Drosophila type IV collagen mutation associates with immune system activation and intestinal dysfunction

Abstract

The basal lamina (BM) contains numerous components with a predominance of type IV collagens. Clinical manifestations associated with mutations of the human COL4A1 gene include perinatal cerebral hemorrhage and porencephaly, hereditary angiopathy, nephropathy, aneurysms and muscle cramps (HANAC), ocular dysgenesis, myopathy, Walker-Warburg syndrome and systemic tissue degeneration. In Drosophila, the phenotype associated with dominant temperature sensitive mutations of col4a1 include severe myopathy resulting from massive degradation of striated muscle fibers, and in the gut, degeneration of circular visceral muscle cells and epithelial cells following detachment from the BM. In order to determine the consequences of altered BM functions due to aberrant COL4A1 protein, we have carried out a series of tests using Drosophila DTS-L3 mutants from our allelic series of col4a1 mutations with confirmed degeneration of various cell types and lowest survival rate among the col4a1 mutant lines at restrictive temperature. Results demonstrated epithelial cell degeneration in the gut, shortened gut, enlarged midgut with multiple diverticulae, intestinal dysfunction and shortened life span. Midgut immunohistochemistry analyses confirmed altered expression and distribution of BM components integrin PSI and PSII alpha subunits, laminin gamma 1, and COL4A1 both in larvae and adults. Global gene expression analysis revealed activation of the effector AMP genes of the primary innate immune system including Metchnikowin, Diptericin, Diptericin B, and edin that preceded morphological changes. Attacin::GFP midgut expression pattern further supported these changes. An increase in ROS production and changes in gut bacterial flora were also noted and may have further enhanced an immune response. The phenotypic features of Drosophila col4a1 mutants confirmed an essential role for type IV collagen in maintaining epithelial integrity, gut morphology and intestinal function and suggest that aberrant structure and function of the COL4A1 protein may also be a significant factor in modulating immunity.

Cathepsin B Regulates Collagen Expression by Fibroblasts via Prolonging TLR2/NF‐κB Activation

“…Collagen IV, as a major component of the BM, participates in the inflammatory responses during tissue repair [7, 28, 29], principally via cellular regulation and migration [9, 30]. Indeed, Col4a1 (human collagen IV gene) mutation-associated phenotypic features include chronic inflammation and immune activation [10, 11]. …”

“…Collagen IV, a nonfibrillar collagen, is a major component of the basement membrane (BM) [7, 8]. Recently, collagen IV has been shown to participate in the innate immune response by regulating cellular adhesion and migration [9], and Col4a1 (the human collagen IV gene) mutation-associated phenotypic features include chronic inflammation and immune activation [10–12]. …”

Novel Phenotypic Elements of Type IV Collagenopathy Revealed by the Drosophila Model

“…In col4a1 fly mutants, we recorded severe myopathy, reduced concentration of COL4A1 protein [24], chronic inflammation, intestinal dysfunction [25], detachment of the cells from the BM by electron microscopy [26], compromised excretory system [27], heavy membrane peroxidation in epithelial cells of the Malpighian tubules [28] and the onset of muscular dystrophy in all mutants [29]. Temperature-sensitive col4a1 alleles in Drosophila were generated by ethyl-methanesulfonate mutagenesis, resulting in G to A transitions in all alleles, in turn leading to glycine substitutions by Glu, Asp and Ser [29].…”

“…The genome of the fruit fly consists of a pair of type IV collagen genes, col4a1 and col4a2 in a head-to-head orientation, similar to mammals [24]. The mutant phenotype is systemic, affecting the gut [25,26], the excretory organ Malpighian tubules [27,28] and the muscles manifested in muscular dystrophy [29]. The recessive phenotype of the col4a1 -/homozygotes leads to lethality in the late embryonic to early larval phases at the permissive temperature [24].…”

In-silicodefinition of theDrosophila melanogastermatrisome

“…Studies using Drosophila have made particularly strong contributions to our understanding of BM secretion and assembly [30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45], and the role BMs play in shaping tissues during development [35,42,[46][47][48][49][50][51][52][53]. They have also shown how BMs heal after injury [54,55] and how they regulate the immune response [56][57][58][59][60]. More recently, work in Drosophila has introduced a new role for BM proteins in intercellular adhesion [31].…”