The Body Plan Concept and Its Centrality in Evo-Devo

A body plan is a suite of characters shared by a group of phylogenetically related animals at some point during their development. The concept of bauplane, or body plans, has played and continues to play a central role in the study of evolutionary developmental biology (evo-devo). Despite the importance of the body plan concept in evo-devo, many researchers may not be familiar with the progression of ideas that have led to our current understanding of body plans, and/or current research on the origin and maintenance of body plans. This lack of familiarity, as well as former ties between the body plan concept and metaphysical ideology is likely responsible for our underappreciation of the body plan concept in its own right, as well as its role in evo-devo. My aim in this review is to outline how we have arrived at our modern definition of body plan, the controversies associated with the concept, its role in evo-devo, and how current research is informing us on body plans. To this end, I integrate concepts such as the nature of phyla, the Cambrian explosion, constraint, evolvability, and results from recent research on gene regulatory networks with the much older concept of the body plan

Global deletion of Panx3 produces multiple phenotypic effects in mouse humeri and femora

© 2016 Anatomical Society. Pannexins form single-membrane channels that allow passage of small molecules between the intracellular and extracellular compartments. Of the three pannexin family members, Pannexin3 (Panx3) is the least studied but is highly expressed in skeletal tissues and is thought to play a role in the regulation of chondrocyte and osteoblast proliferation and differentiation. The purpose of our study is to closely examine the in vivo effects of Panx3 ablation on long bone morphology using micro-computed tomography. Using Panx3 knockout (KO) and wildtype (WT) adult mice, we measured and compared aspects of phenotypic shape, bone mineral density (BMD), cross-sectional geometric properties of right femora and humeri, and lean mass. We found that KO mice have absolutely and relatively shorter diaphyseal shafts compared with WT mice, and relatively larger areas of muscle attachment sites. No differences in BMD or lean mass were found between WT and KO mice. Interestingly, KO mice had more robust femora and humeri compared with WT mice when assessed in cross-section at the midshaft. Our results clearly show that Panx3 ablation produces phenotypic effects in mouse femora and humeri, and support the premise that Panx3 has a role in regulating long bone growth and development

Additive genetic variation in the craniofacial skeleton of baboons (genus Papio) and its relationship to body and cranial size

Objectives Determining the genetic architecture of quantitative traits and genetic correlations among them is important for understanding morphological evolution patterns. We address two questions regarding papionin evolution: (1) what effect do body and cranial size, age, and sex have on phenotypic (VP) and additive genetic (VA) variation in baboon crania, and (2) how might additive genetic correlations between craniofacial traits and body mass affect morphological evolution? Materials and Methods We use a large captive pedigreed baboon sample to estimate quantitative genetic parameters for craniofacial dimensions (EIDs). Our models include nested combinations of the covariates listed above. We also simulate the correlated response of a given EID to selection on body mass alone. Results Covariates account for 1.2%–91% of craniofacial VP. EID VA decreases across models as more covariates were included. The median genetic correlation estimate between each EID and body mass is 0.33. Analysis of the multivariate response to selection reveals that observed patterns of craniofacial variation in extant baboons cannot be attributed solely to correlated response to selection on body mass, particularly in males. Discussion Because a relatively large proportion of EID VA is shared with body mass variation, different methods of correcting for allometry by statistically controlling for size can alter residual VP patterns. This may conflate direct selection effects on craniofacial variation with those resulting from a correlated response to body mass selection. This shared genetic variation may partially explain how selection for increased body mass in two different papionin lineages produced remarkably similar craniofacial phenotypes

Canalization and developmental stability in the Brachyrrhine mouse

The semi-dominant Br mutation affects presphenoid growth, producing the facial retrognathism and globular neurocranial vault that characterize heterozygotes. We analysed the impact of this mutation on skull shape, comparing heterozygotes to wildtype mice, to determine if the effects are skull-wide or confined to the sphenoid region targeted by the mutation. In addition, we examined patterns of variability of shape for the skull as a whole and for three regions (basicranium, face and neurocranium). We found that the Br mice differed significantly from wildtype mice in skull shape in all three regions as well as in the shape of the skull as a whole. However, the significant increases in variance and fluctuating asymmetry were found only in the basicranium of mutant mice. These results suggest that the mutation has a significant effect on the underlying developmental architecture of the skull, which produces an increase in phenotypic variability that is localized to the anatomical region in which the mean phenotype is most dramatically affected. These results suggest that the same developmental mechanisms that produce the change in phenotypic mean also produce the change in variance.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/75710/1/j.1469-7580.2006.00527.x.pd

