TDP-43 is a discriminative protein that is found as intracellular aggregations in the neurons of the cerebral cortex and spinal cord of patients with amyotrophic lateral sclerosis (ALS); however, the mechanisms of neuron loss and its relation to the aggregations are still unclear. In this study, we generated a useful model to produce TDP-43 aggregations in the motor cortex using in utero electroporation on mouse embryos. The plasmids used were full-length TDP-43 and C-terminal fragments of TDP-43 (wild-type or M337V mutant) tagged with GFP. For the full-length TDP-43, both wild-type and mutant, electroporated TDP43 localized mostly in the nucleus, and though aggregations were detected in embryonic brains, they were very rarely observed at P7 and P21. In contrast, TDP-43 aggregations were generated in the brains electroporated with the C-terminal TDP-43 fragments as previously reported in in vitro experiments. TDP43 protein was distributed diffusely not only in the nucleus, but also in the cytoplasm and the inclusion bodies were ubiquitinated and included phosphorylated TDP-43, which reflects the human pathology of ALS. This model using in utero electroporation of pathogenic genes into the brain of the mouse will likely become a useful model for studying ALS and also for evaluation of agents for therapeutic purpose, and may be applicable to other neurodegenerative diseases, as well. (c) 2013 Elsevier Ireland Ltd and the Japan Neuroscience Society. All rights reserved.