Neurogenetics II: complex disorders.

The genetic analysis of common neurological disorders will be a difficult and protracted endeavour. Genetics is only one of many disciplines that will be required but it has already thrown considerable light on the aetiology of several major neurological disorders through the analysis of rare inherited subgroups. The identification of individual susceptibility genes with variants of smaller effect will be more difficult but there is no sharp demarcation between large and small genetic effects, so that many new and important insights will emerge using existing and new technologies. The availability of improved neuroimaging, better animal models of disease and new genetic tools, such as high-throughput gene chips, expression microarrays and proteomics, are extending the range of traditional genetic mapping tools. Finally, an understanding of the genetic and epigenetic mechanisms that restrain the differentiation and integration of human neural stem cells into mature neuronal networks could have a major impact on clinical practice. These approaches will be illustrated in the context of Alzheimer disease, Parkinson disease and synucleinopathies, tauopathies, amyotrophic lateral sclerosis and stroke.