New variants expand the neurological phenotype of COQ7 deficiency.

The protein encoded by COQ7 is required for CoQ10 synthesis in humans, hydroxylating 3-demethoxyubiquinol (DMQ10) in the second to last steps of the pathway. COQ7 mutations lead to a primary CoQ10 deficiency syndrome associated with a pleiotropic neurological disorder. This study shows the clinical, physiological, and molecular characterization of four new cases of CoQ10 primary deficiency caused by five mutations in COQ7, three of which have not yet been described, inducing mitochondrial dysfunction in all patients. However, the specific combination of the identified variants in each patient generated precise pathophysiological and molecular alterations in fibroblasts, which would explain the differential in vitro response to supplementation therapy. Our results suggest that COQ7 dysfunction could be caused by specific structural changes that affect the interaction with COQ9 required for the DMQ10 presentation to COQ7, the substrate access to the active site, and the maintenance of the active site structure. Remarkably, patients' fibroblasts share transcriptional remodeling, supporting a modification of energy metabolism towards glycolysis, which could be an adaptive mechanism against CoQ10 deficiency. However, transcriptional analysis of mitochondria-associated pathways showed distinct and dramatic differences between patient fibroblasts, which correlated with the extent of pathophysiological and neurological alterations observed in the probands. Overall, this study suggests that the combination of precise genetic diagnostics and the availability of new structural models of human proteins could help explain the origin of phenotypic pleiotropy observed in some genetic diseases and the different responses to available therapies.

Arginine-guanidinoacetate-creatine pathway in preterm newborns: creatine biosynthesis in newborns.

The phosphocreatine/creatine system is fundamental for the proper development of the embryonic brain. Being born prematurely might alter the creatine biosynthesis pathway, in turn affecting creatine supply to the developing brain. We enrolled 53 preterm and very preterm infants and 55 full-term newborns. The levels of urinary guanidinoacetate, creatine, creatinine and amino acids were measured in the preterm and very preterm groups, 48 h and 9 days after birth and at discharge, and 48 h after birth in the full-term group. Guanidinoacetate concentrations of both preterm and very preterm newborns were significantly higher at discharge than the values for the full-term group at 48 h, while very preterm infants showed urinary creatine values significantly lower than those measured in the full-term group. Our results suggest an impairment of the creatine biosynthesis pathway in preterm and very preterm newborns, which could lead to creatine depletion affecting the neurological outcome in prematurely born infants.