Henriet, E. | Search bioRxiv

bioRxiv2023

Purine biosynthesis pathways are required for myogenesisin Xenopus laevis

Purines are required for fundamental biological processes and alterations in their metabolism lead to severe genetic diseases associated with developmental defects whose etiology remains unclear. Here, we studied the developmental requirements for purine metabolism using the amphibian Xenopus laevis as a vertebrate model. We provide the first functional characterization of purine pathway-genes and show that these genes are mostly expressed in nervous and muscular embryonic tissues. Morphants were generated to decipher the functions of these genes, with a focus on the adenylosuccinate lyase (ADSL), an enzyme required for both salvage and de novo purine pathways. adsl.L knock-down leads to severe reduction in the expression of the Myogenic Regulatory Factors (MRFs: Myod1, Myf5 and Myogenin), thus resulting in defects in somitogenesis and in the formation and/or migration of both craniofacial and hypaxial muscle progenitors. Similar alterations were observed upon reduced expression of hprt1.L and ppat, two genes specific to the salvage and the de novo pathways, respectively. In conclusion, our data shows for the first time that de novo and recycling purine pathways are essential for myogenesis and highlight new mechanisms in the regulation of MRFs gene expression.

developmental biology↗

bioRxiv2019

Counteracting resistance to targeted therapy in melanoma by inhibiting discoidin domain receptors

Anti-BRAF plus anti-MEK are used as first-line treatment of patients with metastatic melanomas harboring BRAF V600E mutation. The main issue with targeted therapy is acquired cellular resistance. In 70% of acquired resistance, melanoma cells switch their phenotype and become more aggressive and invasive. The molecular signature of this phenotype is MITF low, AXL high associated with actin cytoskeleton reorganization. After this switch, resistant cells present an anarchic cell proliferation due to MAP kinase pathway hyper-activation. We demonstrate that resistant cell lines presenting phenotype switching overexpress DDR1 and DDR2. We show that DDR2 inhibition induces a decrease in AXL and reduces actin stress fiber formation. Once this phenotype switching is acquired, we report that both DDRs promotes tumor cell proliferation, but only DDR2 can over-activate the MAP kinase pathway in resistant invasive cells in vitro and in vivo. Therefore, DDRs inhibition could be a promising strategy for countering this resistance mechanism. SignificanceOur results show that DDR2 is a relevant target in melanoma resistance. DDR2 is required at the beginning of resistance for melanoma cell phenotype switching to occur. After phenotype switching, DDRs promote tumor cell proliferation of resistant invasive melanoma cells, but only DDR2 is able to over-activate the MAP kinase pathway. We put forward dasatinib (a DDR inhibitor) as a potential second-line treatment after targeted dual therapy for resistant patients overexpressing DDRs.

cancer biology↗