Thiagarajan, L. | bioRxiv Science

bioRxiv2024

miRNA-29-CLIP uncovers new targets and functions to improve skin repair

MicroRNAs (miRNAs) control organogenesis in mammals but their role in specific cell types is not fully explored. miRNAs exert their function by binding mRNAs and inhibiting translation. Skin is an excellent model to study the role of miRNAs in primary cells of epidermal (keratinocytes) and mesodermal (fibroblasts) origin, because the growth of these cells is tightly controlled at translation. Previous research demonstrated that miRNA-29 family functions during skin repair, however, the exact mRNA targets and the downstream mechanisms of miRNA-29-mediated regulation of cell growth is missing. Here, we use miRNA crosslinking and immunoprecipitation (miRNA-CLIP) method to find the direct targets of miRNA-29 in keratinocytes and fibroblasts from human skin. We uncover previously unrecognized roles of miRNA-29 in protein folding and RNA processing, common to all cell types tested, and determine the cell-specific role of miRNA-29. Using modified anti-sense oligonucleotides (ASO) in 2D and 3D cultures of keratinocytes and fibroblasts, we enhanced cell-to-matrix adhesion and found an autocrine and paracrine mechanism of miRNA-29-dependent cell growth. Our results include a comprehensive list and functional analyses of mRNAs directly bound by miRNA-29 keratinocytes and fibroblasts, determined by miRNA-CLIP and ASO-mediated inhibition of miRNA-29 followed by RNA-seq. We reveal a full transcriptome of human keratinocytes with enhanced adhesion to the wound matrix, which supports regeneration of the epidermis and is regulated by miRNA-29. The functions of miRNA-29 identified in this study can provide a new approach to improve cutaneous repair by restoring and enhancing the endogenous mechanisms through the stage-specific delivery of miRNA-29 ASO.

cell biology↗

bioRxiv2022

miR targetome of primary human keratinocytes reveals a function for non-conserved binding sites

The homeostasis of the human body is protected by the skin, where the process of keratinocyte differentiation in outer layers has a crucial role. Cessation of proliferation in the basal layer of keratinocytes and initiation of their subrabasal functions are tightly controlled at the level of gene transcription and message translation. A subset of mRNAs has to be repressed during differentiation, and microRNAs are known to contribute to this by directly binding mRNAs at the 3UTRs. Using results of RNA sequencing from human primary keratinocytes during induced differentiation, we evaluated the predicted binding of highly, moderately, and lowly expressed miRs to their target mRNAs. We found that moderately expressed miRs can regulate more mRNAs, and that they do so using both conserved and non-conserved canonical binding. The cumulative score for the majority of repressed mRNAs revealed a surprisingly weak binding to miRs, and we found a significant contribution of non-conserved sites to the repression of the targets. While the presence of at least one conserved site was necessary for the miR function, its weak binding may be reinforced by a non-conserved site. Together, we found that the combination of conserved and non-conserved sites lower the binding threshold for miR-mRNA interactions to assume a tighter repression of the mRNA target during cell differentiation.

molecular biology↗