Single Immunoglobulin Interleukin1-Related Receptor-TWIST1 Axis Regulates Barrier Function in Neonatal Intestine

The genetic basis of impaired intestinal barrier function in preterm infants is poorly understood. Variants in single immunoglobulin interleukin1-related receptor, a negative regulator of Toll-like receptor signaling, have been identified in preterm infants with necrotizing enterocolitis. We hypothesized that single immunoglobulin interleukin1-related receptor variants associated with necrotizing enterocolitis impair gut barrier function to pathobionts. The aim of this study was to determine how single immunoglobulin interleukin1-related receptor genetic variants disrupt neonatal intestinal barrier integrity and promote susceptibility to Gram-negative bacteria implicated in sepsis and necrotizing enterocolitis pathogenesis.

Transgenic mice and preterm infant-derived enteroids expressing SIGIRR variants identified in necrotizing enterocolitis were used to define how single immunoglobulin interleukin1-related receptor regulates epithelial junctional protein assembly. An Escherichia coli strain identified in neonatal sepsis was used for functional evaluation of gut barrier function.

Neonatal mice harboring the SIGIRR p.Y168X mutation (Sigirr^mu/mu), exhibited loss of epithelial junctional proteins, impaired barrier function, and activation of Twist family BHLH transcription factor 1 with exaggerated Toll-like receptor signaling. Sigirr^mu/mu mice were highly susceptible to bacteremia when enterally challenged with pathogenic E coli. Pharmacologic inhibition of Twist family BHLH transcription factor 1 or genetic deletion of Toll-like receptor 4 restored barrier integrity. Preterm human enteroids expressing the SIGIRR p.Y168X and p.P115R variants recapitulated barrier defects and Twist family BHLH transcription factor 1 activation in a bacteria-free environment. Twist family BHLH transcription factor 1 inhibition reversed these defects in both human and murine enteroids.

SIGIRR preserves neonatal intestinal epithelial barrier integrity by repressing TWIST1-mediated disruption of junctional proteins. Loss of SIGIRR function compromises epithelial barrier and promotes bacterial translocation, revealing a genetic mechanism underlying gut barrier dysfunction in necrotizing enterocolitis and neonatal sepsis.