Laminin α5_CD239_Spectrin is a candidate association that compensates the linkage between the basement membrane and cytoskeleton in skeletal muscle fibers

Heterozygous loss-of-function variants in SPTAN1 cause a novel early childhood onset distal myopathy with chronic neurogenic features

Background

Neurogenetic disorders caused by pathogenic variants in four genes encoding non-erythrocytic spectrins ( SPTAN1, SPTBN1, SPTBN2, SPTBN4) range from peripheral and central nervous system involvement to complex syndromic presentations. Heterozygous pathogenic variants in SPTAN1 are exemplary for this diversity with phenotypes spanning almost the entire spectrum.

Methods

Through international collaboration we identified 14 families with genetically unsolved distal weakness and unreported heterozygous SPTAN1 loss-of-function variants including frameshift, nonsense and splice-acceptor variants. Clinical data, electrophysiology, muscle CT or MRI and muscle biopsy findings were collected and standardized. SPTAN1 protein, mRNA expression analysis and cDNA sequencing was performed on muscle tissue from two patients.

Results

All 20 patients presented with early childhood onset distal weakness. The severity varied both within families and between different families. Foot abnormalities ranged from hammer toes and pes cavus to distal arthrogryposis. Electrophysiology showed mixed myogenic and neurogenic features. Muscle MRI or CT in 10 patients showed fatty infiltration of the distal lower limb anterior compartment and/or selective involvement of the extensor hallucis longus muscle. Muscle biopsy revealed myopathic changes with mild dystrophic and chronic neurogenic changes in 7 patients. Finally, we provide proof for nonsense mediated decay in tissues derived from two patients.

Conclusions

We provide evidence for the association of SPTAN1 loss-of-function variants with childhood onset distal myopathy in 14 families. This finding extends the phenotypic spectrum of SPTAN1 loss-of-function variants ranging from intellectual disability to distal weakness with a predominant myogenic cause.

KEY MESSAGES

SPTAN1 loss-of-function variants, including frameshift, nonsense and splice site variants cause a novel childhood onset distal weakness syndrome with primarily skeletal muscle involvement. Hereditary motor neuropathies and distal myopathic disorders present a well-known diagnostic challenge as they demonstrate substantial clinical and genetic overlap. The emergence of SPTAN1 loss-of-function variants serves as a noteworthy example, highlighting a growing convergence in the spectrum of genotypes linked to both hereditary motor neuropathies and distal myopathies.

Tandem Mass Tag Proteomics Provides Insights into the Underlying Mechanism of Flesh Quality Degradation of Litopenaeus vannamei during Refrigerated Waterless Transport at 12 °C

Refrigerated waterless transport at 12 °C of live shrimp (Litopenaeus vannamei) causes flesh quality deterioration, and the underlying mechanism remains unknown. Herein, proteomics and bioinformatics analyses were used to elucidate the molecular mechanism of flesh quality changes. The result showed that 33 and 44 of the differentially abundant proteins (DAPs) were, respectively, identified in the acute cold (AC) group and the combined stress of acute cold and waterless duration (AC+WD) group, which were mostly involved in the metabolism processes and cellular structure of animal tissues, and notably enriched in biological pathways such as lysosome, glycolysis/gluconeogenesis, and focal adhesion. Furthermore, the changes in color and texture properties were closely associated with tubulin, gelsolin, laminin, trypsin-1, dipeptidyl peptidase, triosephosphate isomerase, and aldehyde dehydrogenase. Therefore, these DAPs could be used as potential biomarkers to monitor the deterioration of shrimp flesh quality during refrigerated waterless transportation.