RNA isolation, RT-PCR and qRT-PCR

RNA from murine and human cells was extracted using Trizol reagent (Invitrogen) according to the manufacturer’s protocol. One µg of total RNA was reverse-transcribed using SuperScript II Reverse Transcriptase according to the manufacturer’s protocol (Invitrogen). For RT-PCR, amplification of HN cDNA was performed using Taq DNA polymerase (Invitrogen) in a thermal cycler (UNO II Biometra, Göttingen, Germany) using the following primers: mHN: forward 5′-TGGCTAAAGGAGGGTTCAACTG-3′; reverse 5′-AGAAAACCAAGGGTCTTCTCGTC-3′; hHN: forward 5′-TGTCAACCCAACACAGGCATG-3′; reverse 5′-AAACAGGCGGGGTAAGATTTG-3′. Human β-glucuronidase (hGUSB, forward 5′-CCTGCGTCCCACCTAGAATC-3′; reverse 5′-ATACGGAGCCCCCTTGTCT-3′) and murine cyclophilin (mCYP, forward 5′-TATCTGCACTGCCAAGACTGAGTG-3′; reverse 5′-CTTCTTGCTGGTCTTGCCATTCC-3′) were used as internal controls. Murine HN expression was also assessed by qRT-PCR, using the mCYP as a reference mRNA, and performed as previously described²⁸ (see Supplementary Information).