Variability in the mammalian skull: the relationship between canalization, developmental stability and morphological integration

Bibliography: p. 172-203Some pages are in colour

Anatomical characterization of the inguinal lymph nodes using microcomputed tomography to inform radical inguinal lymph node dissections in penile cancer

© 2020 Wiley Periodicals LLC Background & Objectives: Radical inguinal lymph node dissections (rILND) for penile cancer risk significant postoperative lymphocele and lymphedema. However, reducing the risk of lymphatic complications is limited by our understanding of lymphatic anatomy. Therefore, this study aims to elucidate the lymphatic anatomy within the current surgical borders of a rILND. Methods: To visualize the position of the lymph nodes, tissue packets excised from the inguinal region of five fresh, male cadavers were imaged using microcomputed tomography (µCT). To standardize the position, rotation and size between specimens, each lymph node packet was aligned using a Generalized Procrustes analysis. Results: There was a median of 13.5 lymph nodes (range = 8-18) per packet, with the majority (99%) clustered within a 6 cm radius of the saphenofemoral junction; a region 39%-41% smaller than current surgical borders. No difference existed between the number of nodes between sides, or distribution around the saphenofemoral junction. Conclusions: This study provides the first 3D, in situ, standardized characterization of lymph node anatomy in the inguinal region using µCT. By using knowledge of the normal lymphatic anatomy, this study can help inform the reduction in borders of rILND to limit disruption and ensure a complete lymphadenectomy

Effects of Reduced Connexin43 Function on Mandibular Morphology and Osteogenesis in Mutant Mouse Models of Oculodentodigital Dysplasia

© 2020, Springer Science+Business Media, LLC, part of Springer Nature. Mutations in the gene encoding the gap-junctional protein connexin43 (Cx43) are the cause of the human disease oculodentodigital dysplasia (ODDD). The mandible is often affected in this disease, with clinical reports describing both mandibular overgrowth and conversely, retrognathia. These seemingly opposing observations underscore our relative lack of understanding of how ODDD affects mandibular morphology. Using two mutant mouse models that mimic the ODDD phenotype (I130T/+ and G60S/+), we sought to uncover how altered Cx43 function may affect mandibular development. Specifically, mandibles of newborn mice were imaged using micro-CT, to enable statistical comparisons of shape. Tissue-level comparisons of key regions of the mandible were conducted using histomorphology, and we quantified the mRNA expression of several cartilage and bone cell differentiation markers. Both G60S/+ and I130T/+ mutant mice had altered mandibular morphology compared to their wildtype counterparts, and the morphological effects were similarly localized for both mutants. Specifically, the biggest phenotypic differences in mutant mice were focused in regions exposed to mechanical forces, such as alveolar bone, muscular attachment sites, and articular surfaces. Histological analyses revealed differences in ossification of the intramembranous bone of the mandibles of both mutant mice compared to their wildtype littermates. However, chondrocyte organization within the secondary cartilages of the mandible was unaffected in the mutant mice. Overall, our results suggest that the morphological differences seen in G60S/+ and I130T/+ mouse mandibles are due to delayed ossification and suggest that mechanical forces may exacerbate the effects of ODDD on the skeleton

Discordant growth of nasal cartilage and bone contributes to phenotypic variability of the skull in a mouse model

Background: We previously determined a nonlinear relationship between connexin 43 (Cx43) function and craniofacial phenotypic variation in the mutant mouse model G60S/+, and that this variation was driven by nasal bone deviation. While nonlinearities in the genotype-phenotype map appear to be common, few studies have looked at the developmental processes that underlie this nonlinearity. Here, we investigated the potential tissue-level developmental determinants of the variation in nasal bone phenotype in G60S/+ mice through postnatal development. Results: The deviated nasal bone phenotype arises by postnatal day 21 and becomes more severe by 3 months in G60S/+ mice. Measures of nasal bone remodeling including the number of osteoclasts, mineralizing surface, mineral apposition rate, and bone formation rate are significantly greater in G60S/+ mice compared to wild-type mice at 2 months, but these differences do not correspond with nasal bone deviation. The degree of nasal bone deviation does significantly and negatively correlate with the ratio between nasal bone and cartilaginous nasal septum length. Conclusions: Our findings indicate that the mean phenotypic changes observed between G60S/+ and wild-type mice are due to reduced bone growth, but the increased phenotypic variation found within mutant mice is due to discordant growth between nasal cartilage and bone. </p