ABSTRACT
Aminoacyl-tRNA synthetases (ARSs) are ubiquitously expressed enzymes implicated in several dominant and recessive disease phenotypes. The canonical function of ARSs is to couple an amino acid to a cognate transfer RNA (tRNA). We identified three novel disease-associated missense mutations in the alanyl-tRNA synthetase (AARS) gene in three families with dominant axonal Charcot-Marie-Tooth (CMT) disease. Two mutations (p.Arg326Trp and p.Glu337Lys) are located near a recurrent pathologic change in AARS, p.Arg329His. The third (p.Ser627Leu) is in the editing domain of the protein in which hitherto only mutations associated with recessive encephalopathies have been described. Yeast complementation assays demonstrated that two mutations (p.Ser627Leu and p.Arg326Trp) represent loss-of-function alleles, while the third (p.Glu337Lys) represents a hypermorphic allele. Further, aminoacylation assays confirmed that the third mutation (p.Glu337Lys) increases tRNA charging velocity. To test the effect of each mutation in the context of a vertebrate nervous system, we developed a zebrafish assay. Remarkably, all three mutations caused a pathological phenotype of neural abnormalities when expressed in zebrafish, while expression of the human wild-type messenger RNA (mRNA) did not. Our data indicate that not only functional null or hypomorphic alleles, but also hypermorphic AARS alleles can cause dominantly inherited axonal CMT disease.
Subject(s)
Alanine-tRNA Ligase/genetics , Amino Acyl-tRNA Synthetases/genetics , Charcot-Marie-Tooth Disease/genetics , RNA, Transfer/genetics , Adult , Alleles , Amino Acids/genetics , Animals , Charcot-Marie-Tooth Disease/pathology , Female , Gene Expression Regulation, Enzymologic/genetics , Genetic Heterogeneity , Humans , Male , Middle Aged , Mutation/genetics , Pedigree , Yeasts/genetics , Zebrafish/geneticsABSTRACT
Trigeminal autonomic cephalgias (TACs) include cluster headache, paroxysmal hemicrania, and short-lasting unilateral neuralgiform headache with conjunctival injection and tearing. Associated structural lesions may be found, but a causal relationship is often difficult to establish. We sought to identify clinical predictors of underlying structural abnormalities by reviewing previously described and new TAC and TAC-like cases associated with a structural lesion. We found that even typical TACs can be caused by an underlying lesion. Clinical warning signs and symptoms are relatively rare. We recommend neuroimaging in all patients with a TAC or TAC-like syndrome.