Novel Biochemical And Phenotypical Findings On The Nodal Signaling Components Lefty And Cripto

NOVEL BIOCHEMICAL AND PHENOTYPICAL FINDINGS ON THE NODALSIGNALING COMPONENTS LEFTY AND CRIPTObyAMAPOLA BALANCIODecember 2014Advisor: Dr. William Branford, Jr.Major: Biological Sciences (Molecular and Developmental Biology)Degree: Master of ScienceNodal, a Transforming Growth Factor-β (TGF-B), is a key regulator of properdevelopment along with its atypical TGF-B inhibitor Lefty and its EGF-CFC co-receptorCripto. Studies have shown that Nodal is unable to signal in the absence of a functionalCripto, indicating that it is a Nodal obligate co-receptor. In fact, one of the ways thatLefty prevents Nodal is by binding to Cripto and another way is through directlyinteracting with Nodal.To characterize the regions of Xenopus Lefty (Xlefty) that molecularly interactwith Nodal and XCr1, we created truncated, as well as uncleavable, Xlefty mutants andutilize them in phenotypic and biochemical experiments. We found that the M1 domainof Xlefty is not only the region that interacts with XCr1, but it is also sufficient to inhibit Nodal signaling. Furthermore, previous literature suggested that the mature form ofXlefty blocks Nodal. That means that the cleavage of Xlefty is necessary for Nodalinhibition. We believe our results are the first to show that only mature Xlefty interacts with Cripto. Processing of Xlefty at its first cleavage site is a requirement for Nodalinhibition, yet it has been implied that the second cleavage site is unimportant to its role