Novel mutations in KARS cause hypertrophic cardiomyopathy and combined mitochondrial respiratory chain defect

Abstract

Mutations in KARS, which encodes for both mitochondrial and cytoplasmic lysyl-tRNA synthethase, have been so far associated with three different phenotypes: the recessive form of Charcot Mary-Tooth polyneuropathy, the autosomal recessive non-syndromic hearing loss and the last recently described condition related to congenital visual impairment and progressive microcephaly. Here we report the case of a 14-years-old-girl with severe cardiomyopathy associated to mild psychomotor delay and mild myopathy; moreover, a diffuse reduction of cytochrome C oxidase (COX, complex IV) and a combined enzymatic defect of complex I (CI) and IV (CIV) was evident in muscle biopsy. Using the TruSight One sequencing panel we identified two novel mutations in KARS. Both mutations, never reported previously, occur in a highly conserved region of the catalytic domain and had a dramatic effect on KARS stability. Structural analysis confirmed the pathogenic role of the identified variants. Our findings confirm and emphasize that mt-ARSs enzymes are related to a broad clinical spectrum due to their multiple and still unknown functions.

Graphical Abstract

mutations in KARS impact on the mitochondrial function causing combined mitochondrial CI and CIV deficiencies and a hypertrophic cardiomyopathy.

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