Date Published: April 14, 2016
Publisher: Public Library of Science
Author(s): Maude Rolland, Xiaojun Li, Yann Sellier, Hélène Martin, Teresa Perez-Berezo, Benjamin Rauwel, Alexandra Benchoua, Bettina Bessières, Jacqueline Aziza, Nicolas Cenac, Minhua Luo, Charlotte Casper, Marc Peschanski, Daniel Gonzalez-Dunia, Marianne Leruez-Ville, Christian Davrinche, Stéphane Chavanas, Robert F. Kalejta.
Congenital infection by human cytomegalovirus (HCMV) is a leading cause of permanent sequelae of the central nervous system, including sensorineural deafness, cerebral palsies or devastating neurodevelopmental abnormalities (0.1% of all births). To gain insight on the impact of HCMV on neuronal development, we used both neural stem cells from human embryonic stem cells (NSC) and brain sections from infected fetuses and investigated the outcomes of infection on Peroxisome Proliferator-Activated Receptor gamma (PPARγ), a transcription factor critical in the developing brain. We observed that HCMV infection dramatically impaired the rate of neuronogenesis and strongly increased PPARγ levels and activity. Consistent with these findings, levels of 9-hydroxyoctadecadienoic acid (9-HODE), a known PPARγ agonist, were significantly increased in infected NSCs. Likewise, exposure of uninfected NSCs to 9-HODE recapitulated the effect of infection on PPARγ activity. It also increased the rate of cells expressing the IE antigen in HCMV-infected NSCs. Further, we demonstrated that (1) pharmacological activation of ectopically expressed PPARγ was sufficient to induce impaired neuronogenesis of uninfected NSCs, (2) treatment of uninfected NSCs with 9-HODE impaired NSC differentiation and (3) treatment of HCMV-infected NSCs with the PPARγ inhibitor T0070907 restored a normal rate of differentiation. The role of PPARγ in the disease phenotype was strongly supported by the immunodetection of nuclear PPARγ in brain germinative zones of congenitally infected fetuses (N = 20), but not in control samples. Altogether, our findings reveal a key role for PPARγ in neurogenesis and in the pathophysiology of HCMV congenital infection. They also pave the way to the identification of PPARγ gene targets in the infected brain.
Congenital infection by human cytomegalovirus (HCMV) is a leading cause of permanent abnormalities of the central nervous system . About 1% of newborns are congenitally infected with HCMV each year in the USA, as a result of either primary infection of a seronegative mother, or reinfection / viral reactivation in a seropositive mother during pregnancy. Ten percent of congenitally infected newborns are symptomatic at birth, and most of them (60–90%) display neurological sequelae . Further, 10 to 15% of congenitally infected newborns that are asymptomatic at birth show neurological disorder with onset later in infancy . The most severely affected fetuses or newborns show brain development abnormalities such as microcephaly, lissencephaly or polymicrogyria [2–4]. The most frequent permanent sequelae include mental and/or psychomotor disabilities, sensorineural hearing or vision loss, and/or spastic cerebral palsies. Overall, patients with permanent sequelae represent up to 0.1–0.2% of all live births (>5500 per year in the USA). The direct annual care costs for patients are estimated at $1-$2 billion in the USA . No vaccine or reliable prognosis tools are available to date, except for ultrasound examination of macroscopic brain abnormalities. Considering the dramatic health and societal burden of congenital HCMV infection, it is clear that a better insight on its pathogenesis is urgently needed to provide new therapeutic and prognostic tools.
The main result of our study is the identification of PPARγ activation as a molecular determinant of the pathology induced by HCMV infection in neural precursors, in vitro and presumably in vivo. Our findings unambiguously demonstrate that HCMV infection causes increased PPARγ levels and activity, increased biosynthesis of 9-HODE, impaired neuronogenesis and enhanced viral replication in NSCs (Fig 12).