The bHLH Protein Nulp1 is Essential for Femur Development Via Acting as a Cofactor in Wnt Signaling in Drosophila

Author(s): Q. Zeng, Y. Wan, P. Zhu, M. Zhao, F. Jiang, J. Chen, M. Tang, X. Zhu, Y. Li, H. Zha, Y. Wang, M. Hu, X. Mo, Y. Zhang, Y. Chen, Y. Chen, X. Ye, R. Bodmer, K. Ocorr, Z. Jiang*, J. Zhuang*, W. Yuan*, X. Wu*.

Journal Name: Current Molecular Medicine

Volume 17 , Issue 7 , 2017

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Abstract:

Background: The basic helix-loop-helix (bHLH) protein families are a large class of transcription factors, which are associated with cell proliferation, tissue differentiation, and other important development processes. We reported that the Nuclear localized protein-1 (Nulp1) might act as a novel bHLH transcriptional factor to mediate cellular functions. However, its role in development in vivo remains unknown.

Methods: Nulp1 (dNulp1) mutants are generated by CRISPR/Cas9 targeting the Domain of Unknown Function (DUF654) in its C terminal. Expression of Wg target genes are analyzed by qRT-PCR. We use the Top-Flash luciferase reporter assay to response to Wg signaling.

Results: Here we show that Drosophila Nulp1 (dNulp1) mutants, generated by CRISPR/Cas9 targeting the Domain of Unknown Function (DUF654) in its C terminal, are partially homozygous lethal and the rare escapers have bent femurs, which are similar to the major manifestation of congenital bent-bone dysplasia in human Stuve- Weidemann syndrome. The fly phenotype can be rescued by dNulp1 over-expression, indicating that dNulp1 is essential for fly femur development and survival. Moreover, dNulp1 overexpression suppresses the notch wing phenotype caused by the overexpression of sgg/GSK3β, an inhibitor of the canonical Wnt cascade. Furthermore, qRT-PCR analyses show that seven target genes positively regulated by Wg signaling pathway are down-regulated in response to dNulp1 knockout, while two negatively regulated Wg targets are up-regulated in dNulp1 mutants. Finally, dNulp1 overexpression significantly activates the Top-Flash Wnt signaling reporter.

Conclusion: We conclude that bHLH protein dNulp1 is essential for femur development and survival in Drosophila by acting as a positive cofactor in Wnt/Wingless signaling.

Keywords: bHLH, dNulp1, CRISPR/Cas9, Wnt/Wg signaling, femur, Drosophila.

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Article Details

VOLUME: 17
ISSUE: 7
Year: 2017
Page: [509 - 517]
Pages: 9
DOI: 10.2174/1566524018666180212145714

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