Growth and isolation of Bacterial Artificial Chromosome (BAC) Three BAC clones were purchased from Invitrogen. The DNA was cloned into the EcoRI sites of pBACe3. 6 The DNA of the BAC clones was extracted with Nucleobond PC 2000 EF kit (Macherey-Nagel, Düren Germany) according to the manufacturer's protocol. DNA pellets were dissolved in endotoxin-free water overnight at room temperature, and then used for microinjection.