Infantile onset myofibrillar myopathy due to recessive CRYAB mutations

Forrest, Katharine; Al‐Sarraj, Safa; Sewry, C.; Buk, Stefan; Tan, S. Veronica; Pitt, Matthew; Durward, Andrew; McDougall, Marilyn; Irving, Melita; Hanna, Michael G.; Matthews, Emma; Sárközy, Anna; Hudson, Judith A.; Barresi, Rita; Bushby, Kate; Jungbluth, Heinz; Wraige, Elizabeth

doi:10.1016/j.nmd.2010.11.003

Cited by 58 publications

(50 citation statements)

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“…Although 343delT protein is observed in the patient skeletal muscle biopsy, it does appear at lower levels when compared with a control individual (29). Nonetheless, endogenous detection of the mutant protein was not observed in our iPSC-derived cells.…”

Section: Discussionmentioning

confidence: 51%

“…2, D and E), indicating that lack of detectable 343delT is not due to immaturity of the cells. This result was surprising to us because the muscle biopsy from the patient showed dense, irregular staining of HSPB5 through immunohistochemistry and a 15-kDa-sized protein detectable by Western blotting with the NT HSPB5 antibody (29). Lack of 343delT protein was confirmed in a second iPSC line derived from the patient as well as the isogenic, heterozygous, genecorrected control line derived from that iPSC line (supplemental Fig.…”

Section: Generation Of Ipscs For the Investigation Of 343delt-mentioning

confidence: 93%

“…The skeletal muscle biopsy of the patient shows dense, irregular staining of HSPB5, detectable only by an antibody recognizing the N terminus of HSPB5 (NT-HSPB5). This band runs at the predicted molecular weight of 15 kDa on a Western blot, smaller than the 22-kDa WT HSPB5 protein (29). Additionally, the biopsy shows intense, irregular staining of desmin and myotilin.…”

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confidence: 84%

“…Here we have investigated a recessive mutation in HSPB5, 343delT, found in a patient who presented at age 4 months with profound muscle stiffness, persistent creatine kinase elevation, and histopathological features of a myofibrillar myopathy (29). This homozygous recessive, single base deletion results in a frameshift and formation of a premature stop codon following addition of 14 missense residues (S115fs129X).…”

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confidence: 99%

“…1A shows the family pedigree of the patient harboring the homozygous, recessive 343delT mutation. The non-consanguineous parents are each heterozygous for the mutation and are asymptomatic, whereas the homozygous 343delT patient exhibits a severe, infantile-onset myopathy (29). To examine the effects of 343delT (strategy outlined in Fig.…”

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confidence: 99%

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The Human 343delT HSPB5 Chaperone Associated with Early-onset Skeletal Myopathy Causes Defects in Protein Solubility

Mitzelfelt

Limphong

Choi

et al. 2016

Journal of Biological Chemistry

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Mutations of HSPB5 (also known as CRYAB or ␣B-crystallin), a bona fide heat shock protein and molecular chaperone encoded by the HSPB5 (crystallin, alpha B) gene, are linked to multisystem disorders featuring variable combinations of cataracts, cardiomyopathy, and skeletal myopathy. This study aimed to investigate the pathological mechanisms involved in an earlyonset myofibrillar myopathy manifesting in a child harboring a homozygous recessive mutation in HSPB5, 343delT. To study HSPB5 343delT protein dynamics, we utilize model cell culture systems including induced pluripotent stem cells derived from the 343delT patient (343delT/343delT) along with isogenic, heterozygous, gene-corrected control cells (WT KI/ 343delT) and BHK21 cells, a cell line lacking endogenous HSPB5 expression. 343delT/343delT and WT KI/343delT-induced pluripotent stem cell-derived skeletal myotubes and cardiomyocytes did not express detectable levels of 343delT protein, contributable to the extreme insolubility of the mutant protein. Overexpression of HSPB5 343delT resulted in insoluble mutant protein aggregates and induction of a cellular stress response. Co-expression of 343delT with WT prevented visible aggregation of 343delT and improved its solubility. Additionally, in vitro refolding of 343delT in the presence of WT rescued its solubility. We demonstrate an interaction between WT and 343delT both in vitro and within cells. These data support a loss-of-function model for the myopathy observed in the patient because the insoluble mutant would be unavailable to perform normal functions of HSPB5, although additional gain-of-function effects of the mutant protein cannot be excluded. Additionally, our data highlight the solubilization of 343delT by WT, concordant with the recessive inheritance of the disease and absence of symptoms in carrier individuals.HSPB5 (also known as CRYAB or ␣B-crystallin) is a small molecular weight heat shock protein encoded by the HSPB5 (crystallin, alpha B) gene and functions as a molecular chaperone. Its promoter contains a heat shock element, a stress-responsive binding site of heat shock transcription factor 1 (HSF1), that functionally up-regulates the expression of HSPB5. Increased levels of HSPB5 can then go on to provide

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Section: Discussionmentioning

confidence: 51%

Section: Generation Of Ipscs For the Investigation Of 343delt-mentioning

confidence: 93%

mentioning

confidence: 84%

mentioning

confidence: 99%

mentioning

confidence: 99%

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