Evolution Of Developmental Pathways Research Articles

Phylogeny can inform animal model development for both inherited and induced conditions: Duchenne Muscular Dystrophy (DMD) and Fetal Alcohol Spectrum Disorders (FASD)

Abstract: The use of animal models in research on human and veterinary diseases and disorders is retracting, though it is likely to remain critical for decades. In light of increasing regulation and expectations of judicious use of animal subjects, we examine the idea that the use of animal models can be guided by phylogenetic relationships and modern evolutionary and cladistic analyses. Given that inherited disorders, and indeed, even the developmental and physiological responses to non-inherited conditions, are subject to evolutionary forces, it follows that the observed differences in model organisms are the products of evolutionary divergence. Understanding that divergence has the potential to elucidate which taxa are most likely to exhibit any given symptom or manifest a reaction in a broadly predictable fashion. We examine two case studies, one the inherited disorder Duchenne Muscular Dystrophy, and the other an entirely environmentally induced problem, Fetal Alcohol Spectrum Disorder, or Fetal Alcohol Syndrome. Both case studies reveal symptoms are largely congruent with phylogeny, suggesting relatively conservative evolution of developmental pathways. It follows that it is possible to characterize the manifestation of symptoms or dysmorphologies to broad phylogenetic groups. These data can then be used to inform research into possible treatments based on molecular genetic techniques sourced from unaffected taxa or even provide an evolutionary rationale for maximizing ethical decisions in the use and development of animal models in biomedical research. We argue that the technique should become standard practice in the development of animal models.

Limb ossification in the Paleozoic branchiosaurid Apateon (Temnospondyli) and the early evolution of preaxial dominance in tetrapod limb development

Despite the wide range of shapes and sizes that accompany a vast variety of functions, the development of tetrapod limbs follows a conservative pattern of de novo condensation, branching, and segmentation. Development of the zeugopodium and digital arch typically occurs in a posterior to anterior sequence, referred to as postaxial dominance, with a digital sequence of 4-3-5-2-1. The only exception to this pattern in all of living Tetrapoda can be found in salamanders, which display a preaxial dominance in limb development, a de novo condensation of a basale commune (distal carpal/tarsal 1+2) and a precoccial development of digits I and II. These divergent patterns have puzzled researchers for over a century leading to various explanatory hypotheses. Despite many advances in research on tetrapod limb development, the divergent evolution of these two pathways and its causes are still not understood. Based on an extensive ontogenetic series we investigated the pattern of limb development of the 300 Ma old branchiosaurid amphibian Apateon. This revealed a preaxial dominance in limb development that was previously believed to be unique and derived for modern salamanders. The Branchiosauridae are favored as close relatives of extant salamanders in most phylogenetic hypotheses of the highly controversial origins and relationships of extant amphibians. The findings provide new insights into the evolution of developmental pathways in tetrapod limb development, the relationships of modern amphibians with possible Paleozoic antecedents, and their initial timing of divergence.

Rights (and lefts) of passage: reviews of Gaining ground: the origin and evolution of tetrapods by Jennifer A. Clack and The evolution of developmental pathways by Adam S. Wilkins

Rights (and lefts) of passage: reviews of <i>Gaining ground: the origin and evolution of tetrapods</i> by Jennifer A. Clack and <i>The evolution of developmental pathways</i> by Adam S. Wilkins

Bold yet austere

Bold yet austere

The origin of dorsoventral patterning of the vertebrate nervous system

The fields of evolution and development have a close affinity in that they both concem themselves with the problem of the generation of form. Studies in either discipline complement each other, and have led to a dearer perspective of how the structure and order of the body plan arise. More recently, now that we have a molecular understanding of developmental processes, cross-fertilization between these two fields los greatly increased. This has allowed evolutionary relationships to be probed to a greater extent than before and h~s also revealed a surprising depth of conservation. Moreover, we are now beginning to get information regarding the evolution of developmental pathways themselves. One area in which this is particularly tt-de is in our understanding of the patteming of the nerve cord.