Yula Ma

Genomic loss of imprinting in first-trimester human placenta.

OBJECTIVE The purpose of this study was to investigate imprinting patterns in first-trimester human placentas. STUDY DESIGN Using samples of 17 first-trimester and 14 term placentas from uncomplicated pregnancies, we assessed loss of imprinting (LOI) at the RNA level in a panel of 14 genes that are known to be imprinted in the placenta with the use of a quantitative allele-specific reverse transcriptase polymerase chain reaction analysis of those genes that contained readout single nucleotide polymorphisms in their transcripts. RESULTS There is significant LOI (ie, biallelic expression) in all 14 genes in first-trimester placentas. LOI was more variable and generally at lower levels at term. Although there is little difference in gene expression, the level of LOI is higher in the first-trimester placentas, compared with term placentas. CONCLUSION Genomic imprinting appears to be a dynamic maturational process across gestation in human placenta. In contrast with prevailing theories, epigenetic imprints may continue to evolve past 12 weeks of gestation.

Imprinted gene expression in fetal growth and development.

Experimental studies showed that genomic imprinting is fundamental in fetoplacental development by timely regulating the expression of the imprinted genes to overlook a set of events determining placenta implantation, growth and embryogenesis. We examined the expression profile of 22 imprinted genes which have been linked to pregnancy abnormalities that may ultimately influence childhood development. The study was conducted in a subset of 106 placenta samples, overrepresented with small and large for gestational age cases, from the Rhode Island Child Health Study. We investigated associations between imprinted gene expression and three fetal development parameters: newborn head circumference, birth weight, and size for gestational age. Results from our investigation show that the maternally imprinted/paternally expressed gene ZNF331 inversely associates with each parameter to drive smaller fetal size, while paternally imprinted/maternally expressed gene SLC22A18 directly associates with the newborn head circumference promoting growth. Multidimensional Scaling analysis revealed two clusters within the 22 imprinted genes which are independently associated with fetoplacental development. Our data suggest that cluster 1 genes work by assuring cell growth and tissue development, while cluster 2 genes act by coordinating these processes. Results from this epidemiologic study offer solid support for the key role of imprinting in fetoplacental development.

In utero exposures to environmental organic pollutants disrupt epigenetic marks linked to fetoplacental development.

Abstract While the developing fetus is largely shielded from the external environment through the protective barrier provided by the placenta, it is increasingly appreciated that environmental agents are able to cross and even accumulate in this vital organ for fetal development. To examine the potential influence of environmental pollutants on the placenta, we assessed the relationship between polybrominated diphenyl ethers (PBDEs), polychlorinated biphenyls (PCBs), 1,1-dichloro-2,2-bis(p- chlorophenyl) ethylene (DDE) and several epigenetic marks linked to fetoplacental development. We measured IGF2 / H19 imprint control region methylation, IGF2 and H19 expression, IGF2 loss of imprinting (LOI) and global DNA methylation levels in placenta ( n  = 116) collected in a formative research project of the National Children’s Study to explore the relationship between these epigenetic marks and the selected organic environmental pollutants. A positive association was observed between global DNA methylation and total PBDE levels ( P  < 0.01) and between H19 expression and total PCB levels ( P  = 0.04). These findings suggest that differences in specific epigenetic marks linked to fetoplacental development occur in association with some, but not all, measured environmental exposures.

