Expression of alternatively spliced human latent transforming growth factor β binding protein‐1

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Abstract
Latent transforming growth factor β binding protein‐1 (LTBP1) is important in regulating the localisation and activation of transforming growth factor β (TGFβ). Three forms of LTBP1 mRNA have previously been described, LTBP1L, LTBP1S and LTBPΔ53. Here, we have analysed the LTBP1 coding sequence and identified two other spliced forms, LTBP1Δ55 and LTBP1Δ41. LTBP1Δ55 is a short form of LTBP1L which lacks 55 amino acids including two consensus N‐glycosylation sites and LTBP1Δ41 is a form of LTBP1 which lacks the 12th EGF‐like repeat. Furthermore, sequencing of genomic clones showed that splicing to generate LTBP1L occurs using an intra‐exonic 3′ splice acceptor site in the first coding exon of LTBP1S and that LTBP1Δ55 arises from the alternative use of an exonic 3′ splice acceptor site at the end of the following intron. LTBP1Δ41 arises from skipping the exon which encodes the 12th EGF‐like repeat. LTBP1Δ55 and LTBP1Δ41 mRNA are expressed in a wide variety of human tissues but the proportions of each splice form vary in the tissues.