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Severe dystonia, cerebellar atrophy, and cardiomyopathy likely caused by a missense mutation in TOR1AIP1.

Dorboz I, Coutelier M, Bertrand AT, Caberg JH, Elmaleh-Bergès M, Lainé J, Stevanin G, Bonne G, Boespflug-Tanguy O, Servais L - Orphanet J Rare Dis (2014)

Bottom Line: TOR1AIP1 encodes lamina-associated polypeptide 1 (LAP1), a transmembrane protein ubiquitously expressed in the inner nuclear membrane.In vitro studies in fibroblasts of the patient revealed reduced expression of LAP1 and its mislocalization and aggregation in the endoplasmic reticulum as underlying pathogenic mechanisms.Other cases will help delineate the clinical spectrum of LAP1-related mutations.

View Article: PubMed Central - PubMed

Affiliation: Inserm U1141, Université Paris Diderot-Sorbonne Paris Cité, DHU PROTECT, Paris, F-75019, France. imen.dorboz@inserm.fr.

ABSTRACT

Background: Dystonia, cerebellar atrophy, and cardiomyopathy constitute a rare association.

Methods: We used homozygosity mapping and whole exome sequencing to determine the mutation, western blot and immunolabelling on cultured fibroblasts to demonstrate the lower expression and the mislocalization of the protein.

Results: We report on a boy born from consanguineous healthy parents, who presented at three years of age with rapidly progressing dystonia, progressive cerebellar atrophy, and dilated cardiomyopathy. We identified regions of homozygosity and performed whole exome sequencing that revealed a homozygous missense mutation in TOR1AIP1. The mutation, absent in controls, results in a change of a highly conserved glutamic acid to alanine. TOR1AIP1 encodes lamina-associated polypeptide 1 (LAP1), a transmembrane protein ubiquitously expressed in the inner nuclear membrane. LAP1 interacts with torsinA, the protein mutated in DYT1-dystonia. In vitro studies in fibroblasts of the patient revealed reduced expression of LAP1 and its mislocalization and aggregation in the endoplasmic reticulum as underlying pathogenic mechanisms.

Conclusions and relevance: The pathogenic role of TOR1AIP1 mutation is supported by a) the involvement of a highly conserved amino acid, b) the absence of the mutation in controls, c) the functional interaction of LAP1 with torsinA, and d) mislocalization of LAP1 in patient cells. Of note, cardiomyopathy has been reported in LAP1- mice and in patients with the TOR1AIP1 nonsense mutation. Other cases will help delineate the clinical spectrum of LAP1-related mutations.

No MeSH data available.


Related in: MedlinePlus

Sub-expression and mislocalization of LAP1. A. Three bands were observed using anti-LAP1 antibody in control fibroblasts. Fibroblasts from the patient had significantly less of the larger isoforms, whereas the expression of the shorter isoform was less affected (LAP1 antibodies: courtesy of Dr. W.T. Dauer, anti-GAPDH: Santa Cruz Biotechnology; Olympus FV-1000 confocal microscope). B. Fibroblasts from patient show a strong reduction or total absence of LAP1 at the nuclear envelope. A faint staining for LAP1 was observed at the ER (stained with calnexin antibodies, Santa Cruz Biotechnology; secondary Alexa-conjugates antibodies, Life Technologies; HRP-conjugated antibodies: Jackson ImmunoResearch), and strong staining was observed in some regions (see magnification in the inset). Scale bar: 10 μm. C. Electron micrograph of patient fibroblast did not reveal alterations at the nuclear envelope. Scale bar: 5 μm; inset: 500 nm. Imaging as described before [3].
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Fig2: Sub-expression and mislocalization of LAP1. A. Three bands were observed using anti-LAP1 antibody in control fibroblasts. Fibroblasts from the patient had significantly less of the larger isoforms, whereas the expression of the shorter isoform was less affected (LAP1 antibodies: courtesy of Dr. W.T. Dauer, anti-GAPDH: Santa Cruz Biotechnology; Olympus FV-1000 confocal microscope). B. Fibroblasts from patient show a strong reduction or total absence of LAP1 at the nuclear envelope. A faint staining for LAP1 was observed at the ER (stained with calnexin antibodies, Santa Cruz Biotechnology; secondary Alexa-conjugates antibodies, Life Technologies; HRP-conjugated antibodies: Jackson ImmunoResearch), and strong staining was observed in some regions (see magnification in the inset). Scale bar: 10 μm. C. Electron micrograph of patient fibroblast did not reveal alterations at the nuclear envelope. Scale bar: 5 μm; inset: 500 nm. Imaging as described before [3].

Mentions: To gain insight into the pathogenicity of the TOR1AIP1 mutation, we evaluated primary skin fibroblasts from the patient. By western blot, a strong reduction in the expression of LAP1 isoforms was observed relative to control cells (Figure 2A). Immunolabeling revealed a significant reduction in LAP1 staining in the nuclear envelope of patient cells (Figure 2B). Although the endoplasmic reticulum was generally faintly stained, some areas showed accumulation of LAP1 (Figure 2B), indicating mislocalization of the mutated LAP1. No defects in A-type or B-type lamins, SUN1, SUN2, or nesprin-1 or 2 protein localization were observed (data not shown). Similarly, no blebs [4] in nuclear envelopes were observed by electron microscopy in patient cells (Figure 2C). TorsinA is not normally expressed in fibroblasts, so we were not able to determine if this protein was mislocalized.Figure 2


Severe dystonia, cerebellar atrophy, and cardiomyopathy likely caused by a missense mutation in TOR1AIP1.

