Biology subjects

Bernex, F.

Publications and source records attributed to Bernex, F..

4 recordsLinked to original sources

bioRxiv2026

THE MULTIFUNCTIONAL PROTEIN E4F1 REGULATES MELANOCYTIC FUNCTIONS IN MICE THROUGH PROTEIN TRANSLATION AND MITF EXPRESSION

The multifunctional protein E4 transcription factor 1 (E4F1) is an essential regulator of skin homeostasis, playing a critical role in epidermal stem cell maintenance and keratinocyte differentiation. However, the functions of E4F1 in other skin cell type remain poorly investigated. Here, we describe its role in melanogenesis, the physiological process for synthesis of melanin pigments. Using genetically engineered mouse models that enabled conditional inactivation of E4f1 specifically in melanocytes, we demonstrated that E4f1 loss induces severe pigmentation defects without affecting melanocyte survival nor differentiation. At the molecular level, E4f1 depletion reduces the expression of its direct transcriptional target genes involved in protein translation, including Elp3 and Eef1g, leading to translation alterations and consequently the induction of the Integrated Stress Response (ISR). This response resulted in microphthalmia-associated transcription factor (MITF) downregulation, inducing a decrease in the expression of enzymes involved in melanin synthesis. Consistent with these findings, Elp3 or Eef1g depletion recapitulated the decrease in MITF levels in vitro, and pharmacological inhibition of ISR partially rescued melanin content in vivo, confirming a key role of the E4F1-protein translation-ISR cascade in melanogenesis. Together, our data identify E4F1-associated translation functions as a key regulator of the melanocytic lineage.

physiology↗

bioRxiv2024

Dual CRALBP isoforms unveiled: iPSC-derived retinal modelling and AAV2/5-RLBP1 gene transfer raise considerations for effective therapy

Inherited retinal diseases (IRDs) are clinically and genetically heterogeneous disorders characterised by progressive vision loss. Over 270 causative genes have been identified and variants within the same gene can give rise to clinically distinct disorders. Human induced pluripotent stem cells (iPSCs) have revolutionised disease modelling, by allowing pathophysiological and therapeutic studies in the patient and tissue context. The IRD gene RLBP1 encodes CRALBP, an actor of the rod and cone visual cycles in the retinal pigment epithelium (RPE) and Muller cells, respectively. Variants in RLBP1 lead to three clinical subtypes: Bothnia dystrophy, Retinitis punctata albescens and Newfoundland rod-cone dystrophy. We modelled RLBP1-IRD subtypes by patient-specific iPSC-derived RPE and identified pertinent therapeutic read-outs. We developed an AAV2/5-mediated gene replacement strategy and provided a proof-of-concept in the ex vivo human models that was validated in an in vivo Rlbp1-/- murine model. Most importantly, we identified a previously unsuspected smaller CRALBP isoform that is naturally and differentially expressed in both human and murine retina. The new isoform arises from an alternative methionine initiation site and plays a role in the visual cycle. This work provides novel insights into CRALBP expression and RLBP1-associated pathophysiology and raises important considerations for successful gene supplementation therapy.

molecular biology↗

bioRxiv2023

RIP140 regulates HES1 oscillatory expression and mitogenic activity in colon cancer cells

BackgroundThe transcription factor RIP140 (Receptor Interacting Protein of 140 kDa) regulates intestinal homeostasis and tumorigenesis through the Wnt signaling. In this study, we have investigated its effect on the Notch/HES1 signaling pathway. MethodsThe impact on HES1 expression and activity was evaluated in colorectal cancer (CRC) cell lines and in transgenic mice, invalidated or not for the Rip140 gene in the intestinal epithelium. A tumor microarray and transcriptomic data sets were used to investigate RIP140 and HES1 expression in relation with patient survival. Statistical comparisons were performed with Mann-Whitney or Kruskal-Wallis or Chi2 tests. ResultsIn CRC cells, RIP140 positively regulated HES1 gene expression at the transcriptional level via an RBPJ/NICD-mediated mechanism. In support of these in vitro data, RIP140 and HES1 expression significantly correlated in mouse intestine and in a cohort of CRC samples, analyzed by immunohistochemistry, thus supporting the positive regulation of HES1 gene expression by RIP140. Interestingly, when the Notch pathway is fully activated, RIP140 exerted a strong inhibition of HES1 gene transcription controlled by the level of HES1 itself. Moreover, RIP140 directly interacts with HES1 and reversed its mitogenic activity in human CRC cells. In line with this observation, HES1 levels were associated with a better patient survival only when tumors expressed high levels of RIP140. ConclusionsOur data identify RIP140 as a key regulator of the Notch/HES1 signaling pathway with a dual effect on HES1 gene expression at the transcriptional level and a strong impact on colon cancer cell proliferation.

cancer biology↗

bioRxiv2019

Ki-67 supports global gene expression programmes driving tumourigenesis

Recent studies have shown that the cell proliferation antigen Ki-67 is not required for cell proliferation. Here, we demonstrate that Ki-67 enables implementation of transcriptional programmes conferring cellular plasticity, and is required for each step of tumour initiation, growth and metastasis. Ki-67 knockout causes global transcriptome remodelling, which, in mammary carcinoma cells, inhibits the epithelial-mesenchymal transition in a polycomb-repressive complex 2-dependent manner. This results in suppression of stem cell characteristics and sensitisation to various drug classes. Cancer cells lacking Ki-67 proliferate normally in vivo, but tumour growth is inhibited due to disrupted angiogenesis, and metastasis is abrogated. Finally, mice lacking Ki-67 are resistant to chemical or genetic induction of intestinal tumourigenesis. Thus, Ki-67, which is expressed in all proliferating cancer cells, confers the plasticity required for different steps of carcinogenesis.

cancer biology↗