RESUMO
Autoimmune hepatitis (AIH) is a severe autoimmune disease, characterized by the presence of autoantibodies. However, the role of autoantibodies in the pathophysiology of AIH remains uncertain. Here, we employed Phage Immunoprecipitation-Sequencing (PhIP-Seq) to identify novel autoantibodies in AIH. Using these results, a logistic regression classifier was able to predict which patients had AIH, indicating the presence of a distinct humoral immune signature. To further investigate the autoantibodies most specific to AIH, significant peptides were identified relative to a broad array of controls (298 patients with non-alcoholic fatty liver disease (NAFLD), primary biliary cholangitis (PBC), or healthy controls). Top ranked autoreactive targets included SLA, the target of a well-recognized autoantibody in AIH, and disco interacting protein 2 homolog A (DIP2A). The autoreactive fragment of DIP2A shares a 9-amino acid stretch nearly identical to the U27 protein of HHV-6B, a virus found in the liver. In addition, antibodies against peptides derived from the leucine rich repeat N-terminal (LRRNT) domain of the relaxin family peptide receptor 1 (RXFP1) were highly enriched and specific to AIH. The enriched peptides map to a motif adjacent to the receptor binding domain, which is required for RXFP1 signaling. RXFP1 is a G protein-coupled receptor that binds relaxin-2, an anti-fibrogenic molecule shown to reduce the myofibroblastic phenotype of hepatic stellate cells. Eight of nine patients with antibodies to RXFP1 had evidence of advanced fibrosis (F3 or greater). Furthermore, serum from AIH patients positive for anti-RFXP1 antibody was able to significantly inhibit relaxin-2 signaling in the human monocytic cell line, THP1. Depletion of IgG from anti-RXFP1 positive serum abrogated this effect. These data provide supporting evidence that HHV6 plays a role in the development of AIH and point to a potential pathogenic role for anti-RXFP1 IgG in some patients. Identification of anti-RXFP1 in patient serum may enable risk stratification of AIH patients for fibrosis progression and lead to the development of novel strategies for disease intervention.
RESUMO
The VANGL family of planar cell polarity proteins is implicated in breast cancer however its function in mammary gland biology is unknown. Here, we utilized a panel of Vang1 and Vangl2 mouse alleles to examine the requirement of VANGL family members in the murine mammary gland. We show that Vang1CKOΔ/Δ glands display normal branching while Vangl2flox/flox and Vangl2Lp/Lp tissue exhibit several phenotypes. In MMTV-Cre;Vangl2flox/flox glands, cell turnover is reduced and lumens are narrowed. A Vangl2 missense mutation in the Vangl2Lp/Lp tissue leads to mammary anlage sprouting defects and deficient outgrowth with transplantation of anlage or secondary tissue fragments. In successful Vangl2Lp/Lp outgrowths, three morphological phenotypes are observed: distended ducts, supernumerary end buds, and ectopic acini. Layer specific defects are observed with loss of Vangl2 selectively in either basal or luminal layers of mammary cysts. Loss in the basal compartment inhibits cyst formation, but has the opposite effect in the luminal compartment. Candidate gene analysis on MMTV-Cre;Vangl2flox/flox and Vangl2Lp/Lp tissue reveals a significant reduction in Bmi1 expression, with overexpression of Bmi1 rescuing defects in Vangl2 knockdown cysts. Our results demonstrate that VANGL2 is necessary for normal mammary gland development and indicate differential functional requirements in basal versus luminal mammary compartments.
