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- Altered cogs of the clock: Insights into the embryonic etiology of spondylocostal dysostosisPublication . Nóbrega, Mónica; Maia-Fernandes, Ana C; Andrade, Raquel P.Spondylocostal dysostosis (SCDO) is a rare heritable congenital condition, characterized by multiple severe malformations of the vertebrae and ribs. Great advances were made in the last decades at the clinical level, by identifying the genetic mutations underlying the different forms of the disease. These were matched by extraordinary findings in the Developmental Biology field, which elucidated the cellular and molecular mechanisms involved in embryo body segmentation into the precursors of the axial skeleton. Of particular relevance was the discovery of the somitogenesis molecular clock that controls the progression of somite boundary formation over time. An overview of these concepts is presented, including the evidence obtained from animal models on the embryonic origins of the mutant-dependent disease. Evidence of an environmental contribution to the severity of the disease is discussed. Finally, a brief reference is made to emerging in vitro models of human somitogenesis which are being employed to model the molecular and cellular events occurring in SCDO. These represent great promise for understanding this and other human diseases and for the development of more efficient therapeutic approaches.
- A morphometric characterization of early CHICK embryo elongationPublication . Maia-Fernandes, Ana C; Pais de Azevedo, Tomás; Martins, Nísia Borralho; Ventura Ramalhete, Sara Maria; Martins, G. G.; Palmeirim, Isabel; dos Santos Duarte, Guilhermina Isabel; Marreiros, Ana; Martel, Paulo; Andrade, RaquelThe chicken embryo has long been a pivotal model system to understand the cellular and molecular mechanisms driving amniote embryo development. Its easy access for in vivo experimentation, together with the development of ex ovo culture techniques, has made it a choice model system for elaborate experimental manipulations. Temporal progression of chick embryo development is classically categorized using the Hamburger and Hamilton staging system (Hamburger, V., & Hamilton, 1951). However, this offers limited temporal resolution when comparing embryos within the same developmental stage and may further be hindered by experimental conditions that directly impact the morphological structures used for stage identification. Here, we performed timelapse imaging of early chick embryonic stages HH4 to HH10 and obtained quantitative elongation data of multiple embryonic portions, yielding two valuable and freely accessible data resources for the chick research community. We identified length measurements capable of describing developmental time, thus enabling the alignment of independent embryos with temporal resolution. Notably, the head-fold (C-HF) showed a strong time correlation, even though it elongates above the primary embryonic axis. A morphometric characterization of HH stages further showed that C-HF length can discriminate HH stages of development, albeit with limited resolution. Finally, we present ChEEQ: Chicken Embryo Elongation Quantification (https://colab.research.google.co m/github/EmbryoClock/ChickElong/blob/main/ChEEQ/ChEEQ.ipynb), a new morphometric tool describing HH4-HH10 embryo elongation, that allows the comparison of user-input data with our reference dataset and is capable of inferring quantitative alterations to embryo developmental time using length measurements alone. Together, these resources open new avenues for investigating vertebrate embryo elongation and quantitatively assessing the effects of experimental interventions on development.