Clinical, pathological, imaging, and genetic characterization in a Taiwanese cohort with limb-girdle muscular dystrophy.

BACKGROUND: Limb-girdle muscular dystrophy (LGMD) is a genetically heterogeneous, hereditary disease characterized by limb-girdle weakness and histologically dystrophic changes. The prevalence of each subtype of LGMD varies among different ethnic populations. This study for the first time analyzed the phenotypes and genotypes in Taiwanese patients with LGMD in a referral center for neuromuscular diseases (NMDs). RESULTS: We enrolled 102 patients clinically suspected of having LGMD who underwent muscle biopsy with subsequent genetic analysis in the previous 10 years. On the basis of different pathological categories, we performed sequencing of target genes or panel for NMDs and then identified patients with type 1B, 1E, 2A, 2B, 2D, 2I, 2G, 2 N, and 2Q. The 1B patients with LMNA mutation presented with mild limb-girdle weakness but no conduction defect at the time. All 1E patients with DES mutation exhibited predominantly proximal weakness along with distal weakness. In our cohort, 2B and 2I were the most frequent forms of LGMD; several common or founder mutations were identified, including c.1097_1099delACA (p.Asn366del) in DES, homozygous c.101G > T (p.Arg34Leu) in SGCA, homozygous c.26_33dup (p.Glu12Argfs*20) in TCAP, c.545A > G (p.Tyr182Cys), and c.948delC (p.Cys317Alafs*111) in FKRP. Clinically, the prevalence of dilated cardiomyopathy in our patients with LGMD2I aged > 18 years was 100%, much higher than that in European cohorts. The only patient with LGMD2Q with PLEC mutation did not exhibit skin lesions or gastrointestinal abnormalities but had mild facial weakness. Muscle imaging of LGMD1E and 2G revealed a more uniform involvement than did other LGMD types. CONCLUSION: Our study revealed that detailed clinical manifestation together with muscle pathology and imaging remain critical in guiding further molecular analyses and are crucial for establishing genotype-phenotype correlations. We also determined the common mutations and prevalence for different subtypes of LGMD in our cohort, which could be useful when providing specific care and personalized therapy to patients with LGMD.

Whole-exome sequencing for the genetic diagnosis of congenital red blood cell membrane disorders in Taiwan.

PURPOSE: Congenital hemolytic anemia caused by red blood cell (RBC) membrane defects is a heterogeneous group of disorders. The present study aimed to search the causative gene mutations in patients with RBC membrane disorders in Taiwan. MATERIALS AND METHODS: Next-generation sequencing approach using whole-exome sequencing (WES) was performed. Sanger sequencing was performed for confirmation of variants detected in WES in patients and their family members. RESULTS: Five causative variants, including two ANK1, two SPTA and one SPTB variants, were detected in four patients. All these variants, except one SPTA1 variant c.83G > A (p.R28H), are novel variants. Their pedigree analysis showed one de novo SPTA1 mutation c.83G > A (p.R28H) combined with αLELY, one de novo ANK1 mutation c.1034C > A (p.A345E), one autosomal dominant combined SPTA1 c.4604A > C (p.Q1535P) and SPTB c.6203 T > C (p.L2068P) mutations and one autosomal dominant ANK1 c.4462C > T (p.R1488X) mutation. CONCLUSIONS: Our data demonstrated that WES is an efficient tool for determining genetic etiologies of RBC membrane disorders and can facilitate accurate diagnosis and genetic counseling. Additional studies should be conducted on larger cohorts to investigate the distribution of gene mutations in patients with RBC membrane disorders in Taiwan.

Development of a feasible assay for the detection of GAA mutations in patients with Pompe disease.

BACKGROUND: Pompe disease is an inherited autosomal recessive deficiency of acid α-glucosidase (GAA) and is due to pathogenic sequence variants in the corresponding GAA gene. While the analysis of enzyme activity remains the diagnostic test of choice for individuals with Pompe disease, mutation analysis remains for establishing a definitive diagnosis. METHODS: High resolution melting (HRM) analysis was performed to screen GAA mutations. Genomic DNA was extracted from peripheral blood samples of the two patients with Pompe disease and 250 normal controls. Exons 2 through 20 of the GAA gene were screened by the HRM analysis. The results were subsequently confirmed by direct sequencing. RESULTS: This assay proved to be feasible in detecting seven known (c.2T>C, c.1726G>A, c.1845G>A, c.1935C>A, c.1958C>A, c.2238G>C, and c.2815_2816del) GAA mutations. Each mutation could be readily and accurately identified in the difference plot curves. We estimated the carrier frequency of the most common mutation, c.1935G>A (p.D645E), in the Taiwanese population to be 0.2%. CONCLUSIONS: In clinical practice, we suggest that HRM analysis is assumed as a fast and reliable method for screening GAA gene mutations especially the most common mutations which are responsible for Pompe disease among the Taiwanese populations.

High-resolution melting (HRM) analysis as a feasible method for detecting spinal muscular atrophy via dried blood spots.

BACKGROUND: Spinal muscular atrophy (SMA) is a neurodegenerative disease with the leading genetic cause of infant mortality. More than 95% of patients with SMA have a homozygous disruption in the survival motor neuron1 (SMN1) gene, caused by mutation, deletion, or rearrangement. Recently, treatment in humans in the immediate postnatal period, prior to the development of weakness or very early in the course of the disease, may be effective. Therefore, our objective was to establish a feasible method for SMA screening. High-resolution melting (HRM) analysis is rapidly becoming the most important mutation-scanning methodology that allows mutation scanning and genotyping without the need for costly labeled oligonucleotides. In the current study, we aim to develop a method for identifying the substitution of single nucleotide in SMN1 exon 7 (c.840C>T) by HRM analysis. METHODS: Genomic DNA was extracted from peripheral blood samples and dried blood spots obtained from 30 patients with SMA and 30 normal individuals. All results were previously confirmed by denaturing high-performance liquid chromatography (DHPLC). RESULTS: In order to identify the substitution of single nucleotide in SMN1 exon 7 (c.840C>T) by HRM analysis, a primer set was used in HRM analysis. At first, we failed to identify the substitution of single nucleotide in SMN1 exon 7 (c.840C>T) by HRM analysis because the homozygous CC and homozygous TT cannot be distinguished by HRM analysis. Therefore, all samples were mixed with a known SMN1/SMN2 copy number (SMN1/SMN2=0:3), which we may call driver. This strategy is used to differentiate between homozygous CC and homozygous TT. After mixing with driver, the melting profile of homozygous CC becomes heteroduplex; however, the homozygous TT remains the same in the normalized and temperature-shifted difference plots. CONCLUSIONS: HRM analysis can be successfully applied to screen SMA via DNA obtained from whole blood and dried blood spots. We strongly believe that HRM analysis, a high-throughput method, could be used for identifying affected infants prior to the presentation of clinical symptoms in future.