Sectioning : Brains from mice (6 or 16 weeks old at harvest) are perfusion fixed in 4% paraformaldehyde at the Wellcome Trust Sanger Institute and sent via courier to the Wellcome Trust Centre for Human Genetics , Oxford. On occasion when mice are homozygous lethal, heterozygous mice are sent in their place. On arrival in Oxford, brains are placed in a 30% sucrose phosphate buffered saline (PBS) solution overnight until they reach osmotic equilibrium. Brains are then sliced coronally at a thickness of 40?m. Sections are collected throughout the extent of the hippocampus. All sections are placed in 96 well plates in antifreeze solution (50% PBS, 25% ethylene glycol, 25% glycerol) and stored at -20?C. Nissl Staining : Stereotaxically matched hippocampal sections are placed in a dish containing PBS and mounted onto electrostatic charged glass slides which are then assembled in a vertical slide holder to dry for at least 30 minutes. Following a brief dip in water to remove dust they are placed in a 0.5%, 0.06% cresyl violet acetate/acetic acid solution for approximately 1 minute. Slides are dipped again in water to remove excess staining solution and taken through a 50%, 75%, 95% and 100% alcohol series. They are then placed in Histoclear for 5 minutes, cover-slipped in DPX mounting medium and left to dry overnight. Scanning and Anatomical Assessment : Slides are scanned at 6400dpi via an Epson Perfection V750 Pro scanner. ImageJ freeware is used to quantify images using a scale of 0.251pixels/ ?m. One section per brain is used for quantification and are stereotaxically matched using thalamic anatomical markers. Measurements assess the hippocampus, cortex, ventricles and corpus callosum. In addition to quantified measures, sections are assessed qualitatively. This involves examining sections under light microscopy for evidence of cellular ectopias.