Schematic structure of the cytoplasmic domain of the G-CSF receptor gene. The cytoplasmic domain of the G-CSF receptor is shown including the critical region (nucleotides 2384-2429), which is amplified by primers Q1, Q2, and P2 in the RT-PCR reaction. The nucleotide positions given below indicate the point mutations detected in patients with congenital neutropenia. Hatched boxes indicate the conserved domains homologous to other members of the cytokine receptor family. EC, extracellular; TM, transmembrane; IC, intracellular domain; aa, amino acids; bp, base pairs.