Novel TRIM32 mutation in sarcotubular myopathy

Chiara Panicucci ^*1, Monica Traverso ^*1, Serena Baratto ², Chiara Romeo ³, Michele Iacomino ³, Chiara Gemelli ⁴, Alberto Tagliafico ⁵, Paolo Broda ¹, Federico Zara ³, Claudio Bruno ², Carlo Minetti ¹ and Chiara Fiorillo ¹

¹ Pediatric Neurology and Neuromuscular Disorders, Istituto G. Gaslini and University of Genoa, Italy; ² Centre of Traslational and Experimental Myology, Istituto G. Gaslini, Genoa, Italy; ³ Laboratory of Neurogenetics and Neuroscience, Institute G. Gaslini, Genoa, Italy; ⁴ Department of Neurosciences, Rehabilitation, Ophthalmology, Genetics and Maternal/Child Sciences, University of Genoa, Italy; ⁵ Department of Health Sciences (DISSAL), Radiology Section, University of Genoa, Italy, Radiology, Policlinico San Martino, Genoa, Italy *Both Authors equally contributed to this work

Tripartite motif-containing protein 32 (TRIM32) is a member of the TRIM ubiquitin E3 ligases which ubiquitinates different substrates in muscle including sarcomeric proteins. Mutations in TRIM32 are associated with Limb-Girdle Muscular Dystrophy 2H. In a 66 old woman with disto-proximal myopathy, we identified a novel homozygous mutation of TRIM32 gene c.1781G > A (p. Ser594Asn) localised in the c-terminus NHL domain. Mutations of this domain have been also associated to Sarcotubular Myopathy (STM), a form of distal myopathy with peculiar features in muscle biopsy, now considered in the spectrum of LGMD2H. Muscle biopsy revealed severe abnormalities of the myofibrillar network with core like areas, lobulated fibres, whorled fibres and multiple vacuoles. Desmin and Myotilin stainings also pointed to accumulation as in Myofibrillar Myopathy. This report further confirms that STM and LGMD2H represent the same disorder and suggests to consider TRIM32 mutations in the genetic diagnosis of Sarcotubular Myopathy and Myofibrillar Myopathy.

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