Unique genotype-phenotype correlations within LAMA2-related limb girdle muscular dystrophy in Chinese patients

BackgroundLAMA2-related limb girdle muscular dystrophy (LGMD R23) is rare. The detailed clinical phenotypes and genetic information associated with LGMD R23 are unknown.MethodsWe conducted a retrospective cross-sectional and longitudinal study on 19 LGMD R23 patients.ResultsNormal early motor development was observed in 84.2% patients. Mild orthopedic complications were observed in 42.1% patients. 36.8% patients had seizures, which is unusually frequent in LGMD. Epilepsy was eventually diagnosed in 26.3% patients. 46.7% patients presented with motor neuropathy. Genetic analysis identified 29 pathogenic variants, with missense and frameshift variants being the most common. The mutant sites were mainly distributed in the N-terminal and G-like domains of laminin. The missense variants are distributed near the N-terminus (exons 3–11), whereas frameshift variants are distributed in exons 12–65. Five patients were diagnosed with epilepsy and all of them harbor at least one missense variants in exon 4. 71.4% variants of patients with motor neuropathy located in the LN domain.ConclusionsMissense variants in exon 4 maybe correlated with epilepsy and variants in the LN domain maybe correlated with motor neuropathy in Chinese patients. Our study expands the clinical and genetic spectrum caused by LAMA2 variations and provides novel genotype-phenotype correlations of LGMD R23

Phenotype and genotype of patients.

<p>p.r.: Previously reported.</p><p>Phenotype and genotype of patients.</p

Lamin A/C mislocation in mutant-transfected HEK 293 cells.

<p>Transfection was performed using (A) GFP, (B) pEGFP-N1-LMNA, (C) pEGFP-N1-LMNA-R48P, (D) pEGFP-N1-LMNA-R249W, (E) pEGFP-N1-LMNA-I373V, or (F) pEGFP-N1-LMNA-I497_E536del. Lamin A/C of the mutants (C–F) is distributed in clusters and is mislocated compared with that of the wild type (B).</p

Muscle cell nuclear morphology.

<p>A, C, D: ×12000; B, E, F, G, H: ×25000. (A, B) Normal control. (C, D, G) Abnormal nuclear morphology. (C, D, F) Heterochromatin condensation (arrows). (E) Focal loss of nuclear membrane (arrows). (G) Nucleolar hole (arrows). (H) Accumulation of mitochondria around nucleus (arrows).</p

Clinical and neuroradiological findings of the patients.

<p>CK = creatine kinase; ECG = electrocardiogram; EMG = electromyogram; MRI = magnetic resonance imaging; UL = upper limb; LL = lower limb; ND = not done.</p><p>Clinical and neuroradiological findings of the patients.</p

Muscle biopsy specimens stained with hematoxylin and eosin.

<p>(A) Normal control (×200). (B) Specimen from patient 11 exhibiting inflammatory cellular infiltration with necrotic and regenerative fibers (×200). (C) Specimen from patient 15 exhibiting mild nuclear transfer and regenerative fibers (×400).</p

Schematic of the <i>LMNA</i> gene and lamin A protein indicating mutations.

<p>(A) Schematic of the <i>LMNA</i> gene and lamin A protein. Lamin A is encoded by exons 1–12, whereas lamin C terminates at exon 10 with six unique amino acids at its C-terminal. The alternative splice site for lamin A is indicated. Sequence variations affecting the splice donor or acceptor sites that lead to disease are shown for IVS-8. Missense mutations and deletions are indicated on the lamin A protein, where the head, central rod, and tail domain (incorporating the nuclear localization signal [NLS], and Ig-like fold) are indicated. Novel sequence variants are shown above the gene/protein. (B) Illustration of the evolutionary conservation of residues associated with novel missense mutations located in the coding region of <i>LMNA</i>. Sequences were obtained from the online database, Swiss-Prot (<a href="http://expasy.org/sprot/" target="_blank">http://expasy.org/sprot/</a>) and aligned using the Align online tool (<a href="http://www.uniprot.org/align/" target="_blank">http://www.uniprot.org/align/</a>).</p