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Neuromuscular Disorders 21 (2011) 433–438 www.elsevier.com/locate/nmd
Telethonin-deficiency initially presenting as a congenital muscular dystrophy Ana Ferreiro a,b,c,d,1, Monica Mezmezian e,1, Montse Olive´ e, Danielle Herlicoviez f, Michel Fardeau a,e, Pascale Richard g,h, Norma Beatriz Romero a,e,i,j,⇑ a
AP-HP, Centre de re´fe´rence des maladies neuromusculaires Paris-Est, Groupe Hospitalier-Universitaire Pitie´-Salpeˆtrie`re, Paris F-75013, France b INSERM, U787, Institut de Myologie, Paris F-75013, France c UPMC Univ Paris 06, UMR_S787, Institut de Myologie, IFR14, Paris F-75013, France d AP-HP, Service de Pe´diatrie, Centre de Re´fe´rence Maladies Neuromusculaires (GNMH), Hoˆpital Raymond Poincare´, 92380 Garches, France e Unite´ de Morphologie Neuromusculaire, Institut de Myologie, CHU Pitie´-Salpeˆtrie`re, Paris F-75013, France f Service d’Anatomie Pathologique, Unite´ de Neuropathologie, CHU Caen, Caen 14033, France g INSERM U954, CHU Pitie´-Salpeˆtrie`re, Paris F-75013, France h AP-HP, UF Cardioge´ne´tique et Myoge´ne´tique, Service de Biochimie Me´tabolique, Groupe Hospitalier-Universitaire Pitie´-Salpeˆtrie`re, Paris 75013, France i INSERM U974, Institut de Myologie, CHU Pitie´-Salpeˆtrie`re, Paris F-75013, France j Universite´ Pierre et Marie Curie-Paris, UPMC Univ Paris 06, UMR S974, CNRS UMR 7215, Institut de Myologie, CHU Pitie´-Salpeˆtrie`re, Paris F-75013, France Received 20 October 2010; received in revised form 18 February 2011; accepted 21 March 2011
Abstract Congenital muscular dystrophies are defined by congenital or infantile onset of muscle weakness; while 12 culprit genes have been identified, many cases remain molecularly uncharacterized. On the other hand, mutations in the telethonin gene (TCAP) have been associated with a rare form of recessive limb girdle muscular dystrophy, usually presenting in the second decade. So far, three different mutations in telethonin have been reported in patients suffering from limb muscular dystrophy type 2G. We have identified a novel telethonin mutation in a child presenting with mildly delayed motor development and muscle weakness from infancy, clinically improving over the first decade, indicative of a CMD. Muscle biopsy showed a dystrophic process, with preserved laminin a2, collagen VI, and a-dystroglycan, but absent telethonin immunolabeling. Sequence analysis of TCAP showed a novel non-sense p.Gln58X (c.172C > T) homozygous mutation. Our observation indicates that telethonin deficiency may present in infancy with clinical features overlapping with mild forms of a-dystroglycanopathy. Therefore telethonin analysis should be performed in patients suffering from congenital muscular dystrophy of unknown cause. Ó 2011 Elsevier B.V. All rights reserved. Keywords: Congenital muscular dystrophies; Telethonin gene (TCAP); Telethonin deficiency
1. Introduction Congenital muscular dystrophies (CMDs) are a heterogeneous group of inherited muscular disorders character⇑ Corresponding author at: INSERM UMR S974, Institut de Myologie, Groupe Hospitalier Universitaire Pitie´-Salpeˆtrie`re, Paris F-75013, France. Tel.: +33 1 42 16 22 42; fax: +33 1 42 16 22 40. E-mail address:
[email protected] (N.B. Romero). 1 Both authors contributed equally to this work.
0960-8966/$ - see front matter Ó 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.nmd.2011.03.005
ized by congenital or infantile onset of hypotonia, muscle weakness, delayed motor development and frequent joint contractures. Muscle biopsies from affected patients show variable abnormalities ranging from non-specific myopathic changes to severe dystrophic features comprising muscle fibre necrosis and regeneration and prominent fibroadipous tissue proliferation [1–3]. Clinical features and progression are widely variable, ranging from “pure”, relatively mild CMD to more severe disorders in which muscle dystrophy is combined with central nervous system
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abnormalities, with or without intellectual retardation and eye involvement. Serum creatine kinase (CK) levels can be normal or elevated [1–3]. Currently, mutations in 12 genes have been associated with CMD and define different forms of the disorder [4]. In most cases the pattern of inheritance is autosomal recessive. The more frequent types of CMD are those associated with laminin a2 deficiency (MDC1A) [5], collagen 6 deficiency (Ullrich congenital muscular dystrophy-UCMD) [6] and a-dystroglycanopathies, a group of disorders resulting from defective glycosylation of a-dystroglycan [7]. In spite of the major progress in defining different forms of CMD, there are still many cases for which the causative gene remains unknown. Furthermore, it may also occur that mutations in some of the genes involved in limb girdle muscular dystrophies (LGMD) manifest early as a CMD [8–10], establishing the potential overlap between both types of muscle diseases. Telethonin (or Titin Cap) is a sarcomeric protein of skeletal and cardiac muscles, which binds to titin and other sarcomeric proteins at the Z line. It has been suggested that telethonin plays an important role in sarcomeric assembly, sarcomere-membrane interactions and stretch sensing [11–14]. It is encoded by TCAP gene (NM_003673.3) located on chromosome 17q12.
