Post-transcriptional regulation mediated by specific neurofilament introns in vivo

Abstract

Neurons regulate genes post-transcriptionally to coordinate the supply of cytoskeletal proteins, such as the medium neurofilament (NEFM), with demand for structural materials in response to extracellular cues encountered by developing axons. By using a method for evaluating functionality of cis-regulatory gene elements in vivo through plasmid injection into Xenopus embryos, we discovered that splicing of a specific nefm intron was required for robust transgene expression, regardless of promoter or cell type. Transgenes utilizing the nefm 3′-UTR but substituting other nefm introns expressed little or no protein owing to defects in handling of the messenger (m)RNA as opposed to transcription or splicing. Post-transcriptional events at multiple steps, but mainly during nucleocytoplasmic export, contributed to these varied levels of protein expression. An intron of the β-globin gene was also able to promote expression in a manner identical to that of the nefm intron, implying a more general preference for certain introns in controlling nefm expression. These results expand our knowledge of intronmediated gene expression to encompass neurofilaments, indicating an additional layer of complexity in the control of a cytoskeletal gene needed for developing and maintaining healthy axons.

Posttranscriptional regulation of neurofilament proteins and tau in health and disease

“…Other RBPs like ELAV-like RNA binding protein 2 also binds to 3’UTR of NfM mRNA and can cause an increase in translation initiation of NfM mRNA in transfected cells ( Antic et al, 1999 ). Besides 3’UTR, its introns may also be involved in the posttranscriptional regulation of NfM expression in neurons ( Wang and Szaro, 2016 ). Like in NfL and NfH mRNAs, a small group of ALS-linked miRNAs that are expressed in human motor neurons also directly regulate NfM transcript levels ( Campos-Melo et al, 2018 ).…”