Cell proliferation can be modulated by receptor tyrosine kinase-like orphan receptor 2 in the silkworm, Bombyx mori

Abstract

The receptor tyrosine kinase-like orphan receptor 2 (Ror2) is involved in the Wnt/β-catenin signaling pathway which regulates cell proliferation, polarity, differentiation, migration, metabolism and survival. However, the function of Ror2 in the silkworm Bombyx mori is still undisclosed. In the present investigation, we have made an effort to clone the silkworm Ror2 gene (BmRor2). The sequence analysis showed that the open reading frame (ORF) was 1914 bp in size and encoded a protein with the conserved domains of Ror2 protein. The qRT-PCR results indicated that the BmRor2 gene expression level was the highest in the head among all identified tissues on 3rd day of the fifth instar larvae. In the gonads of the different development stages, the BmRor2 gene expression level was highest on the 4th day of the fourth instar larvae. The immunofluorescence assay indicated that the BmRor2 protein was located at the cytomembrane. The effects of BmRor2 protein on the expression levels of genes related to TGF-β, Hippo, JAK-STAT and Notch signaling pathways were investigated by qRT-PCR. The expression levels of crumbs (crb), warts (wts), α-catenin (cat), four-jointed (fj), decapentaplegic (dpp), kibra ortholog (kibra), serrate (serr) and c-myc (myc) genes were down-regulated, whereas, suppressor of cytokine signaling 2 (socs 2) gene expression was up-regulated in the cultured BmN cells after the BmRor2 expression level was up-regulated. Further, cell proliferation was demoted and the size of cells was decreased when BmRor2 expression level was elevated. Our current finding recommended that BmRo2 can regulate TGF- β, Hippo, JAK-STAT, and Notch signaling pathways, and affect cell proliferation and size.