Matrix metalloproteinases promote motor axon fasciculation in theDrosophilaembryo

Abstract

Matrix metalloproteinases (MMPs) are a large conserved family of extracellular proteases, a number of which are expressed during neuronal development and upregulated in nervous system diseases. Primarily on the basis of studies using pharmaceutical inhibitors, MMPs have been proposed to degrade the extracellular matrix to allow growth cone advance during development and hence play largely permissive roles in axon extension. Here we show that MMPs are not required for axon extension in the Drosophila embryo, but rather are specifically required for the execution of several stereotyped motor axon pathfinding decisions. The Drosophila genome contains only two MMP homologs, Mmp1 and Mmp2. We isolated Mmp1 in a misexpression screen to identify molecules required for motoneuron development. Misexpression of either MMP inhibits the regulated separation/defasciculation of motor axons at defined choice points. Conversely, motor nerves in Mmp1 and Mmp2 single mutants and Mmp1 Mmp2 double mutant embryos are loosely bundled/fasciculated, with ectopic axonal projections. Quantification of these phenotypes reveals that the genetic requirement for Mmp1 and Mmp2 is distinct in different nerve branches, although generally Mmp2 plays the predominant role in pathfinding. Using both an endogenous MMP inhibitor and MMP dominantnegative constructs, we demonstrate that MMP catalytic activity is required for motor axon fasciculation. In support of the model that MMPs promote fasciculation, we find that the defasciculation observed when MMP activity is compromised is suppressed by otherwise elevating interaxonal adhesion -either by overexpressing Fas2 or by reducing Sema-1a dosage. These data demonstrate that MMP activity is essential for embryonic motor axon fasciculation.KEY WORDS: Drosophila melanogaster, Motoneuron, Motor axon pathfinding, Mmp1, Mmp2, Sema-1a, Fasciclin II, Timp Development 135, 95-109 (2008)

Crimpy inhibits the BMP homolog Gbb in motoneurons to enable proper growth control at theDrosophilaneuromuscular junction

“…Embryo fixation, in situ hybridization and immunohistochemistry were carried out as previously described (Miller et al, 2008). For all larval experiments, ten virgin females were crossed to five males, and bottles were maintained at 25°C for 4 days before removing adults.…”

Metalloproteinase MT5-MMP is an essential modulator of neuro-immune interactions in thermal pain stimulation

“…Numerous studies have implicated ADAMs in the formation of neural connections in the developing nervous system (8)(9)(10)(11). In contrast, the potential role of MMPs in axonal elongation and guidance through regulated cleavage of ligands and/or receptors involved in axon navigation has been more elusive (7,(11)(12)(13).…”

Two matrix metalloproteinase classes reciprocally regulate synaptogenesis

“…Drosophila Timp inhibits mammalian Mmps and mammalian Timps inhibit Drosophila Mmps, demonstrating an evolutionarily conserved function (Llano et al, 2000;Wei et al, 2003). Like the roles of mouse Mmps in neurodevelopment, Drosophila Mmps have been shown to regulate embryonic axonogenesis, BMP-dependent motor axon pathfinding and dendritic remodeling in larval sensory neurons (Kuo et al, 2005;Miller et al, 2008Miller et al, , 2011Yasunaga et al, 2010). Importantly, mammalian Mmps are upregulated in neurological disorders (Huntley, 2012), including multiple sclerosis (Agrawal et al, 2008), epilepsy (Pollock et al, 2014;Wilczynski et al, 2008) and Fragile X syndrome (FXS), the most common heritable determinant of intellectual disability and autism spectrum disorders (Gatto and Broadie, 2011).…”