Description

The unc-112 gene in Caenorhabditis elegans encodes a 720-amino acid protein (UNC-112) that colocalizes with integrin and perlecan in cell to ECM adhesion structures and is a component of dense bodies and M-lines (Rogalski et al., 2000). The UNC-112 protein is homologous to the human protein Kindlin-1. Kindlin-1 in humans is implicated in Kindler syndrome, a skin fragility disorder (Siegel et al., 2003). The UNC-112 protein shares a short region of homology (roughly 200 amino acids) with talin and other FERM superfamily proteins that may play a key role in plasma membrane attachment (Rogalski et al., 2000). Previous studies have discovered that UNC-112 is essential for the organization and localization of PAT-3/β-integrin in body wall muscle cells (Rogalski et al., 2000). Null mutations in unc-112 lead to twofold stage arrest during embryogenesis, abnormal body wall muscle, and exhibit the Pat (paralyzed, arrested elongation at twofold) phenotype (Williams and Waterston, 1994). In this study, a novel mutant allele of C. elegans unc-112 was generated using CRISPR-Cas9 gene editing. In this mutant allele, leucine (L) was replaced with glutamate (E) near the C-terminal end of UNC-112. In a biochemical study, the homologous mutation abolished binding of kindlin2 to the membrane distal “phospho-tyrosine” motif of β1 integrin tails (Li et al., 2017). Mutant worms were examined for behavioral and morphological abnormalities. Mutants displayed no notable behavioral abnormalities in a thrashing assay compared to N2 wild-type worms (p=0.5485 according to the Mann-Whitney U Test). However, 35.6% of unc-112 mutants (n=177) were observed to exhibit defective distal tip cell migration (DTC Mig). Mutants displaying this abnormal DTC Mig phenotype had dipping distal gonad arms (Figure 1B), bulging proximal gonads filled with germ cell nuclei (Figure 1D), and oocyte-like nuclei in the distal gonad (ectopic oocytes, Figure 1C). Previous research has shown that integrin-ECM interactions play important roles in directing DTC migration and gonad morphogenesis, and the DTC Mig phenotype observed could be the result of mutant unc-112 disrupting key integrin functions in the somatic gonad (Lee et al., 2001)