Limb-Girdle Muscular Dystrophy Type 2H Associated with Mutation in TRIM32, a Putative E3-Ubiquitin–Ligase Gene

Abstract

Limb-girdle muscular dystrophy type 2H (LGMD2H) is a mild autosomal recessive myopathy that was first described in the Manitoba Hutterite population. Previous studies in our laboratory mapped the causative gene for this disease to a 6.5-Mb region in chromosomal region 9q31-33, flanked by D9S302 and D9S1850. We have now used additional families and a panel of 26 microsatellite markers to construct haplotypes. Twelve recombination events that reduced the size of the candidate region to 560 kb were identified or inferred. This region is flanked by D9S1126 and D9S737 and contains at least four genes. Exons of these genes were sequenced in one affected individual, and four sequence variations were identified. The families included in our study and 100 control individuals were tested for these variations. On the basis of our results, the mutation in the tripartite-motif-containing gene (TRIM32) that replaces aspartate with asparagine at position 487 appears to be the causative mutation of LGMD2H. All affected individuals were found to be homozygous for D487N, and this mutation was not found in any of the controls. This mutation occurs in an NHL (named after the proteins NCL1, HT2A, and LIN-41) domain at a position that is highly conserved. NHL domains are known to be involved in protein-protein interactions. Although the function of TRIM32 is unknown, current knowledge of the domain structure of this protein suggests that it may be an E3-ubiquitin ligase. If proven, this represents a new pathogenic mechanism leading to muscular dystrophy.

Detection of TRIM32 deletions in LGMD patients analyzed by a combined strategy of CGH array and massively parallel sequencing

“…All the reported single nucleotide variations are located in the C-terminal part of the protein, in one of the six NHL domains. 1,9,15,18,19 We report here the eighth point mutation in TRIM32. Interestingly, this mutation, p.Leu535Serfs*21, is also located in a NHL domain.…”

“…Defects in the TRIM32 gene have been reported in two autosomal recessive neuromuscular diseases: limb-girdle muscular dystrophy type 2H (LGMD2H, MIM # 254110) 1 and sarcotubular myopathy (STM). 2 LGMD2H is a rather mild and progressive myopathy initially described in the Hutterite population, characterized by a wide phenotypic heterogeneity with proximal muscle weakness and wasting, and mildly to moderately increased serum CK levels.…”

“…1 The gene is ubiquitously expressed and encodes a 72 kDa protein, member of the tripartite motif (TRIM) family possessing an E3 ubiquitin ligase activity. 7,8 TRIM32 contains a RING-finger, a B-box motif, a coiledcoil region and a C terminal domain constituted of six NHL repeats.…”

“…This last domain is predicted to form a six-bladed beta-propeller structure 9 and is known to be involved in protein-protein interactions. 1,10 In particular, TRIM32 interacts with myosin and is able to ubiquitinate actin, suggesting its participation in myofibrillar turnover. 10 Of note, the small TRIM32 gene is nested within an intron of the long isoform of the ASTN2 gene (NM_014010.4) which is transcribed from the opposite strand of TRIM32 and exhibits key roles in glial-guided neuronal migration during brain development.…”

Limb-girdle muscular dystrophy 2I: phenotypic variability within a large consanguineous Bedouin family associated with a novel FKRP mutation

“…LGMD2A (CAPN3 at 15q15.1), 2,3 LGMD2B (DYSF at 2p12 -16), 4,5 LGMD2C (SGCG at 13q12), 6,7 LGMD2D (ADL at 17q12 -q21.33), 8 -10 LGMD2E (SGCB at 4q12), 11,12 LGMD2F (SGCD at 5q33 -34), 13,14 LGMD2G (TCAP at 17q11 -q12), 1,15 LGMD2H (TRIM32 at 9q31 -q34.1), 16,17 LGMD2I (FKRP at 19q13.3), 18,19 and LGMD2J (TTN at 2q31). 20 The involved genes encode either structural components of muscle, that is, g-, a-, b-, and d-sarcoglycans, responsible for LGMD2C to 2F, respectively, or proteins of other functions.…”