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Lutterschmidt DI, Stratton K, Winters TJ, Martin S, Merlino LJ. Neural thyroid hormone metabolism integrates seasonal changes in environmental temperature with the neuroendocrine reproductive axis. Horm Behav 2024; 161:105517. [PMID: 38422864 DOI: 10.1016/j.yhbeh.2024.105517] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/21/2023] [Revised: 02/15/2024] [Accepted: 02/20/2024] [Indexed: 03/02/2024]
Abstract
We asked if environmental temperature alters thyroid hormone metabolism within the hypothalamus, thereby providing a neuroendocrine mechanism by which temperature could be integrated with photoperiod to regulate seasonal rhythms. We used immunohistochemistry to assess the effects of low-temperature winter dormancy at 4 °C or 12 °C on thyroid-stimulating hormone (TSH) within the infundibulum of the pituitary as well as deiodinase 2 (Dio2) and 3 (Dio3) within the hypothalamus of red-sided garter snakes (Thamnophis sirtalis). Both the duration and, in males, magnitude of low-temperature dormancy altered deiodinase immunoreactivity within the hypothalamus, increasing the area of Dio2-immunoreactivity in males and females and decreasing the number of Dio3-immunoreactive cells in males after 8-16 weeks. Reciprocal changes in Dio2/3 favor the accumulation of triiodothyronine within the hypothalamus. Whether TSH mediates these effects requires further study, as significant changes in TSH-immunoreactive cell number were not observed. Temporal changes in deiodinase immunoreactivity coincided with an increase in the proportion of males exhibiting courtship behavior as well as changes in the temporal pattern of courtship behavior after emergence. Our findings mirror those of previous studies, in which males require low-temperature exposure for at least 8 weeks before significant changes in gonadotropin-releasing hormone immunoreactivity and sex steroid hormones are observed. Collectively, these data provide evidence that the neuroendocrine pathway regulating the reproductive axis via thyroid hormone metabolism is capable of transducing temperature information. Because all vertebrates can potentially use temperature as a supplementary cue, these results are broadly applicable to understanding how environment-organism interactions mediate seasonally adaptive responses.
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Affiliation(s)
| | - Kalera Stratton
- Department of Biology, Portland State University, OR, United States
| | - Treven J Winters
- Department of Biology, Portland State University, OR, United States
| | - Stephanie Martin
- Department of Biology, Portland State University, OR, United States
| | - Lauren J Merlino
- Department of Biology, Portland State University, OR, United States
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Melum VJ, Sáenz de Miera C, Markussen FAF, Cázarez-Márquez F, Jaeger C, Sandve SR, Simonneaux V, Hazlerigg DG, Wood SH. Hypothalamic tanycytes as mediators of maternally programmed seasonal plasticity. Curr Biol 2024; 34:632-640.e6. [PMID: 38218183 DOI: 10.1016/j.cub.2023.12.042] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2023] [Revised: 11/07/2023] [Accepted: 12/13/2023] [Indexed: 01/15/2024]
Abstract
In mammals, maternal photoperiodic programming (MPP) provides a means whereby juvenile development can be matched to forthcoming seasonal environmental conditions.1,2,3,4 This phenomenon is driven by in utero effects of maternal melatonin5,6,7 on the production of thyrotropin (TSH) in the fetal pars tuberalis (PT) and consequent TSH receptor-mediated effects on tanycytes lining the 3rd ventricle of the mediobasal hypothalamus (MBH).8,9,10 Here we use LASER capture microdissection and transcriptomic profiling to show that TSH-dependent MPP controls the attributes of the ependymal region of the MBH in juvenile animals. In Siberian hamster pups gestated and raised on a long photoperiod (LP) and thereby committed to a fast trajectory for growth and reproductive maturation, the ependymal region is enriched for tanycytes bearing sensory cilia and receptors implicated in metabolic sensing. Contrastingly, in pups gestated and raised on short photoperiod (SP) and therefore following an over-wintering developmental trajectory with delayed sexual maturation, the ependymal region has fewer sensory tanycytes. Post-weaning transfer of SP-gestated pups to an intermediate photoperiod (IP), which accelerates reproductive maturation, results in a pronounced shift toward a ciliated tanycytic profile and formation of tanycytic processes. We suggest that tanycytic plasticity constitutes a mechanism to tailor metabolic development for extended survival in variable overwintering environments.
