A case of pseudodominant inheritance of limb-girdle muscular dystrophy caused by mutations in the CAPN3 gene

Introduction. Limb-girdle muscular dystrophy (LGMD) includes more than 30 forms caused by mutations in genes located on autosomes. The most common form is calpain-3-related LGMD, with autosomal recessive inheritance pattern (OMIM 253600). An autosomal dominant form of LGMD (OMIM 618129) caused by c.643_663del heterozygous mutation in the CAPN3 gene is also supposed to exist. This article describes a family case of LGMD caused by mutations in the CAPN3 gene with pseudodominant inheritance. Materials and methods. Two patients with LGMD were studied: a 59-year-old woman and her 38-year-old daughter. Clinical, genealogical and molecular genetics methods were used: limb girdle muscular dystrophy MPS panel, Sanger sequencing of DNA of the proband, her affected daughter, and six first- and second-degree relatives across four generations. Results. It was found that identical variants of the nucleotide sequence, c.598_612del and c.1746-20CG, identified in the CAPN3 gene of the proband and her daughter, are in the trans position (compound heterozygous state), causing autosomal recessive calpain-3-related LGMD. This is an example of an incredibly rare pseudodominant inheritance of an autosomal recessive disease, established through indirect evidence that the probands husband is a heterozygous carrier of a nucleotide substitution in the CAPN3 gene. Conclusion. It is crucial to examine the marriage partner for heterozygous carrier status of a gene mutation responsible for the disease in family planning and when clarifying the childs prognosis for a patient with an autosomal recessive disease. Considering the existence of a late-onset (after 30 years) LGMD phenotype associated with the CAPN3 gene, differential diagnosis should begin with testing this gene in families with late disease onset.

Аutosomal recessive limb-girdle muscular dystrophy type 2A: two cases in Ukraine with different age of onset

The paper reports on two cases of young women from Ukraine with autosomal recessive limb-girdle muscular dystrophy type 2A with different age of symptoms onset and an absence of any family history presented with gradual onset of proximal muscle weakness in four limbs and thinning of shoulders, arms and thighs. Both patients had elevated creatine phosphokinase level and c.550delA mutations in CAPN3 gene. Sequence analysis and deletion/duplication testing of the 159 genes from skeletal muscles disease testing panel of 5-year-old girl identified deletion of exon 8 (heterozygous) and c.550delA (p.Thr184Argfs*36) mutation (heterozygous), were in CAPN3 gene. Magnetic Resonance Imaging of soft tissue of the proximal lower extremities was performed which showed signs of symmetrical atrophic changes in the major adductor muscle, the long and short adductor muscles, the semitendinosus muscle of the thigh, as a manifestations of autosomal recessive limb-girdle muscular dystrophy type 2A. Homozygous, pathogenic variant of the defect in the CAPN3 gene c.550del (p.Thr184Argfs * 36) was identified in a 25-year-old woman. Type 2A is the most common form of limb-girdle muscular dystrophy, accounting for about 30% of cases. The autosomal recessive limb-girdle muscular dystrophy type 2A is on caused by mutations in the CAPN3 gene, and it is characterized by selective atrophy and weakness of proximal limb and girdle muscles. The age of onset of muscle weakness is extremely variable; the most common being between 8 and 15 years, although it can range between 2 and 50 years. The diagnosis can be suspected by findings on a muscle biopsy or when a doctor experienced in muscular dystrophy examines you. A serum creatine kinase blood test may also show raised levels which indicate a problem in the muscles. The diagnosis has to be confirmed by means of identifying a mutation in the CAPN3 gene which is done on a deoxyribonucleic acid sample from a blood test. To date there are no specific treatments for limb-girdle muscular dystrophy, however careful management of the symptoms of the condition can improve a person’s quality of life. Joint contractures (tightening) can occur in limb-girdle muscular dystrophy and therefore regular physiotherapy is recommended.

Allosteric Modulation of GSK-3β as a New Therapeutic Approach in Limb Girdle Muscular Dystrophy R1 Calpain 3-Related

Limb-girdle muscular dystrophy R1 calpain 3-related (LGMDR1) is an autosomal recessive muscular dystrophy produced by mutations in the CAPN3 gene. It is a rare disease and there is no cure or treatment for the disease while the pathophysiological mechanism by which the absence of calpain 3 provokes the dystrophy in muscles is not clear. However, key proteins implicated in Wnt and mTOR signaling pathways, which regulate muscle homeostasis, showed a considerable reduction in their expression and in their phosphorylation in LGMDR1 patients’ muscles. Finally, the administration of tideglusib and VP0.7, ATP non-competitive inhibitors of glycogen synthase kinase 3β (GSK-3β), restore the expression and phosphorylation of these proteins in LGMDR1 cells, opening the possibility of their use as therapeutic options.

Calcium Mechanisms in Limb-Girdle Muscular Dystrophy with CAPN3 Mutations

Limb-girdle muscular dystrophy recessive 1 (LGMDR1), previously known as LGMD2A, is a rare disease caused by mutations in the CAPN3 gene. It is characterized by progressive weakness of shoulder, pelvic, and proximal limb muscles that usually appears in children and young adults and results in loss of ambulation within 20 years after disease onset in most patients. The pathophysiological mechanisms involved in LGMDR1 remain mostly unknown, and to date, there is no effective treatment for this disease. Here, we review clinical and experimental evidence suggesting that dysregulation of Ca2+ homeostasis in the skeletal muscle is a significant underlying event in this muscular dystrophy. We also review and discuss specific clinical features of LGMDR1, CAPN3 functions, novel putative targets for therapeutic strategies, and current approaches aiming to treat LGMDR1. These novel approaches may be clinically relevant not only for LGMDR1 but also for other muscular dystrophies with secondary calpainopathy or with abnormal Ca2+ homeostasis, such as LGMD2B/LGMDR2 or sporadic inclusion body myositis.

Limb Girdle Muscular Dystrophy due to Digenic Inheritance of DES and CAPN3 Mutations

We report the clinical and genetic analysis of a 63-year-old man with progressive weakness developing over more than 20 years. Prior to his initial visit, he underwent multiple neurological and rheumatological evaluations and was treated for possible inflammatory myopathy. He did not respond to any treatment that was prescribed and was referred to our center for another opinion. He underwent a neurological evaluation, electromyography, magnetic resonance imaging of his legs, and a muscle biopsy. All testing indicated a chronic myopathy without inflammatory features suggesting a genetic myopathy. Whole-exome sequencing testing more than 50 genes known to cause myopathy revealed variants in the COL6A3 (rs144651558), RYR1 (rs143445685), CAPN3 (rs138172448), and DES (rs144901249) genes. We hypothesized that the inheritance pattern could follow a digenic pattern of inheritance. Screening for these polymorphisms in an unaffected sister revealed the presence of all these same variants except for that in the CAPN3 gene. All variants were studied to determine their frequency and if they had been previously reported as mutations. They were also subjected to protein modeling programs, including SIFT, PolyPhen, and MutationTaster. This analysis indicated that the CAPN3 variant c.1663G>A (rs138172448), which results in a p.Val555Ile change, and the DES gene variant c.656C>T (rs144901249), which results in a p.Thr219Ile change, are both predicted to be damaging. These 2 variants were further investigated employing the STRING program that analyzes protein networks and pathways. This analysis provided further support for our hypothesis that these mutations in the CAPN3 and DES genes, through digenic inheritance, are the cause of the myopathy in this patient.