[Apical left ventricular aneurysm without atrio-ventricular block due to a lamin A/C gene mutation]

Mutations in LMNA gene encoding two ubiquitously expressed nuclear proteins, lamins A and C, give rise to up to 7 different pathologies affecting specific tissues. Three of these disorders affect cardiac and/or skeletal muscles with atrio-ventricular conduction disturbances, dilated cardiomyopathy and sudden cardiac death as common features.

RESULTS

A new LMNA mutation (1621C>T, R541C) was found in two members of a French family with a history of ventricular rhythm disturbances and an uncommon form of systolic left ventricle dysfunction. The two patients: the proband and his daughter, were affected and exhibited an atypical form of dilated cardiomyopathy with an unexplained left ventricle aneurysm revealed by ventricular rhythm disturbances without atrio-ventricular block.

CONCLUSION

This finding reinforces the highly variable phenotypic expression of LMNA mutation and emphasizes the fact that LMNA mutations can be associated with different cardiac phenotypes.

Nuclear envelope alterations in fibroblasts from patients with muscular dystrophy, cardiomyopathy, and partial lipodystrophy carrying lamin A/C gene mutations

Mutations in LMNA, the gene that encodes nuclear lamins A and C, cause up to eight different diseases collectively referred to as "laminopathies." These diseases affect striated muscle, adipose tissue, peripheral nerve, and bone, or cause features of premature aging. We investigated the consequences of LMNA mutations on nuclear architecture in skin fibroblasts from 13 patients with different laminopathies. Western-blotting showed that none of the mutations examined led to a decrease in cellular levels of lamin A or C. Regardless of the disease, we observed honeycomb nuclear structures and nuclear envelope blebs in cells examined by immunofluorescence microscopy. Concentrated foci of lamin A/C in the nucleoplasm were also observed. Only mutations in the head and tail domains of lamins A and C significantly altered the nuclear architecture of patient fibroblasts. These results confirm that mutations in lamins A and C may lead to a weakening of a structural support network in the nuclear envelope in fibroblasts and that nuclear architecture changes depend upon the location of the mutation in different domains of lamin A/C.

Congestive Heart Failure after Myocardial Infarction in the Rat: Cardiac Force and Spontaneous Sarcomere Activity

The causes of reduced cardiac force development in congestive heart failure (CHF) are still uncertain. We explored the subcellular mechanisms leading to decreased force development in trabeculae from rats with a myocardial infarction. We defined CHF according to clinical and pathological criteria and compared properties of trabeculae from animals with CHF (cMI) to those of animals with a myocardial scar but without evidence of CHF (uMI), and sham-operated animals. The new findings of this study on properties of cMI trabeculae are that (1) maximal twitch force following post-extrasystolic potentiation is unchanged; (2) the sensitivity of cMI trabeculae to [Ca(2+)](o) is increased; (3) spontaneous diastolic sarcomere length (SL) fluctuations (SA) are increased in cMI at all levels of SR Ca(2+) loading; and (4) SA is accompanied by a proportional reduction of F(max). The results suggest that the probability of spontaneous diastolic opening of SR Ca(2+) channels is increased in CHF. These data provide the basis for a novel mechanism underlying systolic and diastolic dysfunction as well as arrhythmias in hearts in CHF. If SA proves to be a component of myocardial dysfunction in human CHF, our thinking about therapy of the patient with CHF may be profoundly changed.

Racial disparity in incidence patterns and outcome of kidney cancer

OBJECTIVES

To identify the subgroups that primarily contribute to the greater incidence and mortality of renal cancer in black Americans compared with white Americans.

METHODS

We analyzed age, stage, and race-related differences in the incidence and survival among patients with renal cancer using the national Surveillance, Epidemiology, and End Results (SEER) registry database. White and black patients with renal cell carcinoma who were older than 19 years of age and had been diagnosed between 1975 and 1998 were included. Incidence trends were analyzed by joinpoint regression with the statistical significance level at P <0.05. The Cox proportional hazards model was used to determine the overall survival of patients with renal cell carcinoma by race (white versus black), age (20 to 59 versus 60+ years), and stage (local versus regional/distant).

