Defining roles for the oncogenic kinase Abl and its substrate Crk in embryonic development

Undergraduates: Alison Bonner, Dr. Andrew Spracklen

Faculty Advisor: Mark Peifer
Department: Biology

---

Coordinated cell adhesion and actin remodeling are required for normal development and tissue homeostasis. Regulatory proteins like Abelson tyrosine kinase (Abl) are essential for this coordination. Abl is a highly conserved, multi-domain protein, with a kinase domain, F-actin binding domain, and domains involved in assembly of signaling complexes. While the role of Abl¿¿¿s kinase activity is well understood during development and disease, such as Leukemia, the role of other domains remains largely unexplored. We began by dissecting the roles of different Abl functional domains during embryonic morphogenesis, using a fruit fly model. Surprisingly, a short, conserved motif (PXXP) in the linker region of Abl is more critical for morphogenesis than both kinase activity and F-actin binding. In mammals, this motif is a binding site for three SH3-domain proteins: Abi, Crk, and Nck. We find knockdown of Crk and Abi, but not Nck, produces phenotypes mimicking that of mutants lacking Abl or Abl¿¿¿s PXXP motif. I am following this by characterizing how loss of Crk disrupts embryonic morphogenesis and how varying Crk levels modifies abl mutant phenotypes, to reveal how Crk and Abl regulate morphogenesis both together and independently. To do so, we generated a crk mutant using CRISPR, and are characterizing phenotypes caused by loss of Crk, to determine Crk¿¿¿s role during processes that require coordination of cell adhesion and the cytoskeleton, including cellularization and CNS patterning.