ERRγ is downregulated in injured motor neuron subpopulations following brachial plexus root avulsion

Guangyin Yu; Prince Last Mudenda Zilundu; Linlin Liu; Ke Zhong; Ying Tang; Zemin Ling; Li-Hua Zhou

doi:10.3892/etm.2019.8209

ERRγ is downregulated in injured motor neuron subpopulations following brachial plexus root avulsion

Exp Ther Med. 2020 Jan;19(1):205-213. doi: 10.3892/etm.2019.8209. Epub 2019 Nov 18.

Authors

Guangyin Yu¹, Prince Last Mudenda Zilundu¹, Linlin Liu¹, Ke Zhong¹, Ying Tang¹, Zemin Ling¹, Li-Hua Zhou²

Affiliations

¹ Department of Anatomy, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, Guangdong 510080, P.R. China.
² Department of Anatomy, School of Medicine, Sun Yat-sen University, Guangzhou, Guangdong 510080, P.R. China.

Abstract

Estrogen-related receptor γ (ERRγ) is a member of a small group of orphan nuclear receptor transcription factors that have been implicated in several physiological and pathological processes, including placental development, regulation of metabolic genes or disease. The pattern of expression of ERRγ, its role in neuronal injury and its co-localization with other transcription factors in the spinal cord of rats with brachial plexus injury has not been determined. The expression profile of ERRγ and its co-localization with RNA binding protein fox-1 homolog 3 (NeuN) or cyclic AMP-dependent transcription factor 3 (ATF-3) in the motor neurons of rats that underwent brachial plexus root avulsion were assessed using western blot analysis, immunohistochemistry and immunofluorescence. Fluorogold (FG) was used to mark neurons whose axons were severed. ATF-3 was expressed in the nuclei of motor neurons whose axons were severed by root avulsion. On day 3 post-avulsion, FG and ATF-3 were all co-localized in the injured motor neurons. The level of ERRγ protein in the ipsilateral half of injured spinal cords was significantly decreased compared with that in the contralateral half on days 3, 14 and 28 post-avulsion (all P<0.05). The numbers of ERRγ-positive motor neurons (ERRγ^on) were also notably decreased in the ipsilateral side compared with that in the contralateral side on days 14 and 28 post-avulsion, implying that the expression occurred in α motor neurons that were progressively being lost, a phenomenon that was expected post-brachial plexus avulsion. Almost all large and small ERRγ-positive motor neurons were also NeuN-positive (NeuN^on). However, a few of these were ERRγ^on/NeuN^off (no NeuN signal). Therefore, these results suggested that ERRγ is a non-specific marker of γ motor neurons in rats, and therefore, this specific transcriptional program cannot be used to define functionally distinct motor neuron sub-populations. However, its downregulation on the injured side suggests that it is an important component of the response to injury in motor neurons.

Keywords: brachial plexus root avulsion; estrogen-related receptor γ; motor neuron injury; α motor neurons; γ motor neurons.