Fig. 1

Human TRKA gene locus and predicted protein isoforms of human, rat and mouse TRKA. Exons are illustrated as boxes and introns as lines. Exons are drawn to scale in a–f and introns in a. a Chromosomal organization of the human TRKA gene. Also shown are two genes encoded from the opposite strand and partially (SH2D2A) or entirely (INSRR) overlapping the TRKA gene. b All human TRKA exons with size in bp-s shown in dark pink. Representational scheme of TRKA alternative transcripts and putative protein isoforms of human (c and d), mouse (e) and rat (f) origin, based on the results of 5′ RACE, RT-PCR study and in silico analysis. The names of encoded proteins are noted on the right. Alternative N-termini as compared to the conventional TRKAII isoform are labeled as α, β, γ, δ, ε, ζ, η, θ, κ, λ, μ and ξ. Only one ORF per transcript has been marked with start site (blue arrowhead) and stop codon (red asterisk). Roman numerals designate protein isoforms missing various parts of the extracellular region as illustrated for TRKAI…TRKAIX d. Exons 10a and 9a can either serve as 5′ exons or be the products of intron retention (due to this, the block of exons upstream of exons 10a and 9a is illustrated in gray). ARF alternative reading-frame. The L0 isoform of rat TRKA is produced from transcripts that do not include exons 2–4 and L1 from mRNAs missing exons 2 and 3. g the protein domains of TRKAII (MSS membrane signal sequence, Cys and Leu rich region cysteine and leucine rich region, IG like immunoglobulin-like domain, TM transmembrane)