Abstract
Fluctuating dental asymmetry has been linked to conditions of unstable pre- and peri-natal development. Familial, nonsyndromic craniosynostosis disrupts early craniofacial development through localized excessive calvarial ossification leading to the premature fusion of the calvarial sutures. Such abnormal gene expression may also produce systemic stress resulting in developmental instability, thereby affecting normal trait symmetry. The present study was designed to test this hypothesis by examining fluctuating dental asymmetry in an inbred strain of rabbits with familial, nonsyndromic coronal craniosynostosis. The mesiodistal (MD) and buccolingual (BL) dimensions of the right and left maxillary first molars were measured in four groups of New Zealand white rabbits (N=176; n=40 with early-onset synostosis, n=65 with delayed-onset synostosis, n=46 in-colony, phenotypically normal rabbits, and n=25 wild-type normal controls). For each variable, raw signed asymmetry was calculated (left-right) and tested for assumptions of fluctuating asymmetry (i.e., normality and non-directionality). Any group that did not meet these assumptions was excluded from further analysis. Using a standard size-adjusted, fluctuating asymmetry index, mean fluctuating asymmetry was calculated and compared across groups with non-parametric statistics. For the MD dimension, no significant (p > 0.05) group differences in mean fluctuating asymmetry were observed among groups. In contrast, rabbits with early-onset synostosis had significantly (p < 0.05) more fluctuating asymmetry in the BL dimension compared to wild-type controls. Results demonstrate increased fluctuating dental asymmetry in rabbits with nonsyndromic, early-onset coronal suture synostosis and suggest that the molecular events producing suture synostosis locally may have also have systemic effects. Knowledge of these systemic interactions may contribute to a fuller understanding of the phenotypic spectrum observed in individuals with nonsyndromic craniosynostosis.
Highlights
Nonsyndromic, simple cranio-‐ synostosis is a relatively rare condi-‐ tion (0.06 – 1.9/1000) that occurs when one or more of the calvarial sutures fuses prematurely during the period of active brain growth, result-‐ ing in aberrant patterns of growth in both the neurocranium and viscer-‐ ocranium [1]
In order to test the hypotheses that ge-‐ nomic stress is elevated in the pres-‐ ence of nonsyndromic craniosynosto-‐ sis, and that such stress increases with the severity of the cranio-‐ synostotic phenotype, we propose to investigate patterns of fluctuating dental asymmetry in a rabbit model with variably expressed, familial, non-‐ syndromic, coronal suture synostosis under controlled laboratory condi-‐ tions
Pothesis; rabbits with early-‐onset synostosis had a significantly greater magnitude of fluctuating dental asymmetry for the BL dimension of the first maxillary molars compared to unaffected controls
Summary
Nonsyndromic, simple cranio-‐ synostosis is a relatively rare condi-‐ tion (0.06 – 1.9/1000) that occurs when one or more of the calvarial sutures fuses prematurely during the period of active brain growth, result-‐ ing in aberrant patterns of growth in both the neurocranium and viscer-‐ ocranium [1]. While the genetic mutations respon-‐ sible for syndromic cases of cranio-‐. Synostosis have been known for some time [4,5], only recently have specific mutations in a number of genes (FGFR3 and MSX2 for e.g.) been iden-‐. The number of familial cases, remains relatively small at around 14% for coronal cases and 6%. While significant progress has been made in elucidating the molecu-‐ lar causes of premature suture fusion, our understanding of the disease at the phenotypic level still remains in-‐ complete. It is unclear how alterations at the genotypic level are translated into the range of varia-‐
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