Reach, Adoption, and Implementation Strategies of a Telehealth Fall Prevention Program: Perspectives From Francophone Communities Across Canada.

Introduction. A fall may impact a person's physical, emotional, and psychological well-being. Fall prevention programs are being implemented to reduce these negative outcomes. However, linguistic barriers in health services may reduce access to such prevention programs. A telehealth fall prevention program was designed to increase access to such programs in French for Francophone minority communities in Canada. This capacity-building project aimed to support community partners to deliver this telehealth program and document strategies used to reach, adopt, and implement the program within various Francophone and Acadian Minority Communities. Methods. A sequential explanatory mixed methodology was used to document reach, adoption, and implementation strategies and describe the lived experiences of program facilitators and organization representatives. Reach, adoption, and implementation were documented and analyzed descriptively, while lived experiences were analyzed using content analysis following the Consortium Framework for Implementation Research. Results. Twelve organization representatives or program facilitators from eight organizations operating in four different provinces participated in the study. Three themes emerged from the qualitative data on reach and adoption: external context, internal context, and capacity building. Four themes were identified as barriers and facilitators to implementation: level of preparation and time management, interpersonal relations and telepresence, exercise facilitation and safety, and technological problem-solving. Conclusion. Using tailored reach and adoption strategies such as prioritizing provinces with higher proportions of needs and training local community program facilitators may lead to the successful implementation of a new telehealth fall prevention program. Results from this study could potentially inform other primary prevention programs or telehealth program implementation.

Deleterious Effects of Intra-arterial Administration of Particulate Steroids on Microvascular Perfusion in a Mouse Model.

Purpose To determine the in vivo effects of several particulate steroids on microvascular perfusion by using intravital microscopy in a mice model and to investigate the in vitro interactions between these particulate steroids and red blood cells (RBCs). Materials and Methods The study was conducted in agreement with the guidelines of the National Committee of Ethic Reflection on Animal Experimentation. By using intravital microscopy of mouse cremaster muscle, the in vivo effects of several particulate steroids on microvascular perfusion were assessed. Four to five mice were allocated to each of the following treatment groups: saline solution, dexamethasone sodium phosphate, a nonparticulate steroid, and the particulate steroids cortivazol, methylprednisolone, triamcinolone, and prednisolone. By using in vitro blood microcinematography and electron microscopy, the interactions between these steroids and human RBCs were studied. All results were analyzed by using nonparametric tests. Results With prednisolone, methylprednisolone, or triamcinolone, blood flow was rapidly and completely stopped in all the arterioles and venules (median RBC velocity in first-order arterioles, 5 minutes after administration was zero for these three groups) compared with a limited effect in mice treated with saline, dexamethasone, and cortivazol (20.3, 21.3, and 27.5 mm/sec, respectively; P < .003). This effect was associated with a large decrease in the functional capillary density (4.21, 0, and 0 capillaries per millimeter for methylprednisolone, triamcinolone, or prednisolone, respectively, vs 21.0, 21.4, and 19.1 capillaries per millimeter in mice treated with saline, dexamethasone, and cortivazol, respectively; P < .003). This was because of the rapid formation of RBC aggregates. However, no change in microvascular perfusion was associated with administration of cortivazol or dexamethasone. In vitro experiments confirmed the formation of RBC aggregates associated with the transformation of RBCs into spiculated RBCs with the same steroids. Conclusion Several particulate steroids have an immediate and massive effect on microvascular perfusion because of formation of RBC aggregates associated with the transformation of RBCs into spiculated RBCs. (©) RSNA, 2016 Online supplemental material is available for this article.

The association between sleep disturbance, depressive symptoms, and health-related quality of life among cardiac rehabilitation participants.

PURPOSE: Recent guidelines from the Canadian Association of Cardiac Rehabilitation highlight the importance of addressing sleep disturbance among participants of cardiac rehabilitation (CR) programs. The primary objective of this study was to examine the relationship between depressive symptoms, health-related quality of life, and sleep disturbance in CR participants. The secondary objective was to estimate the prevalence of sleep disturbance among CR participants with and without depressive symptoms and explore demographic, medical, and psychological predictors of poor sleep quality. METHODS: Cardiac rehabilitation participants (N = 259) were included in this study. Participants completed a standardized questionnaire package including demographic, health-related, and psychosocial measures. Physiologic and anthropometric measurements were taken at baseline. Descriptive statistics were calculated for all variables, and data were analyzed using multivariate logistic regression. RESULTS: Poor sleep quality was reported by 52% of participants in the sample, and 47% of participants in the sample reported experiencing at least mild depressive symptoms. Poor sleep occurred more often in individuals with depressive symptoms, and after adjustment for medical factors and health-related quality of life, participants with symptoms of depression were still more likely to experience sleep disturbance than those without depressive symptoms (OR = 2.80; 95% CI, 1.37-5.77). An important gender difference emerged in the relationship between symptoms of depression and sleep disturbance. CONCLUSION: Among participants of a CR program, disturbed sleep was strongly associated with depressive symptoms and decreased health-related quality of life. Results demonstrate the importance of sleep evaluation in CR programs.

