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Figure 1 | Breast Cancer Research

Figure 1

From: Ltbp1Lis focally induced in embryonic mammary mesenchyme, demarcates the ductal luminal lineage and is upregulated during involution

Figure 1

Latent TGFβ binding protein (Ltbp) function and reporter construct. (A) Ltbp1 sequesters TGFβ ligand encased by its latency associated propeptide (LAP) within the extracellular matrix (ECM). Integrins also interact with LAP. Cytoskeletal tension on integrins stretches LAP and releases TGFβ locally to activate the TGFβ receptor II (TβRII). (B) Two Ltbp1 isoforms (1L and 1S) are transcribed from distinct promoters (black arrows, top). The first four exons (red boxes) encode sequence unique to Ltbp1L. The promoter, transcription start site and unique signal peptide sequence for Ltbp1S (green line and box) lie within the 4th intron of Ltbp1L. Black lines indicate introns. The targeted deletion of Ltbp1L replaces codon 165 in exon 2 through 7.8 kb of intron 2 with a cassette comprising the ROR1 transmembrane domain (pink box), a modified lacZ gene and polyadenylation signal (blue box) as well as a floxed neomycin gene (orange box) driven by the human ubiquitin binding complex promoter (hUBC) that was removed by cre recombination in embryonic stem cells. Orange and blue arrowheads indicate primers used for genotyping. 1L and 1S isoforms contain a signal peptide (SP), 4-Cys (blue), 8-Cys (red) and epidermal growth factor (EGF)-like repeats (gray and green), and unique 8-cys/EGF hybrid domains (brown). The Ltbp1L-LacZ reporter comprises the signal peptide and the first 165 amino acids of Ltbp1L protein followed by the ROR1 transmembrane domain fused in-frame with β-galactosidase and lacks all functional LTBP1 domains.

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