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Developmental pathways inferred from modularity, morphological integration and fluctuating asymmetry patterns in the human face.

ABSTRACT: Facial asymmetries are usually measured and interpreted as proxies to developmental noise. However, analyses focused on its developmental and genetic architecture are scarce. To advance on this topic, studies based on a comprehensive and simultaneous analysis of modularity, morphological integration and facial asymmetries including both phenotypic and genomic information are needed. Here we explore several modularity hypotheses on a sample of Latin American mestizos, in order to test if modularity and integration patterns differ across several genomic ancestry backgrounds. To do so, 4104 individuals were analyzed using 3D photogrammetry reconstructions and a set of 34 facial landmarks placed on each individual. We found a pattern of modularity and integration that is conserved across sub-samples differing in their genomic ancestry background. Specifically, a signal of modularity based on functional demands and organization of the face is regularly observed across the whole sample. Our results shed more light on previous evidence obtained from Genome Wide Association Studies performed on the same samples, indicating the action of different genomic regions contributing to the expression of the nose and mouth facial phenotypes. Our results also indicate that large samples including phenotypic and genomic metadata enable a better understanding of the developmental and genetic architecture of craniofacial phenotypes.

SUBMITTER: Quinto-Sanchez M

PROVIDER: S-EPMC5772513 | biostudies-literature | 2018 Jan

REPOSITORIES: biostudies-literature

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Developmental pathways inferred from modularity, morphological integration and fluctuating asymmetry patterns in the human face.

Quinto-Sánchez Mirsha M Muñoz-Muñoz Francesc F Gomez-Valdes Jorge J Cintas Celia C Navarro Pablo P Cerqueira Caio Cesar Silva de CCS Paschetta Carolina C de Azevedo Soledad S Ramallo Virginia V Acuña-Alonzo Victor V Adhikari Kaustubh K Fuentes-Guajardo Macarena M Hünemeier Tábita T Everardo Paola P de Avila Francisco F Jaramillo Claudia C Arias Williams W Gallo Carla C Poletti Giovani G Bedoya Gabriel G Bortolini Maria Cátira MC Canizales-Quinteros Samuel S Rothhammer Francisco F Rosique Javier J Ruiz-Linares Andres A Gonzalez-Jose Rolando R

Scientific reports 20180117 1

Facial asymmetries are usually measured and interpreted as proxies to developmental noise. However, analyses focused on its developmental and genetic architecture are scarce. To advance on this topic, studies based on a comprehensive and simultaneous analysis of modularity, morphological integration and facial asymmetries including both phenotypic and genomic information are needed. Here we explore several modularity hypotheses on a sample of Latin American mestizos, in order to test if modulari ...[more]

PMID: 29343858

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Project description:The cranium is an anatomically complex structure. One source of its complexity is due to its modular organization. Cranial modules are distinct and partially independent units that interact substantially during ontogeny thus generating morphological integration. Artificial Cranial Deformation (ACD) occurs when the human skull is intentionally deformed, through the use of different deforming devices applied to the head while it is developing. Hence, ACD provides an interesting example to assess the degree to which biomechanical perturbations of the developing neurocranium impact on the degree of morphological integration in the skull as a whole. The main objective of this study was to assess how ACD affects the morphological integration of the skull. This was accomplished by comparing a sample of non-deformed crania and two sets of deformed crania (i.e. antero-posterior and oblique). Both developmental and static modularity and integration were assessed through Generalized Procrustes Analysis by considering the symmetric and asymmetric components of variation in adults, using 3D landmark coordinates as raw data. The presence of two developmental modules (i.e. viscero and neurocranium) in the skull was tested. Then, in order to understand how ACD affects morphological integration, the covariation pattern between the neuro and viscerocranium was examined in antero-posterior, oblique and non-deformed cranial categories using Partial Least-Squares. The main objective of this study was to assess how ACD affects the morphological integration of the skull. This was accomplished by comparing a sample of deformed (i.e. antero-posterior and oblique) and non-deformed crania. Hence, differences in integration patterns were compared between groups. The obtained results support the modular organization of the human skull in the two analyzed modules. The integration analyses show that the oblique ACD style differentially affects the static morphological integration of the skull by increasing the covariance between neuro and viscerocranium in a more constrained way than in antero-posterior and non-deformed skulls. In addition, the antero-posterior ACD style seems to affect the developmental integration of the skull by directing the covariation pattern in a more defined manner as compared to the other cranial categories.

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Developmental pathways inferred from modularity, morphological integration and fluctuating asymmetry patterns in the human face.

Publications

Developmental pathways inferred from modularity, morphological integration and fluctuating asymmetry patterns in the human face.

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