A developmental gene regulatory network for C. elegans anchor cell invasion

Abstract

Cellular invasion is a key part of development, immunity, and disease. Using the in vivo model of C. elegans anchor cell invasion, we characterize the gene regulatory network that promotes cell invasion. The anchor cell is initially specified in a stochastic cell fate decision mediated by Notch signaling. Previous research has identified four conserved transcription factors, fos-1a (Fos), egl-43 (EVI1/MEL), hlh-2 (E/Daughterless) and nhr-67 (NR2E1/TLX), that mediate anchor cell specification and/or invasive behavior. Connections between these transcription factors and the underlying cell biology that they regulate are poorly understood. Here, using genome editing and RNA interference, we examine transcription factor interactions before and after anchor cell specification. Initially, these transcription factors function independently of one another to regulate LIN-12 (Notch) activity. Following anchor cell specification, egl-43, hlh-2, and nhr-67, function largely parallel to fos-1 in a type I coherent feed-forward loop with positive feedback to promote invasion. Together, these results demonstrate that the same transcription factors can function in cell fate specification and differentiated cell behavior, and that a gene regulatory network can be rapidly assembled to reinforce a post-mitotic, pro-invasive state.

The Caenorhabditis elegans homolog of the Evi1 proto-oncogene, egl-43, coordinates G1 cell cycle arrest with pro-invasive gene expression during anchor cell invasion

“…Here, we report that the egl-43 gene, the C. elegans ortholog of the human Evi1 proto-oncogene, functions in a regulatory network together with the transcription factors NHR-67 and FOS-1 to control AC invasion (Fig 7). Our results are consistent with a recent report by Medwig-Kinney et al [34] demonstrating similar interactions between egl-43, nhr-67 and fos-1 during AC invasion. The inclusion of the LIN-12 NOTCH pathway in our model further expands Fig 6.…”

“…Even though no function of JUN-1 in AC invasion has been reported, this observation might indicate that EGL-43 regulates AP-1 activity in other processes, such as ovulation or lifespan [32]. Moreover, EGL-43::GFP was enriched at other previously reported targets, including mig-10 [33], hlh-2 [34] and zmp-1 [11] (S5 Table). On the other hand, no specific binding to the nhr-67 [34] or cdh-3 [11] genes was observed, suggesting that these two genes may be indirectly regulated by EGL-43.…”

“…While overexpression of CKI-1 efficiently rescued the AC proliferation and invasion phenotype caused by nhr-67 RNAi, CKI-1 only slightly suppressed the AC proliferation phenotype and had no effect on the invasion defects caused by egl-43 RNAi. However, it should be noted that the transgene we used to overexpress CKI-1 did not fully suppress the nhr-67 AC proliferation and invasion phenotypes, while a different cki-1 overexpression transgene used by Medwig-Kinney et al [34] caused a complete rescue of nhr-67 RNAi, probably due to higher levels of CKI-1 expression. It is therefore possible that a further increase in CKI-1 levels beyond the concentration we reached may also suppress the egl-43 phenotype.…”

Visualizing the metazoan proliferation-terminal differentiation decisionin vivo

“…Next, we selected the promoter from the 40S ribosomal subunit protein S27 (rps-27), which is ubiquitously expressed in all cycling and terminally differentiated somatic cells during C. elegans development (Ruijtenberg and van den Heuvel, 2015). Using CRISPR/Cas9-genome engineering, we inserted the optimized CDK biosensor into a neutral site on chromosome I (de la Cova et al, 2017;Medwig-Kinney et al, 2019). Examination of single copy insertion lines in a wild-type background showed consistent strong DHB::GFP and H2B::2x-mKate2 localization in all cells from mid-embryogenesis through adulthood ( Figure 1D), with weaker germline expression ( Figure 1D).…”

To Divide or Invade: A Look Behind the Scenes of the Proliferation-Invasion Interplay in the Caenorhabditis elegans Anchor Cell

“…AC invasion in Caenorhabditis elegans is an excellent model to investigate the various checkpoints regulating developmental cell invasion, including G1 cell cycle arrest required for BM breaching (Matus et al, 2015 ; Deng et al, 2020 ; Medwig-Kinney et al, 2020 ). AC invasion occurs during the mid- to late-L3 larval stage in order to establish a connection between the uterus and developing vulva (Sherwood and Sternberg, 2003 ) ( Figure 1 ).…”