Search

Human induced pluripotent stem cells (hiPSCs) hold promises to model and understand human diseases, including those associated with ageing. Here, we describe ABCRIi001-A, a hiPSC line generated from peripheral blood mononuclear cells (PBMCs) of a 79-year-old female enrolled in a study for development of an ageing score (ALFA Score). PBMCs were reprogrammed using three Sendai virus-based reprogramming vectors (hKOS, hc-Myc, and hKlf4). ABCRIi001-A showed normal morphology and karyotype, viral clearance, absence of genomic aberrations, and their pluripotency was confirmed by expression of pluripotency-related markers and their ability to differentiate into the three germ layers. ABCRIi001-A is valuable for ageing-related studies., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Jose Braganca reports financial support was provided by Regional Development and Coordinating Commission of the Algarve. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Author(s). Published by Elsevier B.V. All rights reserved.)

The developing forelimb is patterned along the proximal-distal and anterior-posterior axes by opposing gradients of retinoic acid and fibroblast growth factors and by graded sonic hedgehog signaling, respectively. However, how coordinated patterning along both axes is accomplished with temporal precision remains unknown. The limb molecular oscillator hairy2 was recently shown to be a direct readout of the combined signaling activities of retinoic acid, fibroblast growth factor and sonic hedgehog in the limb mesenchyme. Herein, an integrated time-space model is presented to conciliate the progress zone and two-signal models for limb patterning. We propose that the limb clock may allow temporal information to be decoded into positional information when the distance between opposing signaling gradients is no longer sufficient to provide distinct cell fate specification., (Copyright © 2013 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Body skeletal muscles formation starts with somite differentiation, due to signals from surrounding tissues. Somite ventral portion forms the sclerotome while its dorsal fraction constitutes the dermamyotome, and later the dermatome and myotome. Relative levels of BMP activity have been proposed to control several aspects of somite development, namely the time and location of myogenesis within the somite. The fine-tuning of BMP activity is primarily achieved via negative regulation by diffusible BMP inhibitors, such as Noggin and Chordin, and on a secondary level by proteins cleaving these inhibitors, such as BMP1/Tolloid metalloprotease family members. Herein, we carefully described the somitic expression of colloid-like1, one of the chick BMP1/Tolloid homologues, and found that this gene is specifically expressed in the 10 most anterior somites, suggesting that it may be involved in neck muscle formation. By using in ovo microsurgery and tridimensional embryo tissue culture techniques we assessed the function of surrounding structures, neural tube, notochord, surface ectoderm and lateral plate mesoderm, on the maintenance of somitic colloid-like1 gene expression. We unveil that a signal coming from the neural tube is responsible for this expression and rule out the main candidate pathway, Wnt. By comparing the somitic colloid-like1 gene expression with that of related signaling partners, such as BMP4, Noggin and Chordin, we propose that colloid-like1 plays a role in the reinforcement of BMP4 activity in the medial portion of the 10 most anterior dermomyotomes, thus belonging to the molecular machinery controlling neck muscle development in the chick., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Embryo development proceeds under strict temporal control and an embryonic molecular clock (EC), evidenced by cyclic gene expression, is operating during somite formation and limb development, providing temporal information to precursor cells. In somite precursor cells, EC gene expression and periodicity depends on Retinoic acid (RA) signaling and this morphogen is also essential for limb initiation, outgrowth and patterning. Since the limb EC gene hairy2 is differentially expressed along the proximal-distal axis as growth proceeds, concomitant with changes in flank-derived RA activity in the mesenchyme, we have interrogated the role of RA signaling on limb hairy2 expression regulation. We describe RA as a positive regulator of limb hairy2 expression. Ectopic supplementation of RA induced hairy2 in a short time period, with simultaneous transient activation of Erk/MAPK, Akt/PI3K and Gli3 intracellular pathways. We further found that FGF8, an inducer of Erk/MAPK, Akt/PI3K pathways, was not sufficient for ectopic hairy2 induction. However, joint treatment with both RA and FGF8 induced hairy2, indicating that RA is creating a permissive condition for p-Erk/p-Akt action on hairy2, most likely by enhancing Gli3-A/Gli3-R levels. Finally, we observed an inhibitory action of BMP4 on hairy2 and propose a model whereby RA shapes limb hairy2 expression during limb development, by activating its expression and counteracting the inhibitory action of BMP4 on hairy2. Overall, our work reports a novel role for RA in the regulation of limb clock hairy2 gene expression and elucidates the temporal response of multiple intracellular pathways to RA signaling in limb development., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Temporal control can be considered the fourth dimension in embryonic development. The identification of the somitogenesis molecular clock provided new insight into how embryonic cells measure time. We provide the first evidence of a molecular clock operating during chick fore-limb autopod outgrowth and patterning, by showing that the expression of the somitogenesis clock component hairy2 cycles in autopod chondrogenic precursor cells with a 6 h periodicity. We determined the length of time required to form an autopod skeletal limb element, and established a correlation between the latter and the periodicity of cyclic hairy2 gene expression. We suggest that temporal control exerted by cyclic gene expression can be a widespread mechanism providing cellular temporal information during vertebrate embryonic development.

The apical ectodermal ridge (AER) controls limb outgrowth and patterning, such that its removal causes changes in mesodermal gene expression, cell death and limb truncation. Fibroblast growth factor (FGF) family members are expressed in the AER and can rescue limb bud outgrowth after AER removal. Cells localized underneath the AER are maintained in an undifferentiated state by the FGFs produced by the AER. MAPK phosphatase 3 (mkp3) is a downstream effector of FGF8 signalling during limb bud development and is expressed in the distal limb mesenchyme. The present work evidences a gradient of mkp3 transcripts along the chick limb bud, in a distal to proximal direction. mkp3 transcription occurs only in the most distal limb bud cells and its mRNA gradient throughout the limb results from progressive mRNA decay. We show that FGF8-soaked beads induce ectopic mkp3 expression, indicating that AER-derived FGF8 protein may activate mkp3 in the distal mesenchyme.

Segmentation consists on the progressive formation of repetitive embryonic structures, named somites, which are formed from the most rostral part of the presomitic mesoderm. Somites are subdivided into anterior and posterior compartments and several genes are differentially expressed in either compartment. This has provided evidence for the importance of establishing the anterior-posterior polarity within each somite, which is critical for the correct segmented pattern of the adult vertebrate body. Although all somites appear morphologically similar, fate map studies have shown that the first 4 somites do not give rise to segmented structures, in contrast to more posterior ones. Moreover, in several somitogenesis-related mutants the anterior somites are not affected while posterior somites present clear defects or do not form at all. Altogether these data suggest relevant differences between rostral and caudal somites. In order to check for molecular differences between anterior and posterior somites, we have performed a detailed expression pattern analysis of several Notch signalling related genes. For the first time, we show that the somitic expression pattern profile is not the same along the anterior-posterior axis and that the differences are not observed always at the same somite level.