Epigenetic integration of the developing brain and face

Parsons, Trish E.; Schmidt, Edward M.; Boughner, Julia C.; Jamniczky, Heather A.; Marcucio, Ralph; Hallgrímsson, Benedikt

doi:10.1002/dvdy.22729

Cited by 64 publications

(67 citation statements)

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“…A large component of the facial variation in mammals may, therefore, be associated with their diversity of size, which is orders of magnitude greater than in other vertebrate groups. The covariation between the face and braincase operates both as a constraint, channelling variation along predictable lines, and as a source of variation related to differences in diet and appearance 19 . The constraint is implied by the tight linear axes in the form space.…”

Section: Discussionmentioning

confidence: 99%

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Larger mammals have longer faces because of size-related constraints on skull form

2013

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Facial length is one of the best known examples of heterochrony. Changes in the timing of facial growth have been invoked as a mechanism for the origin of our short human face from our long-faced extinct relatives. Such heterochronic changes arguably permit great evolutionary flexibility, allowing the mammalian face to be remodelled simply by modifying postnatal growth. Here we present new data that show that this mechanism is significantly constrained by adult size. Small mammals are more brachycephalic (short faced) than large ones, despite the putative independence between adult size and facial length. This pattern holds across four phenotypic lineages: antelopes, fruit bats, tree squirrels and mongooses. Despite the apparent flexibility of facial heterochrony, growth of the face is linked to absolute size and introduces what seems to be a loose but clade-wide mammalian constraint on head shape.

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Section: Discussionmentioning

confidence: 99%

“…Shortening of the face is characteristic of domestication in mammals, which often selects for smaller size, and has been reported in pigs, cattle, dogs and cats 21 . In mice mutants, relatively small brains co-occur with prognathic faces 19,22 . This covariation Figure 3 | Procrustes form space trajectories.…”

Section: Discussionmentioning

confidence: 99%

Larger mammals have longer faces because of size-related constraints on skull form

2013

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“…Previous landmark based studies of mouse embryos between E10.5 and E12.5 are typically related to questions of growth and development of facial prominences and the structures derived from them [5,6,23-25]. Therefore, our landmark set, influenced greatly by this previous work, is composed of points at the borders between or at the extreme edges of prominences and/or other craniofacial features.…”

Section: Introductionmentioning

confidence: 99%

Surface landmark quantification of embryonic mouse craniofacial morphogenesis

Percival

Green

Marcucio³

et al. 2014

BMC Dev Biol

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BackgroundMorphometric quantification of subtle craniofacial variation in studies of experimentally modified embryonic mice has proved valuable in determining the effects of developmental perturbations on craniofacial morphogenesis. The direct comparison of landmark coordinate data from embryos of many different mouse strains and mouse models can advance our understanding of the bases for craniofacial variation. We propose a standard set of craniofacial surface landmarks, for use with embryonic day (E) 10.5-12.5 mice, to serve as the foundation for this type of data compilation and analysis. We quantify the intra- and inter-observer landmark placement variation associated with each landmark and determine how the results of a simple ontogenetic analysis might be influenced by selection of landmark set.ResultsIntraobserver landmark placement error for experienced landmarkers generally remains below 0.1 mm, with some landmarks exhibiting higher values at E11.5 and E12.5. Interobserver error tends to increase with embryonic age and those landmarks defined on wide inflections of curves or facial processes exhibit the highest error. Landmarks with highest intra- or inter-observer are identified and we determine that their removal from the dataset does not significantly change the vectors of craniofacial shape change associated with an ontogenetic regression.ConclusionsOur quantification of landmark placement error demonstrates that it is preferable for a single observer to identify all landmark coordinates within a single study and that significant training and experience are necessary before a landmarker can produce data for use in larger meta-analyses. However, we are confident that this standard landmark set, once landmarks with higher error are removed, can serve as a foundation for a comparative dataset of facial morphogenesis across various mouse populations to help identify the developmental bases for phenotypic variation in the craniofacial complex.

