Mutually exclusive splicing is a regulated means to generate protein diversity, but the underlying mechanisms are poorly understood. Here comparative genome analysis revealed the built-in intronic elements for controlling mutually exclusive splicing of the 14-3-3ξ pre-mRNA. These elements are clade specific but are evolutionarily conserved at the secondary structure level. Combined evidence revealed the triple functions of these inter-intronic RNA pairings in synergistically ensuring the selection of only one of multiple exons, through activation of the proximal variable exon outside the loop by the approximation of cis elements, and simultaneous repression of the exon within the loop, in combination with the physical competition of RNA pairing. Additionally, under this model, we also deciphered a similar structural code in exon clusters 4 and 9 of Dscam (38,016 isoforms) and Mhc (480 isoforms). Our findings suggest a broadly applicable mechanism to ensure mutually exclusive splicing.

BackgroundThe working environment of stone miners has been believed to cause their susceptibility to respiratory diseases. Silicosis is an occupational disease caused by exposure to crystalline silica dust which is marked by inflammation and scarring in the lung. The immune system boosted after the silica invasion led to self-damage and lay the foundation of silicosis pathogenesis. Silicosis coexisting with other diseases in one patient has been reported, however, was not reported to coexist with constrictive pericarditis. We, for the first time, reported a patient with silicosis and constrictive pericarditis and thought the immune response was probably the link between the two.Case presentationA 59-year-old Chinese stone miner complained of chest distress was found to have lung nodules which were found to be silica deposits by biopsy. This patient was also found to have constrictive pericarditis at the same time. Later surgical decortication cured his symptoms.ConclusionWe provided the first case having constrictive pericarditis concomitant with silicosis. A probable link between the two diseases was the immune response boosted by the silica deposits.

Serous effusions, including pleural, abdominal and pericardial effusions, are complications of lymphoma. Among these types, pleural effusions are the most common to be observed. However, the involvement of the abdominal or pericardial cavity is rare. An impairment of the lymphatic drainage and direct infiltration have been identified to play significant roles in effusion formation. Multiple techniques, including cytological exams, immunochemistry and cytogenetics, have been applied in the clinic to access the qualities of the effusions and to attain a fast and precise diagnosis. Serous effusions are associated with a poor outcome for patients with lymphoma. The present study describes the case of a 28-year-old male patient with aggressive non-Hodgkin's lymphoma (NHL) involving pleural and abdominal chylous effusions.

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