PgmNr Z628: tp53-deficient zebrafish models of Malignant Nerve Sheath Tumor, Leukemia, Angiosarcoma, Rhabdomyosarcoma, and Germ cell tumors.

Authors:
Myron Ignatius 1 ; Finola Morre 1 ; Madeline Hayes 1 ; Qin Tang 1 ; Riadh Lobbardi 1 ; Sophia Reeder 1 ; Alexander Jin 1 ; Patrick Blackburn 2 ; Eleanor Chen 3 ; Petur Nielsen 1 ; Stephen Ekker 2 ; David Langenau 1


Institutes
1) Harvard Medical School/Department of Pathology, Massachusetts General Hospital, Boston, MA; 2) Mayo Clinic, Rochester, MN; 3) Department of Pathology, University of Washington, Seattle, WA.


Abstract:

      Individuals with Li-Fraumeni Syndrome inherit a mutant TP53 allele and are predisposed to developing a wide range of cancers including sarcomas and leukemia. TP53 is also somatically inactivated in more than half of all sporadic human cancers. Despite the well-studied role of p53 in cancer, mechanistic insights into how specific loss-of-function mutations regulate tumorigenesis are not clearly understood. Here, we have generated a new full-null tp53 deletion allele in syngeneic CG1 strain zebrafish.  Two TALEN pairs were created to efficiently delete the entire 11kb locus. tp53-/- null zebrafish, lack p53 protein, are viable, survive at Mendelian ratios and can develop tumors as early as three months of age. In contrast to existing dominant-negative tp53 alleles available in the zebrafish that develop MPNSTs with long latency, tp53null animals spontaneously develop lymphomas, MPNSTs, angiosarcomas, and germ cell tumors. 40% of null animals develop tumors within the first year of life (n=53 of 134). MPNSTs, lymphomas, and angiosarcomas could efficiently be transplanted into syngeneic recipient fish (2-4x104 cells/fish injected intraperitoneally). To visualize tumor growth in vivo, we next generated tp53null; Tg(Ubi-GFP) CG1 strain syngeneic zebrafish and transplanted tumors from fish with lymphoma into matched recipients. Transplanting either the kidney marrow or bulk tumor cells from diseased fish resulted in robust engraftment and seeding of leukemic cells to the kidney marrow, thymus, and spleen.  Leukemia cells had atypical myeloid cell features, suggestive of myeloid leukemia. tp53 is mutationally inactivated in 50% of human embryonal rhabdomyosarcomas (ERMS). To assess a role for p53 in regulating ERMS growth, onset, tumor-propagating potential, and metastasis; we created zebrafish that were transgenic for kRASG12D and p53 loss. Self-renewal was unaffected in comparing kRASG12D tumors with and without p53 (n=3 tumors per genotype; p=0.66). By contrast, tp53null ERMS were more invasive and had elevated metastatic potential both in the primary and transplant settings (n=6 tumors per group). Taken together, we have developed a full null for the tp53 allele in the zebrafish and show that null mutants develop a spectrum of tumor types with short latency and high penetrance. We are currently sequencing tumors generated in tp53 null mutants to perform comparative genomics with human tumors.



ZFIN Genetics Index
1. tp53
2. kRASG12D