The Δ319 G-CSFR mutant localizes to the WSXWS motif. (A) Heterozygous expression of the WT G-CSFR and Δ319 mutant. PCR amplification products from cDNA from the patient's neutrophils were cloned into pCR4 and restriction digestion with EcoRI was performed, demonstrating a 50:50 mix of clones expressing the WT (upper arrow) or Δ319 (lower arrow) G-CSFR. (B) Schematic diagram of the Δ319 mutant. The mutation in panel A results in a 191-bp deletion and frame shift immediately distal to the W318 codon, producing 29 missense codons followed by a premature stop codon. The deletion disrupts the WSXWS motif and deletes the 3 terminal Fn3 domains in the extracellular region and the entire transmembrane and cytoplasmic domains.