Developmental Dynamics最新文献

Background: Robinow syndrome is a rare developmental syndrome caused by variants in genes in Wnt signaling pathways. We previously showed that expression of patient variants in Dishevelled 1 (DVL1) in Drosophila and chicken models disrupts the balance of canonical and non-canonical Wnt signaling.

Results: In this study, we further examine morphological changes that occur due to expression of DVL1^1519ΔT, which serves as a prototype for other pathogenic variants. We show that epithelial imaginal disc development is disrupted in legs and wings and accompanied by increased cell death, without changes in cell proliferation. By inhibiting caspase-dependent cell death, we show that the altered epithelial morphology is not solely due to variant-induced cell death. Furthermore, we find alterations of basement membrane components and modulators. Notably we find ectopic Mmp1 expression and tissue distortion, which is dependent on JNK signaling. We also find an abnormal abundance of Drosophila collagen IV (Viking) in pupal wing development. Due to the complex nature of appendage development, we also examined the Bone Morphogenetic Protein pathway and found elevated signaling activity via the transcriptional readout dad-lacZ.

Conclusions: Through these studies, we have gained more insight into the developmental consequences of DVL1 variants implicated in autosomal dominant Robinow syndrome.

Background: In eutherian mammals, the embryonic cloaca is partitioned into genitourinary and anorectal canals by the urorectal septum. In the mouse embryo, the urorectal septum contributes to the perineum, which separates the anus from the external genitalia. During the growth of the urorectal septum, endodermal epithelium of the cloaca is displaced to the surface of the perineum, where endodermal cells are integrated into the developing skin. However, it is unknown whether the endodermal lineage of the perineum acquires true epidermal identity, an enigmatic fate for endodermal cells.

Results: We find that endodermal cells that reach the surface of the perineum express markers of basal, spinous, and granular epidermis. During postnatal development, the endodermal lineage of the perineum epidermis undergoes terminal differentiation and desquamation and is replaced by adjacent ectoderm. Live imaging and single-cell tracking show that ectodermal cells move at a faster velocity in a lateral-to-medial direction, indicating convergence toward the narrow band of endoderm that lies between the anus and external genitalia.

Conclusions: Cloacal endoderm differentiates into a non-renewing, transient epidermis at the midline of the perineum. Differences in directionality and velocity of cell movement patterns between endodermal and ectodermal cells suggest that the perineum epidermis develops by convergent extension.

Background: Schwann cells provide peripheral nerve trophic support, myelinate axons, and assist in repair. However, Schwann cell repair capacity is limited by chronic injury, disease, and aging. Schwann cell reprogramming is a cellular conversion strategy that could provide a renewable cell supply to repair injured nerves. Here, we developed a plasmid-based approach to test the Schwann cell conversion potential of four glial transcription factors.

Results: We employed four transcription factors implicated in Schwann cell differentiation and repair: Sox10, Sox2, Jun, and Pax3. Expression vectors were generated for Sox10 alone and two triple transcription factor combinations: Jun-Pax3-Sox2 (triple 1, T1) and Sox10-Jun-Sox2 (triple 2, T2). Mouse embryonic fibroblasts (MEFs) were transfected with these vectors, transferred to glial inductive media, and Schwann cell-marker expression was in assessed by immunostaining, flow cytometry, and qPCR. All expression vectors repressed fibroblast-specific gene expression. However, T2 was most efficient at generating O4⁺ Schwann cell-like cells, which had some capacity to myelinate denervated axons from explanted dorsal root ganglia. In comparison, T1 more efficiently induced repair Schwann cell-marker expression in converted O4⁺ cells.

Conclusions: T1 and T2 convert MEFs to Schwann cells with different efficacies and gene expression profiles, and may provide cell-based therapies for peripheral nerve repair.

Background: Dentitions have diversified enormously during vertebrate evolution, involving reductions, modifications, or allocations to prey seizing and processing regions. A combination of ancient and novel features related to dental and oropharyngeal apparatuses is found in extant lineages of non-teleost fishes, such as the gars. While relevant to evolutionary-developmental studies, gars have largely been overlooked regarding how their dentition arises, thus leaving our comprehension of the evolutionary history of vertebrate dentitions incomplete.