RESULTS

Localized disease predominantly accounted for the rise in incidence. Both black age groups with localized disease had a greater estimated annual percentage of incidence increase (4.46% for 20 to 59 years and 4.35% for 60+ years) compared with their white counterparts (2.87% and 3.06%, respectively). The magnitude of survival difference was largest between black versus white patients younger than 60 years of age who had local stage disease, with a median survival time of 190 and 259 months, respectively (P <0.0001).

CONCLUSIONS

Young black patients with localized renal cancer appear to have had a greater rise in incidence and a poorer outcome than white patients of the same age and disease stage. Additional investigation is warranted to define the role of these race, stage, and age-related disparities in the etiology, prognosis, treatment, and follow-up of kidney cancer.

Expanding the phenotype of LMNA mutations in dilated cardiomyopathy and functional consequences of these mutations

AIMS

Mutations in the lamin A/C gene (LMNA) have been reported to be involved in dilated cardiomyopathy (DCM) associated with conduction system disease and/or skeletal myopathy. The aim of this study was to perform a mutational analysis of LMNA in a large white population of patients affected by dilated cardiomyopathy with or without associated symptoms.

METHODS

We performed screening of the coding sequence of LMNA on DNA samples from 66 index cases, and carried out cell transfection experiments to examine the functional consequences of the mutations identified.

RESULTS

A new missense (E161K) mutation was identified in a family with early atrial fibrillation and a previously described (R377H) mutation in another family with a quadriceps myopathy associated with DCM. A new mutation (28insA) leading to a premature stop codon was identified in a family affected by DCM with conduction defects. No mutation in LMNA was found in cases with isolated dilated cardiomyopathy. Functional analyses have identified potential physiopathological mechanisms involving identified mutations, such as haploinsufficiency (28insA) or intermediate filament disorganisation (E161K, R377H).

CONCLUSION

For the first time, a specific phenotype characterised by early atrial fibrillation is associated with LMNA mutation. Conversely, mutations in LMNA appear as a rare cause of isolated dilated cardiomyopathy. The variable phenotypes observed in LMNA-DCM might be explained by the variability of functional consequences of LMNA mutations.

Accuracy of European diagnostic criteria for familial hypertrophic cardiomyopathy in a genotyped population

BACKGROUND

Since the sensitivity of conventional diagnostic criteria for familial hypertrophic cardiomyopathy (HCM) is low, new diagnostic criteria were proposed by a European collaboration. However, their diagnostic value remains unknown. The aim of the study was to evaluate the accuracy of these new criteria, using the genetic status as the criterion of reference.

METHODS

We studied 109 genotyped adults (54 genetically affected, 55 unaffected) from 7 families (mutations in 3 genes). Major European echographic criteria were a maximal wall thickness >or=13 mm or >or=15 mm according to the segment involved, or the presence of SAM. Major European ECG criteria were abnormal Q waves, left ventricular hypertrophy, or marked ST-T changes. Combined major/minor European criteria were also evaluated.

RESULTS

Sensitivity and specificity of major European criteria (72 and 92%, respectively) were similar to those of major conventional criteria (70 and 94%) and were not improved by combined major/minor European criteria (72 and 90%). When all the minor European criteria were considered, sensitivity increased to 87% but specificity dramatically decreased to 51%. However, one of these minor ECG criteria, deep S V2, was of interest and when added to major European criteria, sensitivity increased to 76% and specificity remained good (90%).

CONCLUSIONS

The diagnostic value of new European criteria for HCM was evaluated for the first time. We found that it was not different from that of conventional criteria, with a good specificity but a low sensitivity. Additional criteria should be studied to improve the early identification of HCM.

Cell transplantation for post-ischemic heart failure

Post-ischemic heart failure is becoming a major issue for public health in occidental countries and therapeutical options are limited. Therefore cell transplantation was developed as an alternative strategy to improve cardiac structure and function. This review describes the multiple cell types and clinical trials considered for use in this indication. The transplantation of fetal or neonatal cardiomyocytes has proven to be functionally successful, but ethical as well as technical reasons make their clinical use limited. Recent reports, however, suggested that adult autologous cardiomyocytes could be prepared from stem cells present in various mesenchymal tissues. Alternatively, endothelial progenitors originating from bone marrow or peripheral blood could promote the neoangiogenesis within the scar tissue. Finally, the transplantation of skeletal muscle cells (SMC) in the infarcted area improved myocardial function, in correlation with the development of skeletal muscle tissue in various animal models. The latter results paved the way for the development of a first phase I clinical trial of SMC transplantation in patients with severe ischemic heart failure. It required the scale-up of human cell production according to Good Manufacturing Procedures, it started in June 2000 in Paris and was terminated in November 2001, and it was followed by several others. The results were encouraging and prompted the onset of a blinded, multicentric phase II clinical trial for SMC transplantation. Meanwhile, clinical trials also evaluate the safety and efficacy of various cells types originating from the bone marrow.

