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1.  Progeroid laminopathy with restrictive dermopathy-like features caused by an isodisomic LMNA mutation p.R435C 
Aging (Albany NY)  2013;5(6):445-459.
The clinical course of a female patient affected by a progeroid syndrome with Restrictive Dermopathy (RD)-like features was followed up. Besides missing hairiness, stagnating weight and growth, RD-like features including progressive skin swelling and solidification, acrocontractures, osteolysis and muscular hypotension were observed until the patient died at the age of 11 months. A homozygous LMNA mutation c.1303C>T (p.R435C) was found by Sanger sequencing. Haplotyping revealed a partial uniparental disomy of chromosome 1 (1q21.3 to 1q23.1) including the LMNA gene. In contrast to reported RD patients with LMNA mutations, LMNA p.R435C is not located at the cleavage site necessary for processing of prelamin A by ZMPSTE24 and leads to a distinct phenotype combining clinical features of Restrictive Dermopathy, Mandibuloacral Dysplasia and Hutchinson-Gilford Progeria. Functionally, LMNA p.R435C is associated with increasing DNA double strand breaks and decreased recruitment of P53 binding protein 1 (53BP1) to DNA-damage sites indicating delayed DNA repair. The follow-up of the complete clinical course in the patient combined with functional studies showed for the first time that a progressive loss of lamin A rather than abnormal accumulation of prelamin A species could be a pathophysiological mechanism in progeroid laminopathies, which leads to DNA repair deficiency accompanied by advancing tissue degeneration.
PMCID: PMC3824411  PMID: 23804595
2.  Familial partial lipodystrophy, mandibuloacral dysplasia and restrictive dermopathy feature barrier-to-autointegration factor (BAF) nuclear redistribution 
Cell Cycle  2012;11(19):3568-3577.
Prelamin A processing impairment is a common feature of a restricted group of rare genetic alterations/disorders associated with a wide range of clinical phenotypes. Changes in histone posttranslational modifications, alterations in non-histone chromatin proteins and chromatin disorganization have been specifically linked to impairment of specific, distinct prelamin A processing steps, but the molecular mechanism involved in these processes is not yet understood . In this study, we show that the accumulation of wild-type prelamin A detected in restrictive dermopathy (RD), as well as the accumulation of mutated forms of prelamin A identified in familial partial lipodystrophy (FPLD) and mandibuloacral dysplasia (MADA), affect the nuclear localization of barrier-to-autointegration factor (BAF), a protein able to link lamin A precursor to chromatin remodeling functions. Our findings, in accordance with previously described results, support the hypothesis of a prelamin A involvement in BAF nuclear recruitment and suggest BAF-prelamin A complex as a protein platform usually activated in prelamin A-accumulating diseases. Finally, we demonstrate the involvement of the inner nuclear membrane protein emerin in the proper localization of BAF-prelamin A complex.
doi:10.4161/cc.21869
PMCID: PMC3478308  PMID: 22935701
BAF; BANF1; prelamin A; lamin A/C; laminopathies; emerin; EDMD1
3.  Altered chromatin organization and SUN2 localization in mandibuloacral dysplasia are rescued by drug treatment 
Histochemistry and Cell Biology  2012;138(4):643-651.
Mandibuloacral dysplasia type A (MADA) is a rare laminopathy characterized by growth retardation, craniofacial anomalies, bone resorption at specific sites including clavicles, phalanges and mandibula, mottled cutaneous pigmentation, skin rigidity, partial lipodystrophy, and insulin resistance. The disorder is caused by recessive mutations of the LMNA gene encoding for A-type lamins. The molecular feature of MADA consists in the accumulation of the unprocessed lamin A precursor, which is detected at the nuclear rim and in intranuclear aggregates. Here, we report the characterization of prelamin A post-translational modifications in MADA cells that induce alterations in the chromatin arrangement and dislocation of nuclear envelope-associated proteins involved in correct nucleo-cytoskeleton relationships. We show that protein post-translational modifications change depending on the passage number, suggesting the onset of a feedback mechanism. Moreover, we show that treatment of MADA cells with the farnesyltransferase inhibitors is effective in the recovery of the chromatin phenotype, altered in MADA, provided that the cells are at low passage number, while at high passage number, the treatment results ineffective. Moreover, the distribution of the lamin A interaction partner SUN2, a constituent of the nuclear envelope, is altered by MADA mutations, as argued by the formation of a highly disorganized lattice. Treatment with statins partially rescues proper SUN2 organization, indicating that its alteration is caused by farnesylated prelamin A accumulation. Given the major role of SUN1 and SUN2 in the nucleo-cytoskeleton interactions and in regulation of nuclear positioning in differentiating cells, we hypothesise that mechanisms regulating nuclear membrane–centrosome interplay and nuclear movement may be affected in MADA fibroblasts.
