TOBACCO EXPOSURE BIOMARKERS AND MUTATIONS OF MSX1 AND IRF6 GENES IN PREGNANCY

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Exposure to tobacco smoke during pregnancy places the developing fetus at an elevated risk of severe outcomes related to smoke exposure. Most notably, intrauterine growth retardation as well as decrease in birth weight have been measured as direct consequence of tobacco exposure in utero. However, other harmful effects of tobacco smoking during pregnancy have also been identified, including an elevated risk of birth defects. Of the thousands of compounds found in tobacco, only a few have been studied in detail with respect to these changes. Most notably are the tobacco specific nitrosamines, which have clearly been linked to experimental orofacial defects in animal models. Epidemiological studies have established a significant positive correlation between maternal smoking and an increased risk for orofacial clefts in humans. Studies analyzing the effect of tobacco constituents on mouse craniofacial development have provided clear evidence that the morphologic events can be disrupted by exposure to tobacco smoke. Specific genes related to the development of birth defects, especially orofacial defects have been widely studied, but the link between these genes and specific compounds in tobacco that may alter these genes expression and the metabolism and detoxification of specific tobacco carcinogens has not been carried out. In the proposed study we will recruit mothers that have smoked during pregnancy and investigate the relationship between smoking during pregnancy and the effects that tobacco exposure has in utero on specific genes related to birth defects. We will qualitatively and quantitatively assess exposure to tobacco and specifically to the tobacco specific nitrosamines NNN (N'-nitrosonornicotine) and NNK (4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone) as well as benzo(a)pyrene by assessment of protein adducts to the compounds in maternal and fetal blood samples obtained at delivery. We will carry out genotyping to specific enzymes related to metabolic activation and deactivation of tobacco carcinogens, CYP1A1 and microsomal epoxide hydrolase (MeH). We will isolate maternal and fetal DNA and characterize genes that are potentially related to the birth defects caused by tobacco smoke. In order to link tobacco exposure with specific genes related to birth defects, we will examine and sequence two genes that are known to play a role in the etiology of orofacial defects, the MSX1 and IRF6 genes. We will correlate mutations in the various genes with smoking status as well as biomarkers detected for the tobacco specific compounds. This link will assist in determining the relationships between smoking, especially during pregnancy, specific known teratogens in tobacco, and mutations in specific genes that are known to be related to birth defects.