Biology subjects

Paillard, L.

Publications and source records attributed to Paillard, L..

5 recordsLinked to original sources

bioRxiv2026

Mapping of CELF1-RNA interactions reveals post-transcriptional control of lens development

Precise post-transcriptional regulation of gene expression is essential for vertebrate lens development. Disruption of the gene encoding the RNA-binding protein CELF1 leads to early-onset cataract in mice. Here, using iCLIP-seq in lenses, we mapped transcriptome-wide CELF1 binding sites, revealing interactions with the 3'UTRs of key transcripts involved in lens development and pathology like Gja8, Jag1, Maf, Pax6, or Prox1. Integrated analysis with transcriptomic data and luciferase reporter assays demonstrated that binding of CELF1 protein represses its target mRNAs by destabilizing transcripts and/or inhibiting their translation. Indeed, the cataract-linked genes Maf and Gja8 are upregulated in Celf1cKO lenses. In Xenopus laevis, overexpression of maf resulted in abnormal lens structure and eye morphology, confirming the developmental relevance of CELF1-mediated repression. Our findings uncover a post-transcriptional network in which CELF1 controls lens morphogenesis by limiting the expression of critical genes at the mRNA level to achive their proper dosage.

developmental biology↗

bioRxiv2023

Eye lens organoids going simple: characterization of a new 3-dimensional organoid model for lens development and pathology

The ocular lens, along with the cornea, focuses light on the retina to generate sharp images. Opacification of the lens, or cataract, is the leading cause of blindness worldwide. Presently, the best approach for cataract treatment is to surgically remove the diseased lens and replace it with an artificial implant. Although effective, this is costly and can have post-surgical complications. Toward identifying alternate treatments, it is imperative to develop organoid models relevant for lens studies and anti-cataract drug screening. Here, we demonstrate that by culturing mouse lens epithelial cells under defined 3-dimensional (3D) culture conditions, it is possible to generate organoids that display optical properties and recapitulate many aspects of lens organization at the tissue, cellular and transcriptomic levels. These 3D cultured lens organoids can be rapidly produced in large amounts. High-throughput RNA-sequencing (RNA-seq) on specific organoid regions isolated by laser capture microdissection (LCM) and immunofluorescence assays demonstrate that these lens organoids display spatiotemporal expression of key lens genes, e.g., Jag1, Pax6, Prox1, Hsf4 and Cryab. Further, these lens organoids are amenable to induction of opacities. Finally, knockdown of a cataract-linked RNA-binding protein encoding gene, Celf1, induces opacities in these organoids, indicating their use in rapidly screening for genes functionally relevant to lens biology and cataract. In sum, this lens organoid model represents a compelling new tool to advance the understanding of lens biology and pathology, and can find future use in the rapid screening of compounds aimed at preventing and/or treating cataract.

cell biology↗

bioRxiv2022

EXONIZATION BY THE EMERGENCE OF A CLEAVAGE-POLYADENYLATION SITE

Exonization is the evolutionary process of recruitment of new exonic regions from previously intronic regions. It is a major contributor to the increased complexity of alternative splicing. Here, we explore exonization mediated by the emergence of a novel cleavage-polyadenylation site in an intron. In Xenopus laevis, the tpm1 gene, which encodes muscular tropomyosin, contains alternative terminal exons. In adult muscles and embryonic hearts, exon 9A is joined to the terminal exon 9B. In embryonic somites, it is joined to the exonic region 9, which is transcribed from the intron immediately downstream of exon 9A. Consequently, exon 9A is either an internal exon when ligated to exon 9B, or a part of a terminal exon along with region 9. We show here that region 9 is present only in amphibians and coelacanths. This suggests that it emerged in sarcopterygians and was lost in amniotes. We used antisense morpholino oligonucleotides to mask the regions of tpm1 pre-mRNA that potentially regulate the inclusion of exon 9A9. This revealed that the definition of exon 9A9 relies on a weak cleavage-polyadenylation site and an intronic enhancer, but is independent of the 3 splice site. We demonstrate that RNAs containing exon 9B are toxic in somites. This may have contributed to the evolutionary pressure that led to the exonization of region 9 in sarcopterygians. These findings reveal the emergence of a novel cleavage-polyadenylation site that avoids the accumulation of a toxic RNA as a novel mechanism for exonization-mediated diversification of terminal exons.

evolutionary biology↗

bioRxiv2021

THE SPLICING FACTOR PTBP1 REPRESSES TP63 γ ISOFORM PRODUCTION IN SQUAMOUS CELL CARCINOMA

The TP63 gene encodes the transcription factor p63. It is frequently amplified or overexpressed in squamous cell carcinomas. Owing to alternative splicing, p63 has multiple isoforms called , {beta}, {gamma} and {delta}. The regulatory functions of p63 may be isoform-specific. The isoform inhibits the epithelial to mesenchymal transition (EMT) and controls apoptosis, while the {gamma} isoform promotes EMT. Here, we observed in TCGA data that a high ratio of the TP63{gamma} isoform to the other isoforms is a pejorative factor for the survival of patients with head and neck squamous cell carcinoma (HNSCC). We therefore addressed the regulation of the {gamma} isoform. In several tissues (GTEX data), the expression of the RNA-binding protein PTBP1 (polypyrimidine tract binding protein 1) is negatively correlated with the abundance of TP63{gamma}. Accordingly, we demonstrated that PTBP1 depletion in HNSCC cell lines leads to an increase in abundance of the {gamma} isoform. By RNA immunoprecipitation and in vitro interaction assays, we showed that PTBP1 directly binds to TP63 pre-mRNA in close proximity to the TP63{gamma}-specific exon. The region around the TP63{gamma}-specific exon was sufficient to elicit a PTBP1-dependent regulation of alternative splicing in a splice reporter minigene assay. Finally, we demonstrated that the regulation of TP63{gamma} production by PTBP1 is conserved in amphibians, revealing that it encounters a strong evolutionary pressure. Together, these results identify TP63{gamma} as a prognostic marker in HNSCC, and identify PTBP1 as a direct negative regulator of its production.

cancer biology↗

bioRxiv2018

The RNA-binding proteins CELF1 and ELAVL1 cooperatively control alternative splicing

ELAVL1 and CELF1 are RNA-binding proteins that are involved in alternative splicing control. To explore their functional relationship, we looked for mRNAs that are differentially spliced following the depletion of CELF1, ELAVL1, or both. We found that these proteins control the usage of their target exons in the same direction. Double depletion has a greater effect than individual depletions, showing that CELF1 and ELAVL1 exert additive control. To confirm these results, we carried out RT-PCR on the alternative cassette exons of several mRNAs, including CD44, WNK1, PHACTR2, MICAL3, SPTBN1, and PPP3CB. Using FRET, we found that CELF1 and ELAVL1 directly interact in cell nuclei. We demonstrated that the combined levels of CELF1 and ELAVL1 are a valuable biomarker in several cancers, even when their individual levels may yield very limited information. CD44 alternative splicing probably accounts in part for the effects of CELF1 and ELAVL1 levels on patient survival. These data point to strong functional interactions between CELF1 and ELAVL1 in the control of mRNA isoform production, resulting in significant impacts on human pathology.

molecular biology↗