Evolutionary conservation of Notch signaling inhibition by TMEM131L overexpression
Introduction
The human KIAA0922/TMEM131L gene is a complex locus on chromosome 4q31 comprising 35 exons as well as multiple transcription initiation and alternative splicing sites. It encodes a prototypic type I transmembrane protein and a variety of lower molecular weight variants, the majority of which reside in the nuclear compartment. Combining in vivo and in vitro approaches, we have previously shown that, through its ectodomain (ECD), TMEM131L regulates the canonical Wnt/β-catenin signaling pathway by eliciting the lysosome-dependent degradation of phosphorylated LRP6 co-receptor (pLRP6) [1]. Here, we used a hetero-specific transgenic approach in Drosophila melanogaster to test the potential conservation of this function. Unexpectedly, we found that TMEM131L interference with the Wnt pathway proceeds indirectly through Notch signaling inhibition. Consistent with an evolutionary conservation of Notch signaling inhibition, overexpression of human TMEM131L conferred intrinsic resistance to Notch1 ligation in human CD34+ hematopoietic progenitor cells.
Section snippets
Production and analysis of TMEM131L transgenic Drosophila melanogaster
Flies carrying UAS-TMEM131L were generated by P element transformation. Full-length TMEM131L coding sequence was subcloned in frame into a pUAS-expression vector as described [2]. Transgene injection and production of the corresponding transgenic lines were performed by BestGene. The following Drosophila strains were used: w1118, ptc-GAL4, and pnr-GAL4 provided by Bloomington Stock Center, and hh-GAL4 [3] provided by A. M. Pret (Institut de Biologie Intégrative de la Cellule, Gif-sur-Yvette,
Results and discussion
To examine whether Wnt signaling inhibition by TMEM131L is evolutionary conserved, we expressed a transgene encoding human full-length TMEM131L in Drosophila, by using the UAS-GAL4 system [7] (Fig. 1A). A hedgehog (hh)-GAL4 driver was first used to express TMEM131L in the posterior compartment of the adult wing [8], allowing the anterior compartment to serve as internal control (Fig. 1B). TMEM131L-overexpression resulted in the reduction of wing posterior compartment size associated with a
Conflict of interest
The authors disclose no potential conflicts of interest.
Acknowledgements
We are grateful to Jean-Claude Gluckman for his critical readings of the manuscript. This work was supported by the Ligue Nationale Contre le Cancer and by the Ecole Pratique des Hautes Etudes.
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