The phenotype of dysferlin-deficient mice is not rescued by adeno-associated virus-mediated transfer of anoctamin 5.

Mutations in dysferlin and anoctamin 5 are the cause of muscular disorders, with the main presentations as limb-girdle muscular dystrophy or Miyoshi type of distal myopathy. Both these proteins have been implicated in sarcolemmal resealing. On the basis of similarities in associated phenotypes and protein functions, we tested the hypothesis that ANO5 protein could compensate for dysferlin absence. We first defined that the main transcript of ANO5 expressed in skeletal muscle is the 22-exon full-length isoform, and we demonstrated that dysferlin-deficient (Dysf (prmd)) mice have lower Ano5 expression levels, an observation that further enhanced the rational of the tested hypothesis. We then showed that AAV-mediated transfer of human ANO5 (hANO5) did not lead to apparent toxicity in wild-type mice. Finally, we demonstrated that AAV-hANO5 injection was not able to compensate for dysferlin deficiency in the Dysf (prmd) mouse model or improve the membrane repair defect seen in the absence of dysferlin. Consequently, overexpressing hANO5 does not seem to provide a valuable therapeutic strategy for dysferlin deficiency.

A human skeletal muscle interactome centered on proteins involved in muscular dystrophies: LGMD interactome.

BACKGROUND: The complexity of the skeletal muscle and the identification of numerous human disease-causing mutations in its constitutive proteins make it an interesting tissue for proteomic studies aimed at understanding functional relationships of interacting proteins in both health and diseases. METHOD: We undertook a large-scale study using two-hybrid screens and a human skeletal-muscle cDNA library to establish a proteome-scale map of protein-protein interactions centered on proteins involved in limb-girdle muscular dystrophies (LGMD). LGMD is a group of more than 20 different neuromuscular disorders that principally affect the proximal pelvic and shoulder girdle muscles. RESULTS AND CONCLUSION: The interaction network we unraveled incorporates 1018 proteins connected by 1492 direct binary interactions and includes 1420 novel protein-protein interactions. Computational, experimental and literature-based analyses were performed to assess the overall quality of this network. Interestingly, LGMD proteins were shown to be highly interconnected, in particular indirectly through sarcomeric proteins. In-depth mining of the LGMD-centered interactome identified new candidate genes for orphan LGMDs and other neuromuscular disorders. The data also suggest the existence of functional links between LGMD2B/dysferlin and gene regulation, between LGMD2C/γ-sarcoglycan and energy control and between LGMD2G/telethonin and maintenance of genome integrity. This dataset represents a valuable resource for future functional investigations.

The MyHealthCheckup study: Training graduate students to implement cardiovascular risk screening programs in community pharmacies.

BACKGROUND: Hypertension is a major risk factor for cardiovascular morbidity and mortality. Despite this fact and the development of effective antihypertensive drug therapy, hypertension is often poorly controlled. Community pharmacies are an ideal site for the management of hypertension and other modifiable cardiovascular risk factors. The purpose of the current study was to develop and assess a pharmacy-based cardiovascular risk screening program implemented by graduate students. METHODS: Four graduate students trained as health coaches screened a convenience sample of adults who were interested in cardiovascular risk assessment in 21 Montreal area pharmacies. On the screening day, we assessed cardiovascular risk factors, including blood pressure, used the Cardiovascular Life Expectancy Model, which includes cardiovascular age, to inform patients of their personalized risk profile, delivered an individualized health coaching intervention and conducted a participant satisfaction survey. This was followed by an individualized health coaching intervention. The intervention program was implemented by trained graduate students and supported by pharmacists. RESULTS: Among the 238 patients who participated (57% female, mean age 60.6 years), 67% had a body mass index (BMI) greater than 25 kg/m(2), 52% had abdominal obesity, 58% reported insufficient physical activity and 14% were smokers. A total of 120 patients (51%) were taking antihypertensive medication, yet 63 (53%) had blood pressure readings above currently accepted targets. Higher BMI and physical inactivity were associated with increased rates of poorly controlled hypertension. CONCLUSION: The screening program identified individuals with modifiable cardiovascular risk factors and poorly controlled hypertension. The intervention program was well received by participants and the majority provided contact information for future cardiovascular screening clinics. These findings support the feasibility of screening programs run by graduate students in the pharmacy setting.

