Elsevier

Neuromuscular Disorders

Volume 9, Issue 8, 1 December 1999, Pages 573-579
Neuromuscular Disorders

Case report
Homozygosity for a nonsense mutation in the alpha-tropomyosin slow gene TPM3 in a patient with severe infantile nemaline myopathy

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Abstract

The nemaline myopathies are muscle disorders of variable severity and age of onset, with characteristic nemaline bodies in the sarcoplasm. Genes for dominant (NEM1) and recessive (NEM2A) nemaline myopathy have been localised to chromosomes one and two, respectively. A missense mutation in the alpha-tropomyosin gene (TPM3) has been associated with NEM1 in one family. Probands from 76 other nemaline myopathy families have now been screened for TPM3 mutations. One proband, who was not noted to have any weakness neonatally, but who died at 21 months of age, was shown to be homozygous for a single strand conformation polymorphism (SSCP) in skeletal-muscle-specific exon 1 of TPM3. Sequencing revealed homozygosity for a nonsense mutation at codon 31 (CAG to TAG). The patient should have no functioning alpha-tropomyosin slow protein. The nemaline bodies in this patient were exclusively in type one fibres, consistent with the expression of TPM3 only in type one fibres.

Introduction

Nemaline myopathy was first described in 1963 [1], [2], and most commonly presents as a non-progressive, or slowly progressive congenital myopathy [3]. There is however a spectrum of nemaline myopathies from a severe congenital form, through to adult-onset forms [4], [5]. All forms are however characterised by the presence in muscle fibre sarcoplasm of nemaline bodies. These nemaline bodies demonstrate characteristic periodicity in both longitudinal and transverse sections, are of the same electron density as the Z disc, have been considered to be abnormal extensions of the Z disc and can also be seen to be continuous with muscle thin filaments [6]. Nemaline myopathy has thus been considered a disease of the sarcomeric proteins [7], [8].

Nemaline myopathy may appear sporadic, or may show apparent autosomal recessive, or autosomal dominant inheritance [4]. The gene for an autosomal dominant form of the disease in one family has been localised to chromosome 1 [9]. A missense mutation in the gene TPM3 for the thin filament protein slow-twitch alpha-tropomyosin has been shown to be associated with the disease in this family [10]. One gene for recessive nemaline myopathy has been assigned to chromosome 2 [11] and identified as mutated nebulin [12].

The identification of the missense mutation in the alpha-tropomyosin slow gene TPM3 in one family with dominant nemaline myopathy [10] prompted the screening of the TPM3 gene for mutations in the probands from 76 other nemaline myopathy families where the patient was sporadic or the family showed apparent dominant or recessive inheritance. These cases were mostly gathered through members of the European Neuromuscular Centre International Consortium on Nemaline Myopathy [8], [13].

Section snippets

From blood

DNA was extracted from blood samples of nemaline myopathy patients using standard procedures [14], [15].

From paraffin sections

Ten to 20 sections of 10–15 μm thickness were taken from a block with a tissue area of 0.5–1 cm2. The sections were de-waxed by three washes in xylene, the first in 5 ml and the second and third in 2 ml. The sections were washed with 2 ml 100% ethanol, followed by 2 ml 70% ethanol. The tissue was then dried at 60°C (1–2 h). Digest buffer (600 μl–50 mM Tris pH8, 1 mM EDTA, 1% SDS, with 3 mg

Mutation screen

The PCR products from each of the exons forming the muscle-specific transcript of the TPM3 gene (Fig. 1) were amplified from genomic DNA and sequenced to verify that the desired product was being amplified. We observed a number of differences from the published TPM3 genomic sequences [16] (Table 2).

The amplified exons of the muscle-specific transcript were subjected to SSCP analysis [19] under a number of different conditions. No SSCP was seen in exons IIsk, II, VI and VII, VIIIsk, or IXsk. A

Discussion

We previously identified a missense mutation in the alpha-tropomyosin slow gene TPM3 associated with an autosomal dominant nemaline myopathy showing onset at junior school age [9]. The missense mutation changes a highly conserved methionine to an arginine [10]. In this study we describe apparent homozygosity for a nonsense mutation in the same exon of TPM3 in one case of severe infantile nemaline myopathy out of 76 nemaline myopathy probands examined. The majority of cases of nemaline myopathy

Acknowledgements

This work was supported by the National Health and Medical Research Council of Australia (grant numbers 940122 and 970104) and the Neuromuscular Foundation of Western Australia (MRD, NGL, PT, SDW). We thank the European Neuromuscular Centre for organisational support. We should like to thank Lori Blechynden and Nicky Binz for the automatic DNA sequencing service, and Drs R. Barohn, P. Barth, M. Bourgeoise, D. Castle, A. Clarke, G. Danta, M. Delatycki, M. de Visser, W. Dobyns, V. Dubowitz, I.

References (32)

  • C. Wallgren-Petterson et al.

    Inherited neuromuscular disorders: clinical and molecular genetics

  • N.G. Laing

    Inherited disorders of contractile proteins in skeletal and cardiac muscle

    Curr Opin Neurol

    (1995)
  • N.G. Laing et al.

    Assignment of a gene (NEM1) for autosomal dominant nemaline myopathy to chromosome 1

    Am J Hum Genet

    (1992)
  • N.G. Laing et al.

    A mutation in the α-tropomyosin gene TPM3 associated with autosomal dominant nemaline myopathy

    Nat Genet

    (1995)
  • K. Pelin et al.

    Mutations in the nebulin gene associated with autosomal recessive nemaline myopathy

    Proc Natl Acad Sci USA

    (1999)
  • C. Wallgren-Pettersson et al.

    51st ENMC International workshop: nemaline myopathy

    Neuromusc Disord

    (1998)

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