumar & Chaube , ; Prasad et al . , , ; Tiwari et al . ).…”

Spontaneous Exit from Diplotene Arrest Associates with the Increase of Calcium and Reactive Oxygen Species in Rat Oocytes Cultured In Vitro

“…Achievement of meiotic competency starts with EDA and oocyte progresses into metaphase-I (M-I) stage [7,12,14,17] and further gets physiologically arrested at metaphase-II (M-II) stage by extruding first polar body (PB-I) at the time of ovulation in most of the mammalian species [19][20][21][22][23][24][25][26]. These oocytes remain arrested at M-II stage even after ovulation until fertilization [2,19,[22][23][24][25][26].…”

Role of Mitogen Activated Protein Kinase and Maturation Promoting Factor During the Achievement of Meiotic Competency in Mammalian Oocytes

“…This event is mediated by chromatin condensation and spindle formation in rat and mouse oocytes [Josefsberg et al, ; Kong et al, ]. The increased level of destabilized MPF leads to meiotic exit from M‐II arrest that results in abortive spontaneous egg activation (SEA) in rat [Cui et al, ; Premkumar and Chaube, , ; Prasad et al, , , ; Tiwari et al, , ,].…”