For the purpose of studying neurological diseases, the relatively homogeneous nature of the iN cells we here generated (which differs from the properties of neurons generated by most other approaches; Table 1) is an advantage as well as a disadvantage. It is advantageous in that phenotypes will not be occluded by heterogeneous properties of different types of neurons, but it might be disadvantageous if phenotypes that are specific to a particular subset of neurons will be examined. Thus, this system will be generally applicable to analysis of mutations in genes with a general neuronal action, for example FMRP, neuroligins, and MECP2. However, even for analysis of diseases that manifest in specific types of neurons, such as Parkinson’s disease, Ngn2 iN cells may be useful because in many neurological diseases the pathological processes are not restricted to the specfiic types of neurons in which the disease becomes manifest. Specifically, even if disease such as Parkinson’s or Huntington’s disease manifest in a dysfunction of dopaminergic or striatal neurons, respectively, this manifestation likely represents a particular vulnerability of specific types of neurons to
