were grown at 37oC for 4–7 days until confluent, and then split once before being frozen. After thawing, cells were cultured on 15cm plates and allowed to become confluent before being split onto plates for infections using 0.25% Trypsin. Postnatal tail tip fibroblasts were prepared by removing the bottom third of tail from 3-day-old pups using surgical scissors. Cells were rinsed in ethanol, washed with HBSS (Sigma), and then dissociated using scissors and 0.25% Trypsin. Tail tip fibroblasts were cultured in MEF media until confluent and passaged once before being pooled together and frozen down for further use.
