Focused Examination of the Intestinal Epithelium Reveals Transcriptional Signatures Consistent with Disturbances in Enterocyte Maturation and Differentiation during the Course of SIV Infection

Mahesh Mohan,Ronald S Veazey,Deepak Kaushal,Xavier Alvarez,Pyone P Aye,Andrew A Lackner,Roger Le Grand

doi:10.1371/journal.pone.0060122

Abstract

The Gastrointestinal (GI) tract plays a pivotal role in AIDS pathogenesis as it is the primary site for viral transmission, replication and CD4+ T cell destruction. Accordingly, GI disease (enteropathy) has become a well-known complication and a driver of AIDS progression. To better understand the molecular mechanisms underlying GI disease we analyzed global gene expression profiles sequentially in the intestinal epithelium of the same animals before SIV infection and at 21 and 90 days post infection (DPI). More importantly we obtained sequential excisional intestinal biopsies and examined distinct mucosal components (epithelium. intraepithelial lymphocytes, lamina propria lymphocytes, fibrovascular stroma) separately. Here we report data pertaining to the epithelium. Overall genes associated with epithelial cell renewal/proliferation/differentiation, permeability and adhesion were significantly down regulated (<1.5–7 fold) at 21 and 90DPI. Genes regulating focal adhesions (n = 6), gap junctions (n = 3), ErbB (n = 3) and Wnt signaling (n = 4) were markedly down at 21DPI and the number of genes in each of these groups that were down regulated doubled between 21 and 90DPI. Notable genes included FAK, ITGA6, PDGF, TGFβ3, Ezrin, FZD6, WNT10A, and TCF7L2. In addition, at 90DPI genes regulating ECM-receptor interactions (laminins and ITGB1), epithelial cell gene expression (PDX1, KLF6), polarity/tight junction formation (PARD3B&6B) and histone demethylase (JMJD3) were also down regulated. In contrast, expression of NOTCH3, notch target genes (HES4, HES7) and EZH2 (histone methyltransferase) were significantly increased at 90DPI. The altered expression of genes linked to Wnt signaling together with decreased expression of PDX1, PARD3B, PARD6B and SDK1 suggests marked perturbations in intestinal epithelial function and homeostasis leading to breakdown of the mucosal barrier. More importantly, the divergent expression patterns of EZH2 and JMJD3 suggests that an epigenetic mechanism involving histone modifications may contribute to the massive decrease in gene expression at 90DPI leading to defects in enterocyte maturation and differentiation.

Highlights

HIV/SIV infection of the gastrointestinal (GI) tract results in massive destruction of CD4+ T cells, increased viral replication and persistent inflammation resulting in significant damage to GI structure and function [1,2,3,4,5,6]
The intestinal epithelium comprises a single layer of differentiated polarized simple columnar cells that functions in nutrient absorption and at the same time protects the underlying lamina propria cells from the external environment
The enterocytes lining the villi are shed into the lumen every 5 to 7 days to be replaced by new cells that migrate up the villi from the proliferating crypt cell compartment

Summary

Introduction

HIV/SIV infection of the gastrointestinal (GI) tract results in massive destruction of CD4+ T cells, increased viral replication and persistent inflammation resulting in significant damage to GI structure and function [1,2,3,4,5,6]. The damage inflicted to the GI tract both directly by the virus and indirectly by the host’s immune/ inflammatory response generally involves all mucosal compartments (epithelium, lamina propria cells, fibrovascular stroma., etc) and plays an important role in driving AIDS progression [7,8,9,10]. A major shortcoming with these approaches is the difficulty to assign a particular transcriptional signature, be it normal or pathological, conclusively to a certain cellular/mucosal compartment. In HIV/SIV infection the dramatic shifts in lymphocyte populations in the lamina propria in response to viral replication can significantly mask molecular pathological events evolving in other mucosal compartments, most notably, the intestinal epithelium [1]. To circumvent these problems we have doi:10.1371/journal.pone.0060122.g001

Methods

Results

Conclusion