Missense mutations in the central domains of cardiac myosin binding protein-C and their potential contribution to hypertrophic cardiomyopathy.

Myosin binding protein-C (MyBP-C) is a multidomain protein that regulates muscle contraction. Mutations in MYBPC3, the gene encoding for the cardiac variant (henceforth called cMyBP-C), are amongst the most frequent causes of hypertrophic cardiomyopathy. Most mutations lead to a truncated version of cMyBP-C, which is most likely unstable. However, missense mutations have also been reported, which tend to cluster in the central domains of the cMyBP-C molecule. This suggests that these central domains are more than just a passive spacer between the better characterized N- and C-terminal domains. Here, we investigated the potential impact of four different missense mutations, E542Q, G596R, N755K, and R820Q, which are spread over the domains C3 to C6, on the function of MyBP-C on both the isolated protein level and in cardiomyocytes in vitro. Effect on domain stability, interaction with thin filaments, binding to myosin, and subcellular localization behavior were assessed. Our studies show that these missense mutations result in slightly different phenotypes at the molecular level, which are mutation specific. The expected functional readout of each mutation provides a valid explanation for why cMyBP-C fails to work as a brake in the regulation of muscle contraction, which eventually results in a hypertrophic cardiomyopathy phenotype. We conclude that missense mutations in cMyBP-C must be evaluated in context of their domain localization, their effect on interaction with thin filaments and myosin, and their effect on protein stability to explain how they lead to disease.

Evaluating 3D-printed models of coronary anomalies: a survey among clinicians and researchers at a university hospital in the UK.

OBJECTIVE: To evaluate the feasibility of three-dimensional (3D) printing models of coronary artery anomalies based on cardiac CT data and explore their potential for clinical applications. DESIGN: Cardiac CT datasets of patients with various coronary artery anomalies (n=8) were retrospectively reviewed and processed, reconstructing detailed 3D models to be printed in-house with a desktop 3D printer (Form 2, Formlabs) using white resin. SETTING: A University Hospital (division of cardiology) in the UK. PARTICIPANTS: The CT scans, first and then 3D-printed models were presented to groups of clinicians (n=8) and cardiovascular researchers (n=9). INTERVENTION: Participants were asked to assess different features of the 3D models and to rate the models' overall potential usefulness. OUTCOME MEASURES: Models were rated according to clarity of anatomical detail, insight into the coronary abnormality, overall perceived usefulness and comparison to CT scans. Assessment of model characteristics used Likert-type questions (5-point scale from 'strongly disagree' to 'strongly agree') or a 10-point rating (from 0, lowest, to 10, highest). The questionnaire included a feedback form summarising overall usefulness. Participants' imaging experience (in a number of years) was also recorded. RESULTS: All models were reconstructed and printed successfully, with accurate details showing coronary anatomy (eg, anomalous coronary artery, coronary roofing or coronary aneurysm in a patient with Kawasaki syndrome). All clinicians and researchers provided feedback, with both groups finding the models helpful in displaying coronary artery anatomy and abnormalities, and complementary to viewing 3D CT scans. The clinicians' group, who had substantially more imaging expertise, provided more enthusiastic ratings in terms of models' clarity, usefulness and future use on average. CONCLUSIONS: 3D-printed heart models can be feasibly used to recreate coronary artery anatomy and enhance understanding of coronary abnormalities. Future studies can evaluate their cost-effectiveness, as well as potentially explore other printing techniques and materials.