Estimating the benefits of patient and physician adherence to cardiovascular prevention guidelines: the MyHealthCheckup Survey.

BACKGROUND: The management of cardiovascular risk factors such as hypertension and dyslipidemia is poorly described in many communities, and the benefits associated with tighter control remain unknown. We used data from the 2007 MyHealthCheckup survey to document the treatment gaps and estimated the potential benefits of better adherence to recommended guidelines. METHODS: Cardiovascular risk factors, lifestyle habits, and prescribed medications were evaluated among Canadian adults recruited primarily in pharmacies. The Cardiovascular Life Expectancy Model was used to estimate the potential benefits of optimally treating hypertension or dyslipidemia (defined as not smoking, regular physical activity, an acceptable body weight, and maximal medication as needed). RESULTS: Among 2674 screened individuals, 1266 (47%) were receiving pharmacotherapy for either dyslipidemia or hypertension, including 772 (61%) and 656 (63%), respectively, who remained above treatment targets. Among those above lipid or blood pressure targets, 27% and 22%, respectively, were optimally treated. The average increased life expectancy or life-years gained associated with making appropriate lifestyle changes included 2.2 to 4.7 years from smoking cessation, 0.7 to 1.1 years from regular exercise, and 0.4 to 0.7 years from weight reduction. The life-years gained following better risk factor treatment included maximal pharmacotherapy for elevated blood pressure (0.6-0.8), low-density lipoprotein cholesterol (0.5-0.6), and the ratio of total cholesterol to high-density lipoprotein cholesterol (0.3-0.4). Years of life free of cardiovascular disease would be similarly increased. CONCLUSIONS: Better treatment of cardiovascular risk factors could result in a substantial reduction in morbidity and mortality among Canadians. Given current physician prescribing and patient habits, lifestyle modification should be considered a priority before additional medications are prescribed.

A new pathway encompassing calpain 3 and its newly identified substrate cardiac ankyrin repeat protein is involved in the regulation of the nuclear factor-κB pathway in skeletal muscle.

A multiprotein complex encompassing a transcription regulator, cardiac ankyrin repeat protein (CARP), and the calpain 3 protease was identified in the N2A elastic region of the giant sarcomeric protein titin. The present study aimed to investigate the function(s) of this complex in the skeletal muscle. We demonstrate that CARP subcellular localization is controlled by the activity of calpain 3: the higher the calpain 3, the more important the sarcomeric retention of CARP. This regulation would occur through cleavage of the N-terminal end of CARP by the protease. We show that, upon CARP over-expression, the transcription factor nuclear factor NF-κB p65 DNA-binding activity decreases. Taken as a whole, CARP and its regulator calpain 3 appear to occupy a central position in the important cell fate-governing NF-κB pathway. Interestingly, the expression of the atrophying protein MURF1, one of NF-κB main targets, remains unchanged in presence of CARP, suggesting that the pathway encompassing calpain 3/CARP/NF-κB does not play a role in muscle atrophy. With NF-κB also having anti-apoptotic effects, the inability of calpain 3 to lower CARP-driven inhibition of NF-κB could reduce muscle cell survival, hence partly accounting for the dystrophic pattern observed in limb girdle muscular dystrophy 2A, a pathology resulting from the protease deficiency.

Interactions with M-band titin and calpain 3 link myospryn (CMYA5) to tibial and limb-girdle muscular dystrophies.

