STATEMENT 24 Basement membrane invasion by the C. elegans anchor cell is coordinated by a 25 dynamic gene regulatory network encompassing cell cycle dependent and independent 26 sub-circuits. 27 28 ABSTRACT 29 Cellular invasion is a key part of development, immunity, and disease. Using the in vivo 30 model of C. elegans anchor cell invasion, we characterize the gene regulatory network 31 that promotes invasive differentiation. The anchor cell is initially specified in a stochastic 32 cell fate decision mediated by Notch signaling. Previous research has identified four 33 conserved transcription factors, fos-1a (Fos), egl-43 (EVI1/MEL), hlh-2 (E/Daughterless) 34and nhr-67 (NR2E1/TLX), that mediate anchor cell specification and/or invasive 35 differentiation. Connections between these transcription factors and the underlying cell 36 biology that they regulate is poorly understood. Here, using genome editing and RNA 37 interference, we examine transcription factor interactions prior to and after anchor cell 38 specification. During invasion we identify that egl-43, hlh-2, and nhr-67 function together 39 in a type I coherent feed-forward loop with positive feedback. Conversely, prior to 40 specification, these transcription factors function independent of one another to regulate 41 LIN-12 (Notch) activity. Together, these results demonstrate that, although the same 42 transcription factors can function in fate specification and differentiated cell behavior, a 43 gene regulatory network can be rapidly re-wired to reinforce a post-mitotic, pro-invasive 44 state. 45 46 Medwig-Kinney, et al. (2019) GRN for invasive differentiation 3