Fig. 1.
Isoform-specific effects of collagen XVIII on BW, adiposities, and liver weights. (A) Horizontal and vertical stripes denote signal sequences of short (Top) and medium/long isoforms of mouse collagen XVIII, respectively. White and gray boxes depict collagenous and NC regions, respectively. Brick pattern denotes the DUF. Black dots denote the Fz homology domain containing 10 conserved cysteines (cys) followed by the Tsp1 homology domain depicted in diagonal stripes. Predicted HS attachment sites, recombinant fragments produced, and epitopes of the anti–all-18 and anti–medium/long-18 antibodies are shown. (B) Collagen XVIII isoforms derive from utilization of alternative promoters. Exons 1 and 2 are specific to the short variant. Exon 3 (subject to alternative splicing) encodes middle and long variants. Exons 5–43 (not shown) are common to all isoforms. (C) Specified 12-wk-old mice were fed a Western diet for 5 wks. Ventral views (Upper) and eWAT of representative mice. (D) BW of 12-wk-old, male WT (n = 15), Col18a1−/− (n = 5), Col18a1P1/P1 (n = 7), and Col18a1P2/P2 (n = 5) mice fed a Western diet for 5 wk. (E) Weights of eWAT (total mass of both fat pads) and livers of mice in D, expressed as percentage of BW. (F) Relative Col18a1 RNA levels in liver, eWAT, and kidney of 12-wk-old WT mice fed standard chow were quantified by RT-qPCR. Data (mean ± SD), normalized to β-actin, are relative to eWAT. *P < 0.05, ***P < 0.001.