International Journal of Developmental Biology最新文献

Elysia diomedea, otherwise known as the "Mexican dancer", aries in adult size and color across its geographical distribution in Ecuador. Because of morphological variation and the absence of genetic information for this species in Ecuador, we analyzed mtDNA sequences in three populations (Ballenita, La Cabuya, and Mompiche) and confirmed that individuals from the three locations belonged to E. diomedea and that there was no population structure that could explain their morphological differences. Next, we analyzed general aspects about the reproductive biology and embryology of this species. Live slugs from the Ballenita population were maintained and reproduced ex situ. Egg ribbons and embryos were fixed and observed by brightfield and confocal microscopy. We observed a single embryo per capsule, 98 embryos per mm² of egg ribbon, and compared the cleavage pattern of this species to that of other heterobranchs and spiralians. E. diomedea early development was characterized by a slight unequal first cleavage, occurrence of a 3-cell stage in the second cleavage, and the formation of an enlarged second quartet of micromeres. We observed clear yolk bodies in the egg capsules of some eggs ribbons at early stages of development. Both reproductive and embryological characteristics, such as presence of stomodeum in the larva, and ingestion of particles after hatching confirmed the planktotrophic veliger larvae of this species, consistent with the majority of sacoglossans from the Eastern and Northeast Pacific Oceans.

The amount of proteins of the regulatory pluripotency network can be determinant for somatic cell reprogramming into induced pluripotent stem cells (iPSCs) as well as for the maintenance of pluripotent stem cells (PSCs). Here, we report a transposon-based reprogramming system (PB-Booster) that allowed high expression levels of a polycistronic transgene containing Myc, Klf4, Oct4 and Sox2 (MKOS) and showed increased reprogramming efficiency of fresh mouse embryonic fibroblasts (MEFs) into iPSCs under low, but not under high, MKOS expression levels. In contrast, MEFs after 2 passages derived into a similar number of iPSC colonies as fresh MEFs at a high MKOS dose, but this number was reduced at a low MKOS dose. Timing of reprogramming was not affected by MKOS expression levels but, importantly, exogenous MKOS expression in established PSCs caused a significant cell loss. At high but not at low MKOS expression levels, MEFs of the CD1 strain produced more initial cell clusters than iPSCs and, although reprogrammed at a similar efficiency as MEFs of the 129/Sv strain, iPSCs could not be maintained in the absence of exogenous MKOS. In CD1-iPSCs, Oct4, Nanog, Rex1 and Esrrb expression levels were reduced when compared with the levels in PSCs derived from the 129/Sv strain. Culture of CD1-iPSCs in medium with MEK and GSK3β inhibitors allowed their self-renewal in the absence of exogenous MKOS, but the expression levels of Oct4, Nanog, Rex1 and Esrrb were only partially increased. Despite the reduced levels of those pluripotency factors, CD1-iPSC kept high capacity for contribution to chimeric mouse embryos. Therefore, levels of regulatory pluripotency factors influence reprogramming initiation and PSC maintenance in vitro without affecting their differentiation potential in vivo.

Development without a free-living tadpole is common among Ibero American frogs. The most derived condition is direct development where the tadpole has been eliminated, and the most investigated direct developing frog is Eleutherodactylus coqui. To provide a different point-of-view, an imaginary interview with a coqui is conducted. Opinions are offered on invasive species, developmental features that are surprisingly conserved, and novelty in germ layer specification.

The cell differentiation of the musculoskeletal system is highly coordinated during limb development. In the distal-most region of the limb, WNT and FGF released from the apical ectodermal ridge maintain mesenchymal cells in the undifferentiated stage. Once the cells stop receiving WNT and FGF, they respond to differentiation signals. Particularly during tendon development, mesenchymal cells enter the cell differentiation program once Scleraxis (Scx) gene expression occurs. Among the signals that trigger the cell differentiation programs, TGFβ signaling has been found to be closely involved in tendon differentiation. However, whether Scx gene expression depends merely on TGFβ signaling or other signals is still not fully understood. In the present study, considering that WNT/β-catenin is an inhibitory signal of cell differentiation, we speculated possible antagonistic or additive effects between canonical Wnt/β-catenin and TGFβ/SMAD signaling pathways to control Scx gene expression. We found that the blockade of WNT/β-catenin promoted Scx gene expression. In contrast, the inhibition of TGFβ/SMAD signaling did not maintain Scx gene expression. Interestingly, the blockade of both WNT/β-catenin and TGFβ/SMAD signaling at the same time promoted Scx gene expression. Thus the inhibition of WNT/β-catenin signaling appears to be necessary and sufficient to induce Scx gene expression.

The adaptive role of amphibian oocyte melanic pigmentation and its molecular control are still elusive. Here we present evidence of a polymorphism in egg pigmentation in the emerald glass frog Espadarana prosoblepon. In Ecuadorian natural populations of this species, females can lay dark brown or pale eggs that develop into normal pigmented tadpoles and adults. This trait is a sex-limited phenotype which is inherited like a recessive allele that we called pale eggs like (pel). The pel phenotype is exclusive of oocyte cortical melanic pigmentation, which is reduced in comparison to wild type (wt) dark pigmented oocytes. Consequently, pel early embryos are paler in appearance, with reduced melanic pigmentation distributed to early blastomeres and embryonic ectoderm. However, these embryos form normal melanocyte derived pigmentation. Finally, we discuss the origin of this polymorphism and propose the use of E. prosoblepon as a model to study the adaptive role of egg pigmentation.