Results: Here, we complement this knowledge gap by studying dental development in the tropical gar, Atractosteus tropicus. We follow ontogenetic changes from the initiation, tooth germ addition to the establishment of the larval replacing dentition. We pay attention to the progressive appearance of tooth fields, the emergence of dental patterns, the development of folded dentin morphology, and features related to tooth resorption and replacement. Furthermore, we identify snout elongation as the critical period when the general dentition layout becomes established.

Conclusions: Our study depicts the gar oropharyngeal apparatus as a system that is established based on patterned initiation, differential growth, replacement, and complex shaping of teeth. These features form a reference standpoint for the likely developmental processes employed in dentitions of fossil stem and crown bony vertebrates, including ray-finned fishes and tetrapods.

Background: Midline establishment is a fundamental process during early embryogenesis for Bilaterians. Midline morphogenesis in non-amniotes can occur without mitosis, through Planar Cell Polarity (PCP) signaling. By contrast, amniotes utilize both cellular processes for developing the early midline landmark, the primitive streak (PS). This study focused on the role of cell proliferation for midline development at pre- and post-PS-extension stages and analyzed PCP signaling components at post-PS-extension stages.

Results: In contrast to pre-PS-extension stages, embryos under mitotic arrest during the post-PS-extension preserved notochord (NC) extension and Hensen's node (HN)/PS regression judged by both morphology and marker genes; although they became shorter, their lengths remained proportional to the embryo length. Laterality and segmentation of paraxial mesoderm were lost upon mitotic arrest. Accompanied by mitotic arrest-induced embryonic size reduction, cells including midline tissue displayed hypertrophy.

Conclusion: This study has identified at least two distinct mitosis sensitivity phases during early midline development: One is PS extension that requires both mitosis and PCP, and the other is mitotic arrest-resistant midline development at post-PS-extension stages, with a still undefined influence by PCP signaling components.

Background: RSPO1 and FOXL2 are female sex-determining genes involved in the differentiation and organization of the ovary in some eutherian mammals. Mutations or loss of function of these genes are associated with partial to full sex reversal in mice, humans, and goats. RUNX1 may also play a role in ovarian development, but its expression in marsupials has not been examined as yet. We studied the conservation and protein localization of RSPO1, FOXL2, and RUNX1 orthologs in the marsupial tammar wallaby (Notamacropus eugenii) compared to other vertebrates.

Results: RSPO1, FOXL2, and RUNX1 were highly conserved in their sequences across all vertebrates examined. The localization of these proteins in the tammar ovary was studied from Day 18 postpartum to adulthood. RSPO1, FOXL2, and RUNX1 were expressed in the granulosa cells of the early ovary and granulosa cells of the mature ovary, while RSPO1 expression was also found in the intra-ovarian rete and cell membrane of germ cells during the period of germ cell meiosis and meiotic arrest.

Conclusions: RSPO1, FOXL2, and RUNX1 are highly conserved in the vertebrate ovary-determining pathway and were expressed in the tammar wallaby in a manner consistent with their role in the ovarian differentiation of eutherian mammals.

Background: Previous experiments inducing leakage of embryonic cerebrospinal fluid (CSF) suggest the necessity of intraventricular CSF pressure (P_CSF) for brain morphogenesis. Nevertheless, how embryonic P_CSF occurs is unclear, especially in utero.

Results: Using a Landis water manometer, we measured P_CSF in fetal mice isolated from the amniotic cavity (P_CSF-ISO) and found that P_CSF-ISO rose from 20 Pa at embryonic day (E) 10 to 100-110 Pa at E14-16. At E13, intraventricular injections of ≥3 μL of saline elevated P_CSF-ISO by ~30%, whereas those of inhibitors of CSF secretion decreased P_CSF-ISO by ~30%. Shh-mediated cerebral wall expansion did not significantly increase P_CSF-ISO. Removal of the brain-surrounding contractile tissues decreased P_CSF-ISO by 80%-90%. We then found that the intraamniotic pressure measured in utero (P_AF-IU) declined from 2000 Pa at E10 to 500 Pa at E15-18 but was always much greater than P_CSF-ISO. Direct measurement of P_CSF in utero (P_CSF-IU) at E13 and E15 coupled with the measurement of P_CSF-ISO under hydrostatic pressure loading to mimic P_AF-IU at various embryonic ages revealed the following relationship: P_CSF-IU = P_CSF-ISO + P_AF-IU.

Conclusions: The P_CSF of mice in utero is influenced by external factors, most strongly by intraamniotic pressure and less strongly by brain-confining tissues.