Adult preterm birth survivors, especially those who developed BPD, continue to experience respiratory symptoms and exhibit clinically important levels of pulmonary impairment.

Coronary artery disease (CAD) has a strong genetic component, but is also greatly influenced by environmental factors such as diet and smoking, and disorders such as diabetes mellitus and hypertension. This interaction makes prediction of CAD risk generally difficult. However, in familial hypercholesterolaemia (FH), risk of early CAD is considerably increased by the mutation of a single gene, and genetic testing may be appropriate. We summarize current knowledge concerning DNA-based tests in the identification and management of FH, and propose specific recommendations for genetic testing and further research. The major value of DNA tests for FH is in genetic tracing programs to identify and treat affected individuals. DNA testing is appropriate for: (a) diagnosis of FH when physical signs or family history are equivocal or absent (important given the increased risk of CAD associated with FH compared to other hypercholesterolaemias); (b) detection of a mutation causing FH in immediate family members (particularly children) where there is a family history of premature CAD. A positive DNA-based test for a mutation is especially useful in children, in whom plasma lipid levels may not be diagnostic. Current clinical practice is to test relatives for raised cholesterol. Testing for mutation carriers in distant relatives, although feasible, is not currently recommended. Research projects should now be started to address two issues: (i) whether genetic tests for FH better predict clinical outcome than does measurement of plasma lipid levels; (ii) whether genetic testing for FH confers overall benefit both to the patient and their relatives, and to the NHS. Answers to these questions will guide the subsequent development and implementation of genetic tests for CAD risk in general, if and when the considerably more complex genetic causes of CAD are identified.

The proper folding of many proteins can only be achieved by interaction with molecular chaperones. The molecular chaperone UNC-45B is required for the folding of striated muscle myosin II. However, the precise mechanism by which it contributes to proper folding of the myosin head remains unclear. UNC-45B contains three domains: an N-terminal TPR domain known to bind Hsp90, a Central domain of unknown function, and a C-terminal UCS domain known to interact with the myosin head. Here we used fluorescence titrations methods, dynamic light scattering, and single-molecule atomic force microscopy (AFM) unfolding/refolding techniques to study the interactions of the UCS and Central domains with the myosin motor domain. We found that both the UCS and the Central domains bind to the myosin motor domain. Our data show that the domains bind to distinct subsites on the myosin head, suggesting distinct roles in forming the myosin-UNC-45B complex. To determine the chaperone activity of the UCS and Central domains, we used two different methods: 1), prevention of misfolding using single-molecule AFM, and 2), prevention of aggregation using dynamic light scattering. Using the first method, we found that the UCS domain is sufficient to prevent misfolding of a titin mechanical reporter. Application of the second method showed that the UCS domain but not the Central domain prevents the thermal aggregation of the myosin motor domain. We conclude that while both the UCS and the Central domains bind the myosin head with high affinity, only the UCS domain displays chaperone activity.

a b s t r a c t Molecular chaperones are required for successful folding and assembly of sarcomeric myosin in skeletal and cardiac muscle. Here, we show that the chaperone UNC-45B inhibits the actin translocation function of myosin. Further, we show that Hsp90, another chaperone involved in sarcomere development, allows the myosin to resume actin translocation. These previously unknown activities may play a key role in sarcomere development, preventing untimely myosin powerstrokes from disrupting the precise alignment of the sarcomere until it has formed completely.

The multidomain UNC‐45B chaperone is crucial for the proper folding and function of sarcomeric myosin. We recently found that UNC‐45B inhibits the translocation of actin by myosin. The main functions of the UCS and TPR domains are known but the role of the central domain remains obscure. Here, we show—using in vitro myosin motility and ATPase assays—that the central domain alone acts as an inhibitor of the myosin power stroke through a mechanism that allows ATP turnover. Hence, UNC‐45B is a unique chaperone in which the TPR domain recruits Hsp90; the UCS domain possesses chaperone‐like activities; and the central domain interacts with myosin and inhibits the actin translocation function of myosin. We hypothesize that the inhibitory function plays a critical role during the assembly of myofibrils under stress and during the sarcomere development process.