  We introduce a signed variant of (valued) quivers and a mutation rule that
generalizes the classical Fomin-Zelevinsky mutation of quivers. To any signed
valued quiver we associate a matrix that is a signed analogue of the Cartan
counterpart appearing in the theory of cluster algebras. From this matrix, we
construct a Lie algebra via a "Serre-like" presentation.
  In the mutation Dynkin case, we define root systems using the signed Cartan
counterpart and show compatibility with mutation of roots as defined by
Parsons. Using results from Barot-Rivera and P\'erez-Rivera, we show that
mutation equivalent signed quivers yield isomorphic Lie algebras, giving
presentations of simple complex Lie algebras.