Mutations in the C terminus of titin, situated at the M-band of the striated muscle sarcomere, cause tibial muscular dystrophy (TMD) and limb-girdle muscular dystrophy (LGMD) type 2J. Mutations in the protease calpain 3 (CAPN3), in turn, lead to LGMD2A, and secondary CAPN3 deficiency in LGMD2J suggests that the pathomechanisms of the diseases are linked. Yeast two-hybrid screens carried out to elucidate the molecular pathways of TMD/LGMD2J and LGMD2A resulted in the identification of myospryn (CMYA5, cardiomyopathy-associated 5) as a binding partner for both M-band titin and CAPN3. Additional yeast two-hybrid and coimmunoprecipitation studies confirmed both interactions. The interaction of myospryn and M-band titin was supported by localization of endogenous and transfected myospryn at the M-band level. Coexpression studies showed that myospryn is a proteolytic substrate for CAPN3 and suggested that myospryn may protect CAPN3 from autolysis. Myospryn is a muscle-specific protein of the tripartite motif superfamily, reported to function in vesicular trafficking and protein kinase A signaling and implicated in the pathogenesis of Duchenne muscular dystrophy. The novel interactions indicate a role for myospryn in the sarcomeric M-band and may be relevant for the molecular pathomechanisms of TMD/LGMD2J and LGMD2A.

Discussing coronary risk with patients to improve blood pressure treatment: secondary results from the CHECK-UP study.

OBJECTIVES: Hypertension is common among patients with dyslipidemia but is often poorly treated. The objective of this analysis was to evaluate how a decision aid, used by primary care physicians to improve lipid therapy, impacted on the treatment of hypertension. STUDY DESIGN: Data were analyzed from patients enrolled in a randomized trial focusing primarily on the treatment of dyslipidemia. Patients received usual care or a coronary risk profile every three months to monitor the risk reduction following lifestyle changes and/or pharmacotherapy to treat dyslipidemia. Hypertension management was assessed based on a post hoc analysis of individuals whose blood pressure exceeded current national hypertension guidelines. RESULTS: There were 2,631 subjects who completed the study. Among 1,352 patients without diagnosed hypertension, 30% were above target on at least three consecutive visits. Among 1,279 individuals with known hypertension, 69% were above target on at least two consecutive visits. Overall, patients receiving risk profiles were more likely to receive appropriate antihypertensive therapy (OR = 1.40, 95% CI 1.11-1.78) compared to those receiving usual care. After adjustment for inter-physician variability and potential confounders, the use of the risk profile was associated with an increased likelihood of starting therapy (OR = 1.78, 95% CI 1.06-3.00) or modifying therapy (OR = 1.40, 95% CI 1.03-1.91). CONCLUSIONS: In this clinical trial of dyslipidemia management, inadequately controlled hypertension was common, occurring in nearly 50% of individuals. Ongoing coronary risk assessment was associated with more appropriate blood pressure management. Cardiovascular risk assessment decision aids should be further evaluated in a randomized trial of hypertension therapy.

Truncating mutations in C-terminal titin may cause more severe tibial muscular dystrophy (TMD).

Mutations in C-terminal titin cause autosomal dominant tibial muscular dystrophy (TMD) as reported previously. Samples from 25 new families and 25 sporadic new distal myopathy cases were screened for titin mutations. Three novel mutations were discovered in two families from Spain and two families from France. Two mutations, g.292998delT and g.293376delA lead to frameshift and premature stop codons in the second last and the last titin gene (TTN) exons, Mex5 and Mex6, respectively. The third was a nonsense mutation g.293379C>T (p.Q33396X) in Mex6. Patients with the upstream Mex5 mutation showed a more severe phenotype with earlier onset implying a genotype-phenotype correlation.

Patient knowledge of coronary risk profile improves the effectiveness of dyslipidemia therapy: the CHECK-UP study: a randomized controlled trial.

BACKGROUND: Despite increasing evidence that treating dyslipidemia reduces cardiovascular events, many patients do not achieve recommended lipid targets. METHODS: To determine whether showing physicians and patients the patient's calculated coronary risk can improve the effectiveness of treating dyslipidemia in a primary care setting, patients were randomized to receive usual care or ongoing feedback regarding their calculated coronary risk and the change in this risk after lifestyle changes, pharmacotherapy, or both to treat dyslipidemia. Outcomes, based on intention-to-treat analysis, included changes in blood lipid levels, coronary risk, and the frequency of reaching lipid targets. RESULTS: Two hundred thirty primary care physicians enrolled 3,053 patients. After 12 months of follow-up, 2,687 patients (88.0%) remained in the study. After adjustment for baseline lipid values, significantly greater mean reductions in low-density lipoprotein cholesterol levels and the total cholesterol to high-density lipoprotein cholesterol ratio were observed in patients receiving risk profiles (51.2 mg/dL [to convert to millimoles per liter, multiply by 0.0259] and 1.5, respectively) vs usual care (48.0 mg/dL and 1.3, respectively), but the differences were small (-3.3 mg/dL; 95% confidence interval [CI], -5.4 to -1.1 mg/dL; and -0.1; 95% CI, -0.2 to -0.1, respectively). Patients in the risk profile group were also more likely to reach lipid targets (odds ratio, 1.26; 95% CI, 1.07 to 1.48). A significant dose-response effect was also noted when the impact of the risk profile was stronger in those with worse profiles. CONCLUSIONS: Discussing coronary risk with the patient is associated with a small but measurable improvement in the efficacy of lipid therapy. The value of incorporating risk assessment in preventive care should be further evaluated.

