Founding the Wnt gene family: How wingless was found to be a positional signal and oncogene homolog

The Wnt family of developmental regulators were named after the Drosophila segmentation gene wingless and the murine proto-oncogene int-1. Homology between these two genes connected oncogenesis to cell-cell signals in development. I review how wingless was initially characterized, and cloned, as part of the quest to identify developmental cell-to-cell signals, based on predictions of the Positional Information Model, and on the properties of homeotic and segmentation gene mutants. The requirements and cell-nonautonomy of wingless in patterning multiple embryonic and adult structures solidified its status as a candidate signaling molecule. The physical location of wingless mutations and transcription unit defined the gene and its developmental transcription pattern. When the Drosophila homolog of int-1 was then isolated, and predicted to encode a secreted proto-oncogene homolog, it's identity to the wingless gene confirmed that a developmental cell-cell signal had been identified and connected cancer to development.