Murine Tlr4 encodes two variant transcripts: exon structure and expression of variant transcripts in BMMs. (a) Genome viewer tracks. Mouse Toll-like receptor Tlr4 maps to the minus strand of chromosome 4. Probe track indicates the exon junctions spanned by oligoprobes on the splicing array. Probe 1C spans the junction between exons 1 and 2. 2A spans the junction between exons 2 and 3, and is unique to the full-length Tlr4 variant. 3A and 4C span exons 2-4 and 4-5, respectively. Both probes detect the variant Tlr4 transcript. Transcripts are shown by exon-boxed cartoon. Variant 1 is a full-length Tlr4 transcript, variant 2 skips exon 3 and so lacks the transmembrane and cytoplasmic domains. (b) 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 BMMs (y axis). Junction probes are indicated by a triangle; intronic or intergenic controls are indicated by open boxes; and exon probes are indicated by black circles. The microarray detects expression of both Tlr4 transcripts in unstimulated and +7 hr LPS stimulated BMMs, and demonstrates a higher level of expression of the full-length variant.