Figure 4

LALBA transcription. (A) RT-PCR shows equal expression of each LALBA transgene with one major mRNA transcript for each species. Markers are shown (bp). (B) Otariid and phocid LALBA gene structure and mRNA splice variants. The LALBA gene comprises four exons that undergo alternative splicing. Identified transcript variants (indicated by i, ii, iii and iv) comprise (i) a correctly spliced phocid LALBA transcript; (ii) an otariid LALBA transcript which is formed by use of a 3' splice site in the LALBA 3'UTR (shown) prior to the LALBA termination codon (shown) causing a loss of exon 4; (iii) an otariid LALBA transcript which contains intron 3 caused by lack of splicing due to a mutation in the 3' splice site of intron 3 (mutation shown for otariid LALBA gene compared with correct splice sequence in phocid LALBA gene); and (iv) a transcript which is formed by use of a 5' splice site within exon 1 causing a 60 bp deletion of exon 1, shown here for phocid LALBA. The Otariid LALBA gene also has this 5' splice site (transcripts not shown here). (C) Northern blot (left panel) confirms one major LALBA transcript is detected in the Cape fur seal mammary gland. Right panel shows corresponding ethidium bromide-stained mRNA prior to blotting.