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Affiliation(s)
- Vebjørn J Melum
- Arctic seasonal timekeeping initiative (ASTI), UiT-The Arctic University of Norway, Department of Arctic and Marine Biology, Arctic Chronobiology and Physiology Research Group, NO-9037 Tromsø, Norway; University of Strasbourg, Institute of Cellular and Integrative Neurosciences, Strasbourg 67000, France
| | - Cristina Sáenz de Miera
- University of Michigan Medical School, Department of Molecular and Integrative Physiology, Ann Arbor, MI 48109, USA
| | - Fredrik A F Markussen
- Arctic seasonal timekeeping initiative (ASTI), UiT-The Arctic University of Norway, Department of Arctic and Marine Biology, Arctic Chronobiology and Physiology Research Group, NO-9037 Tromsø, Norway
| | - Fernando Cázarez-Márquez
- Arctic seasonal timekeeping initiative (ASTI), UiT-The Arctic University of Norway, Department of Arctic and Marine Biology, Arctic Chronobiology and Physiology Research Group, NO-9037 Tromsø, Norway
| | - Catherine Jaeger
- University of Strasbourg, Institute of Cellular and Integrative Neurosciences, Strasbourg 67000, France
| | - Simen R Sandve
- Faculty of Biosciences, Norwegian University of Life Sciences (NMBU), NO-1432 Ås, Norway
| | - Valérie Simonneaux
- University of Strasbourg, Institute of Cellular and Integrative Neurosciences, Strasbourg 67000, France
| | - David G Hazlerigg
- Arctic seasonal timekeeping initiative (ASTI), UiT-The Arctic University of Norway, Department of Arctic and Marine Biology, Arctic Chronobiology and Physiology Research Group, NO-9037 Tromsø, Norway.
| | - Shona H Wood
- Arctic seasonal timekeeping initiative (ASTI), UiT-The Arctic University of Norway, Department of Arctic and Marine Biology, Arctic Chronobiology and Physiology Research Group, NO-9037 Tromsø, Norway.
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Hazlerigg DG, Appenroth D, Tomotani BM, West AC, Wood SH. Biological timekeeping in polar environments: lessons from terrestrial vertebrates. J Exp Biol 2023; 226:jeb246308. [PMID: 38031958 DOI: 10.1242/jeb.246308] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2023]
Abstract
The polar regions receive less solar energy than anywhere else on Earth, with the greatest year-round variation in daily light exposure; this produces highly seasonal environments, with short summers and long, cold winters. Polar environments are also characterised by a reduced daily amplitude of solar illumination. This is obvious around the solstices, when the Sun remains continuously above (polar 'day') or below (polar 'night') the horizon. Even at the solstices, however, light levels and spectral composition vary on a diel basis. These features raise interesting questions about polar biological timekeeping from the perspectives of function and causal mechanism. Functionally, to what extent are evolutionary drivers for circadian timekeeping maintained in polar environments, and how does this depend on physiology and life history? Mechanistically, how does polar solar illumination affect core daily or seasonal timekeeping and light entrainment? In birds and mammals, answers to these questions diverge widely between species, depending on physiology and bioenergetic constraints. In the high Arctic, photic cues can maintain circadian synchrony in some species, even in the polar summer. Under these conditions, timer systems may be refined to exploit polar cues. In other instances, temporal organisation may cease to be dominated by the circadian clock. Although the drive for seasonal synchronisation is strong in polar species, reliance on innate long-term (circannual) timer mechanisms varies. This variation reflects differing year-round access to photic cues. Polar chronobiology is a productive area for exploring the adaptive evolution of daily and seasonal timekeeping, with many outstanding areas for further investigation.
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Affiliation(s)
- David G Hazlerigg
- Arctic Seasonal Timekeeping Initiative (ASTI), Arctic chronobiology and physiology research group, Department of Arctic and Marine Biology, UiT - The Arctic University of Norway, Tromsø NO-9037, Norway
| | - Daniel Appenroth
- Arctic Seasonal Timekeeping Initiative (ASTI), Arctic chronobiology and physiology research group, Department of Arctic and Marine Biology, UiT - The Arctic University of Norway, Tromsø NO-9037, Norway
| | - Barbara M Tomotani
- Arctic Seasonal Timekeeping Initiative (ASTI), Arctic chronobiology and physiology research group, Department of Arctic and Marine Biology, UiT - The Arctic University of Norway, Tromsø NO-9037, Norway
| | - Alexander C West
- Arctic Seasonal Timekeeping Initiative (ASTI), Arctic chronobiology and physiology research group, Department of Arctic and Marine Biology, UiT - The Arctic University of Norway, Tromsø NO-9037, Norway
| | - Shona H Wood
- Arctic Seasonal Timekeeping Initiative (ASTI), Arctic chronobiology and physiology research group, Department of Arctic and Marine Biology, UiT - The Arctic University of Norway, Tromsø NO-9037, Norway
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