CFTR and cystic fibrosis: This protocol was used to differentiate induced pluripotent stem cells (iPSC) from CF patients carrying a homozygous deletion of F508 in the CFTR gene (resulting in a defective processing of CFTR to the cell membrane) and corrected using clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR associated protein 9 (Cas9) genome editing to target corrective sequences to the endogenous CFTR genomic locus, using a completely excisable piggyBac transposase system [131].