Variation in the Developmental and Morphological Interaction Between the Nasal Septum and Facial Skeleton

While the nasal septum exerts a morphogenetic influence on the facial skeleton, there is evidence that this relationship is highly variable. To better appreciate the precise role of the septum, it is important understand the variable interaction between the septum and surrounding skeleton during ontogeny. Here we analyzed nasal septal and facial skeletal postnatal phenotypic variation using cross-sectional samples of C3H/HeJ and C57BL/6J mice. Initial observations indicated between-strain variation in the magnitude of septal deviation, suggesting differences in septal and facial skeletal interaction. We examined whether variation in septal deviation is due to ontogenetic differences in septal size, or whether variation in facial skeletal growth imposes spatial constraints on the septum. Using microCT we quantified septal size and deviation, and collected coordinate landmark data, which we analyzed using geometric morphometrics. C3H/HeJ mice were significantly more deviated than C57BL/6J during development. We found no differences in septal size between the two strains. However, while both strains exhibited an ontogenetic increase in snout length, C3H/HeJ mice exhibited a non-allometric reduction in nasal bone length. This appears to be influenced by between-strain variation in the spatial relationship between the nasal septum and nasofrontal suture. Unlike C57BL/6J mice, the C3H/HeJ nasal septum is positioned anterior to the nasofrontal suture potentially limiting an early direct influence of septal growth (e.g., through interstitial expansion) on sutural growth. Ultimately, our results underscore that while the septum is a key facial growth center, its precise influence on facial growth varies even in narrow morphological and taxonomic ranges. (C) 2016 Wiley Periodicals, Inc.