Abstract LB-089: Defining windows of susceptibility for low-dose exposure to endocrine disruptors in rat mammary development by microRNA profiling

BACKGROUND: Endocrine disruptors (EDs) constitute a class of chemicals that can interfere with the endocrine system, possibly influencing breast cancer risk. EDs exposure has been associated with changes in the epigenome such as methylation; their ability to modify other epigenetic processes, such as microRNA, has not been thoroughly investigated, especially in the context of mammary development. METHODS: We investigated the influence on microRNA of three EDs widely used in personal care products: diethyl phthalate (DEP), methyl paraben (MPB) and triclosan (TCS). Sprague-Dawley rats were treated with these EDs at six windows of susceptibility (prenatal, neonatal, prepubertal and pubertal, parous, and nulliparous) from in utero to young adulthood. Oral treatment doses were selected to produce urinary metabolite levels comparable to those found in the US population. MicroRNAs were profiled using the NanoString platform. RESULTS: Of 420 microRNAs analyzed, 90 were stably detected in >90% samples across all windows, with let-7 family members showing the highest expression. In the meantime, 132 microRNA species were expressed below the detection level in >90% of the samples; other miRNAs were expressed at different levels in some but not all samples. Principal component analysis revealed that different developmental windows displayed markedly different microRNA profiles. Importantly, we found that ED exposure, TCS in particular, resulted in measurable difference in rat mammary microRNAs, and the changes were window-specific. More specifically, the TCS-related changes were mainly present in prenatal, neonatal and pubertal windows; among these the neonatal period appeared to be the most susceptible window to EDs with the largest number of differentially expressed microRNAs (7 microRNA species with adjusted p CONCLUSIONS: Low-dose ED exposure, even at levels comparable to human exposure, was able to modify microRNA expression in rat mammary tissues in a window-specific fashion. The study also demonstrates dynamic changes of microRNA profiles in developing mammary glands and highlights the importance of taking the normal developmental gene signal into account when searching for environment-induced gene signatures. Citation Format: Vasily N. Aushev, Maya Kappil, Kalpana Gopalakrishnan, Qian Li, Yula Ma, Luca Lambertini, Fabiana Manservisi, Laura Falcioni, Luciano Bua, Fiorella Belpoggi, Susan L. Teitelbaum, Jia Chen. Defining windows of susceptibility for low-dose exposure to endocrine disruptors in rat mammary development by microRNA profiling. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr LB-089. doi:10.1158/1538-7445.AM2015-LB-089

Abstract 3262: Windows of susceptibility to endocrine disruptors and gene expression in mammary tissue

Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA Breast cancer is hormonally driven. Endocrine disruptors (EDs) are exogenous substances that mimic or antagonize endogenous hormone action and disrupt endocrine system function. While EDs have been shown to modulate the risk for mammary tumors in animal models, their effects at biologically relevant doses and during critical developmental windows remain poorly understood. We sought to examine the individual and combinatorial effects of three common EDs, diethyl phthalate, methyl paraben and triclosan in rats exposed at five distinct developmental windows of susceptibility - prenatal, neonatal, prepubertal, pubertal and parous/nulliparous. Pathological features and whole genome expression of normal rat mammary tissues were profiled to provide both qualitative and quantitative biological effects of EDs. ED exposure at levels comparable to human exposure resulted in profound changes in both gross phenotypes (e.g. reproductive mortality and mammary gland morphology) as well as in molecular genome profiles. Specifically, ED exposure appeared to hamper normal breast development and resulted in increased mortality in the offspring, possibly due to reduced milk production. Whole genome expression profiling of mammary tissues revealed that in the course of development, the number of differentially expressed genes was lower in ED-exposed rats compared to controls, suggesting developmental delay or suppression by EDs. Pathway enrichment analysis indicated that several processes including inflammation, metabolism and development were disrupted by ED exposure. Taken together, our findings reveal novel mechanisms of ED action in mammary development and strongly suggest the importance of taking into account the timing of exposure when studying the relationship between environment and disease. Citation Format: Kalpana Gopalakrishnan, Qian Li, Yula Ma, Luca Lambertini, Jia Chen, Susan L. Teitelbaum, Fabiana Manservisi, Fiorella Belpoggi, Luciano Bua, Laura Falcioni. Windows of susceptibility to endocrine disruptors and gene expression in mammary tissue. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3262. doi:10.1158/1538-7445.AM2014-3262