2,3,7,8-Tetrachlorodibenzo-p-dioxin affects fluctuating asymmetry of molar shape in mice, and an epistatic interaction of two genes for molar size

Abstract

Fluctuating asymmetry (FA), random variation between left and right sides in a bilaterally symmetrical character, is a commonly used measure of developmental instability that is expected to increase with increasing environmental stress. One potential stressor is 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), a powerful toxicant known to disturb tooth development. In this study, mice in the F 2 generation produced from an intercross between two inbred strains (C57BL/6J and AKR/J) were exposed in utero to TCDD. We hypothesized that TCDD would increase FA in the molars of exposed mice over that of the control mice. In addition, we hypothesized that we would discover genes for molar size, shape or asymmetry whose expression would be affected by TCDD. We detected a very small, but significant, increase in FA of molar shape (but not size) in the TCDD-exposed mice compared to the control mice, although molar size and shape did not differ between these groups. Although we did not uncover any genes that acted differently in the TCDD exposed and control groups, we did identify two genes whose dominance by additive epistatic effect on molar size was affected by TCDD. We concluded that although TCDD may be affecting the expression of some genes governing the development of molars in our population of mice, FA of molar size and shape is not a particularly sensitive indicator of this effect.

Reproductive and developmental toxicity of dioxin in fish

“…Some of the endpoints of TCDD toxicity such as alterations in heart and craniofacial development also have been observed in mammals (Allen and Leamy, 2001; Ikeda et al, 2000; Ivnitski et al, 2001; Keller et al, 2007; Thackaberry et al, 2005a, 2005b;) and may have implications for human health. The adverse effects of TCDD and PCB 126 on zebrafish larval heart development resemble hypoplastic left heart failure in human newborns (Grimes et al, 2008).…”

Fluctuating Asymmetry as Risk Marker for Stress and Structural Defects in a Toxicologic Experiment

“…In a follow‐up experiment, Keller et al. () found an increase in FA in molar shape but not size. Earlier works investigated the effect of different kinds of stressors, such as heat, cold, noise, and behavioral modification in dental characters and long bones in mice and rats exposed to stress for varying perinatal periods, reporting, in general, an increase in dental asymmetry with stress and a mix of positive and negative results for limb bones (Siegel and Smookler, ; Siegel and Doyle, , , ; Doyle et al., ; Siegel et al., ; Gest et al., ).…”

Analyzing Fluctuating Asymmetry with Geometric Morphometrics: Concepts, Methods, and Applications

“…Not all toxins affect fluctuating asymmetry of shape: an experiment showed that even applications of sodium pentachlorophenate that were sufficiently severe to suppress cranial growth of zebrafish did not produce increased fluctuating asymmetry of shape [137]. Administering TCDD had no effect on fluctuating asymmetry of shape in mouse mandibles, but affected average shape [43], whereas the same toxin both increased fluctuating asymmetry and changed the average shape of molar teeth [373].…”