Hu-Bcl-2 transgenic mice with supernumerary neurons exhibit timing impairment in a complex motor task

Programmed neuronal cell death is common during development, and is thought to be important in the elimination of errors in axonal projection, cell position and sculpting of neuronal circuits. However, the potential importance of programmed cell death for complex behaviour in the adult animal has never been addressed. We studied motor abilities in a strain of transgenic mice with neuronal overexpression of the human Bcl-2 protein, which have supernumerary neurons due to reduced developmental cell death. Our results show that these mice have a clear deficiency in fine timing of motor coordination without impairment of basic motor functions. This is the first indication that altered developmental cell death and the consequent neuronal surplus can impair complex behaviour in the adult animal.