Mechanisms involved in epigenetic down-regulation of Gfap under maternal hypothyroidism Praveen Kumar a , Nachiket M. Godbole b , Chandra P. Chaturvedi c , Ravi S. Singh a , Nelson George d , Aditya Upadhyay a , B. Anjum a , Madan M. Godbole a, ** , Rohit A. Sinha d, * a Department of Molecular Medicine & Biotechnology, Sanjay Gandhi Postgraduate Institute of Medical Science, Lucknow, 226014, India b Department of Microbiology, Sanjay Gandhi Postgraduate Institute of Medical Science, Lucknow, 226014, India c Stem Cell Research Facility, Department of Hematology, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, 226014, India d Department of Endocrinology, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, 226014, India article info Article history: Received 21 May 2018 Accepted 26 May 2018 Keywords: GFAP Maternal hypothyroidism Neocortex Astrocytes Gliogenesis Epigenetics abstract Thyroid hormones (TH) of maternal origin are crucial regulator of mammalian brain development during embryonic period. Although maternal TH deficiency during the critical periods of embryonic neo-cortical development often results in irreversible clinical outcomes, the fundamental basis of these abnormalities at a molecular level is still obscure. One of the key developmental process affected by maternal TH insufficiency is the delay in astrocyte maturation. Glial fibrillary acidic protein (Gfap) is a predominant cell marker of mature astrocyte and is regulated by TH status. Inspite, of being a TH responsive gene during neocortical development the mechanistic basis of Gfap transcriptional regulation by TH has remained elusive. In this study using rat model of maternal hypothyroidism, we provide evidence for an epigenetic silencing of Gfap under TH insufficiency and its recovery upon TH supplementation. Our re- sults demonstrate increased DNA methylation coupled with decreased histone acetylation at the Gfap promoter leading to suppression of Gfap expression under maternal hypothyroidism. In concordance, we also observed a significant increase in histone deacetylase (HDAC) activity in neocortex of TH deficient embryos. Collectively, these results provide novel insight into the role of TH regulated epigenetic mechanisms, including DNA methylation, and histone modifications, which are critically important in mediating precise temporal neural gene regulation. © 2018 Elsevier Inc. All rights reserved. 1. Introduction Astrocytes play an important role in the maintenance, devel- opment, disease processes, and injury responses of the brain [1]. In the developing brain, astrocytes facilitate the formation of complex neocortical circuitries involving a complex process of synapto- genesis, maturation, and synaptic pruning [2]. The differentiation and maturation of astrocytes in the rodent neocortex coincides with he period of extensive synapse formation and maturation starting from the late embryonic period to the 2e3 postnatal week [3]. Astrocytes are derived from a common neural precursor radial glia, and their transition to mature astrocytes is marked with the appearance of Glial fibrillary acidic protein (Gfap). Gfap transcrip- tional regulation has been studied extensively because of its asso- ciation with astrocyte development [4]. Maternal thyroid hormones (TH), are essential for the embry- onic neurodevelopmental process before the onset of the fetal thyroid function (FTF) [5]. One of the neuronal process, affected by the deficiency of maternal TH, is the maturation of astrocytes [6,7]. Coincidently, maternal hypothyroidism also results in defective neocortical synaptogenesis [8] which itself relies on timely matu- ration of astrocytes. TH have long been known to regulate Gfap expression in developing brain [6,7 ,9e11]. Experiments in rodents have shown that TH affects the devel- opment of astroglia in forebrain and hippocampus, accelerating the transition from vimentin-positive to Gfap-positive cells in both the above brain regions [12]. Furthermore, TH treatment induces cortical astrocytes which had flatten morphology in vitro to become process-bearing cells followed by an increase in the Gfap content in midbrain and cerebral hemisphere astrocytes [13]. Although * Corresponding author. ** Corresponding author. E-mail addresses: madangodbole@yahoo.co.in (M.M. Godbole), anthony.rohit@ gmail.com (R.A. Sinha). Contents lists available at ScienceDirect Biochemical and Biophysical Research Communications journal homepage: www.elsevier.com/locate/ybbrc https://doi.org/10.1016/j.bbrc.2018.05.173 0006-291X/© 2018 Elsevier Inc. All rights reserved. Biochemical and Biophysical Research Communications 502 (2018) 375e381