C-terminal titin deletions cause a novel early-onset myopathy with fatal cardiomyopathy.

OBJECTIVE: The giant protein titin is essential for striated muscle development, structure, and elasticity. All titin mutations reported to date cause late-onset, dominant disorders involving either skeletal muscle or the heart. Our aim was to delineate the phenotype and determine the genetic defects in two consanguineous families with an early-onset, recessive muscle and cardiac disorder. METHODS: Clinical and myopathological reevaluation of the five affected children, positional cloning, immunofluorescence, and Western blot studies were performed. RESULTS: All children presented with congenital muscle weakness and childhood-onset fatal dilated cardiomyopathy. Skeletal muscle biopsies showed minicores, centrally located nuclei, and/or dystrophic lesions. In each family, we identified a homozygous titin deletion in exons encoding the C-terminal M-line region. Both deletions cause a frameshift downstream of the titin kinase domain and protein truncation. Immunofluorescence confirmed that truncated titins lacking the C-terminal end were incorporated into sarcomeres. Calpain 3 was secondarily depleted. INTERPRETATION: M-line titin homozygous truncations cause the first congenital and purely recessive titinopathy, and the first to involve both cardiac and skeletal muscle. These results expand the spectrum of early-onset myopathies and suggest that titin segments downstream of the kinase domain are dispensable for skeletal and cardiac muscle development, but are crucial for maintaining sarcomere integrity.

Do the benefits of finasteride outweigh the risks in the prostate cancer prevention trial?

PURPOSE: The Prostate Cancer Prevention Trial demonstrated that finasteride could reduce the incidence of prostate cancer by 25%. However, its use was also associated with an increased risk of high grade cancer resulting in uncertainty surrounding the net benefits of therapy. MATERIALS AND METHODS: We used the Montreal Prostate Cancer Model, a validated Markov model of prostate cancer progression, to compare the forecasted survival in treated and untreated men. The conditions of the model were varied to reflect different assumptions about whether the cancer grade difference observed in the PCPT was real or a treatment associated artifact, and whether cancers detected on end of study biopsies were clinically significant. RESULTS: For a hypothetical cohort of 1,000, 62-year-old men treated with finasteride, an increased survival of 140 life-years (0.14 years per individual) is forecasted if all diagnosed cancers are considered. If tumor grade differences are held to be artifactual, the forecasted benefits increase to 200 life-years. However, if the tumor grade difference is real and only clinically detected cancers are considered, estimated increased survival is only 20 life-years (0.02 years per individual). CONCLUSIONS: The primary prevention of prostate cancer with finasteride looks promising. However, at the present time it should only be considered with caution until we have answered critical questions surrounding the difference in cancer grade observed in the PCPT and the clinical significance of cancers detected on protocol directed end of study biopsies.

The prevalence of erectile dysfunction in the primary care setting: importance of risk factors for diabetes and vascular disease.

BACKGROUND: The prevalence of erectile dysfunction (ED) and associated risk factors has been described in many clinical settings, but there is little information regarding men seen by primary care physicians. We sought to identify independent factors associated with ED in a primary care setting. METHODS: We surveyed a cross-sectional sample of 3921 Canadian men, aged 40 to 88 years, seen by primary care physicians. Participants completed a full medical history, physical examination, and measurement of fasting blood glucose and lipid levels. We used the International Index of Erectile Function to define ED as a score of less than 26 on the erectile function domain. RESULTS: The overall prevalence of ED was 49.4%. The presence of cardiovascular disease (odds ratio [OR], 1.45; 95% confidence interval [CI], 1.16-1.81; P<.01) or diabetes (OR, 3.13; 95% CI, 2.35-4.16; P<.001) increased the probability of ED after adjustment for other confounders. Among those individuals without cardiovascular disease or diabetes, the calculated 10-year Framingham coronary risk (OR, 1.03 per 1% increase; 95% CI, 1.02-1.05; P<.001) and fasting blood glucose levels (OR, 1.14 per 18-mg/dL [1-mmol/L] increase; 95% CI, 1.04-1.24; P<.01) were independently associated with ED. Erectile dysfunction was also independently associated with undiagnosed hyperglycemia (OR, 1.46; 95% CI, 1.02-2.10; P = .04), impaired fasting glucose (OR, 1.26; 95% CI, 1.08-1.46; P = .004), and the metabolic syndrome (OR, 1.45; 95% CI, 1.24-1.69; P<.001). CONCLUSIONS: Cardiovascular disease, diabetes, future coronary risk, and increasing fasting glucose levels are independently associated with ED. It remains to be determined if ED precedes the development of these conditions.

