Abstract
The strains of inbred laboratory mice are isogenic and homogeneous for over 98.6% of their genomes. However, geometric morphometric studies have demonstrated clear differences among the skull shapes of various mice strains. The question now arises: why are skull shapes different among the mice strains? Epigenetic processes, such as morphological interaction between the muscles and bones, may cause differences in the skull shapes among various mice strains. To test these predictions, the objective of this study is to examine the morphological association between a specific part of the skull and its adjacent muscle. We examined C57BL6J, BALB/cA, and ICR mice on embryonic days (E) 12.5 and 16.5 as well as on postnatal days (P) 0, 10, and 90. As a result, we found morphological differences between C57BL6J and BALB/cA mice with respect to the inferior spine of the hypophyseal cartilage or basisphenoid (SP) and the tensor veli palatini muscle (TVP) during the prenatal and postnatal periods. There was a morphological correlation between the SP and the TVP in the C57BL6J, BALB/cA, and ICR mice during E15 and P0. However, there were not correlation between the TVP and the SP during P10. After discectomy, bone deformation was associated with a change in the shape of the adjacent muscle. Therefore, epigenetic modifications linked to the interaction between the muscles and bones might occur easily during the prenatal period, and inflammation seems to allow epigenetic modifications between the two to occur.
Highlights
To date, over 450 inbred mouse strains have been described and developed, providing abundant phenotypes and genomic backgrounds for genetic studies
The ala temporalis did not differ between the C57BL6J and BALB/cA mice (medial part (2), P = 0.36; lateral part (3), P = 0.42) (Fig 2A–2F and 2M)
The cross-sectional area (CSA) of the anterior part of the tensor veli palatini muscle (TVP) was smaller in the BALB/cA mice than that in the C57BL6J mice (P < 0.01) (Fig 2H, 2K and 2N)
Summary
Over 450 inbred mouse strains have been described and developed, providing abundant phenotypes and genomic backgrounds for genetic studies. Domesticus housed within a few research facilities and laboratories [1]. Most inbred laboratory strains have originated from a limited founder population of Mus musculus and M. m. Most of these strains have been bred for over 150 generations and are isogenic and homogeneous for over 98.6% of their genomes [2]. Supported by the Private University Research Branding Project from MEXT of Japan. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript
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