Embryonic diapause: development on hold

Abstract

Embryonic diapause, the temporary suspension of development of the embryo, is a fascinating reproductive strategy that has been frequently exploited across the animal kingdom. It is characterized by an arrest in development that occurs at the blastocyst stage in over 130 species of mammals. Its presumed function is to uncouple mating from parturition, to ensure that both occur at the most propitious moment for survival of the species. Diapause can be facultative, i.e. induced by physiological conditions, or obligate, i.e. present in every gestation of a species. In the latter case, the proximal signals for regulation are related to photoperiod. Three diverse models, the mouse, the mustelid carnivores and the wallaby have been studied in detail. From these studies it can be discerned that, although the endocrine cues responsible for induction of diapause and re-initiation of development vary widely between species, there are a number of commonalities. Evidence to date indicates that the uterus exercises the proximal regulatory influence over whether an embryo enters into and when it exits from diapause. Some factors have been identified that appear crucial to this regulation, in particular, the polyamines. Recent studies indicate that diapause can be induced in species where it does not exist in nature. This suggests that the potential for diapause in mammals to be due to a single evolutionary event, to which control mechanisms adapted when the trait was beneficial to reproductive success. Further work at the molecular, cellular and organismic levels will be required before the physiological basis of diapause is resolved.

Metabolic features of chronic fatigue syndrome

“…The decreases in these metabolites correlated with disease severity as measured by Karnofsky scores (SI Appendix, Table S1 A-D). Much research has been done on the hypometabolic phenotype in other biologic systems, including dauer (35), diapause (40), hibernation (41), estivation (42), torpor (43), ischemic preconditioning (44), ER stress (45), the unfolded protein response (46), autophagy (47,48), and caloric restriction (49). Dauer, which means persistence or long-lived in German, is an example of one well-studied system.…”

Mammalian Reproduction Overview

“…One approach involves the prolonged storage of spermatozoa in the female reproductive tract (Holt, 2011;Holt and Fazeli, 2016); this is usually limited to several days in mammals, although sperm storage in some bat species can last several months (Krishna and Dominic, 1978;Racey et al, 1987;Roy and Krishna, 2011). An alternative approach to the temporal uncoupling of mating and fetal development, known as delayed implantation (Fenelon et al, 2014;Lopes et al, 2004) has been adopted by at least 130 eutherian mammals. In species such as the seal (Pomeroy, 2011), badger (Yamaguchi et al, 2006), Giant panda (Zhang et al, 2009), armadillo and stoat (reviewed by Mead, 1993), the embryos do not develop for some weeks or even months, before the diapause ends and the pregnancy resumes.…”

“…Mechanisms for the control of embryonic diapause in mammals are usually classified as either "facultative" or "obligate" (Fenelon et al, 2014). Facultative diapause is induced by the metabolic stress of lactation, and implantation occurs when the stress is relieved.…”

Embryonic Diapause and Maternal Recognition of Pregnancy in Diapausing Mammals

“…B. Renfree School of BioSciences, The University of Melbourne , Melbourne , VIC 3010 , Australia e-mail: m.renfree@unimelb.edu.au et al 2003 ). Approximately 130 mammalian species have diapause, of which 38 are marsupial, but the morphological and molecular changes that take place during the onset and reactivation from diapause have been examined in very few (Fenelon et al 2014a ;Renfree and Calaby 1981 ). Rodents, especially the mouse, have been the primary model, but two other species, namely, the mink Mustela vison and the tammar wallaby Macropus eugenii have been extensively studied (Cha and Dey 2014 ;Dey and Lim 2006 ;Dey et al 2004 ;Fenelon et al 2014a ;Lopes et al 2006 ;Mead 1993 ;Murphy 2012a , b ;Shaw 2000 , 2014 ;Tyndale-Biscoe and Renfree 1987 ).…”

“…Approximately 130 mammalian species have diapause, of which 38 are marsupial, but the morphological and molecular changes that take place during the onset and reactivation from diapause have been examined in very few (Fenelon et al 2014a ;Renfree and Calaby 1981 ). Rodents, especially the mouse, have been the primary model, but two other species, namely, the mink Mustela vison and the tammar wallaby Macropus eugenii have been extensively studied (Cha and Dey 2014 ;Dey and Lim 2006 ;Dey et al 2004 ;Fenelon et al 2014a ;Lopes et al 2006 ;Mead 1993 ;Murphy 2012a , b ;Shaw 2000 , 2014 ;Tyndale-Biscoe and Renfree 1987 ). Interestingly, the fi rst species in which diapause was recognised was the roe deer, Capreolus capreolus , but it is the only confi rmed ungulate with diapause although there have been suggestions that Pere David's deer ( Elaphurus davidianus ) also may have a period of diapause (Brinklow and Loudon 1993 ).…”