Research in my laboratory is directed toward achieving a better understanding of the mechanisms, pathogenesis, and pathology associated with a variety of environmentally-induced and genetically-based birth defects. This information is then applied to development of preventative/ameliorative measures relative to these defects.
Regarding teratogen-induced birth defects, our major emphasis is on Fetal Alcohol Spectrum Disorders (FASD). For this work, we employ cell and whole embryo culture systems, as well as in vivo ethanol exposure in a mouse FASD model. Acute maternal ethanol exposure at early stages of embryogenesis have been of particular interest (Sulik, 2005). Recently, an acute ethanol exposure paradigm involving maternal dietary intake has been developed for use in these studies (Parnell et al, 2006). Currently, in collaboration with MRPath (http://www.mrpath.com/) high resolution magnetic resonance imaging (MRI) is being utilized to identify, characterize, and correlate the craniofacial, ocular, otic and CNS dysmorphology that results from prenatal ethanol exposure at specific stages of embryogenesis (see Figure below). These studies are designed to inform human clinical research and to expand the diagnostic criteria for prenatal alcohol exposure.
Illustrated are control (upper row) and ethanol-affected GD17 mouse fetuses, one of which is more mildly affected (middle row) than the other. 3-D reconstruction of faces (second column), color-coded brains (third column) [forebrain= yellow, midbrain= green, hindbrain=magenta] and their ventricles (fifth column) [third and lateral ventricles=blue, cerebral aqueduct and fourth ventricle=red] made from MR images illustrate ethanol-induced changes in shape and size. Regional brain volume differences were assessed from voxel counts (fourth column).
Study of the pathogenesis underlying ethanol-induced birth defects has focused on identification of excessive apoptosis in selected cell populations (Dunty et al, 2001). Characteristics that impart selective vulnerability have been studied using microarray, PCR, in situ hybridization, Western blotting and proteomic approaches. Sensitivity to reactive oxygen species (ROS)-mediated damage appears to be a key factor. This is supported with work showing that antioxidants can diminish the apoptosis and structural abnormalities caused by ethanol (Chen et al, 2004). Studies conducted in collaboration with Dr. M. Charness and co-workers have also illustrated the effectiveness of ADNF and ADNP-derived peptides in reducing ethanol-induced apoptosis and teratogenesis (Chen et al, 2005; Wilkemeyer et al, 2004; 2003).
Regarding genetically-based birth defects, our focus has been on those that are cholesterol deficiency-mediated. For this purpose, a mouse model was developed for Smith-Lemli Opitz syndrome, a malformation/mental retardation syndrome resulting from an inborn error in 3beta-hydroxysteroid Delta7-reductase (DHCR7), the terminal enzyme required for cholesterol biosynthesis . Characteristic of the Dhcr7-/- mice are CNS abnormalities including commissural deficiencies, hippocampal abnormalities, and hypermorphic development of serotonergic (5-HT) neurons (Waage-Baudet et al, 2003;). Microarray analyses comparing hindbrain regions microdissected from gestational day 14 Dhcr7-/-, Dhcr7+/- and Dhcr7+/+ fetuses revealed altered expression of genes associated with cholesterol homeostasis, cell cycle control and apoptosis, neurodifferentiation and embryogenesis, transcription and translation, cellular transport, neurodegeneration, and neuronal cytoskeleton (Waage-Baudet et al, 2005). Of particular interest, Dhcr7 gene modification elicited dynamic changes in genes involved in axonal guidance. In support of the microarray findings, immunohistochemical analyses of the netrin/deleted in colorectal cancer axon guidance pathway have illustrated midline commissural deficiencies and hippocampal pathfinding errors in Dhcr7-/- mice. In addition to developmental abnormalities resulting from genetic alterations in cholesterol biosynthesis, we have examined those resulting from deficiency in apolipoprotein B (apoB), which transports cholesterol, lipids, and vitamin E in the circulation. Neural tube defects (exencephaly/anencephaly) and hydrocephaly was associated with excessive cell death involving the alar plate of the hindbrain (Homanics et al, 1995). Gene-environment interactions resulting from the combination of apoB deficiency and chemically-mediated cholesterol synthesis inhibition in mice resulted in a spectrum of facial abnormalities consistent with those in Smith Lemli Opitz Syndrome (Lanoue et al, 1997). At the severe end of the spectrum is holoprosencephaly. Additionally, abnormalities of the mid- and hindbrain were observed and included stenosis of the cerebral aqueduct at the level of the isthmus and apparent absence of the progenitor for the cerebellar vermis. Limb and external genital defects were also a notable outcome in this multifactorially-based cholesterol deficiency model.
In addition to birth defects basic research, our efforts are directed toward education-based reduction in the occurrence of FASD. To this end, a science-based curriculum entitled “Better Safe Than Sorry” has been created. It is available on the NIAAA website at http://pubs.niaaa.nih.gov/publications/Science/curriculum.html . Additional science-based curricula and educational programs are under development .
Center Line Articles
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Green ML, Singh AV, Zhang Y, Nemeth KA, Sulik KK, Knudsen TB. Reprogramming of genetic networks during initiation of the Fetal Alcohol Syndrome. Dev Dyn. 2007 Feb;236(2):613-31.
Parnell SE, Dehart DB, Wills TA, Chen SY, Hodge CW, Besheer J, Waage-Baudet HG, Charness ME, Sulik KK. Maternal oral intake mouse model for fetal alcohol spectrum disorders: ocular defects as a measure of effect. Alcohol Clin Exp Res. 2006 Oct;30(10):1791-8.
Niakan KK, Davis EC, Clipsham RC, Jiang M, Dehart DB, Sulik KK, McCabe ER. Novel role for the orphan nuclear receptor Dax1 in embryogenesis, different from steroidogenesis. Mol Genet Metab. 2006 Jul;88(3):261-71.
Waage-Baudet H, Dunty WC Jr, Dehart DB, Hiller S, Sulik KK. Immunohistochemical and microarray analyses of a mouse model for the smith-lemli-opitz syndrome. Dev Neurosci. 2005;27(6):378-96.
Sulik KK. Genesis of alcohol-induced craniofacial dysmorphism. Exp Biol Med (Maywood). 2005 Jun;230(6):366-75.
Chen SY, Charness ME, Wilkemeyer MF, Sulik KK. Peptide-mediated protection from ethanol-induced neural tube defects. Dev Neurosci. 2005 Jan-Feb;27(1):13-9.
Chen SY, Dehart DB, Sulik KK. Protection from ethanol-induced limb malformations by the superoxide dismutase/catalase mimetic, EUK-134. FASEB J. 2004 Aug;18(11):1234-6.
Wilkemeyer MF, Chen SY, Menkari CE, Sulik KK, Charness ME. Ethanol antagonist peptides: structural specificity without stereospecificity. J Pharmacol Exp Ther. 2004 Jun;309(3):1183-9.
Waage-Baudet H, Lauder JM, Dehart DB, Kluckman K, Hiller S, Tint GS, Sulik KK. Abnormal serotonergic development in a mouse model for the Smith-Lemli-Opitz syndrome: implications for autism. Int J Dev Neurosci. 2003 Dec;21(8):451-9.
Wilkemeyer MF, Chen SY, Menkari CE, Brenneman DE, Sulik KK, Charness ME. Differential effects of ethanol antagonism and neuroprotection in peptide fragment NAPVSIPQ prevention of ethanol-induced developmental toxicity. Proc Natl Acad Sci U S A. 2003 Jul 8;100(14):8543-8. 2003 Jun 13.