Genetic testing and genetic counselling in hypertrophic cardiomyopathy: the French experience

AIMS

A major breakthrough in the molecular genetics of hypertrophic cardiomyopathy (HCM) has made genetic testing now available in clinical practice, raising new questions about its implications, potential benefits, and the organisation of the procedure. The aim of this work was (1) to discuss the different questions related to genetic testing in HCM, and propose guidelines for the different situations, (2) to report our preliminary experience with a specific procedure.

METHODS AND RESULTS

The main questions asked by patients and relatives concern presymptomatic diagnosis and prenatal counselling/diagnosis, while clinicians sometimes discuss diagnostic and prognostic testing. To take into account the complex medical and psychological implications of this new approach, we developed a specific, multidisciplinary, and multiple step procedure, including a cardiologist, a geneticist, and a psychologist. Seventy subjects were examined, including (1) 29 adults for presymptomatic diagnosis (of whom 10 left the procedure after the first visit and 19 continued, among whom six had a mutation and two experienced negative psychological impact, observed during follow up), (2) nine couples of parents for presymptomatic diagnosis in their children (the procedure was stopped after the first visit in eight and continued in one), (3) 22 couples for prenatal counselling (no prenatal genetic testing was asked for after the first visit), and (4) 10 subjects for diagnostic testing. We decided to perform no prognostic testing.

CONCLUSION

Our preliminary experience confirms the complexity of the situation and suggests the necessity for a specific procedure to ensure good practice in genetic testing of HCM.

Lamin A/C mutations with lipodystrophy, cardiac abnormalities, and muscular dystrophy

Mutations in the lamin A/C gene are found in Emery-Dreifuss muscular dystrophy, limb girdle muscular dystrophy with cardiac conduction disturbances, dilated cardiomyopathy with conduction system disease, and familial partial lipodystrophy. Cases with lamin A/C mutations presenting with lipodystrophy in combination with cardiac and/or skeletal muscle abnormalities are described.

Relation between QT duration and maximal wall thickness in familial hypertrophic cardiomyopathy

BACKGROUND

QT abnormalities have been reported in left ventricular hypertrophy and hypertrophic cardiomyopathy.

OBJECTIVE

To determine the relation between left ventricular hypertrophy and increased QT interval in familial hypertrophic cardiomyopathy.

METHODS

The QT interval was measured in 206 genotyped adult subjects with familial hypertrophic cardiomyopathy from 15 unrelated families carrying mutations in the beta myosin heavy chain (beta-MHC) gene (five families, n = 68) or the cardiac myosin binding protein C (MyBPC) gene (10 families, n = 138). Subjects were classified as genetically unaffected (controls, n = 112), affected with left ventricular hypertrophy (penetrants, n = 58), or affected without left ventricular hypertrophy (non-penetrants, n = 36).

RESULTS

There was a significant increase in QTmax and QTmin from controls to non-penetrants and penetrants for both the MyBPC group (p < or = 0.001 and p < or = 0.001, respectively) and the beta-MHC group (p < or = 0.001 and p < or = 0.001, respectively). In the MyBPC group, the increase in the QT interval could be explained by increased left ventricular hypertrophy. In the beta-MHC group, non-penetrants had a significantly longer QTmax than controls despite the absence of left ventricular hypertrophy, and a similar QT interval to penetrants despite a lesser degree of left ventricular hypertrophy.

CONCLUSIONS

In familial hypertrophic cardiomyopathy, genetically affected subjects without left ventricular hypertrophy may have a prolonged QT duration, which depends not only on the degree of left ventricular hypertrophy, when present, but also on the causative mutation.

