A novel davunetide (NAPVSIPQQ to NAPVSIPQE) point mutation in activity-dependent neuroprotective protein (ADNP) causes a mild developmental syndrome.

NAP (NAPVSIPQ, drug candidate name, davunetide) is the neuroprotective fragment of activity-dependent neuroprotective protein (ADNP). Recent studies identified NAPVSIP as a Src homology 3 (SH3) domain-ligand association site, responsible for controlling signaling pathways regulating the cytoskeleton. Furthermore, the SIP motif in NAP/ADNP was identified as crucial for direct microtubule end binding protein interaction facilitating microtubule dynamics and Tau microtubule interaction, at the microtubule end binding protein site EB1 and EB3. Most de novo ADNP mutations reveal heterozygous STOP or frameshift STOP aberrations, driving the autistic/intellectual disability-related ADNP syndrome. Here, we report, for the first time on a de novo missense mutation, resulting in ADNP containing NAPVISPQE instead of NAPVSIPQQ, in a child presenting developmental hypotonia, possibly associated with inflammation affecting food intake in early life coupled with fear of peer interactions and suggestive of a novel case of the ADNP syndrome. In silico modeling showed that, the mutation Q (polar side chain) to E (negative side chain) affected the electrostatic characteristics of ADNP (reducing, while scattering the electrostatic positive patch). Comparison with the most prevalent pathogenic ADNP mutation, p.Tyr719* indicated a further reduction in the electrostatic patch. Previously, exogenous NAP partially ameliorated deficits associated with ADNP p.Tyr719* deficits in transfected cells and in CRISPR/Cas9 mutated cell and mouse models. These findings stress the importance of the NAP sequence in ADNP and as a future putative therapy for the ADNP syndrome.