3.6 | The significant expansion of the actin family in Ascariasis and positive selection genes (PSGs) in B. schroederi
The migration of roundworms is the main cause of VLM (Fig. 4a). Actin polymerization is controlled by intracellular signals that are mediated by small GTPases of the Rho family (RhoA , Rac1 , andCdc42 ; Fig. 4c) (Ammassari-Teule & Segal, 2017). We observed a very significant expansion of the actin family in the B. schroederi genome (Fig. 3d). Surprisingly, the three upstream regulators of actin (Rac1 , ROCK and MLCK ), were under strong positive selection (P <0.01). ROCKphosphorylates the LIM-kinase which then phosphorylates cofilin to promote rho-induced actin cytoskeleton reorganization (Maekawa & M., 1999). These finding suggest a possible effect on myosin-actin interaction. Using the branch-site model implemented in PAML, 475 genes in the B. schroederi genome were found to be under strong positive selection compared with other three roundworms (Supplementary Data 3a). Compared with three roundworms, the acetylcholine receptor subunit alpha-type deg-3 (P=6.5×10-3), which is an important drug target (Jones, Davis, Hodgkin, & Sattelle, 2007), was shown to be under strong positive selection in the B. schroederigenome (Supplementary Data 3a).