BCL2L1 and thanatophoric dysplasia: In contrast to the protection observed against TD, loss of βII spectrin offered no appreciable protection against axon degeneration caused by direct activation of the apoptotic pathway (by the Bcl-2/Bcl-xL/Bcl-w antagonist ABT-737), or direct damage to the mitochondria (by rotenone) or to the microtubule cytoskeleton (by vincristine) (Figure 5—figure supplement 1C).