Muscle contraction alters hemicentin dynamics at the B-LINK: a newly identified basement membrane adhesion system that connects tissues.

Abstract

Basement membranes (BMs) are thin, dense sheets of extracellular matrix found covering most tissues in multicellular organisms. In some instances, BMs of adjacent tissues can become linked and attach tissues together. A better understanding of BM-BM adhesion can help elucidate the mechanisms of conditions like Alport syndrome, a human pathology characterized by a loss of kidney function due to a failed BM-BM linkage. In order to further characterize the linkage of neighboring tissues through their BMs, I investigated how the Basement Membrane Linkage complex (B-LINK), a complex that mediates BM-BM adhesion at the uterine-hypodermal juncture in C. elegans, responds to biomechanical force. To accomplish this, I determined the necessity of specific BM proteins to B-LINK structural integrity by performing gene knockdown with RNA interference (RNAi) and scoring for vulval rupture, a phenotype that results from a disrupted B- LINK. Type IV collagen was the only common BM component to be identified as an important factor in BM adhesion due to high vulval rupture percentages when it was knocked down at the L1 (80.5%) and L4 (20.0%) larval stages (Fisher’s exact = 0.0001). Additionally, I used fluorescence recovery after photobleaching (FRAP) to measure the rate of the protein turnover of the B-LINK component hemicentin under different conditions. These FRAP experiments revealed that muscle contraction in animals significantly increases the hemicentin turnover rate when compared to immobilized worms over the same 15-minute time course (76.7% vs. 24.3%, p-value = 0.0041). These results provide a better understanding of which BM components are essential to B-LINK function and has revealed that muscle contraction influences B-LINK dynamics.