The Mechanisms Behind Diapause
A literature review focused on the process of diapause and its underlying mechanisms across five species of mammal.
This review is accompanied by a lay summary written for non-specialist audiences, which can be viewed here.
Abstract
Diapause is a biological enigma in which the development of an embryo can be interrupted, marked by a reduction in metabolic activity. It is a natural phenomenon occurring in insects, crustaceans, and over 130 species of mammals. This review identifies key findings from studies to present the current understanding of diapause in mammals. The various factors involved in the control of facultative and obligate diapause across five species of mammal are compared. Conserved mechanisms regarding environmental, hormonal, and genetic regulation are discussed in detail. Common factors between species are identified to determine whether the state of diapause can be induced in closely related species. Potential future applications in conservation and medicine are discussed.
Facultative diapause is induced by suckling young, which releases prolactin. This hormone has inhibitory effects on the corpus luteum and prevents the release of progesterone, aiding in the delay of implantation. Termination of diapause is brought about by the removal of suckling young and the subsequent decrease in prolactin concentrations. Obligate diapause is induced through the alterations of photoperiod length and the levels of melatonin which influence prolactin concentrations. Notable exceptions to these mechanisms include the tammar wallaby, which demonstrates both facultative and obligate diapause, and the roe deer, in which hormones such as prolactin do not appear to play significant roles in the induction or termination of diapause. Instead, it is theorised that genetic factors including Msx genes and mTORC1 are responsible for the induction and termination of diapause, though further study is required to confirm their involvement.
Recent studies suggest that a greater understanding of the biological mechanisms behind this developmental enigma could aid in the treatment of cancer through the prevention of drug-tolerant persister states in tumours. In addition, tolerance to environmental changes could be introduced in various species through the activation of diapause mechanisms, conferring stress resistance towards climate change and resource loss and aiding in the preservation of endangered species.
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