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. 2017 Dec 20;7(1):17955.
doi: 10.1038/s41598-017-18199-9.

Shape Analysis of the Basioccipital Bone in Pax7-deficient Mice

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Free PMC article

Shape Analysis of the Basioccipital Bone in Pax7-deficient Mice

Joshua Cates et al. Sci Rep. .
Free PMC article

Abstract

We compared the cranial base of newborn Pax7-deficient and wildtype mice using a computational shape modeling technology called particle-based modeling (PBM). We found systematic differences in the morphology of the basiooccipital bone, including a broadening of the basioccipital bone and an antero-inferior inflection of its posterior edge in the Pax7-deficient mice. We show that the Pax7 cell lineage contributes to the basioccipital bone and that the location of the Pax7 lineage correlates with the morphology most effected by Pax7 deficiency. Our results suggest that the Pax7-deficient mouse may be a suitable model for investigating the genetic control of the location and orientation of the foramen magnum, and changes in the breadth of the basioccipital.

Conflict of interest statement

C.K. is inventor of a related microCT Imaging Technology for reproductive toxicology, not used in this study.

Figures

Figure 1
Figure 1
Volume rendering visualizing the microCT scans for specimens with median skull length from the wildtype Pax7 (WT/WT), homozygous Pax7 (LacZ/LacZ) and heterozygous Pax7 (LacZ/WT) groups. Row A depicts the neonatal skull base, with the temporo-parietal bones cropped away. Row B is a closer view of the cranial base and the basioccipital bone. Row C compares the overall jaw and skull lengths. Side-view images for the sagittal hemi-sections of each sample are shown in Row D and images looking onto lower jaws from bottom are given in Row E. Row F compares craniofacial features of the front side of the skull. These images were created using the freely available open source ImageVis3D volume rendering software (ImageVis3D, http://www.sci.utah.edu/cibc/software). The jaw lengths and overall skull lengths were calculated using MicroView http://microview.sourceforge.net/ (GE Healthcare, London, Ontario, Canada) such that three dimensional landmark coordinates were collected from two dimensional images. Each dash in the scale bar reflects a 0.1 mm increase.
Figure 2
Figure 2
A visual comparison of the group mean shapes. Shape surfaces are reconstructed from the Euclidean means of the correspondence positions for each group. Mean correspondence positions are indicated by spheres. (A) wild type, (B) homozygous, (C) heterozygous.
Figure 3
Figure 3
Variation in each of the top 4 principal components of the homozygous basioccipital model. Shape (yellow surface) is reconstructed from correspondence positions (green points) at 1, 2, and 3 standard deviations (σ) from the mean shape. (A) PC1 top, (B) PC1 end, (C) PC2, (D) PC3, (E) PC4, (1) −3 σ, (2) −2 σ, (3) −1 σ, (4) 1 σ, (5) 2 σ, (6) 3 σ.
Figure 4
Figure 4
Visualization of the linear discriminant from the Hotelling T 2 test for the homozygous shape model (TOP ROW) and the heterozygous shape model (BOTTOM ROW). Arrows indicate direction from the wildtype distribution to the mutant distribution.
Figure 5
Figure 5
Pax7 expression in the murine basioccipital bone. Representative bright field (1) and fluorescent images (tdTomato, red (2); GFP, green (3)) of the dorsal aspect of basal occipital bones were obtained from 4 to 5-week-old (A) Pax7 ICNm/WT Rosa WT/WT (Pax7ICN), (B) Pax7 WT/WT Rosa nT-nG/WT (RosanTom/nGFP), and (C) Pax7 ICNm/WT Rosa nT-nG/WT (Pax7ICN RosanTom/nGFP) mice. Rostral region is visualized on the right and the caudal region on the left of each image. Eight mice were analyzed per genotype. White dots denote the anatomical boundary of the basioccipital bone. Eight mice were analyzed per genotype. Three of the eight Pax7 ICNm/WT Rosa nT-nG/WT mice did not demonstrate RFP or GFP fluorescence, which was attributed to transgene silencing for the reporter allele. Images were acquired at 7X magnification.

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