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Fatal cardiac arrhythmia and long-QT syndrome in a new form of congenital generalized lipodystrophy with muscle rippling (CGL4) due to PTRF-CAVIN mutations.

Rajab A, Straub V, McCann LJ, Seelow D, Varon R, Barresi R, Schulze A, Lucke B, L├╝tzkendorf S, Karbasiyan M, Bachmann S, Spuler S, Schuelke M - PLoS Genet. (2010)

Bottom Line: Additionally, we found impaired bone formation with osteopenia, osteoporosis, and atlanto-axial instability.Absence of PTRF-CAVIN did not influence abundance of its binding partner caveolin-1 and caveolin-3.In patient fibroblasts, however, caveolin-1 failed to localize toward the cell surface and electron microscopy revealed reduction of caveolae to less than 3%.

View Article: PubMed Central - PubMed

Affiliation: Genetics Unit, Ministry of Health, Directorate General of Health Affairs, Royal Hospital, Muscat, Oman.

ABSTRACT
We investigated eight families with a novel subtype of congenital generalized lipodystrophy (CGL4) of whom five members had died from sudden cardiac death during their teenage years. ECG studies revealed features of long-QT syndrome, bradycardia, as well as supraventricular and ventricular tachycardias. Further symptoms comprised myopathy with muscle rippling, skeletal as well as smooth-muscle hypertrophy, leading to impaired gastrointestinal motility and hypertrophic pyloric stenosis in some children. Additionally, we found impaired bone formation with osteopenia, osteoporosis, and atlanto-axial instability. Homozygosity mapping located the gene within 2 Mbp on chromosome 17. Prioritization of 74 candidate genes with GeneDistiller for high expression in muscle and adipocytes suggested PTRF-CAVIN (Polymerase I and transcript release factor/Cavin) as the most probable candidate leading to the detection of homozygous mutations (c.160delG, c.362dupT). PTRF-CAVIN is essential for caveolae biogenesis. These cholesterol-rich plasmalemmal vesicles are involved in signal-transduction and vesicular trafficking and reside primarily on adipocytes, myocytes, and osteoblasts. Absence of PTRF-CAVIN did not influence abundance of its binding partner caveolin-1 and caveolin-3. In patient fibroblasts, however, caveolin-1 failed to localize toward the cell surface and electron microscopy revealed reduction of caveolae to less than 3%. Transfection of full-length PTRF-CAVIN reestablished the presence of caveolae. The loss of caveolae was confirmed by Atomic Force Microscopy (AFM) in combination with fluorescent imaging. PTRF-CAVIN deficiency thus presents the phenotypic spectrum caused by a quintessential lack of functional caveolae.

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Immunohistochemistry of a muscle biopsy specimen from patient FII:201.In the patient caveolin-3 expression in skeletal muscle fibers was reduced and irregular; caveolin-1 staining of intramuscular fat cells (red arrowheads) was completely absent. In the control, strong PTRF-staining can be seen in the walls of the small arterioles, representing the smooth muscle layer. It is virtually absent in the patient, nota bene: The nuclear staining of the anti-PTRF-antibody is unspecific. In the patient the intensity of the subsarcolemmal anti-NOS1 staining seems to be stronger and less patchy than in the control muscle. Overall the muscle of the patient shows myopathic changes, mild variation in fiber sizes without necrosis, inflammation or fibrosis and increased regeneration. These regenerating fibers (ca. 25%) are marked through positive staining for neo-MHC, an isofom of the myosin heavy chain protein that is characteristically expressed in neonatal muscle and in regenerating fibers.
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pgen-1000874-g005: Immunohistochemistry of a muscle biopsy specimen from patient FII:201.In the patient caveolin-3 expression in skeletal muscle fibers was reduced and irregular; caveolin-1 staining of intramuscular fat cells (red arrowheads) was completely absent. In the control, strong PTRF-staining can be seen in the walls of the small arterioles, representing the smooth muscle layer. It is virtually absent in the patient, nota bene: The nuclear staining of the anti-PTRF-antibody is unspecific. In the patient the intensity of the subsarcolemmal anti-NOS1 staining seems to be stronger and less patchy than in the control muscle. Overall the muscle of the patient shows myopathic changes, mild variation in fiber sizes without necrosis, inflammation or fibrosis and increased regeneration. These regenerating fibers (ca. 25%) are marked through positive staining for neo-MHC, an isofom of the myosin heavy chain protein that is characteristically expressed in neonatal muscle and in regenerating fibers.

