Amano Izuki, Takatsuru Yusuke, Toya Syutaro, Haijima Asahi, Iwasaki Toshiharu, Grasberger Helmut, Refetoff Samuel, Koibuchi Noriyuki
1 Department of Integrative Physiology, Gunma University Graduate School of Medicine , Maebashi, Japan .
2 Department of Medicine, The University of Chicago , Chicago, Illinois.
Thyroid. 2016 May;26(5):741-52. doi: 10.1089/thy.2015.0034. Epub 2016 Mar 23.
Thyroid hormone (TH) plays a key role in the developing brain, including the cerebellum. TH deficiency induces organizational changes of the cerebellum, causing cerebellar ataxia. However, the mechanisms causing these abnormalities are poorly understood. Various animal models have been used to study the mechanism. Lacking dual oxidase (DUOX) and its maturation factor (DUOXA) are major inducers of congenital hypothyroidism. Thus, this study examined the organizational changes of the cerebellum using knockout mice of the Duoxa gene (Duoxa-/-).
The morphological, behavioral, and electrophysiological changes were analyzed in wild type (Wt) and Duoxa-deficient (Duoxa-/-) mice from postnatal day (P) 10 to P30. To detect the changes in the expression levels of presynaptic proteins, Western blot analysis was performed.
The proliferation and migration of granule cells was delayed after P15 in Duoxa-/- mice. However, these changes disappeared by P25. Although the cerebellar structure of Duoxa-/- mice was not significantly different from that of Wt mice at P25, motor coordination was impaired. It was also found that the amplitude of paired-pulse facilitation at parallel fiber-Purkinje cell synapses decreased in Duoxa-/- mice, particularly at P15. There were no differences between expression levels of presynaptic proteins regulating neurotransmitter release at P25.
These results indicate that the anatomical catch-up growth of the cerebellum did not normalize its function because of the disturbance of neuronal circuits by the combined effect of hypothyroidism and functional disruption of the DUOX/DUOXA complex.
甲状腺激素(TH)在包括小脑在内的大脑发育中起关键作用。甲状腺激素缺乏会引起小脑的组织学改变,导致小脑性共济失调。然而,导致这些异常的机制尚不清楚。已使用各种动物模型来研究该机制。缺乏双氧化酶(DUOX)及其成熟因子(DUOXA)是先天性甲状腺功能减退症的主要诱因。因此,本研究使用Duoxa基因敲除小鼠(Duoxa-/-)研究小脑的组织学变化。
分析出生后第10天(P)至P30天野生型(Wt)和Duoxa基因缺陷型(Duoxa-/-)小鼠的形态、行为和电生理变化。为检测突触前蛋白表达水平的变化,进行了蛋白质免疫印迹分析。
Duoxa-/-小鼠在P15后颗粒细胞的增殖和迁移延迟。然而,这些变化在P25时消失。尽管Duoxa-/-小鼠在P25时的小脑结构与Wt小鼠无显著差异,但运动协调性受损。还发现Duoxa-/-小鼠中平行纤维-浦肯野细胞突触处的双脉冲易化幅度降低,尤其是在P15时。在P25时,调节神经递质释放的突触前蛋白表达水平无差异。
这些结果表明,由于甲状腺功能减退和DUOX/DUOXA复合物功能破坏的联合作用扰乱了神经回路,小脑的解剖学追赶生长并未使其功能正常化。