Naa12 rescues embryonic lethality in Naa10-Deficient Mice in the amino-terminal acetylation pathway

There is an enormous amount of variation in proteins introduced by co- and post-translational modifications, including N-terminal acetylation (NTA), catalyzed by a set of N terminal acetyltransferases (NATs). The NatA complex (including X-linked Naa10 and Naa15) is the major acetyltransferase, with 40-50% of all mammalian proteins being potential substrates. However, the overall role of NTA on a whole-organism level is poorly understood, particularly in mammals. Male mice lacking Naa10 show no globally apparent in vivo NTA impairment and, surprisingly, do not exhibit embryonic lethality. Rather Naa10 nulls display increased neonatal lethality, and the majority of surviving undersized mutants exhibit a combination of hydrocephaly, cardiac defects, homeotic anterior transformation (including an extra thoracic rib), piebaldism and urogenital anomalies. The lack of complete embryonic lethality in Naa10-null mice is explained by the discovery of Naa12, a previously unannotated Naa10-like paralogue with NAT activity that genetically compensates for Naa10. Mice deficient for Naa12 have no apparent phenotype, except for decreased fertility, whereas mice doubly deficient for Naa10 and Naa12 display embryonic lethality, thus presenting the complete machinery for NatA mediated NTA in mouse development.