title: A novel role for the DNA repair gene Rad51 in Netrin-1 signalling.
abstract: Mutations in RAD51 have recently been linked to human Congenital Mirror Movements (CMM), a developmental disorder of the motor system. The only gene previously linked to CMM encodes the Netrin-1 receptor DCC, which is important for formation of corticospinal and callosal axon tracts. Thus, we hypothesised that Rad51 has a novel role in Netrin-1-mediated axon development. In mouse primary motor cortex neurons, Rad51 protein was redistributed distally down the axon in response to Netrin-1, further suggesting a functional link between the two. We next manipulated Rad51 expression, and assessed Netrin-1 responsiveness. Rad51 siRNA knockdown exaggerated Netrin-1-mediated neurite branching and filopodia formation. RAD51 overexpression inhibited these responses, whereas overexpression of the CMM-linked R250Q mutation, a predicted loss-of-function, had no effect. Thus, Rad51 appears to negatively regulate Netrin-1 signalling. Finally, we examined whether Rad51 might operate by modulating the expression of the Unc5 family, known negative regulators of Netrin-1-responsiveness. Unc5b and Unc5c transcripts were downregulated in response to Rad51 knockdown, and upregulated with RAD51 overexpression, but not R250Q. Thus, Rad51 negatively regulates Netrin-1 signalling, at least in part, by modulating the expression of Unc5s. Imbalance of positive and negative influences is likely to lead to aberrant motor system development resulting in CMMs.
authors.affiliation: Brain Health Research Centre, Department of Anatomy, University of Otago, Dunedin, New Zealand.
authors.forename: K A
authors.initials: KA
authors.lastname: Glendining
authors.affiliation: Department of Pathology, University of Otago, Dunedin, New Zealand.
authors.forename: D
authors.initials: D
authors.lastname: Markie
authors.affiliation: Clinical Genetics Group, Department of Women's and Children's Health, University of Otago, Dunedin, New Zealand.
authors.forename: R J M
authors.initials: RJ
authors.lastname: Gardner
authors.affiliation: Department of Psychology and fMRIOtago, University of Otago, Dunedin, New Zealand.
authors.forename: E A
authors.initials: EA
authors.lastname: Franz
authors.affiliation: Clinical Genetics Group, Department of Women's and Children's Health, University of Otago, Dunedin, New Zealand.
authors.forename: S P
authors.initials: SP
authors.lastname: Robertson
authors.affiliation: Brain Health Research Centre, Department of Anatomy, University of Otago, Dunedin, New Zealand.
authors.forename: C L
authors.initials: CL
authors.lastname: Jasoni
mesh_terms: D000818:Animals; D001369:Axons / Q000378:metabolism; D002478:Cells, Cultured; D051379:Mice; D008810:Mice, Inbred C57BL; D009044:Motor Cortex / Q000166:cytology / Q000254:growth & development / Q000378:metabolism*; D009154:Mutation; D000075386:Netrin Receptors / Q000235:genetics / Q000378:metabolism; D000075388:Netrin-1 / Q000235:genetics / Q000378:metabolism*; D000071446:Neuronal Outgrowth; D051135:Rad51 Recombinase / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction
chemical_list: D000075386:Netrin Receptors; C000617353:Ntn1 protein, mouse; D000075388:Netrin-1; D051135:Rad51 Recombinase; C495154:Rad51 protein, mouse