Abstract
Numerous studies have revealed that Rap1 (Ras-proximate-1 or Ras-related protein 1), a small GTPase protein, plays a crucial role in mediating cAMP signaling in isolated cardiac tissues and cell lines. However, the involvement of Rap1 in the cardiac development in vivo is largely unknown. By injecting anti-sense morpholino oligonucleotides to knock down Rap1a and Rap1b in zebrafish embryos, and in combination with time-lapsed imaging, in situ hybridization, immunohistochemistry and transmission electron microscope techniques, we seek to understand the role of Rap1 in cardiac development and functions. At an optimized low dose of mixed rap1a and rap1b morpholino oligonucleotides, the heart developed essentially normally until cardiac contraction occurred. Morphant hearts showed the myocardium defect phenotypes, most likely due to disrupted myofibril assembly and alignment. In vivo heart electrocardiography revealed prolonged P-R interval and QRS duration, consistent with an adherens junction defect and reduced Connexons in cardiac myocytes of morphants. We conclude that a proper level of Rap1 is crucial for heart morphogenesis and function, and suggest that Rap1 and/or their downstream factor genes are potential candidates for genetic screening for human heart diseases.
Highlights
In the heart, cardiomyocytes are responsible for pumping blood into the circulation, a process called the cardiac contraction, which is cAMP-dependent
Loss of rap1 Functions Led to Specific Defects, Including the Heart Malformation, in Zebrafish To investigate the role of rap1 in zebrafish development, we used morpholino anti-sense (MO) oligonucleotides that were previously used to block the translational start site of rap1a [18] and a splice donor site of rap1b [19]
Because the specificity of rap1bMO could confirmed by RT-PCR, to ensure the specificity of rap1aMO, we used a mismatch rap1aMO to test if the consistent phenotypes observed in rap1a morphants was entirely due to rap1aMO
Summary
Cardiomyocytes are responsible for pumping blood into the circulation, a process called the cardiac contraction, which is cAMP-dependent. Epac regulates the activity of various cellular compartments of cardiac myocytes and influences calcium homeostasis and excitation-contraction coupling, and is potentially involved in many cardiovascular disorders, such as cardiac hypertrophy and remodeling [4,5]. Somekawa et al showed that cAMP treatment increases GJs through activating Epac-Rap signaling and adherens junctions [22]; whereas the activation of Rap by Epac results in impeding ERK5, and in the decreasing of myocyte growth [23]. This suggests a role of Rap in myocardium function, likely to change cardiac development (the GJ remodeling). We believe that Rap plays an essential role in development/remodeling of cardiac functions, resembles the in vivo observation using mammalian cultured cardiac cells
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
