FIGURE 1.

The CXCR4 locus is highly conserved between human and mouse genomes and encodes two CXCR4 isoforms, CXCR-A and CXCR4-B. A, comparison of human and mouse CXCR4 gene loci (analyzed using NCBI DCODE comparative genomics resources). The y axis indicates levels of homology, with the x axis level at ≤50% homology. Exons are shaded, with coding regions indicated in black and untranslated regions in gray. Schematic of two transcripts generated, CXCR4-B and CXCR4-A, are shown above the alignment graph. Length of genomic region is indicated in the scale bar below the graph in kilobases (kb), with the transcriptional start of exon 1/CXCR4-B transcript assigned as zero. B, schematics of genomic segments in construct utilized in studies. The diagrams are in alignment with their genomic locations in A. C, schematic of CXCR4-B and CXCR4-A transcripts, with the amino acid sequences indicated. The protein sequences are identical except for the most N-terminal residues. D and E, both CXCR4 transcripts are expressed in melanoma cells. All cell lines in the panel expressed the canonical CXCR4-B transcript (D) as detected by quantitative PCR analysis, whereas 3/7 expressed the non-canonical CXCR4-A transcript (E).