In this study we aimed to generate mouse antibodies against epitopes found on NPCs. We isolated one antibody (NSC-6) and characterized it in detail. Mass spectrometry using human hippocampal tissue revealed the identity of the recognized antigen as BASP1, a signaling protein that plays a key role in neurite outgrowth and plasticity14,15,16,17,18,19, but here, we demonstrate that it might be utilized as a marker of NSCs in the adult brain.
Similar approaches to developing antibodies against mouse embryonic stem cells have been attempted in the past utilizing mice46,47 and rabbits48. Major drawbacks in mice include immune tolerance to mouse embryonic stem cell surface antigens leading to low antibody production, which could be overcome by immunizing rabbits instead. Regardless of the animal used as a host, a significant number of antibodies are typically generated against intracellular epitopes when animals are immunized with whole cells as was observed in our study.
We found that NSC-6-labeled BASP1 localizes to all radial glia at the E12 stage of brain development, while postnatally, it restricts to the neurogenic areas of the mouse brain but not the cortex. This expression pattern contrasts previous study using DAB-based immunolabeling for NAP-22 (BASP1 alias) in the adult rat brain, which demonstrated robust labeling of cerebral cortex27. While we do not know the basis of this difference in immunolabeling of cortex, possibilities include species variations between rat and mouse expression of BASP1, or differences in epitope recognition between the two antibodies used that could yield distinct patterns of immunoreactivity. Indeed, the two commercial BASP1 polyclonal antibodies did not immunolabel NSCs and in general, exhibited poor staining of the mouse brain tissue.