Normal Variation of Craniometric Traits In Inbred Mouse Strains

Objectives: The purpose of this study was to investigate the normal variation of craniometric traits among different inbred strains of mice. Specifically, the region of the snout anterior to the infraorbital foramen composed of the maxilla and nasal bones. We are interested in the genetics underlying morphogenesis of the anterior nasal structure.
Methods: Digitized dorsoventral radiographs and body weights (BW) from 23 inbred strains of mice (~7 to 8 weeks old and ~10 males and ~10 females for each strain) were available. Landmarks include: nasale; right and left anterior notches on frontal processes lateral to infraorbital fissures (IF); and midline of the posterior palatine process at the level of the infraorbital foramen (PP) were used to calculate the midline of the palatine process to nasale (mm); right IF to nasale (mm); left IF to nasale (mm); and the distance between the left and right IF (mm). Each measurement was done in triplicate. Descriptive statistics and comparison of means were analyzed using SPSS ver. 22, p<0.05 was considered significant.
Results: A total of 448 mice were examined. For DBA/LacJ and SPRET/Ei, only female mice were available for study. We observed generalized interstrain variation for each trait. For strains with males and females, BW differed significantly between males and females. BW among the strains showed considerable variation with MOLF/Ei the smallest and AKR/J the largest. Sexual dimorphism was noted for PP to nasale (MOLF/Ei, PL/J, SM/J and SWR/J); right IF to nasale (129S1/SvImJ, C3H/HeJ, CBA/J, and PL/J); left IF to nasale (C57BL/10J, C57/J, CBA/J, and SJL/J); and distance between the left and right IF (C57BL/10J and PERA/Ei).
Conclusions: Inter-strain variation occurs for the anterior snout as well as sexual dimorphism for some traits and strains. These data form the foundation for additional genetic studies.