Electronic supplementary material
The online version of this article (doi:10.1007/s00418-012-0977-5) contains supplementary material, which is available to authorized users.
doi:10.1007/s00418-012-0977-5
PMCID: PMC3432780  PMID: 22706480
Mandibuloacral dysplasia type A (MADA); Prelamin A forms; SUN2; Heterochromatin defects; Statins; Trichostatin A
4.  The empowerment of translational research: lessons from laminopathies 
The need for a collaborative approach to complex inherited diseases collectively referred to as laminopathies, encouraged Italian researchers, geneticists, physicians and patients to join in the Italian Network for Laminopathies, in 2009. Here, we highlight the advantages and added value of such a multidisciplinary effort to understand pathogenesis, clinical aspects and try to find a cure for Emery-Dreifuss muscular dystrophy, Mandibuloacral dysplasia, Hutchinson-Gilford Progeria and forms of lamin-linked cardiomyopathy, neuropathy and lipodystrophy.
doi:10.1186/1750-1172-7-37
PMCID: PMC3458975  PMID: 22691392
Laminopathies; Emery-Dreifuss Muscular Dystrophy; Dilated Cardiomyopathy with Conduction Defects; Mandibuloacral Dysplasia; Familial Partial Lipodystrophy Type 2; Hutchinson-Gilford Progeria Syndrome; Rare Diseases; Networking activity; interdisciplinary approach to diseases
5.  Prelamin A mediated recruitment of SUN1 to the nuclear envelope directs nuclear positioning in human muscle 
Cell death and differentiation  2011;18(8):1305-1315.
Lamin A is a nuclear lamina constituent expressed in differentiated cells. Mutations in the LMNA gene cause several diseases, including muscular dystrophy and cardiomyopathy. Among nuclear envelope partners of lamin A are SUN1 and SUN2, which mediate nucleo-cytoskeleton interactions critical to the anchorage of nuclei. In this study, we show that differentiating human myoblasts accumulate farnesylated prelamin A, which elicits upregulation and recruitment of SUN1 to the nuclear envelope and favors SUN2 enrichment at the nuclear poles. Indeed, impairment of prelamin A farnesylation alters SUN1 recruitment and SUN2 localization. Moreover, nuclear positioning in myotubes is severely affected in the absence of farnesylated prelamin A. Importantly, reduced prelamin A and SUN1 levels are observed in Emery-Dreifuss muscular dystrophy myoblasts, concomitant with altered myonuclear positioning. These results demonstrate that the interplay between SUN1 and farnesylated prelamin A contributes to nuclear positioning in human myofibers and may be implicated in pathogenetic mechanisms.
doi:10.1038/cdd.2010.183
PMCID: PMC3097169  PMID: 21311568
6.  Ankrd2/ARPP is a novel Akt2 specific substrate and regulates myogenic differentiation upon cellular exposure to H2O2 
Molecular Biology of the Cell  2011;22(16):2946-2956.
A proteomic-based search for novel substrates of Akt was undertaken in C2C12 murine muscle cells. Our data demonstrate that Akt isoform 2 phosphorylates Ankrd2 at Serine 99 in response to H2O2 stimuli, regulating muscle differentiation rate.
Activation of Akt-mediated signaling pathways is crucial for survival, differentiation, and regeneration of muscle cells. A proteomic-based search for novel substrates of Akt was therefore undertaken in C2C12 murine muscle cells exploiting protein characterization databases in combination with an anti–phospho-Akt substrate antibody. A Scansite database search predicted Ankrd2 (Ankyrin repeat domain protein 2, also known as ARPP) as a novel substrate of Akt. In vitro and in vivo studies confirmed that Akt phosphorylates Ankrd2 at Ser-99. Moreover, by kinase assay with recombinant Akt1 and Akt2, as well as by single-isoform silencing, we demonstrated that Ankrd2 is a specific substrate of Akt2. Ankrd2 is typically found in skeletal muscle cells, where it mediates the transcriptional response to stress conditions. In an attempt to investigate the physiological implications of Ankrd2 phosphorylation by Akt2, we found that oxidative stress induced by H2O2 triggers this phosphorylation. Moreover, the forced expression of a phosphorylation-defective mutant form of Ankrd2 in C2C12 myoblasts promoted a faster differentiation program, implicating Akt-dependent phosphorylation at Ser-99 in the negative regulation of myogenesis in response to stress conditions.
doi:10.1091/mbc.E10-11-0928
PMCID: PMC3154889  PMID: 21737686
7.  Prelamin A processing and functional effects in restrictive dermopathy 
Cell Cycle  2010;9(23):4766-4768.
doi:10.4161/cc.9.23.14210
PMCID: PMC3048041  PMID: 21127399
restrictive dermopathy; prelamin A; chromatin; nuclear envelope; ZMPSTE24; laminopathies
8.  CD99 Acts as an Oncosuppressor in Osteosarcoma 
Molecular Biology of the Cell  2006;17(4):1910-1921.
CD99 was recently reported to be under control of the osteoblast-specific transcription factor Cbfa1 (RUNX2) in osteoblasts, suggesting a role in the phato-physiology of these cells. No extensive information is available on the role(s) of this molecule in malignant phenotype, and osteosarcoma, in particular, has never been studied. We report that in 11 different cell lines and 17 clinical samples CD99 expression is either undetectable or very low. Being expressed in the normal counterpart, we tested the hypothesis that CD99 down-regulation may have a role in osteosarcoma development and progression. CD99-forced expression in two osteosarcoma cell lines significantly reduced resistance to anoikis, inhibited growth in anchorage independence as well as cell migration, and led to abrogation of tumorigenic and metastatic ability. Therefore, the molecule acts as a potent suppressor of malignancy in osteosarcoma. CD99 gene transfection induces caveolin-1 up-regulation and the two molecules were found to colocalize on the cell surface. Treatment with antisense oligonucleotides to caveolin-1 abrogates the effects of CD99 on migration. The findings point to an antioncogenic role for CD99 in osteosarcoma, likely through the regulation of caveolin-1 and inhibition of c-Src kinase activity.
doi:10.1091/mbc.E05-10-0971
PMCID: PMC1415319  PMID: 16421247

Results 1-8 (8)