F9 and hemoglobin measurement: Although rAAV‐mediated site‐specific repair of a mutated F9 gene has successfully restored hemostasis in HB mice (Li et al, 2011; Barzel et al, 2015), it will be valuable to evaluate the genome editing efficiency in an HB model using rAAV to deliver a short form of Cas9 derived from Staphylococcus aureus (Ran et al, 2015) since CRISPR/Cas9 is the most efficient genome editing tool currently available.