MicroRNAs show a wide diversity of expression profiles in the developing and mature central nervous system

Abstract

Background: MicroRNA (miRNA) encoding genes are abundant in vertebrate genomes but very few have been studied in any detail. Bioinformatic tools allow prediction of miRNA targets and this information coupled with knowledge of miRNA expression profiles facilitates formulation of hypotheses of miRNA function. Although the central nervous system (CNS) is a prominent site of miRNA expression, virtually nothing is known about the spatial and temporal expression profiles of miRNAs in the brain. To provide an overview of the breadth of miRNA expression in the CNS, we performed a comprehensive analysis of the neuroanatomical expression profiles of 38 abundant conserved miRNAs in developing and adult zebrafish brain.

New meaning in the message: Noncoding RNAs and their role in retinal development

“…In the mouse retina, these mature miRNAs are strongly expressed in photoreceptors, bipolar cells, and amacrine cells of the inner nuclear layer (INL) , while in zebrafish expression is more strongly photoreceptor-specific (Kapsimali et al, 2007). Expression of these miRNAs is reduced several-fold in rd1 mice where rod photoreceptors have fully degenerated, confirming that they are photoreceptor-enriched, though not entirely photoreceptor-specific.…”

“…Studies in zebrafish have also identified several miRNAs with cellspecific expression in retina (Kapsimali et al, 2007). Hundreds of different miRNAs are expressed in the retina, with several dozen showing substantially enriched expression in retina relative to the brain or peripheral tissues (Table 1).…”

“…In zebrafish, miR-9 and miR-92 are highly expressed in the mitotically active ciliary marginal zone (CMZ), and are likely to be progenitor-enriched in mouse (Kapsimali et al, 2007). The targets of these embryonic and early postnatally-enriched mouse miRNAs have yet to be investigated, and no key developmental regulatory genes have yet (Loscher et al, 2007;Xu et al, 2007), species in which retinal expression is observed (Arora et al, 2007;Kapsimali et al, 2007;Karali et al, 2007;Loscher et al, 2007;Xu et al, 2007), developmental expression pattern , mouse cellular expression pattern (Karali et al, 2007;Loscher et al, 2007;Xu et al, 2007), zebrafish cellular expression pattern (Kapsimali et al, 2007), cellular targets (Arora et al, 2007;Xu et al, 2007), expression change in rd animals (Loscher et al, 2007). AC, amacrine cells; CMZ, ciliary marginal zone; GC, ganglion cells; GCL, ganglion cell layer; HC, horizontal cells; HD, homeodomain; INL, inner nuclear layer; MG, Muller glia; NA, not applicable; ND, not determined; NHR, nuclear hormone receptor; ONL, outer nuclear layer; Prog, retinal progenitors; s(prefix) ϭ subset (cell type).…”

MicroRNAs Role in the Central Nervous System Development and Abnormalities

“…The strikingly regulatory effects of miRNAs on the brain during development vary depending on developmental stages and/or the specific brain regions [10,[12][13][14], contributing to the balance between neural stem cell proliferation and differentiation, therefore directing neural cell fates and brain morphogenesis. In general, miR-124, miR-125b, miR-137, miR-7 are contributing to neuronal differentiation, whereas miR-134, miR-184 are effective in maintaining neural stem cells at the undifferentiated status [15,16].…”

Les multiples facettes d’un petit régulateur

“…En effet, des neurones continuent à être générés dans le cerveau des vertébrés à l'âge adulte, à partir des cellules souches neurales. Une expression de miR-9 a été détectée dans les régions de neurogenèse du cerveau adulte chez le poisson zèbre et la souris [28,29]. miR-9 régulerait-il là aussi la dynamique de choix cellulaire ?…”