About 15% of Duchenne muscular dystrophy (DMD) cases are caused by point mutations leading to premature stop codons and disrupted synthesis of the dystrophin protein. Stop codon read-through therapy is available with the drug Ataluren (Translarna® by PTC Therapeutics). Following positive results in ambulatory nmDMD (non-sense mutation Duchenne muscular dystrophy) patients, Ataluren received conditional approval in ambulant nmDMD patients by the EMA in 2014. However, there are limited data on non-ambulatory nmDMD patients treated with Ataluren. Here, we report our experience in four non-ambulatory nmDMD patients. Routine investigations included cardiac function, pulmonary function tests and muscle strength. We compared changes in left ventricular fractional shorting, forced volume vital capacity and BMI from two defined time periods (18–26-month period prior to and after Ataluren start). Mean age at loss of ambulation was 10.1 ± 0.5 years, mean age when initiating Ataluren treatment 14.1 ± 1.4 years. Serial echocardiography, pulmonary lung function tests, and assessment of muscle strength indicated mild attenuation of disease progression after initiation of Ataluren treatment. A possible side effect of Ataluren was a reduction in BMI. There were no adverse clinical effects or relevant abnormalities in routine laboratory values. We conclude that Ataluren appears to mildly ameliorate the clinical course in our patients with a good safety profile. However, larger clinical trials are required to assess the role of Ataluren and its long-term impact on disease progression in non-ambulant nmDMD patients.

Background: Nearly one in 100 live births presents with congenital heart defects (CHD). CHD is frequently associated with laterality defects, such as situs inversus , a mirrored positioning of internal organs. Body laterality is established by a complex process: monocilia at the embryonic left-right organizer facilitate both the generation and sensing of a leftward fluid flow. This induces the conserved left-sided Nodal signaling cascade to initiate asymmetrical organogenesis. Primary ciliary dyskinesia originates from dysfunction of motile cilia, causing symptoms such as chronic sinusitis, bronchiectasis and frequently situs inversus totalis . The most frequently mutated gene in primary ciliary dyskinesia, DNAH5 is associated with randomization of body asymmetry resulting in situs inversus totalis in half of the patients; however, its relation to CHD occurrence in humans has not been investigated in detail so far. Methods: We performed genotype/phenotype correlations in 132 patients with primary ciliary dyskinesia carrying disease-causing DNAH5 mutations, focusing on situs defects and CHD. Using high-speed video microscopy-, immunofluorescence-, and in situ hybridization analyses, we investigated the initial steps of left-right axis establishment in embryos of a Dnah5 -mutant mouse model. Results: In patients with primary ciliary dyskinesia carrying disease-causing DNAH5 mutations, 65.9% (87/132) had laterality defects: 88.5% (77/87) presented with situs inversus totalis , 11.5% (10/87) presented with situs ambiguus ; and 6.1% (8/132) presented with CHD. In Dnah5 mut/mut mice, embryonic left-right organizer monocilia lack outer dynein arms resulting in immotile cilia, impaired flow at the left-right organizer, and randomization of Nodal signaling with normal, reversed or bilateral expression of key molecules. Conclusions: For the first time, we directly demonstrate the disease-mechanism of laterality defects linked to DNAH5 deficiency at the molecular level during embryogenesis. We highlight that mutations in DNAH5 are not only associated with classical randomization of left-right body asymmetry but also with severe laterality defects including CHD.

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