microRNA‐124 regulates Notch and NeuroD1 to mediate transition states of neuronal development

Abstract

MicroRNAs regulate gene expression by destabilizing target mRNA and/or inhibiting translation in animal cells. The ability to mechanistically dissect miR‐124′s function during specification, differentiation, and maturation of neurons during development within a single system has not been accomplished. Using the sea urchin embryo, we take advantage of the manipulability of the embryo and its well‐documented gene regulatory networks (GRNs). We incorporated NeuroD1 as part of the sea urchin neuronal GRN and determined that miR‐124 inhibition resulted in aberrant gut contractions, swimming velocity, and neuronal development. Inhibition of miR‐124 resulted in an increased number of cells expressing transcription factors (TFs) associated with progenitor neurons and a concurrent decrease of mature and functional neurons. Results revealed that in the early blastula/gastrula stages, miR‐124 regulates undefined factors during neuronal specification and differentiation. In the late gastrula/larval stages, miR‐124 regulates Notch and NeuroD1 during the transition between neuronal differentiation and maturation. Overall, we have improved the neuronal GRN and identified miR‐124 to play a prolific role in regulating various transitions of neuronal development.

Early transcriptional similarities between two distinct neural lineages during ascidian embryogenesis

“…Within the second intron of this gene, are two tandem copies of the miR-124 micro-RNA (Chen et al, 2011). The miR-124 family is highly conserved across metazoans with its expression enriched in nervous systems, in particular, in neuronal lineages (Aboobaker et al, 2005; Clark et al, 2010; Konrad and Song, 2023; Lagos-Quintana et al, 2002; Rajasethupathy et al, 2009; Vidyanand et al, 2017). In Ciona embryos, previously published in situ hybridisation against the mature miR-124 product revealed an expression pattern very similar to Pans itself (Chen et al, 2011).…”

Transcription of microRNAs is regulated by developmental signaling pathways and transcription factors

“…For this investigation, we define the beginning of the search region as either the first base of the annotated miRNA feature in Echinobase, if the miRNA is annotated, or, if it is not, the beginning of the BLASTn alignment of the miRNA precursor sequence (as catalogued in miRbase) to the S. purpuratus genome. To evaluate which experimental results were statistically significant, and thus warranted analysis of bioinformatic predictions, fold changes in miRNA levels determined from qPCR data using the Ct -2ΔΔ method were compared to the control miR-200 using a two-tailed Student’s t-test ( Livak and Schmittgen, 2001 ; Konrad and Song, 2023 ). Following generation of a list of predicted binding sites on the same strand of DNA as the miRNA locus, the statistical significance of each predicted site was used to evaluate predictions, with a threshold of p <(1 × 10 −5 ) applied to filter algorithmic output.…”

Evolution and Function of the Notch Signaling Pathway: An Invertebrate Perspective

“…Delta–Notch plays a role in neurogenesis in sea urchin embryos, as Delta is specifically expressed in serotonergic neural precursors in sea urchin embryos and is co-expressed with the zinc finger homeobox (zfhx1/z81), which is one of the targets of anti-neural signaling inhibition and which plays a role in the specification of individual anterior neural precursors and in the differentiation of serotonergic neurons [ 112 ]. The inhibition of Notch signaling by inhibition of γ-secretase , injection of SpDelta morpholinos, CRISPR/Cas9 -induced mutation of SpDelta, or miR-124 regulation all result in more neural precursors and neurons [ 116 , 117 ] In fact, Delta–Notch signaling is used by all three neural subtypes as a lineage-restriction mechanism in L. variegatus [ 120 ]. Thus, Notch signaling limits the number of recruited neural progenitors and regulates the fate of asymmetrically dividing progeny [ 116 ].…”