title: Mechanisms of vertebrate embryo segmentation: Common themes in trunk and limb development.
abstract: Various ultradian rhythms ensure proper temporal regulations during embryo development. The embryo molecular clock, which was first identified in the presomitic mesoderm (PSM) underlying periodic somite formation, is one among them. Somites are the earliest manifestation of the segmented vertebrate body and they are formed with strict temporal precision. The tetrapod limb is also a segmented structure and the formation of limb bone elements have also been associated with a molecular clock, operating in the distal limb mesenchyme. In both the PSM and the distal limb mesenchyme, the molecular clock (MC) is influenced by FGF, SHH and RA, which are also the key regulators of the development of these tissues. While somitogenesis has been continuously scrutinized to understand the mechanisms of the MC, the limb bud has served as an outstanding paradigm to study how a cohort of undifferentiated cells is organized into functional 3D structures. The fact that both the trunk and limb development are shaped by the MC and by common signaling molecules has prompted the exciting possibility of establishing parallelisms between somitogenesis and limb development. Systematically correlating various parameters during trunk and limb development will help us to appreciate the common principles underlying segmented structure formation and allow the rise of new questions in order to fill the gaps in our present understanding. In this review we have established the parallelisms between somitogenesis and limb development at the level of gene expression patterns and their regulation. Finally, we have also discussed the most evident new avenues this exercise could open to the scientific community.
authors.affiliation: Randall Division of Cell and Molecular Biophysics, King's College London, Guy's Campus, London SE1 1UL, UK; Life and Health Sciences Research Institute (ICVS), School of Health Sciences, University of Minho, 4710-057 Braga, Portugal; ICVS/3B's-PT Government Associate Laboratory, Braga/Guimarães, Portugal; Regenerative Medicine Program, Department of Medicine and Biomedical Sciences, University of Algarve, 8005-139 Faro, Portugal; CBMR, Centre for Biomedical Research, Universidade do Algarve, 8005-139 Faro, Portugal. Electronic address: caroline.daniel_sunder_singh@kcl.ac.uk.
authors.forename: Caroline J
authors.initials: CJ
authors.lastname: Sheeba
authors.affiliation: Regenerative Medicine Program, Department of Medicine and Biomedical Sciences, University of Algarve, 8005-139 Faro, Portugal; CBMR, Centre for Biomedical Research, Universidade do Algarve, 8005-139 Faro, Portugal.
authors.forename: Raquel P
authors.initials: RP
authors.lastname: Andrade
authors.affiliation: Regenerative Medicine Program, Department of Medicine and Biomedical Sciences, University of Algarve, 8005-139 Faro, Portugal; CBMR, Centre for Biomedical Research, Universidade do Algarve, 8005-139 Faro, Portugal.
authors.forename: Isabel
authors.initials: I
authors.lastname: Palmeirim
mesh_terms: D000818:Animals; D019521:Body Patterning; D047108:Embryonic Development; D005121:Extremities / Q000196:embryology*; D018507:Gene Expression Regulation, Developmental; D006801:Humans; D008648:Mesoderm / Q000196:embryology; D038081:Organogenesis; D015398:Signal Transduction; D060726:Torso / Q000196:embryology; D014212:Tretinoin / Q000502:physiology
chemical_list: D014212:Tretinoin
keywords: HES gene oscillations; Limb development; Signaling gradients; Trunk development