Differential regulation of CASZ1 protein expression during cardiac and skeletal muscle development.

Background: The zinc-finger transcription factor CASZ1 is required for differentiation of a distinct population of cardiomyocytes during development. However, expression of Casz1 mRNA is detected throughout the developing heart, suggesting the spatial regulation of CASZ1 occurs at the protein level. Relatively little is known about posttranscriptional regulation of Casz1 in the heart.

Results: We generated antibodies that specifically recognize CASZ1 in developing Xenopus embryos, and performed immunofluorescence analysis of CASZ1 during cardiac development. CASZ1 was detected throughout the developing myocardium. CASZ1 was restricted to terminally differentiated cardiomyocytes, and was down-regulated in cells that re-enter the cell cycle. We determined that CASZ1 expression correlated with terminal differentiation in cardiac muscle cells, skeletal muscle cells, and lymph-heart musculature.

Conclusions: This study indicates that spatially distinct expression of CASZ1 protein may be due to posttranscriptional control of Casz1 mRNA during cardiac development. The results of this study provide insights into the role of Casz1 in cardiac function and in the differentiation of other cell types, including skeletal muscle and lymph heart.