Dorboz I, Coutelier M, Bertrand AT, Caberg JH, Elmaleh-Bergès M, Lainé J, Stevanin G, Bonne G, Boespflug-Tanguy O, Servais L - Orphanet J Rare Dis (2014)

Sub-expression and mislocalization of LAP1. A. Three bands were observed using anti-LAP1 antibody in control fibroblasts. Fibroblasts from the patient had significantly less of the larger isoforms, whereas the expression of the shorter isoform was less affected (LAP1 antibodies: courtesy of Dr. W.T. Dauer, anti-GAPDH: Santa Cruz Biotechnology; Olympus FV-1000 confocal microscope). B. Fibroblasts from patient show a strong reduction or total absence of LAP1 at the nuclear envelope. A faint staining for LAP1 was observed at the ER (stained with calnexin antibodies, Santa Cruz Biotechnology; secondary Alexa-conjugates antibodies, Life Technologies; HRP-conjugated antibodies: Jackson ImmunoResearch), and strong staining was observed in some regions (see magnification in the inset). Scale bar: 10 μm. C. Electron micrograph of patient fibroblast did not reveal alterations at the nuclear envelope. Scale bar: 5 μm; inset: 500 nm. Imaging as described before [3].
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4302636&req=5

Fig2: Sub-expression and mislocalization of LAP1. A. Three bands were observed using anti-LAP1 antibody in control fibroblasts. Fibroblasts from the patient had significantly less of the larger isoforms, whereas the expression of the shorter isoform was less affected (LAP1 antibodies: courtesy of Dr. W.T. Dauer, anti-GAPDH: Santa Cruz Biotechnology; Olympus FV-1000 confocal microscope). B. Fibroblasts from patient show a strong reduction or total absence of LAP1 at the nuclear envelope. A faint staining for LAP1 was observed at the ER (stained with calnexin antibodies, Santa Cruz Biotechnology; secondary Alexa-conjugates antibodies, Life Technologies; HRP-conjugated antibodies: Jackson ImmunoResearch), and strong staining was observed in some regions (see magnification in the inset). Scale bar: 10 μm. C. Electron micrograph of patient fibroblast did not reveal alterations at the nuclear envelope. Scale bar: 5 μm; inset: 500 nm. Imaging as described before [3].
Mentions: To gain insight into the pathogenicity of the TOR1AIP1 mutation, we evaluated primary skin fibroblasts from the patient. By western blot, a strong reduction in the expression of LAP1 isoforms was observed relative to control cells (Figure 2A). Immunolabeling revealed a significant reduction in LAP1 staining in the nuclear envelope of patient cells (Figure 2B). Although the endoplasmic reticulum was generally faintly stained, some areas showed accumulation of LAP1 (Figure 2B), indicating mislocalization of the mutated LAP1. No defects in A-type or B-type lamins, SUN1, SUN2, or nesprin-1 or 2 protein localization were observed (data not shown). Similarly, no blebs [4] in nuclear envelopes were observed by electron microscopy in patient cells (Figure 2C). TorsinA is not normally expressed in fibroblasts, so we were not able to determine if this protein was mislocalized.Figure 2

Bottom Line: TOR1AIP1 encodes lamina-associated polypeptide 1 (LAP1), a transmembrane protein ubiquitously expressed in the inner nuclear membrane.In vitro studies in fibroblasts of the patient revealed reduced expression of LAP1 and its mislocalization and aggregation in the endoplasmic reticulum as underlying pathogenic mechanisms.Other cases will help delineate the clinical spectrum of LAP1-related mutations.

View Article: PubMed Central - PubMed

Affiliation: Inserm U1141, Université Paris Diderot-Sorbonne Paris Cité, DHU PROTECT, Paris, F-75019, France. imen.dorboz@inserm.fr.

ABSTRACT

Background: Dystonia, cerebellar atrophy, and cardiomyopathy constitute a rare association.

Methods: We used homozygosity mapping and whole exome sequencing to determine the mutation, western blot and immunolabelling on cultured fibroblasts to demonstrate the lower expression and the mislocalization of the protein.

Results: We report on a boy born from consanguineous healthy parents, who presented at three years of age with rapidly progressing dystonia, progressive cerebellar atrophy, and dilated cardiomyopathy. We identified regions of homozygosity and performed whole exome sequencing that revealed a homozygous missense mutation in TOR1AIP1. The mutation, absent in controls, results in a change of a highly conserved glutamic acid to alanine. TOR1AIP1 encodes lamina-associated polypeptide 1 (LAP1), a transmembrane protein ubiquitously expressed in the inner nuclear membrane. LAP1 interacts with torsinA, the protein mutated in DYT1-dystonia. In vitro studies in fibroblasts of the patient revealed reduced expression of LAP1 and its mislocalization and aggregation in the endoplasmic reticulum as underlying pathogenic mechanisms.

Conclusions and relevance: The pathogenic role of TOR1AIP1 mutation is supported by a) the involvement of a highly conserved amino acid, b) the absence of the mutation in controls, c) the functional interaction of LAP1 with torsinA, and d) mislocalization of LAP1 in patient cells. Of note, cardiomyopathy has been reported in LAP1- mice and in patients with the TOR1AIP1 nonsense mutation. Other cases will help delineate the clinical spectrum of LAP1-related mutations.

No MeSH data available.


Related in: MedlinePlus