Impact of Mutations in Aminoacyl tRNA Synthetases on Protein Translation and Cellular Stress (FIBROMARS)

Impact of Loss-of-function Mutations of Genes Encoding Cytosolic Aminoacyl-tRNA Synthetases on Protein Translation and Responses to Cellular Stress

Mutations in the genes encoding cytosolic aminoacyl-tRNA synthetases are responsible for early-onset multisystemic diseases including to varying degrees interstitial lung disease, liver damage, neurological and digestive disorders, and systemic inflammation. These are rare and severe diseases whose pathophysiology is poorly understood. The investigative team hypothesizes that mutations within these genes are responsible for a decrease in protein translation and lead to a cellular stress response similar to that induced by amino acid deprivation. The investigative team also hypothesizes that these alterations could be corrected by high-dose supplementation in the culture medium of the corresponding amino acid. The main objective of the study is to precisely determine the consequences of cytosolic aminoacyl-tRNA synthetase mutations at the cell level on protein translation.

Mutations in the genes encoding cytosolic aminoacyl-tRNA synthetases are responsible for early-onset multisystemic diseases including to varying degrees interstitial lung disease, liver damage, neurological and digestive disorders, and systemic inflammation. These are rare and severe diseases whose pathophysiology is poorly understood. The investigative team hypothesizes that mutations within these genes are responsible for a decrease in protein translation and lead to a cellular stress response similar to that induced by amino acid deprivation. The investigative team also hypothesizes that these alterations could be corrected by high-dose supplementation in the culture medium of the corresponding amino acid. The main objective of the study is to precisely determine the consequences of cytosolic aminoacyl-tRNA synthetase mutations at the cell level on protein translation. The parameters below will be studied in vitro in cell culture from skin biopsies of patients and commercially available human dermal fibroblasts from newborns and adults: Determination of total protein content The incorporation of d-methionine, leucine, tyrosine or phenylalanine into proteins The study of polysomes profiling The study of the assembly of the ribosomal 43S pre-initiation complex The phosphorylation of eIF2α and 4EBP and the expression of ATF4 Ribosome profiling Transfer RNA (tRNA) sequencing The production of reactive oxygen species (ROS) The results of these studies will be compared: Between patient cells and control cells Between genetically corrected patient cells, by stable transfection of the wild-type cDNA of the concerned genes and uncorrected cells Between patient cells cultured in medium enriched with methionine, phenylalanine, tyrosine or leucine and cells cultured in standard medium.

Interstitial Lung and Liver Disease, Infantile Liver Failure Syndrome 1, Neurologic, Endocrine and Pancreatic Disease, Multisystem, Infantile-Onset 2, Rajab Interstitial Lung Disease With Brain Calcifications 2

Cytosolic aminoacyl-tRNA synthetase, Mutations in the MARS1 gene, Mutations in the LARS1 gene, Mutations in the YARS1 gene, Mutations in the FARSA gene

A skin biopsy performed on the forearm or thigh depending on the patient's age and wishes, with a biopsy punch with a diameter of 3 to 4 mm depending on the child's age (3 for children under 3 years, 4 beyond). Culture of fibroblasts and immortalization.

Incorporation of methionine and phenylalanine by labelled amino-acid fluorescent assays using ready-to-use kits.

Study of the assembly of the ribosomal 43S pre-initiation complex by co-immunoprecipitation experiments.

Production of reactive oxygen species (ROS) by fluorescent measurement after cells' incubation with 2',7'- dichlorodihydrofluorescein diacetate (H2DCFDA).

Inclusion Criteria: Patients carrying mutations in the MARS1, LARS1, YARS1 or FARSA gene responsible for a multi-systemic phenotype Information and consent of the patient if an adult and of the holders of parental authority if a minor patient and of the minor patient Exclusion Criteria: - Non-consent of one of the holders of parental authority or of the minor patient or of adult patient