Selective muscle involvement on magnetic resonance imaging in autosomal dominant Emery-Dreifuss muscular dystrophy

OBJECTIVE

The aim of this study was to evaluate the spectrum of muscle involvement on MRI in patients with autosomal dominant Emery-Dreifuss muscular dystrophy (EDMD2) due to mutations in the lamin A/C gene and to compare it to the pattern found in other conditions with similar phenotype.

PATIENTS AND METHODS

Nine patients with a diagnosis of EDMD2 had MRI scanning of their leg muscles. Seven other patients, four with the X-linked form of Emery-Dreifuss muscular dystrophy (EDMD) and three with an Emery-Dreifuss-like phenotype but no detectable mutations in either the emerin or the lamin A/C gene were also scanned as disease controls.

RESULTS

All patients with EDMD2 showed a characteristic involvement of the posterior calf muscles. The medial head of the gastrocnemius was always predominantly involved while the lateral head was relatively spared. This pattern was more obvious in mildly affected patients in whom the other calf muscles were spared or only mildly involved but was also recognisable in the patients with more advanced disease. In contrast, none of the patients with the X-linked EDMD or with Emery-Dreifuss-like phenotype but no mutation in either genes showed this pattern of muscle involvement.

CONCLUSIONS

Our results suggest that patients with EDMD2 have a specific pattern of muscle involvement and that muscle MRI can be used, in combination with other techniques, to distinguish various genetic forms of Emery-Dreifuss muscular dystrophy.

Autosomal dominant Emery-Dreifuss muscular dystrophy: a new family with late diagnosis

Emery-Dreifuss muscular dystrophy is characterized by the clinical triad of early onset contractures of elbows, Achilles tendons and spine, wasting and weakness with a predominantly humero-peroneal distribution and life-threatening cardiac conduction defects and/or cardiomyopathy. Two main types of inheritance have been described: the X-linked form is caused by mutations in the STA gene on locus Xq28 and the gene for the autosomal dominant form (LMNA gene) has been localized on chromosome 1q11-q23. Recently, mutations in this LMNA gene have been also found to be responsible for the less frequent autosomal recessive form of the disease. Although all forms share a similar clinical presentation, some differences appear to exist between them as has been described recently in a large number of patients. We present the first documented Spanish family genetically confirmed to have autosomal dominant Emery-Dreifuss muscular dystrophy. Clinical, pathological and genetic data are described. We emphasize the difficulties in diagnosis, especially in sporadic cases or young patients in whom the clinical picture is not completely established.

Properties of lamin A mutants found in Emery-Dreifuss muscular dystrophy, cardiomyopathy and Dunnigan-type partial lipodystrophy

Autosomal dominant Emery-Dreifuss muscular dystrophy is caused by mutations in the LMNA gene, which encodes lamin A and lamin C. Mutations in this gene also give rise to limb girdle muscular dystrophy type 1B, dilated cardiomyopathy with atrioventricular conduction defect and Dunnigan-type partial lipodystrophy. The properties of the mutant lamins that cause muscular dystrophy, lipodystrophy and dilated cardiomyopathy are not known. We transfected C2C12 myoblasts with cDNA encoding wild-type lamin A and 15 mutant forms found in patients affected by these diseases. Immunofluorescence microscopy showed that four mutants, N195K, E358K, M371K and R386K, could have a dramatically aberrant localization, with decreased nuclear rim staining and formation of intranuclear foci. The distributions of endogenous lamin A/C, lamin B1 and lamin B2 were also altered in cells expressing these four mutants and three of them caused a loss of emerin from the nuclear envelope. In the yeast two-hybrid assay, the 15 lamin A mutants studied interacted with themselves and with wild-type lamin A and lamin B1. Pulse-chase experiments showed no decrease in the stability of several representative lamin A mutants compared with wild-type. These results indicate that some lamin A mutants causing disease can be aberrantly localized, partially disrupt the endogenous lamina and alter emerin localization, whereas others localize normally in transfected cells.

Is skeletal myoblast transplantation clinically relevant in the era of angiotensin-converting enzyme inhibitors?

BACKGROUND

There is compelling experimental evidence that autologous skeletal muscle (SM) cell transplantation improves postinfarction cardiac function. This study assessed whether this benefit is still manifested in the clinically relevant setting of a treatment by ACE inhibitors.

