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Developmental Biology - Placental Function/Stem Cell Transplants
What Regulates Early Placental Growth?
CRISPR technology reveals function of a very large gene found only in the placenta, stem cells and certain cancers...
Abnormal formation and growth of the placenta is considered an underlying cause of various pregnancy complications such as miscarriages, preeclampsia and fetal growth restriction. But much needs to be learned about all the molecular mechanisms regulating the placenta which is so vital to the health of a pregnant woman and her growing fetus.
A new study conducted by University of South Florida Health (USF Health) Morsani College of Medicine has revealed how a very large human non-protein coding gene regulates epithelial-to-mesenchymal transition (EMT). This is the process contributing to placental implantation in early pregnancy — as well as to the progression and spread of some cancers.
USF Health researchers used a powerful genome editing technology called CRISPR (short for "CRISPR-dCas9) to activate the chromosome 19 microRNA cluster (C19MC) for study of its function in early pregnancy.
C19MC, one of the largest microRNA gene clusters in the human genome, is normally turned off and only expressed in placental cells and in embryonic stem cells, as well as in some cancers.
In their study published Feb. 20 in Scientific Reports, a Nature research journal, the USF Health team found that by robustly activating C19MC they inhibited EMT cancer cell transitions.
EMT happens early in the formation of the placenta, an organ which attaches to the lining of the uterus during pregnancy and supplies oxygen and nutrients from mother to the growing fetus. During the first trimester, fetal trophoblasts penetrate the maternal uterine lining and modify its blood vessels. This remodeling of the mother's spiral arteries allows oxygenated blood to flow from the mother to fetus.
However, the trophoblast invasion prompted by EMT is a tightly coordinated balancing act. If the invasion is too shallow to adequately remodel the maternal blood vessels, preeclampsia and fetal growth restriction can occur. Invasion that progresses too deeply — beyond normal anchoring of the placenta to the uterine wall — leads to placenta accreta, a rare condition that can cause dangerous bleeding and often require pregnancy termination.
"We were the first to use CRISPR to efficiently activate the entire (C19MC) gene, not just a few regions of this huge gene, in human cell lines.
Our study indicates C19MC plays a key role in regulating many genes important in early implantation, placental development and function. The regulation of these genes is critical for proper fetal growth."
Hana Totary-Jain PhD, Associate Professor and senior author, Department of Molecular Pharmacology and Physiology, USF Health Morsani College of Medicine; collaborations with colleagues in the Department of Obstetrics and Gynecology facilitated the project.
This study offers new insight into how trophoblasts interact with the maternal uterine environment to become more or less invasive in forming the placenta.
"More research on microRNA expression and how it inhibits the epithelial-to-mesenchymal transition may help us better understand and control preeclampsia and fetal growth restriction, which account for 5-to-10 percent of all pregnancy complications and premature births."
Umit Kayisli PhD, Professor of Obstetrics and Gynecology, USF Health and co-author.
Abstract
During implantation, cytotrophoblasts undergo epithelial-to-mesenchymal transition (EMT) as they differentiate into invasive extravillous trophoblasts (EVTs). The primate-specific microRNA cluster on chromosome 19 (C19MC) is exclusively expressed in the placenta, embryonic stem cells and certain cancers however, its role in EMT gene regulation is unknown. In situ hybridization for miR-517a/c, a C19MC cistron microRNA, in first trimester human placentas displayed strong expression in villous trophoblasts and a gradual decrease from proximal to distal cell columns as cytotrophoblasts differentiate into invasive EVTs. To investigate the role of C19MC in the regulation of EMT genes, we employed the CRISPR/dCas9 Synergistic Activation Mediator (SAM) system, which induced robust transcriptional activation of the entire C19MC cistron and resulted in suppression of EMT associated genes. Exposure of human iPSCs to hypoxia or differentiation of iPSCs into either cytotrophoblast-stem-like cells or EVT-like cells under hypoxia reduced C19MC expression and increased EMT genes. Furthermore, transcriptional activation of the C19MC cistron induced the expression of OCT4 and FGF4 and accelerated cellular reprogramming. This study establishes the CRISPR/dCas9 SAM as a powerful tool that enables activation of the entire C19MC cistron and uncovers its novel role in suppressing EMT genes critical for maintaining the epithelial cytotrophoblasts stem cell phenotype.
Authors
Ezinne F. Mong, Ying Yang, Kemal M. Akat, John Canfield, Jeffrey VanWye, John Lockhart, John C. M. Tsibris, Frederick Schatz, Charles J. Lockwood, Thomas Tuschl, Umit A. Kayisli and Hana Totary-Jain.
Acknowledgements
USF Health's mission is to envision and implement the future of health. It is the partnership of the USF Health Morsani College of Medicine, the College of Nursing, the College of Public Health, the College of Pharmacy, the School of Physical Therapy and Rehabilitation Sciences, the Biomedical Sciences Graduate and Postdoctoral Programs, and the physicians of USF Health, the largest multispecialty group practice on Florida's west coast. The University of South Florida, established in 1956 and located in Tampa, is a high-impact, global research university dedicated to student success. USF ranks in the top 25 nationally for research expenditures among public universities, according to the National Science Foundation. In 2018, the Florida Board of Governors designated USF as a Preeminent State Research University, placing USF in the most elite category among the state's 12 public universities.
Dr Adashi serves as cochair of the Safety Advisory Board of Ohana Biosciences, Inc.
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Mar 2 2020 Fetal Timeline Maternal Timeline News
 in mouse placenta.png) In preparation for pregnancy, fetal trophoblast cells (BROWN) give rise to the placenta, invading maternal decidual cells (PINK) in the uterine lining. CREDIT Image courtesy Hana Totary-Jain of USF Health, originally published in Scientific Reports.
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