title: Long-day suppressed expression of type 2 deiodinase gene in the mediobasal hypothalamus of the Saanen goat, a short-day breeder: implication for seasonal window of thyroid hormone action on reproductive neuroendocrine axis.
abstract: In most animals that live in temperate regions, reproduction is under photoperiodic control. In long-day breeders such as Japanese quail and Djungarian hamsters, type 2 deiodinase (Dio2) plays an important role in the mediobasal hypothalamus, catalyzing the conversion of prohormone T4 to bioactive T3 to regulate the photoperiodic response of the gonads. However, the molecular basis for seasonal reproduction in short-day breeders remains unclear. Because thyroid hormones are also known to be involved in short-day breeders, we examined the effect of an artificial long-day stimulus on Dio2 expression in the male Saanen goat (Capra hircus), a short-day breeder. Dio2 expression was observed in the caudal continuation of the arcuate nucleus, known as the target site for both melatonin and T4 action. In addition, expression of Dio2 and T3 content in the mediobasal hypothalamus was suppressed by artificial long-day conditions, which is the opposite of the results of long-day breeders. Thyroid hormone action on the development of neuroendocrine anestrus is known to be limited to a specific seasonal window. This long-day suppression of Dio2 may provide a mechanism that accounts for the lack of responsiveness to thyroxine during the mid to late anestrus.
authors.affiliation: Division of Biomodeling, Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa-ku, Nagoya 464-8601, Japan.
authors.forename: Shinobu
authors.initials: S
authors.lastname: Yasuo
authors.forename: Nobuhiro
authors.initials: N
authors.lastname: Nakao
authors.forename: Satoshi
authors.initials: S
authors.lastname: Ohkura
authors.forename: Masayuki
authors.initials: M
authors.lastname: Iigo
authors.forename: Satoko
authors.initials: S
authors.lastname: Hagiwara
authors.forename: Akemitsu
authors.initials: A
authors.lastname: Goto
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Ando
authors.forename: Takashi
authors.initials: T
authors.lastname: Yamamura
authors.forename: Miwa
authors.initials: M
authors.lastname: Watanabe
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Watanabe
authors.forename: Sen-ichi
authors.initials: S
authors.lastname: Oda
authors.forename: Kei-ichiro
authors.initials: K
authors.lastname: Maeda
authors.forename: Gerald A
authors.initials: GA
authors.lastname: Lincoln
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Okamura
authors.forename: Shizufumi
authors.initials: S
authors.lastname: Ebihara
authors.forename: Takashi
authors.initials: T
authors.lastname: Yoshimura
mesh_terms: D000818:Animals; D001947:Breeding; D015971:Gene Expression Regulation, Enzymologic; D006041:Goats; D007453:Iodide Peroxidase / Q000235:genetics*; D009490:Neurosecretory Systems / Q000502:physiology*; D012333:RNA, Messenger / Q000235:genetics; D012098:Reproduction / Q000235:genetics / Q000502:physiology*; D012621:Seasons; D013963:Thyroid Hormones / Q000502:physiology*
chemical_list: D012333:RNA, Messenger; D013963:Thyroid Hormones; D007453:Iodide Peroxidase