METHODS AND RESULTS

A myocardial infarction was created in 99 rats by coronary artery ligation. They were divided into 4 groups. Two groups did not receive any drug and were intramyocardially injected 7 days after the infarct with either culture medium alone (control rats, n=16) or autologous SM cells (2.3x10(6) myoblasts) previously expanded ex vivo for 7 days (myoblasts, n=24). Two other groups received the ACE inhibitor perindoprilat (1 mg. kg(-1). d(-1)), started the day of the infarct and continued uninterruptedly thereafter, and underwent time-matched procedures, that is, they were intramyocardially injected at 7 days after infarction with either culture medium alone (ACE inhibitors, n=22) or autologous SM cells (2.5x10(6) myoblasts) previously expanded ex vivo for 7 days (ACE inhibitors+myoblasts, n=37). Left ventricular function was assessed by 2D echocardiography. At the end of the 2-month study, left ventricular ejection fraction (%, mean+/-SEM) was increased in all groups (myoblasts, 37.4+/-1.2; ACE inhibitors, 31.6+/-1.7; ACE inhibitors+myoblasts, 43.9+/-1.4) compared with that in control rats (19.8+/-0.7) (P<0.0001). The improvement in ejection fraction was similar in the ACE inhibitor and the myoblast groups (31.6+/-1.7 versus 37.4+/-1.2, P=0.0636). However, in the ACE inhibitor+myoblast group, this improvement was greater than that seen in hearts receiving either treatment alone (43.9+/-1.4 versus 31.6+/-1.7 in the ACE inhibitor group and 43.9+/-1.4. versus 37.4+/-1.2 in the myoblast group, P<0.0001 and P=0.0084, respectively).

CONCLUSIONS

These data provide further support for the clinical relevance of autologous SM cell transplantation in that its cardioprotective effects are additive to those observed with ACE inhibitors.

A missense mutation in the exon 8 of lamin A/C gene in a Japanese case of autosomal dominant limb-girdle muscular dystrophy and cardiac conduction block

A case of autosomal dominant limb-girdle muscular dystrophy with atrioventricular conduction block (LGMD1B) has been documented. In this family, 13 members, nine males and four females, had cardiac arrhythmia requiring pacemakers. The proband, a 67-year-old male, had longstanding proximal muscle weakness later associated with cardiac arrhythmia but showed neither rigid spine nor joint contracture. His muscle enzymes were within normal range and muscle biopsy showed myopathic changes. Gene analysis of the proband revealed Tyr481His mutation in the exon 8 of lamin A/C (LMNA) gene which is adjacent to the codon mutated in reported cases of familial partial lipodystrophy. This is the first report of muscular dystrophy shown to have a mutation of LMNA in a Japanese family as well as the first case of missense mutation in the exon 8 with LGMD1B phenotype.

Electrotransfer of naked DNA in the skeletal muscles of animal models of muscular dystrophies

The electrotransfer of naked DNA has recently been adapted to the transduction of skeletal muscle fibers. We investigated the short- and long-term efficacy of this methodology in wild-type animals and in mouse models of congenital muscular dystrophy (dy/dy, dy(2J)/dy(2J)), or Duchenne muscular dystrophy (mdx/mdx). Using a reporter construct, the short-term efficacy of fiber transduction reached 40% and was similar in wild-type, dy/dy and dy(2J)/dy(2J) animals, indicating that ongoing muscle fibrosis was not a major obstacle to the electrotransfer-mediated gene transfer. Although the complete rejection of transduced fibers was observed within 3 weeks in the absence of immunosuppression, the persistency was prolonged over 10 weeks when transient or continuous immunosuppressive regimens were used. Using therapeutic plasmids, we demonstrated that electrotransfer also allowed the transduction of large constructs encoding the laminin alpha2 chain in dy/dy mouse, or a chimeric dystrophin-EGFP protein in mdx/mdx mouse. The correct sarcolemmal localization of these structural proteins demonstrated the functional relevance of their expression in vivo, with a diffusion domain estimated to be 300 to 500 microm. However, degeneration-regeneration events hampered the long-term stability of transduced fibers. Given its efficacy for naked DNA transfer in these models of muscular dystrophies, and despite some limitations, gene electrotransfer methodology should be further explored as a potential avenue for treatment of muscular dystrophies.