Dll3 Knockout mouse models

Dll3, the mouse ortholog of human DLL3, encodes a divergent Delta-like protein that lacks a functional DSL domain and fails to trans-activate Notch, instead accumulating in the Golgi and late endosomes where it acts as a cis-inhibitor by retaining NOTCH1 and DLL1 and preventing their surface presentation, thereby modulating the segmentation clock. Loss in mouse yields the pudgy phenotype with severely disorganized vertebrae and ribs, matching human biallelic mutations that cause spondylocostal dysostosis type 1, so constitutive nulls are directly informative for axial skeletal endpoints. The dominant contemporary interest is oncologic: aberrant surface expression in small cell lung cancer and neuroendocrine tumors makes the protein a target for antibody drug conjugates, bispecific T cell engagers such as tarlatamab, and CAR designs, none of which cross-react between species. Consequently, epitope-matched humanized knockins are the correct allele for efficacy and on-target toxicity studies, while floxed conditionals suit developmental questions. Related Dll1 partially overlaps in presomitic mesoderm but cannot substitute for cis-inhibition.

Whole body loss of Dll3 gives the clearest readout when the question is whether the gene is required at all. Follow up tissue work can still move to a conditional allele if lethality or compensation appears.