FOS and severe congenital neutropenia: The DUU category was characterized, for the Minus cells, with a pattern more similar to the Plus cells' UDU in that GADD45, gelatinase B, and a chloroacetate esterase followed the DUU pattern, along with FOS, part of the AP-1 transcription factor, and Colony Stimulating Factor 3 Receptor (CSF3R), mutations in which are associated with severe congenital neutropenia.