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Rapamycin, a potent immunosuppressive drug that prevents rejection of organ transplants in many animals, caused profound growth inhibition in an immature B cell lymphoma, BKS-2, at very low concentrations (2 ng/ml). Similar growth inhibition was also observed in a series of B cell lymphomas (i.e., L1.2, NFS.1.1, and WEHI-279) as well as in thymoma cells. The cell death induced by rapamycin in BKS-2 lymphoma was found to be via programmed cell death, or apoptosis. In contrast to rapamycin, neither FK506 nor CsA affected the normal growth of these cells. FK506, but not CsA antagonized the effect of rapamycin and rescued the BKS-2 cells from undergoing apoptosis. Further, suboptimal concentrations of anti-IgM antibodies and rapamycin acted synergistically in causing the growth inhibition of BKS-2 cells and this inhibitory effect was also completely reversed by FK506. Thus, rapamycin appeared to inhibit lymphoma growth by binding to FK506 binding protein. These results indicate that rapamycin should be evaluated as an effective immunosuppressive therapeutic agent to prevent the incidence of lymphoma after transplantations.

Objective: To study the role of TDP-43 in a zebrafish model of Amyotrophic Lateral Sclerosis. Background Amyotrophic lateral sclerosis is a devastating neurodegenerative condition. TDP-43 positive inclusions, have been reported as the hallmark pathology of ALS and FTLD-U. A major RNA processing function of TDP-43 is regulation of splicing. In mouse and drosophila models, TDP-43 has been shown to be important during early embryogenesis. TDP-43 has been observed to mis-localize from the nucleus to the cytoplasm of the surviving motor neurons in the postmortem brain and spinal cord tissues. Thus raising the possibility that the loss of nuclear function of TDP-43 might be responsible in the disease pathogenesis. Zebrafish is a robust vertebrate model, which we have used as a platform to study the loss of function effects of TDP-43. Design/Methods: We identified tardbp and tardbpl as zebrafish orthologues of TARDBP. We have used Antisense Morpholino Oligonucleotides (AMO) to transiently knock down tardbp and tardbpl. We generated tardbp mutant, Y220X, which results in a nonsense mediated decay of tardbp. We studied the motor neurons, axonal out growth, swimming behavior, survival and neuromuscular junction architecture, immuno blotting, immunohistochemistry and qRT-PCR to characterize and confirm our findings. Results: In a transient knockout of tardbp resulted in a phenotype similar to ALS. The stable homozygous tardbp Y220X mutant zebrafish shows significant reduction in weight and length at 6 months of age (p tardbp and tardbpl sequences we have discovered a novel alternative splicing event and a resultant novel splice variant of tardbpl. Conclusions: We have demonstrated that tardbp and tardbpl are essential for the normal development of the zebrafish motor neurons. Loss of tardbp results in a novel alternative splice isoform and up regulation of the same, thus providing an in vivo model of TDP-43 auto-regulation. Understanding this novel regulatory loop could play a key role in the successful generation of zebrafish models relating to ALS genes such as TDP-43 and FUS-1, which have important RNA processing functions. Supported by: CAH is funded by an MRC Clinical Research Fellowship from MRC Centre for Developmental Biomedical Genetics (CDBG). Disclosure: Dr. Hewamadduma has nothing to disclose. Dr. Grierson has nothing to disclose. Dr. Moens has nothing to disclose. Dr. Helde has nothing to disclose. Dr. Ingham has nothing to disclose. Dr. Ramesh has nothing to disclose. Dr. Shaw has received personal compensation for activities with Sanofi Aventis. Dr. Shaw has received research support from Trophos and Biogen Idec.