Mutations in the telethonin gene were found as causative of autosomal recessive muscular dystrophy type 2 G (LGMD 2G) [15] and dilated or hypertrophic cardiomyopathy [16–18]. Here, we report on a child suffering from telethonin deficiency initially presenting as a congenital muscular dystrophy. 2. Case report The patient is a 12-year-old French boy. He was the first child from healthy parents without known consanguinity, originating from the same area in north-western France. The only relevant medical history in the family was type A hemophilia, affecting the patient and his 4.5 year-old brother. Pregnancy, birth and the neonatal period were considered normal, although the patient was noticed to be a very quiet baby. His motor milestones were partially delayed; head control was poor at 4 months and he was not able to sit until 9 months, but walked at 16 months. The parents remarked a waddling gait from the end of the second year of life. He was first referred at the age of 4 years for frequent falls and difficulties for climbing stairs; clinical examination showed mild hyperlordosis, scapular
Fig. 1. Clinical phenotype of the patient at ages 4 (a and b), 9.8 (c–e) and 11 (f–h) years. Note stability of scapular winging, hyperlordosis and calf hypertrophy (a, c and f). Mild joint hyperlaxity was observed in early childhood (b), but tended to decrease with age (d and e) and was not associated to major joint contractures except for some degree of rigidity of the lumbar spine (g).
A. Ferreiro et al. / Neuromuscular Disorders 21 (2011) 433–438
winging and a waddling gait. Muscle strength was reduced in proximal limb muscles; he stood up from the floor with Gower’s maneuver. There was mild upper limb distal joint hyperlaxity (Fig. 1) contrasting with minor contractures of the Achilles’ tendons. There was not obvious muscular atrophy. Serum creatine kinase (CK) levels were elevated at 633 U/L (normal T) mutation at the homozygous state. The parents, aged 43 and 45, were found to be heterozygous for the mutation; their clinical and cardiological (including echocardiography) examinations were strictly normal. 3. Discussion We report on a patient suffering from an early onset telethonin-deficiency initially mimicking a CMD. The CMDs
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of two base pairs in a stretch of G (g.637–640del2) generating a shift in the reading frame [15,20]. So far, only one additional mutation in the TCAP gene (p.Trp25X) has been identified in a Moldavian patient suffering from LGMD 2G [21], therefore the p.Gln58X found in our patient represents the fourth muscular dystrophy-associated mutation in telethonin gene identified to date. Interestingly, all of the reported TCAP mutations associated with LGMD known so far are recessive non-sense mutations that generate either a truncated protein or an absence of the protein, as observed by immunolabeling, by a mRNA non sense mediated decay mechanism. This is in contrast with the dominant missense substitutions found in patients suffering from dilated or hypertrophic cardiomyopathy [16–18]. In this context, it is worth stressing that clinical and cardiac evaluation of the patient’s parents, both heterozygous for the p.Gln58X mutation, revealed no abnormalities. Although the direct consequence of nonsense homozygous mutations is the lack of a part or even complete absence of the protein, the position of the stop mutation in the gene cannot explain by itself the greater severity of the initial phenotype and thus the earlier presentation in our patient, which probably involves other mechanisms. Thus, the p.Gln35X TCAP mutation originally reported in the Brazilian families has been found recently in a 50-year-old Portuguese man suffering from slowly progressive proximal and distal muscle weakness starting in his twenties, mild scapular winging and calf hypertrophy. Interestingly, this patient had prominent contractures at the elbows and ankles [22]. Taken together, the cases with TCAP mutations reported so far demonstrate a fairly homogeneous clinical phenotype characterized by onset in the second decade of life in most cases, proximal weakness in lower limbs, accompanied or followed by weakness of anterior tibialis muscles, and later involvement of the upper limb muscles. Calf hypertrophy, scapular winging, and joint contractures are additional features in some patients (Table 1). Although in one previously reported LGMD 2G family the age of onset varied from 2 to 15 years [15], none of the patients reported so far had presented the clinical
