Figure 1.

Transcriptional variation and expression of Nitr9. (a) Exon organization of the nitr9 gene depicting the three transcript variants. Primer positions for PCR are indicated below. (b) The predicted Nitr9 protein isoforms encoded by the three nitr9 transcripts. Transmembrane (TM) and immunoglobulin domains (of the variable (V) and intermediate (I) types) of Nitr9 are indicated. The I domain of Nitr9 was used as the antigen for antibody production. The positive charge within the TM domain of Nitr9 is represented by a plus sign. (c) RT-PCR with primers whose positions are depicted in (a) detects transcripts of all three nitr9 isoforms. (d) Quantitative RT-PCR with nitr9 primers (Table 1), whose positions are depicted in (a), and a TaqMan probe that spans an exon-exon boundary reveal relative levels of nitr9L/S transcripts in different tissues. (e) Schematic representation of the recombinant Nitr9 expression constructs used in this paper. Constructs include an internal ribosomal entry sequence (IRES2) permitting the expression of two proteins from a single transcript.