The temporal pattern of brachial plexus root avulsion-induced lncRNA and mRNA expression prior to the motoneuron loss in the injured spinal cord segments

The neuronal mechanisms underlying brachial plexus roots avulsion-induced motoneuron death are unknown. Our previous studies showed that the avulsion induced obvious temporal and spatial expression of both degenerative and regenerative genes in the injured spinal cord tissue. Therefore, we hypothesized that lncRNAs (responsible for epigenetic molecular mechanisms) are altered (resulting in altered gene expression patterns) at days 3 and 14 after avulsion. In the present microarray study, 121 lncRNAs (83 up/38 down) and 844 mRNAs (726 up/118 down) were differentially expressed (ipsilateral vs contralateral) after avulsion. We further used qRT-PCR as a validation tool to confirm the expression patterns of 5 lncRNAs and 5 mRNAs randomly selected from our microarray analysis data. The gene ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analyses were performed to identify the critical biological processes and pathways. The noted downregulation of the AF128540 (which targets the nNOS gene) is consistent with the high expression of nNOS protein observed at day 14 post-avulsion. The downregulation of MRAK034299, whose target is the Adra1d gene, is consistent with the downregulation of Adra1d mRNA and protein at days 3 and 14 post avulsion. Immunofluorescence evaluation showed cytoplasmic translocation of ECEL1 after avulsion injury. Moreover, we also found that IL6 and Rac2 are the core genes at days 3 and 14 after unilateral brachial plexus roots avulsion, respectively. Overall, our present data suggest that the altered LncRNAs (avulsion-induced), via unknown epigenetic mechanisms, certainly contribute to the molecular mechanism underpinning motoneuron death or survival. Therefore, the avulsion-induced differentially expressed lncRNAs and mRNAs may offer potential diagnostic and therapeutic targets for BPRA.