Without proper autophagosome formation, there is no autophagy. ATG16L1 is necessary for the formation of the double-membrane vesicle, the autophagosome, during autophagy ( 16– 18). During periods of cellular stress, autophagy is critical in cell survival by encapsulating and degrading intracellular bacteria and damaged cellular products to maintain homeostasis.

In the absence of stress, basal autophagy functions to eliminate and recycle damaged or long-lived cellular components that could otherwise become toxic. This amino acid substitution causes increased sensitivity of the ATG16L1 protein to caspase 3-mediated cleavage during death-receptor activation and starvation-induced metabolic stress, resulting in decreased levels of full-length ATG16L1 protein and diminished macroautophagy, hereafter referred to as autophagy ( 10– 12).Īutophagy is the evolutionarily conserved degradation pathway that delivers unwanted cellular debris to the lysosome for destruction ( 13– 15). Individuals who possess a single, nonsynonymous adenine to guanine polymorphism resulting in a threonine to alanine substitution directly preceded by a caspase cleavage motif in the ATG16L1 protein (ATG16L1 T300A) have an increased predisposition for CD over those who retain a threonine in this position (ATG16L1 T300) ( 9). More than 230 genetic alleles have been linked to CD, one of the most common of which lies in the autophagy-related 16-like 1 ( ATG16L1) gene ( 5– 8). Familial linkage, twin studies, and previously established genome-wide association studies confirm the important role of genetics in IBD ( 1– 4). These Atg16l1 strains are valuable new animal models for the study of both autophagy and CD susceptibility.Ĭrohn’s disease (CD) is one of the two chronic inflammatory bowel diseases (IBD) that affect the lining of the gastrointestinal (GI) system. Analysis of the gut microbiota does not show inherent differences in bacterial composition between wild-type and genetically modified animals. Consistent with studies of the effects of human ATG16L1 polymorphisms, models exhibit morphological abnormalities in both Paneth and goblet cells, but do not develop spontaneous intestinal permeability or inflammatory bowel disease. These are the first reported rat strains with alterations of the Atg16l1 gene. Using CRISPR-Cas9 genome editing technology, we developed a knock-in rat model for the human ATG16L1 T300A CD risk polymorphism, as well as a knock-out rat model to evaluate the role of Atg16l1 in autophagy as well as its potential effect on CD susceptibility. We identified four alternative splice variants with tissue-specific expression. To generate novel rat strains carrying genetic alterations in the rat Atg16l1 gene, we first characterized the wild-type rat gene. The mechanism behind this increased susceptibility is still being elucidated, however, the amino acid change caused by this point mutation results in increased ATG16L1 protein sensitivity to caspase 3-mediated cleavage. A single, nonsynonymous adenine to guanine polymorphism resulting in a threonine to alanine amino acid substitution (T300A) directly preceded by a caspase cleavage site (DxxD) causes an increased susceptibility to Crohn’s disease (CD) in humans. ATG16L1 is a ubiquitous autophagy gene responsible, in part, for formation of the double-membrane bound autophagosome that delivers unwanted cellular debris and intracellular pathogens to the lysosome for degradation.

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