Mentions: To verify the absence of PTRF-CAVIN at the protein level we performed a Western blot with protein-extracts from patient fibroblasts (FI:201) and skeletal muscle (FII:201) and probed it with anti-caveolin-1 and anti-PTRF antibodies. PTRF-CAVIN protein was completely absent from fibroblasts and skeletal muscle, whereas the caveolin-1 and caveolin-3 abundance was unchanged (Figure 4D and 4G). Immunohistochemistry of patient muscle showed absence of PTRF-CAVIN from the smooth muscle layer of the intramuscular small vessels (Figure 5). As caveolae are particularly abundant on adipocyte membranes [19], we searched for fat cells in the muscle of patient FII:201 and found complete absence of caveolin-1 immunoreactivity from the adipocyte cell membranes (red arrowheads on Figure 5). As caveolin-1 is essential for lipolysis, lipid droplet formation and lipoprotein metabolism [20] and patients with CAV1 mutations suffer from lipodystrophy [5] we thus show that a severe reduction of caveolae per se may lead to a similar adipose tissue phenotype. In contrast, subsarcolemmal caveolin-3 immunoreactivity was still present, albeit at reduced levels and in a patchy distribution (Figure 5). The patient muscle showed 25% regenerating fibers as verified by reemergence of the neonatal myosin heavy chain isoform (neo-MHC).


Fatal cardiac arrhythmia and long-QT syndrome in a new form of congenital generalized lipodystrophy with muscle rippling (CGL4) due to PTRF-CAVIN mutations.

Rajab A, Straub V, McCann LJ, Seelow D, Varon R, Barresi R, Schulze A, Lucke B, L├╝tzkendorf S, Karbasiyan M, Bachmann S, Spuler S, Schuelke M - PLoS Genet. (2010)

Immunohistochemistry of a muscle biopsy specimen from patient FII:201.In the patient caveolin-3 expression in skeletal muscle fibers was reduced and irregular; caveolin-1 staining of intramuscular fat cells (red arrowheads) was completely absent. In the control, strong PTRF-staining can be seen in the walls of the small arterioles, representing the smooth muscle layer. It is virtually absent in the patient, nota bene: The nuclear staining of the anti-PTRF-antibody is unspecific. In the patient the intensity of the subsarcolemmal anti-NOS1 staining seems to be stronger and less patchy than in the control muscle. Overall the muscle of the patient shows myopathic changes, mild variation in fiber sizes without necrosis, inflammation or fibrosis and increased regeneration. These regenerating fibers (ca. 25%) are marked through positive staining for neo-MHC, an isofom of the myosin heavy chain protein that is characteristically expressed in neonatal muscle and in regenerating fibers.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2837386&req=5

