Murine Mapk14/p38-α encodes four variant proteins: exon structure and expression in BMMs. (a) Genomic arrangement of murine mitogen-activated protein kinase (Mapk)14 on the plus strand of mouse chromosome 17. The probe track indicates the exon junctions spanned by oligoprobes on the splicing array. (b) Variant transcripts are indicated by boxed exon cartoon. Variants 1 and 3 are 359 amino acid proteins that alternate exon 10 (variant 1) or exon 11 (variant 3). Piccolo (variant 2) is a 258 amino acid dominant-negative isoform. Variant 4 originates from a novel transcription start site (TSS) with a predicted 283 amino acid open reading frame (ORF) lacking the ATP-domain. Variant 5 included a novel exon that interrupts the ORF. (c) Scatter plot shows the distribution of expression detected by each probe. The average signal of each probe (unstimulated bone-marrow derived macrophages (BMMs) and BMMs subjected to seven hours of stimulation with lipopolysaccharide (+7 hrs LPS); x axis) was plotted against the normalized ratio of +7 hrs LPS/unstimulated BMM (y axis). Open triangles indicate constitutive junction probes, black triangles indicate alternate junction probes, and exon probes are indicated by black squares. Probe 3A measures the inducible expression of variant 4 after LPS treatment (P < 0.05). Probes 13A and 15EOL measure the expression of variant 2 (piccolo), which was low compared with variant 1 or 4 (measured by probe 14A). Probe 12A confirms a low expression of variant 3 in macrophages.