RRM
2007 Rustbelt RNA Meeting
RRM
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Poster abstracts
Abstract:
Members of the muscle-like (MBNL) family have been shown to regulate pre-mRNA alternative splicing, and have been implicated in developmental-stage specific splicing in heart and skeletal muscle during the fetal-to-adult transition. To investigate the role of MBNL proteins during embryonic cardiogenesis, we examined MBNL expression in the developing chicken heart. By whole mount in situ hybridization, MBNL1 and MBNL2 were first detected in the embryonic heart at 48 hours (H&H stage 14), several hours after the primitive heart tube has formed, when cardiac looping is well underway. Expression continues in the heart during subsequent cardiac morphogenesis, as endocardial cushion outgrowth septates the heart into chambers (H&H stages 18-23). In situ hybridization on sections of H&H stage 23 embryos reveals strong MBNL1 and MBNL2 expression in the myocardium and in endocardial cells within the endocardial cushions, but not within the endocardium in other regions of the heart. MBNL3 is not detected in the heart at any stage. MBNL1 and MBNL2 are themselves alternatively spliced, and undergo changes in alternative splicing in the heart during endocardial cushion induction, outgrowth, and remodeling (H&H stages 14-29). Consistent with this, western blot analyses on total protein samples from whole hearts revealed that multiple MBNL1 protein isoforms are expressed in the embryonic heart, and the expression of these isoforms is dynamic during endocardial cushion development. These changes in MBNL expression coincide with a change in the pattern of cardiac troponin T (cTNT) alternative splicing, a known pre-mRNA target of MBNL activity. Together, these results suggest that MBNL proteins not only participate in fetal-to-adult heart development, but may also influence developmentally regulated splicing events during embryonic cardiac morphogenesis.
Keywords: alternative splicing, muscleblind-like, development
