A functional role for semaphorin 4D/plexin B1 interactions in epithelial branching morphogenesis during organogenesis

Abstract

Semaphorins and their receptors, plexins, carry out important functions during development and disease. In contrast to the wellcharacterized plexin A family, however, very little is known about the functional relevance of B-type plexins in organogenesis, particularly outside the nervous system. Here, we demonstrate that plexin B1 and its ligand Sema4d are selectively expressed in epithelial and mesenchymal compartments during key steps in the genesis of some organs. This selective expression suggests a role in epithelial-mesenchymal interactions. Importantly, using the developing metanephros as a model system, we have observed that endogenously expressed and exogenously supplemented Sema4d inhibits branching morphogenesis during early stages of development of the ureteric collecting duct system. Our results further suggest that the RhoA-ROCK pathway, which is activated downstream of plexin B1, mediates these inhibitory morphogenetic effects of Sema4d and suppresses branch-promoting signalling effectors of the plexin B1 signalling complex. Finally, mice that lack plexin B1 show early anomalies in kidney development in vivo. These results identify a novel function for plexin B1 as a negative regulator of branching morphogenesis during kidney development, and suggest that the Sema4d-plexin B1 ligand-receptor pair contributes to epithelial-mesenchymal interactions during organogenesis via modulation of RhoA signalling.

Mechanochemical Control of Mesenchymal Condensation and Embryonic Tooth Organ Formation

“…Importantly, mesenchymal condensation and Pax9 induction were also inhibited when DE isolated at E11 from Sema3f-knockdown embryos was overlaid on DM cell monolayers in vitro , and DE from Sema3f knockdown embryos exhibited significantly reduced repulsion of underlying DM cells (data not shown). These results are consistent with past proposals that short-range repulsion by semaphorins not only defines the epithelial boundary, but also dictate the patterns and size of epithelial buds during development of other ectomesenchymal organs (Chung et al, 2007; Korostylev et al, 2008; Horowitz and Simons, 2008). Taken together, these results confirm that mesenchymal condensation is critical for Pax9 induction, and that it is driven by the opposing actions of Fgf8 and Sema3f that act respectively as attractive and repulsive cues for mesenchymal cell migration in vitro and in vivo .…”

Gene Deletion Mutants Reveal a Role for Semaphorin Receptors of the Plexin-B Family in Mechanisms Underlying Corticogenesis

“…Preparation of recombinant Sema4D. The soluble, N-terminal fragment of recombinant Sema4D was generated as described in detail previously (12,22). Briefly, the calcium phosphate method was applied to transfect HEK293T cells with a plasmid expressing alkaline phosphatase (AP)-tagged Sema4D (Sema4D-AP) or the empty AP expression vector (mock transfection) and cell supernatants were centrifuged and concentrated 60-fold using Amicon-Millipore Centricon Plus-20 concentrators with a cutoff of 100 kDa.…”

Effect of cancer-associated mutations in the PlexinB1 gene

“…Semaphorins affect cell behaviour in diverse ways, regulating cell motility [3], invasive capacity [4], adhesion [5] and cell and axon growth cone collapse [6]. Semaphorins consequently have a function in many physiological processes including angiogenesis [7], cell migration [8,9], immune regulation [10] and organogenesis, affecting nervous system [11,12], lung [13], kidney [14] and cardiovascular development [15,16] and epithelial-mesenchymal interactions [14]. The response of a cell to semaphorin stimulation depends on the type of responding cell and particular semaphorins can generate opposite reactions depending on cell type [17].…”