delta-Ca(2+)/calmodulin-dependent protein kinase II expression pattern in adult mouse heart and cardiogenic differentiation of embryonic stem cells.

delta-isoforms of the Ca(2+)/calmodulin-dependent protein kinase type II (CaMKII) are considered to substantially influence cardiac functions. However, no data exist on the expression of these isoforms in the mouse heart. We analyzed the transcript pattern of non-neuronally expressed delta-isoforms in heart and skeletal muscle of adult mice by RT-PCR. For members of the delta-CaMKII subclass with both variable domains (subclass II), weak transcriptional expression of isoforms delta(2) and delta(3) was found in the heart. In skeletal muscle no delta(3)-specific transcript was detectable. In cardiac tissue, stronger signals result from amplifications of delta(9) and from members of the subclass I lacking the second variable domain. Western blotting was performed using a subclass II-specific antibody. In murine cardiac and skeletal muscle tissue a delta-CaMKII protein pattern was obtained similar to that described for rat. To gain insight into the expression of delta-CaMKII during the earliest steps of cardiogenic differentiation, we analyzed the transcript pattern of murine embryonic stem cell-derived cardiomyocytes in various differentiation stages. Reproducible RT-PCR signals could be obtained for delta(6) and delta(10), both belonging to the delta-CaMKII subclass I. Transcripts for delta(6) were ubiquitously expressed, whereas transcripts for delta(10) were detectable in increasing amounts after 7-10 days of the onset of cardiogenic differentiation. Our results point to a differentiation-dependent expression of the two delta-CaMKII subclasses, and also to differences in the expression of individual members of subclass I during the early stages of cardiogenic differentiation.