Abstract
The second to fourth digit ratio (2D∶4D) is sexually differentiated in a variety of species, including humans, rats, birds, and lizards. In humans, this ratio tends to be lower in males than in females. Lower digit ratios are believed to indicate increased prenatal testosterone exposure, and are associated with more masculinized behavior across a range of traits. The story seems more complicated in laboratory mice. We have previously shown that there is no sex difference in the digit ratios of inbred mice, but found behavioral evidence to suggest that higher 2D∶4D is associated with more masculinized behaviors. Work examining intrauterine position effects show that neighbouring males raise pup digit ratio, suggesting again that higher digit ratios are associated with increased developmental androgens. Other work has suggested that masculinization is associated with lower digit ratios in lab mice. Here, we examine the fore- and hindlimb digit ratios of 20 inbred mouse strains. We find large inter-strain differences, but no sexual dimorphism. Digit ratios also did not correlate with mice behavioral traits. This result calls into question the use of this trait as a broadly applicable indicator for prenatal androgen exposure. We suggest that the inbred mice model presents an opportunity for researchers to investigate the genetic, and gene-environmental influence on the development of digit ratios.
Highlights
Prenatal androgen exposure is thought to organize many of the male-female differences in the morphology and behavior of both humans and mice alike [reviewed in 1–3]
Digit ratios on the left side were slightly larger than the right on forelimbs (left: 0.938, right: 0.930, Welch’s t(529.553) = 2.39, p = 0.017) while the reverse was true on hindlimbs (left: 0.985, right: 0.999, Welch’s t(536.664) = 4.01, p,0.0001)
This study demonstrates significant digit ratio variation between mouse strains but not between the sexes
Summary
Prenatal androgen exposure is thought to organize many of the male-female differences in the morphology and behavior of both humans and mice alike [reviewed in 1–3]. Male laboratory mice exhibit lower hind paw digit ratios than females, though this was only found in an outbred strain [17], and in a strain of unspecified genetic composition [18]. No such effect was seen in a larger study of inbred laboratory mice [19], or in the control group of a very large artificial selection study [20]. We examine the sex and strain differences in the digit ratios of 20 inbred mice strains to establish the relationship between digit ratio on the four paws with respect to sex and strain
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