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“…Sophisticated tools for making measurements by hand (47) have been replaced largely by instruments permitting three-dimensional (3D) digitization (36) and by x-ray computed tomography (CT) (32,79). The positions and relationships of prominent skull features (landmarks) provide a measure of shape, often using combinations of principal component or related analyses (41,73,99,101), thin-plate splines (41,80) or three-dimensional (3D) finiteelement analysis (25) for morphometric analysis.…”

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confidence: 99%

“…In previous work, mouse skull measurements have been made on the basis of manually identified landmarks in 3D images (26,45,46,59,78,96,100). Similar analyses have also been conducted in 3D images of the embryo (84) and the brain (7,61,73). We have also evaluated the morphometry of the brain and skull separately by computerautomated registration methods, which eliminate the need for manual identification of landmarks (68).…”

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confidence: 99%

If the skull fits: magnetic resonance imaging and microcomputed tomography for combined analysis of brain and skull phenotypes in the mouse

Nieman

Blank

Roman

et al. 2012

Physiological Genomics

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KJ. If the skull fits: magnetic resonance imaging and microcomputed tomography for combined analysis of brain and skull phenotypes in the mouse. Physiol Genomics 44: 992-1002. First published September 4, 2012 doi:10.1152/physiolgenomics.00093.2012.-The mammalian brain and skull develop concurrently in a coordinated manner, consistently producing a brain and skull that fit tightly together. It is common that abnormalities in one are associated with related abnormalities in the other. However, this is not always the case. A complete characterization of the relationship between brain and skull phenotypes is necessary to understand the mechanisms that cause them to be coordinated or divergent and to provide perspective on the potential diagnostic or prognostic significance of brain and skull phenotypes. We demonstrate the combined use of magnetic resonance imaging and microcomputed tomography for analysis of brain and skull phenotypes in the mouse. Co-registration of brain and skull images allows comparison of the relationship between phenotypes in the brain and those in the skull. We observe a close fit between the brain and skull of two genetic mouse models that both show abnormal brain and skull phenotypes. Application of these three-dimensional image analyses in a broader range of mouse mutants will provide a map of the relationships between brain and skull phenotypes generally and allow characterization of patterns of similarities and differences. craniofacial development; mouse phenotyping; mouse imaging; oculodentodigital dysplasia; Dandy-Walker malformation THE DEVELOPMENT OF THE BRAIN and skull is an intricate and coordinated process that results in two complex structures fitting tightly together. Both physical and genetic factors participate in the direction of this process, and changes in either may result in an altered brain and/or skull morphometry. Characterization of such alterations, and of how brain and skull alterations relate to one another, will provide insight into the process of normal brain and skull development and into conditions where this development is perturbed.It is recognized that the physical interaction between structures in the developing brain and skull can induce covariation in their shape (61). Premature fusion of a cranial suture, for example, results in an abnormal skull shape due to growth restriction in one direction (51). Brain growth is also physically constrained in these circumstances, and the brain is similarly altered in shape (5,6,77). Fear of increased intracranial pressure and abnormal craniofacial development motivates corrective surgery in these patients to partly normalize anatomical outcome (71). Furthermore, simple geometric measurements of the skull, such as the angle between the skull base and the front of the brain or landmarks on the facial bones, show a high degree of correlation with the total volume of the brain (16,59,81,82). This observation seems to hold true in multiple species of mammals, a fact that informs some studies in anthropology and evoluti...

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Epigenetic integration of the developing brain and face

Cited by 64 publications

References 55 publications

Larger mammals have longer faces because of size-related constraints on skull form

Larger mammals have longer faces because of size-related constraints on skull form

Surface landmark quantification of embryonic mouse craniofacial morphogenesis

If the skull fits: magnetic resonance imaging and microcomputed tomography for combined analysis of brain and skull phenotypes in the mouse

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