G. A. Rutter thanks the Medical Research Council (UK) for Programme grant MR/J0003042/1, the Biotechnology and Biological Sciences Research Council (UK) for a Project grant (BB/J015873/1), the Royal Society for a Wolfson Research Merit Award, and the Wellcome Trust for a Senior Investigator Award (WT098424AIA). T. J. Pullen was a Diabetes research and Wellness Foundation postdoctoral Fellow (SCA/01/F/12). The work leading to this publication has received support from the Innovative Medicines Initiative Joint Undertaking under Grant Agreement no. 155005 (IMIDIA), resources of which are composed of a financial contribution from the European Union's Seventh Framework Programme (FP7/2007-2013) and EFPIA companies' in-kind contribution (G. A. Rutter, P.M.). Additional support was obtained from a Wellcome Trust core grant (075491/Z/04) and from the Advocacy for Neuroacanthocytosis Patients (to A. P. Monaco and A. Velayos-Baeza).