Biology subjects

Rakotopare, J.

Publications and source records attributed to Rakotopare, J..

3 recordsLinked to original sources

bioRxiv2024

Oncogenic and teratogenic effects of p53Y217C, a mouse model of the human hotspot mutant p53Y220C

Missense "hotspot" mutations localized in six p53 codons account for 20% of TP53 mutations in human cancers. Hotspot p53 mutants have lost the tumor suppressive functions of the wildtype protein, but whether and how they may gain additional functions promoting tumorigenesis remain controversial. Here we generated Trp53Y217C, a mouse model of the human hotspot mutant TP53Y220C. DNA damage responses were lost in Trp53Y217C/Y217C cells, and Trp53Y217C/Y217C fibroblasts exhibited increased chromosome instability compared to Trp53-/- cells. Furthermore, Trp53Y217C/Y217C male mice died earlier than Trp53-/- males, with more aggressive thymic lymphomas. This correlated with an increased expression of inflammation-related genes in Trp53Y217C/Y217C thymic cells compared to Trp53-/- cells. Surprisingly, we recovered only one Trp53Y217C/Y217C female for 22 Trp53Y217C/Y217C males at weaning, a skewed distribution explained by a high frequency of Trp53Y217C/Y217C female embryos with exencephaly and the death of most Trp53Y217C/Y217C female neonates. Strikingly however, when we treated pregnant females with the anti-inflammatory drug supformin (LCC-12) we observed a five-fold increase in the proportion of viable Trp53Y217C/Y217C weaned females in their progeny. Together, these data suggest that the p53Y217C mutation not only abrogates wildtype p53 functions but also promotes inflammation, with oncogenic effects in males and teratogenic effects in females.

cancer biology↗

bioRxiv2023

Mutant mice lacking alternatively spliced p53 isoforms unveil Ackr4 as a male-specific prognostic factor in Myc-driven B-cell lymphomas

The Trp53 gene encodes several isoforms of elusive biological significance. Here we show that mice lacking the Trp53 Alternatively Spliced (AS) exon, thereby expressing the canonical p53 protein but not isoforms with the AS C-terminus, have unexpectedly lost a male-specific protection against Myc-induced B-cell lymphomas. Lymphomagenesis was delayed in p53+/+ E-Myc males compared to p53{Delta}AS/{Delta}AS E-Myc males, but also compared to p53+/+ E-Myc and p53{Delta}AS/{Delta}AS E-Myc females. Pre-tumoral splenic cells from p53+/+ E-Myc males exhibited a higher expression of Ackr4, encoding an atypical chemokine receptor with tumor suppressive effects. We identified Ackr4 as a p53 target gene whose p53-mediated transactivation is inhibited by estrogens, and as a male-specific factor of good prognosis relevant for murine E-Myc-induced and human Burkitt lymphomas. Furthermore, the knockout of ACKR4 increased the chemokine-guided migration of Burkitt lymphoma cells. These data demonstrate the functional relevance of alternatively spliced p53 isoforms and reveal sex disparities in Myc-driven lymphomagenesis.

cancer biology↗

bioRxiv2023

A systematic approach identifies p53-DREAM target genes associated with blood or brain abnormalities

p53 is mainly known as a tumor suppressor, but mouse models revealed that increased p53 activity may cause bone marrow failure, through mechanisms that likely include gene repression mediated by the p53-DREAM pathway. Here we designed a systematic approach to identify p53-DREAM targets whose repression might contribute to abnormal hematopoiesis. We used gene ontology to analyze transcriptomic changes associated with bone marrow cell differentiation and p53 activation, then ChIP-seq data to find promoters bound by the DREAM complex. We next created positional frequency matrices to identify evolutionary conserved sequence elements potentially bound by DREAM. The same approach was developed to find p53-DREAM targets associated with brain abnormalities, also observed in mice with increased p53 activity. Putative DREAM binding sites were found for 151 candidate p53-DREAM target genes, of which 106 are mutated in a blood or brain genetic disorder. Twenty-one DREAM binding sites were tested and found to impact on gene expression in luciferase reporter assays, notably regulating genes mutated in dyskeratosis congenita (Rtel1), Fanconi anemia (Fanca), Diamond-Blackfan anemia (Tsr2), primary microcephaly (Casc5, Ncaph, Wdr62) or pontocerebellar hypoplasia (Toe1). These results provide clues on the role of the p53-DREAM pathway in regulating hematopoiesis and brain development, with implications for tumorigenesis. Author SummaryThe capacity of p53 to activate the transcription of genes important for cell cycle arrest, apoptosis or cellular metabolism has been recognized for decades. By contrast, the potential importance of p53-dependent transcriptional repression emerged more recently. Although p53 frequently appears to repress genes indirectly via the DREAM repressor complex, only a few studies attempted to define p53-DREAM target gene repertoires, often by analyzing cell cycle regulation in fibroblasts. Here we aimed to gain a better appreciation of the clinical relevance of the p53-DREAM pathway by designing a systematic approach for the identification of p53-DREAM targets. Because mouse models with increased p53 activity suffer from bone marrow failure or brain hypoplasia, we relied on transcriptomic changes associated with bone marrow cell differentiation, blood- and brain-related gene ontology terms and RNAseq data from hematopoietic or neural progenitor cells to identify p53-DREAM targets, then created positional frequency matrices to find putative DREAM binding sites. Our study provides a resource of predicted DREAM binding sites for 151 genes associated with blood and/or brain abnormalities, many of which were not previously known to be DREAM targets. Furthermore, our analysis suggests that p53-DREAM alterations may contribute to phenotypic variations in glioblastoma cells.

genetics↗