• Hongqiang Cheng, Kensuke Kimura, Angela K Peter, Li Cui, Kunfu Ouyang, Tao Shen, Yujie Liu, Yusu Gu, Nancy D Dalton, Sylvia M Evans, Kirk U Knowlton, Kirk L Peterson, and Ju Chen.
• Department of Medicine, University of California San Diego, La Jolla, 92093, USA.
• Circ. Res. 2010 Aug 6; 107 (3): 348-56.

RationaleThe Z-line, alternatively termed the Z-band or Z-disc, is a highly ordered structure at the border between 2 sarcomeres. Enigma subfamily proteins (Enigma, Enigma homolog protein, and Cypher) of the PDZ-LIM domain protein family are Z-line proteins. Among the Enigma subfamily, Cypher has been demonstrated to play a pivotal role in the structure and function of striated muscle, whereas the role of Enigma homolog protein (ENH) in muscle remains largely unknown.ObjectiveWe studied the role of Enigma homolog protein in the heart using global and cardiac-specific ENH knockout mouse models.Methods And ResultsWe identified new exons and splice isoforms for ENH in the mouse heart. Impaired cardiac contraction and dilated cardiomyopathy were observed in ENH null mice. Mice with cardiac specific ENH deletion developed a similar dilated cardiomyopathy. Like Cypher, ENH interacted with Calsarcin-1, another Z-line protein. Moreover, biochemical studies showed that ENH, Cypher short isoform and Calsarcin-1 are within the same protein complex at the Z-line. Cypher short isoform and Calsarcin-1 proteins are specifically downregulated in ENH null hearts.ConclusionsWe have identified an ENH-CypherS-Calsarcin protein complex at the Z-line. Ablation of ENH leads to destabilization of this protein complex and dilated cardiomyopathy.

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