Correction: Clusters of Conserved Beta Cell Marker Genes for Assessment of Beta Cell Phenotype. - Geert A. Martens; Lei Jiang; Karine H. Hellemans; Geert Stangé; Harry Heimberg; Finn C. Nielsen; Olivier Sand; Jacques Van Helden; Frans K. Gorus; Daniel G. Pipeleers (PLoS ONE, 2012)