Figure 2.

Alternative splicing events identified in the human and dog HADH2 genes. A) Schematic illustration of the splicing pathways of human and dog HADH2 genes. The typical exon-intron organization of human and dog HADH2 genes is shown. Exons (E), which are of same lengths in human and dog genes, are represented by coloured boxes and shown to scale (bar = 200 bp). Introns and UTR regions are schematized by unscaled lines and boxes with black streaks, respectively. Intron phases are indicated by numbers above the lines. Alternative splicing (AS) pathway A, identified in human and dog, involves utilization of an alternative donor splice site (ss) in the exon 5, resulting in a nine amino acid deletion. The sequences of human and dog intron 5 splice sites (ss) and of the alternative donor splice site are shown. The conserved nucleotides that identify the U2-type consensus sequences for the GT splice donor site (MAGGTRAGT), GC splice donor site (MAGGCAAGT) and acceptor splice site (NCAGGT) are in red, violet, and green. Alternative splicing (AS) pathway B, identified in dog, involves the skipping of exon 5 which, due to the different phase of introns 4 and 5, leads to the appearance of an earlier stop codon (TGA) in the exon 6, resulting in the replacement of the last 92 amino acids by seven new ones. B) Amino acid sequences of the dog ABAD/HSD10 and variants produced by AS. The nine amino acids deleted in the variant 2 (252 amino acids) are in red (The nine amino acids deleted in the human variant 2 homologue are identical). The seven new amino acids in the variant 3 are in blue.