Background: Human induced pluripotent stem cells (hiPSCs) need to be thoroughly characterized to exploit their potential advantages in various aspects of biomedicine. The aim of this study was to compare the efficiency of cardiomyogenesis of two hiPSCs and two human embryonic stem cell (hESC) lines by genetic living cardiomyocyte labeling. We also analyzed the influence of spontaneous beating on cardiac differentiation.

Methods: H1 and H9 hESC lines and C2a and C6a hiPSC lines were induced into in vitro directed cardiac differentiation. Cardiomyogenesis was evaluated by the analysis of cell cluster beating, cardiac protein expression by immunocytochemistry, ability of cells to generate calcium transients, and cardiomyocyte quantification by the myosin light chain 2v-enhanced green fluorescent protein gene construct delivered with a lentiviral vector.

Results: Differentiation of all cell lines yielded spontaneously beating cell clusters, indicating the presence of functional cardiomyocytes. After the cell dissociation, H1-hESC-derived cardiomyocytes exhibited spontaneous calcium transients, corresponding to autonomous electrical activity and displayed ability to transmit them between the cells. Differentiated hESC and hiPSC cells exhibited striated sarcomeres and expressed cardiac proteins sarcomeric α-actinin and cardiac troponin T. Cardiomyocytes were the most abundant in differentiated H1 hESC line (20% more than in other tested lines). In all stem cell lines, cardiomyocyte enrichment was greater in beating than in non-beating cell clusters, irrespective of cardiomyogenesis efficiency.

Conclusion: Although C2a and C6a hiPSC and H9 hESC lines exhibited efficient cardiomyogenesis, H1 hESC line yielded the greatest cardiomyocyte enrichment of all tested lines. Beating of cell clusters promotes cardiomyogenesis in tested hESCs and hiPSCs.

Regeneration of lost or injured organs is an intriguing process in which numerous cellular events take place to form the new structure. Studies of this process during reconstitution of the intestine have been performed in echinoderms, particularly in holothurians. Many cellular events triggered during regeneration have been described using the sea cucumber Holothuria glaberrima as a research model. More recent experiments have targeted the molecular mechanisms behind the process, a task that has been facilitated by the new sequencing technologies now available. In this review, we present studies involving cellular processes and the genes that have been identified to be associated with the early events of gut regeneration. We also present ongoing efforts to perform functional studies necessary to establish the role(s) of the identified genes. A synopsis of the studies is given with the course of the regenerative process established so far.

Alejandro Sánchez Alvarado represents a younger generation of Latin American scientists that have achieved international scientific recognition. His work, together with that from other labs, has positioned the planaria Schmidtea mediterranea as a dynamic model system in which the cellular and molecular bases of regeneration in metazoans can be probed. During his professional career he has established strong ties with Latin America, hosting and training students and participating in seminars, workshops and courses throughout the region. In this interview he discusses his early scientific development and training, and his views on various issues related to the professional development of young scientists.

The development of multicellular organisms involves three main events: differentiation, growth, and morphogenesis. These processes need to be coordinated for a correct developmental program to work. Mechanisms of cell segregation and the formation of boundaries during development play essential roles in this coordination, allowing the generation and maintenance of distinct regions in an organism. These mechanisms are also at work in the nervous system. The process of regionalization involves first the patterning of the developing organism through gradients and the expression of transcription factors in specific regions. Once different tissues have been induced, segregation mechanisms may operate to avoid cell mixing between different compartments. Three mechanisms have been proposed to achieve segregation: (1) differential affinity, which mainly involves the expression of distinct pools of adhesion molecules such as members of the cadherin superfamily; (2) contact inhibition, which is largely mediated by Eph-ephrin signaling; and (3) cortical tension, which involves the actomyosin cytoskeleton. In many instances, these mechanisms collaborate in cell segregation. In the last three decades, there have been several advances in our understanding of how cell segregation and boundaries participate in the development of the nervous system. Interestingly, as in other aspects of development, the molecular players are remarkably similar between vertebrates and invertebrates. Here we summarize the main concepts of cell segregation and boundary formation, focusing on the nervous system and highlighting the similarities between vertebrate and invertebrate model organisms.

The mechanisms controlling evolutionary shifts between dry and fleshy fruits in angiosperms are poorly understood. In Solanaceae, Cestrum and Brugmansia represent cases of convergent evolution of fleshy and dry fruits, respectively. Here we study the anatomical and genetic bases of the independent origin of fleshy fruits in Cestrum and the reversion to dry dehiscent fruits in Brugmansia. We also characterize the expression of candidate fruit development genes, including ALCATRAZ/SPATULA, FRUITFULL, HECATE1/2/3, REPLUMLESS and SHATTERPROOF. We identify anatomical changes to establish developmental stages in the ovary-to-fruit transition in Cestrum nocturnum and Brugmansia suaveolens. We generate reference transcriptomes for both species, isolate homologs for all genes in the fruit genetic regulatory network (GRN) and perform gene expression analyses for ALC/SPT, FUL, HEC1/2/3, RPL and SHP throughout fruit development. Finally, we compare our results to expression patterns found in typical capsules of Nicotiana tabacum and berries of Solanum lycopersicum available in public repositories. We have identified homologous, homoplasious and unique anatomical features in C. nocturnum and B. suaveolens fruits, resulting in their final appearance. Expression patterns suggest that FUL, SHP and SPT might control homologous characteristics, while ALC and RPL likely contribute to homoplasious anatomical features. The fruit GRN changes considerably in these genera when compared to typical capsules and berries of Solanaceae, particularly in B. suaveolens, where expression of FUL2 and RPL1 is lacking.