Defining cell-intrinsic trophoblast defenses to HCMV infection - PROJECT SUMMARY/ABSTRACT: Human cytomegalovirus (HCMV) infection is among the most common congenital infections, occurring in approximately 1 out of every 200 pregnancies. Congenital HCMV infection can lead to a wide range of developmental complications including intrauterine growth restriction, sensorineural hearing loss, microcephaly, and fetal demise. To infect and directly damage the developing fetus, HCMV must cross the placenta, which is the primary barrier between maternal and fetal circulation. HCMV infection has also been proposed to impair several critical functions of trophoblasts, the predominant cell type of the placenta, suggesting HCMV infection could indirectly damage the fetus through placental dysfunction. However, due to limited models of HCMV infection at the maternal-fetal interface we currently have an incomplete understanding of 1) how trophoblasts defend against HCMV and 2) how HCMV infection alters normal trophoblast function. I propose to use trophoblast organoids (TOs) to model HCMV infection. TOs are a novel model that recapitulates many key aspects of the cellular and immunological complexity of the human placenta. Our lab has reported that TOs are refractory to HCMV replication. My preliminary data demonstrate that this occurs post-viral entry, signifying that trophoblasts may express cell-intrinsic factors that restrict HCMV replication. I have preliminarily identified that the transcription factor DUX4 and its target gene TRIM43 (a recently described herpesvirus restriction factor) are uniquely induced following HCMV infection in TOs, suggesting this pathway may contribute to trophoblast resistance to HCMV replication. Aberrant expression of DUX4 in adult muscle cells alters normal cellular function and drives pathology in facioscapulohumeral muscular dystrophy. My preliminary data suggest that DUX4 expression in trophoblasts may similarly impair normal trophoblast function. The objectives of this proposal are to identify factors that restrict HCMV replication in trophoblasts, uncover the impacts of HCMV infection on normal trophoblast function, and build upon TOs as a model of HCMV infection at the maternal-fetal interface. The specific aims of this proposal are 1) to determine if TRIM43 and DUX4 restrict HCMV replication in TOs and 2) define the impacts of HCMV-induced DUX4 expression on trophoblast function. Aim 1 will define the expression kinetics of TRIM43 and DUX4 in TOs following HCMV infection. It will then test whether TRIM43 and DUX4 restrict HCMV replication in TOs. Finally, this aim will test whether TRIM43 and DUX4 restrict the replication of other teratogenic herpesviruses in TOs. Aim 2 will map the trophoblast cell type- specific transcriptional response to DUX4 expression to define potential mechanisms by which HCMV can cause dysfunction in trophoblasts. Aim 2 will test whether HCMV-induced DUX4 expression impairs trophoblast differentiation as well as key functions of trophoblasts such as hormone secretion and invasion. Completing the proposed aims will provide training in several key areas, better equipping me to progress towards independence as a scientist.
