Loss of non-canonical translation initiation factors impairs perinatal cardiac function in mice.

Translation regulation is crucial for cellular homeostasis. Recent studies have demonstrated that, in addition to the conventional AUG start codon, eukaryotic mRNA can also possess non-canonical start codons. These non-canonical start codons, including non-AUG codons, can be found both upstream and downstream of the conventional AUG start codon. Translation of these non-canonical open reading frames (ORFs) has been implicated in the development of diseases, such as cardiac diseases, neurodegeneration and cancer development. Non-AUG translation initiation is regulated by eukaryotic initiation factor (eIF) 2A and eIF2D; however, their target non-canonical ORFs, roles in disease development, and the underlying precise mechanisms of translation regulation remain poorly understood. To address these gaps, we generated mice lacking either or both of Eif2a and Eif2d genes on an ICR background and investigated their cardiac function using echocardiography. The results indicated that simultaneous disruption of both Eif2a and Eif2d led to perinatal cardiac impairment, as evidenced by a significant reduction in cardiac contractility as measured by ejection fraction. Furthermore, the absence of phenotypic changes in single knockouts of either Eif2a or Eif2d suggests that eIF2A and eIF2D function redundantly in their molecular roles. These findings underscore the importance of non-AUG translation initiation in maintaining cardiac function and suggest its broader implications in other physiological and pathological processes. We propose the Eif2a and Eif2d double-knockout mice as a novel stress-sensitive animal model to investigate the molecular mechanisms of translation regulation and their contribution to disease pathogenesis.