**Acknowledgements**

The authors wish to express their sincere thanks to Dionisio Martín, Alberto Pendás (Spanish Research Council, CSIC), for their scientific assistance. We thank all the members at the Transgenic Facility (Nucleus, University of Salamanca), Verónica Alonso and Adrian Montaño for their technical assistance and contribution to our CRISPR/Cas9 studies.

### **Conflict of interest-**

The authors declare that they have no conflicts of interest.-