are loosely defined as congenital or infantile onset disorders of muscle in which the muscle biopsy is compatible with the presence of dystrophic pathology [1]. Usually, the diagnosis of CMD is established on the basis of clinical data, the presence of dystrophic features of variable severity on muscle biopsy and by the demonstration of abnormal protein expression (most often laminin a2, collagen VI, or a-dystroglycan) on muscle biopsies after immunofluorescence or immunohistochemistry and/or Western blot studies [1–7], although definite diagnosis requires gene testing. In the patient described here, delayed motor milestones, muscle weakness starting in infancy, high CK levels and dystrophic features on the muscle biopsy fulfilled the diagnostic criteria of CMD [1]. However, collagen VI, laminin a2 or a-dystroglycan, which are defective in Ullrich CMD, MDC1A and a-dystroglycanopathies respectively [5,7], were found to be normally expressed in the patient’s muscle. Moreover, the child’s clinical condition did not worsen over the years; on the contrary, on successive clinical evaluations from 3 to 12 years there was an obvious improvement of his motor performance and muscle strength, a feature possibly related with motor maturation. Nevertheless, development of calf hypertrophy and a pelvic and shoulder girdle weakness typical of LGMD at the end of the first decade prompted us to reconsider a very early onset form of this latter diagnosis, despite the atypical clinical improvement, and to perform telethonin immunohistochemical analysis. Interestingly, telethonin labeling was completely absent on the patient’s muscle as seen on immunohistochemical analysis. Subsequent sequencing of TCAP gene revealed a novel homozygous p.Gln58X nonsense mutation in the TCAP gene thus demonstrating telethonin deficiency as the cause of the disease in our patient. Telethonin-deficiency was first reported in 2000 in three Brazilian families of Italian ancestry suffering from an autosomal recessive LGMD [15,19]. The disease in this family was previously mapped to a locus on chromosome 17q11–12 and designated as LGMD 2G. Two of the families were found to be homozygous for a p.Gln35X TCAP mutation (c.157C > T), whereas a third family was found to be compound heterozygous for p.Gln35X and a deletion Table 1 Summary of patients with telethonin deficiency reported so far. Family/number of studied patients
Age at onset
Distribution of weakness
Joint retractions
Calf Hypertrophy
Distal joint laxity
Muscle biopsy
TCAP mut
Reference
I LG-61/5
9–15
Proximal and distal anterior
No
No
No
Dystrophic, rimmed vacuoles
[15,19,20]
II LG-11/3
9–15
No
No
No
III LG-18/3
2–15
No
Yes
No
[19,20]
15
Ankles
Yes
No
p.Trp25X
[21]
V/1
20
Ankles, elbows
Yes
No
p.Gln35X
[22]
VI/1
Infancy
Ankles, hip, lumbar spine
Yes
Yes
Dystrophic, rare rimmed vacuoles Dystrophic, no vacuoles Dystrophic, no vacuoles Dystrophic, rimmed vacuoles Dystrophic, no vacuoles
p.Gln35X
IV/1
Proximal and distal anterior Proximal and distal anterior Proximal and distal anterior Proximal and distal anterior Proximal and distal anterior
p.Gln35X g.637640del2 p.Gln35X
p.Gln58X
Current description
[15,19,20]
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features of a congenital muscular dystrophy, including onset within the first year and a stable or improving course. Analysis of muscle biopsies in LGMD2G patients reported so far revealed mild dystrophic changes, type I fiber atrophy and rimmed vacuoles in some cases [20–22]. The presence of rimmed vacuoles does not seem to be related with the patient’s age at the time of biopsy nor with the site of the biopsy, since in the vast majority of the patients the muscle samples were taken from the same muscle. Moreover, it is worth stressing that in contrast to other muscle disorders resulting from mutations in Z disk proteins [23], telethonin deficiency does not cause major sarcomere disruption. Indeed, recent studies in zebrafish depleted of TCAP by antisense morpholino showing preserved sarcomere structure but abnormal T-tubule system development suggest that disruption of the sarcomere-membrane interactions, but not of sarcomeric assembly, leads to muscular dystrophy/weakness in patients with TCAP mutations [24]. In summary, this report illustrates that telethonin deficiency may present early in life with clinical features overlapping with the collagen 6 or alpha-dystroglycan deficient congenital muscular dystrophies. For that reason, this rare myopathy has to be considered as an alternative diagnosis in patients presenting with congenital muscular dystrophy with preserved laminin a2, collagen VI, or a-dystroglycan immunostaining. Acknowledgements We would like to thank Maud Beuvin, Emmanuelle Lace`ne, Linda Mane´re and Laurence Demay for excellent technical assistance. We thank Dr France Leturcq for the WB analyses. AF is the recipient of a Contrat d’Interface INSERM/APHP. References [1] Voit T, Tome´ FMS. The congenital muscular dystrophies. In: Engel AG, Franzini-Armstrong A, editors. Myology. McGraw-Hill; 2004. p. 1203–38. [2] Muntoni F, Voit T. The congenital muscular dystrophies in 2004: a century of exciting progress. Neuromusc Disord 2004;14:635–49. [3] Muntoni F, Voit T. 133rd ENMC International Workshop on Congenital Muscular Dystrophy (IXth International CMD Workshop) 21–23 January 2005, Naarden, The Netherlands. Neuromuscul Disord 2005;15:794–801. [4] Gene table of monogenic neuromuscular disorders. Neuromusc Disord 2010;20:72–94. [5] Helbling-Leclerc A, Zhang X, Topaloglu H, et al. Mutations in the laminin alpha-2-chain gene (LAMA2) cause merosin-deficient congenital muscular dystrophy. Nature Genet 1995;11:216–8.
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