pgen-1000874-g005: Immunohistochemistry of a muscle biopsy specimen from patient FII:201.In the patient caveolin-3 expression in skeletal muscle fibers was reduced and irregular; caveolin-1 staining of intramuscular fat cells (red arrowheads) was completely absent. In the control, strong PTRF-staining can be seen in the walls of the small arterioles, representing the smooth muscle layer. It is virtually absent in the patient, nota bene: The nuclear staining of the anti-PTRF-antibody is unspecific. In the patient the intensity of the subsarcolemmal anti-NOS1 staining seems to be stronger and less patchy than in the control muscle. Overall the muscle of the patient shows myopathic changes, mild variation in fiber sizes without necrosis, inflammation or fibrosis and increased regeneration. These regenerating fibers (ca. 25%) are marked through positive staining for neo-MHC, an isofom of the myosin heavy chain protein that is characteristically expressed in neonatal muscle and in regenerating fibers.
Mentions: To verify the absence of PTRF-CAVIN at the protein level we performed a Western blot with protein-extracts from patient fibroblasts (FI:201) and skeletal muscle (FII:201) and probed it with anti-caveolin-1 and anti-PTRF antibodies. PTRF-CAVIN protein was completely absent from fibroblasts and skeletal muscle, whereas the caveolin-1 and caveolin-3 abundance was unchanged (Figure 4D and 4G). Immunohistochemistry of patient muscle showed absence of PTRF-CAVIN from the smooth muscle layer of the intramuscular small vessels (Figure 5). As caveolae are particularly abundant on adipocyte membranes [19], we searched for fat cells in the muscle of patient FII:201 and found complete absence of caveolin-1 immunoreactivity from the adipocyte cell membranes (red arrowheads on Figure 5). As caveolin-1 is essential for lipolysis, lipid droplet formation and lipoprotein metabolism [20] and patients with CAV1 mutations suffer from lipodystrophy [5] we thus show that a severe reduction of caveolae per se may lead to a similar adipose tissue phenotype. In contrast, subsarcolemmal caveolin-3 immunoreactivity was still present, albeit at reduced levels and in a patchy distribution (Figure 5). The patient muscle showed 25% regenerating fibers as verified by reemergence of the neonatal myosin heavy chain isoform (neo-MHC).

Bottom Line: Additionally, we found impaired bone formation with osteopenia, osteoporosis, and atlanto-axial instability.Absence of PTRF-CAVIN did not influence abundance of its binding partner caveolin-1 and caveolin-3.In patient fibroblasts, however, caveolin-1 failed to localize toward the cell surface and electron microscopy revealed reduction of caveolae to less than 3%.

View Article: PubMed Central - PubMed

Affiliation: Genetics Unit, Ministry of Health, Directorate General of Health Affairs, Royal Hospital, Muscat, Oman.

ABSTRACT
We investigated eight families with a novel subtype of congenital generalized lipodystrophy (CGL4) of whom five members had died from sudden cardiac death during their teenage years. ECG studies revealed features of long-QT syndrome, bradycardia, as well as supraventricular and ventricular tachycardias. Further symptoms comprised myopathy with muscle rippling, skeletal as well as smooth-muscle hypertrophy, leading to impaired gastrointestinal motility and hypertrophic pyloric stenosis in some children. Additionally, we found impaired bone formation with osteopenia, osteoporosis, and atlanto-axial instability. Homozygosity mapping located the gene within 2 Mbp on chromosome 17. Prioritization of 74 candidate genes with GeneDistiller for high expression in muscle and adipocytes suggested PTRF-CAVIN (Polymerase I and transcript release factor/Cavin) as the most probable candidate leading to the detection of homozygous mutations (c.160delG, c.362dupT). PTRF-CAVIN is essential for caveolae biogenesis. These cholesterol-rich plasmalemmal vesicles are involved in signal-transduction and vesicular trafficking and reside primarily on adipocytes, myocytes, and osteoblasts. Absence of PTRF-CAVIN did not influence abundance of its binding partner caveolin-1 and caveolin-3. In patient fibroblasts, however, caveolin-1 failed to localize toward the cell surface and electron microscopy revealed reduction of caveolae to less than 3%. Transfection of full-length PTRF-CAVIN reestablished the presence of caveolae. The loss of caveolae was confirmed by Atomic Force Microscopy (AFM) in combination with fluorescent imaging. PTRF-CAVIN deficiency thus presents the phenotypic spectrum caused by a quintessential lack of functional caveolae.

Show MeSH
Related in: MedlinePlus