Project Title: The effects of the endocrine disruptor vinclozolin on digit ratio development
Faculty Mentor’s Name: Dr. Martin Cohn
Student’s Name: Lindsey North
The second to fourth digit ratio (2D:4D) is sexually dimorphic in humans and mice. On average, the second digit is typically shorter than the fourth digit (2D:4D<1) in males. However, the second digit is typically longer than the fourth (2D:4D≥1) in females (Manning, Scutt, Wilson, Lewis-Jones, 1998). This 2D:4D ratio has been shown to be reflective of in utero androgen (AR) and estrogen receptor (ER) activity levels in mice (Zheng & Cohn, 2011). Furthermore, it has been suggested that 2D:4D can act as a measurable proxy for prenatal hormonal exposure in humans. Several other hormonally influenced characteristics including health, gender identity, and sexual orientation have also been shown to correlate with digit ratio (Manning, 2002). However, disruption of the normal in utero hormonal environment can result in developmental alterations in the embryo.
Such changes may occur due to the introduction of endocrine disrupting compounds into the in utero environment. The United States EPA recognized vinclozolin as a potential anti-androgenic endocrine disruptor in the 1980s. At that time vinclozolin was used as a fungicide on fruits, vines, vegetables, and turf grasses (van Ravenzwaay, Kolle, Ramirez, Kamp, 2013). A low dose combination of BPA, an estrogenic endocrine disruptor, and vinclozolin was shown to significantly feminize the second to fourth digit ratios (2D:4D≥1) of male Wistar rats (Auger et al. 2013). However, it remains unknown how vinclozolin alone affects 2D:4D. Investigation into how anti-androgenic endocrine disruptors, such as vinclozolin, may affect the in utero hormonal environment remains essential as the increase use of such chemicals has been hypothesized to be correlated with the increasing number of congenital penile anomalies, such as hypospadias (Nelson et al., 2005). Altered 2D:4D has the potential to provide a permanent, measurable indication of these altered in utero hormonal environments and will help establish the role of vinclozolin as an anti-androgenic compound.