Popa, A. | bioRxiv Science

bioRxiv2018

The ERBB-STAT3 Axis Drives Tasmanian Devil Facial Tumor Disease

The marsupial Tasmanian devil (Sarcophilus harrisii) faces extinction due to transmissible devil facial tumor disease (DFTD). To unveil the molecular underpinnings of DFTD, we designed an approach that combines sensitivity to drugs with an integrated systems-biology characterization. Sensitivity to inhibitors of the ERBB family of receptor tyrosine kinases correlated with their overexpression, suggesting a causative link. Proteomic and DNA methylation analyses revealed tumor-specific signatures linked to oncogenic signaling hubs including evolutionary conserved STAT3. Indeed, ERBB inhibition blocked phosphorylation of STAT3 and arrested cancer cells. Pharmacological blockade of ERBB signaling prevented tumor growth in a xenograft model and resulted in recovery of MHC class I gene expression. This link between the hyperactive ERBB-STAT3 axis and MHC class I mediated tumor immunosurveillance provides mechanistic insights into horizontal transmissibility and led us to the proposition of a dual chemo-immunotherapeutic strategy to save Tasmanian devils from DFTD.

cancer biology↗

bioRxiv2017

The fitness cost of mis-splicing is the main determinant of alternative splicing patterns

Most eukaryotic genes are subject to alternative splicing (AS), which may contribute to the production of functional protein variants or to the regulation of gene expression, notably via nonsense-mediated mRNA decay (NMD). However, a fraction of splice variants might correspond to spurious transcripts, and the question of the relative proportion of splicing errors vs. functional splice variants remains highly debated. We propose here a test to quantify the fraction of AS events corresponding to errors. This test is based on the fact that the fitness cost of splicing errors increases with the number of introns in a gene and with expression level. We first analyzed the transcriptome of the intron-rich unicellular eukaryote Paramecium tetraurelia. We show that both in normal and in NMD-deficient cells, AS rates (intron retention, alternative splice site usage or cryptic intron splicing) strongly decrease with increasing expression level and with increasing number of introns. This relationship is observed both for AS events that are detectable by NMD or not, which invalidates the hypothesis of a possible link with the regulation of gene expression. Our results indicate that in genes with a median expression level, 92%-98% of observed splice variants correspond to errors. Interestingly, we observed the same patterns in human transcriptomes. These results are consistent with the mutation-selection-drift theory, which predicts that genes under weaker selective pressure should accumulate more maladaptive substitutions, and therefore should be more prone to errors of gene expression.

genomics↗