LAMB2 and Down syndrome: While the most abundant basement membrane laminin chain (Lamc1) was unaltered in both abundance (Fig. 6d) and solubility (Fig. 6g), serving as a control for overall integrity of the basement membrane and the quality of our data, the basement membrane-associated trimeric Fraser Syndrome complex (consisting of Fras1, Frem1, and Frem2) was downregulated (Fig. 6e) and more soluble (Fig. 6h) in old age.