RT Journal Article SR Electronic T1 Rewiring of an ancestral Tbx1/10-Ebf-Mrf network for pharyngeal muscle specification in distinct embryonic lineages JF bioRxiv FD Cold Spring Harbor Laboratory SP 039289 DO 10.1101/039289 A1 Theadora Tolkin A1 Lionel Christiaen YR 2016 UL http://biorxiv.org/content/early/2016/02/09/039289.abstract AB Skeletal muscles arise from diverse embryonic origins, yet converge on common regulatory programs involving muscle regulatory factor (MRF)-family genes. Here, we compare the molecular basis of myogenesis in two separate muscle groups in the simple chordate Ciona: the atrial and oral siphon muscles. Here, we describe the ontogeny of OSM progenitors and characterize the clonal origins of OSM founders to compare mechanisms of OSM specification to what has been established for ASM. We determined that, as is the case in the ASM, Ebf and Tbx1/10 are both expressed and function upstream of Mrf in the OSM founder cells. However, regulatory relationships between Tbx1/10, Ebf and Mrf differ between the OSM and ASM lineages: while Tbx1/10, Ebf and Mrf form a linear cascade in the ASM, Ebf and Tbx1/10 are expressed in the inverse temporal order and are required together in order to activate Mrf in the OSM founder cells.