The kinase domain of titin controls muscle gene expression and protein turnover.

The giant sarcomeric protein titin contains a protein kinase domain (TK) ideally positioned to sense mechanical load. We identified a signaling complex where TK interacts with the zinc-finger protein nbr1 through a mechanically inducible conformation. Nbr1 targets the ubiquitin-associated p62/SQSTM1 to sarcomeres, and p62 in turn interacts with MuRF2, a muscle-specific RING-B-box E3 ligase and ligand of the transactivation domain of the serum response transcription factor (SRF). Nuclear translocation of MuRF2 was induced by mechanical inactivity and caused reduction of nuclear SRF and repression of transcription. A human mutation in the titin protein kinase domain causes hereditary muscle disease by disrupting this pathway.

Bidirectional transcriptional activity of the Pgk1 promoter and transmission ratio distortion in Capn3-deficient mice.

A calpain 3 (Capn3) deficiency model was created by targeted disruption of the mouse Capn3 gene through homologous recombination in ES cells. Analysis of the genotype of pups from heterozygous crosses revealed a transmission ratio distortion (TRD) in favor of homozygous Capn3-deficient mice. This TRD was not observed in a second model of Capn3 deficiency, ruling out a possible involvement of Capn3 deficiency in this phenotype. The molecular nature of the TRD was investigated by quantitative RT-PCR and RACE-PCR analyses. We observed the presence in testis and ovaries of abundant, novel transcripts of the Capn3 gene arising from the antisense strand of the Pgk1-neomycin cassette. Although we could not detect corresponding translation products, our results suggest that the activity of the Pgk1 promoter could be the causative factor of TRD. This first example of TRD induced by an introduced cassette further emphasizes the care that should be taken in interpreting phenotypes of animal models, especially when dealing with reproductive functions, and further supports the rationale of using excisable cassettes in inactivation strategies.

Tibial muscular dystrophy in a Belgian family.

We report a Belgian family with autosomal dominant, late-onset, distal myopathy with selective foot extensor muscle involvement of the lower legs. Linkage to the tibial muscular dystrophy (TMD) locus 2q31 was not evident at first because of incomplete disease penetrance in a 50-year-old asymptomatic family member. An abnormal tibialis anterior muscle biopsy established her subclinical status and linkage of the family to the TMD locus. Mutation analysis showed a disease-specific, heterozygous point mutation in the last exon, Mex6, of the titin gene. This is the third mutation found in TMD and the second European family with TMD outside the Finnish population, suggesting that titinopathies may occur in various populations.

Tibial muscular dystrophy is a titinopathy caused by mutations in TTN, the gene encoding the giant skeletal-muscle protein titin.

Tibial muscular dystrophy (TMD) is an autosomal dominant late-onset distal myopathy linked to chromosome 2q31. The linked region includes the giant TTN gene, which encodes the central sarcomeric protein, titin. We have previously shown a secondary calpain-3 defect to be associated with TMD, which further underscored that titin is the candidate. We now report the first mutations in TTN to cause a human skeletal-muscle disease, TMD. In Mex6, the last exon of TTN, a unique 11-bp deletion/insertion mutation, changing four amino acid residues, completely cosegregated with all tested 81 Finnish patients with TMD in 12 unrelated families. The mutation was not found in 216 Finnish control samples. In a French family with TMD, a Leu-->Pro mutation at position 293,357 in Mex6 was discovered. Mex6 is adjacent to the known calpain-3 binding site Mex5 of M-line titin. Immunohistochemical analysis using two exon-specific antibodies directed to the M-line region of titin demonstrated the specific loss of carboxy-terminal titin epitopes in the TMD muscle samples that we studied, thus implicating a functional defect of the M-line titin in the genesis of the TMD disease phenotype.