Developmental Dynamics最新文献

Background: Endocytosis of enamel matrix proteins (EMPs) by ameloblasts is a key process in the mineralization of enamel during the maturation stage of amelogenesis. However, the relevant receptor mediating endocytosis of EMPs is still unclear. The aim of this study was to explore potential endocytic receptors involved in this process.

Results: Two endocytic receptors, megalin, and cubilin, were found to be distributed in ameloblasts of mouse incisors and molars during the secretory and maturation stages. Megalin was located at the distal end of ameloblasts during the maturation stage when proteolysis and recycling were the most active. Megalin and cubilin were also expressed in an ameloblast-lineage cell (ALC) line. The immunoelectron microscopy results showed that megalin was positively labeled on the vesicle structures of ALC, where endocytosis happened. Immunofluorescence showed that megalin and cubilin were colocalized with amelogenin, and the absorption of amelogenin was significantly reduced when megalin and cubilin were inhibited by their inhibitor, receptor-associated protein (RAP). Knockdown of megalin and cubilin with siRNA also reduced the ability of ALC to absorb amelogenin.

Conclusions: The results of this study suggest that megalin and cubilin are involved in the absorption process of ameloblasts during amelogenesis.

Disruption of extracellular pH and proton-sensing can profoundly impact cellular and protein functions, leading to developmental defects. To visualize changes in extracellular pH in the developing embryo, we generated a zebrafish transgenic line that ubiquitously expresses the ratiometric pH-sensitive fluorescent protein pHluorin2, tethered to the extracellular face of the plasma membrane using a glycosylphosphatidylinositol (GPI) anchor. Monitoring of pHluorin2 with ratiometric fluorescence revealed dynamic and discrete domains of extracellular acidification over the first 72 h of embryonic development. These included acidification of the notochord intercalations, transient acidification of the otic placode, and persistent acidification of the extracellular space of the myotome at distinctly different pH from that within the T-tubules. Knockdown of centronuclear myopathy genes Bin1b (OMIM: 255200) and MTM1 (OMIM: 310400), which disrupt T-tubule formation, also disrupted myotome acidification. In this study we visualize extracellular acidic microdomains in the tissues of whole live animals. This real-time reporter line for directly measuring changes in extracellular pH can be used to illuminate the role of extracellular pH in normal physiological development and disease states.

Background: Previous studies with Gfi1-mutated lines have shown that Gfi1 is essential for hair cell maturation and survival.

Results: We analyzed the phenotype of another Gfi1-mutated line Gfi1^GFP/GFP in the inner ears of neonates at P5-7 and found that the cochlea phenotypically differed from the vestibule in the Gfi1^GFP/GFP mouse. Specifically, there was a marked reduction in hair cells in the cochlea, which was characterized by greater reductions in the outer hair cells but far less reductions (mainly in the basal turn) in the inner hair cells, whereas the vestibular hair cells remained unaffected. These results were consistent with findings from previous studies. Unexpectedly, the number of cochlear non-sensory supporting cells significantly decreased. However, the vestibular supporting cells did not demonstrate any abnormalities in number.

Conclusion: Gfi1 exhibits different functions in the cochlea and vestibule during inner ear development.

Background: Insights into the development and evolution of asymmetrical jaws will require an understanding of the gene regulatory networks that underpin the differential morphogenesis of the maxillary and mandibular domains of the first pharyngeal arch in a variety of gnathostomes. While a robust relationship has been demonstrated between jaw patterning and the Endothelin-Dlx gene axis, much less is known of the next level of genes in the jaw patterning hierarchy.

Results: Several genes, whose expression depends on Dlx5 and/or Dlx6, have been identified in mice. Here, we examined the expression patterns of the chick orthologues of some of those genes, namely GSC, PITX1, HAND2, and GBX2, and tested their dependence on endothelin signaling to assess whether there is a conserved regulatory relationship between those genes in the chick embryo. To further validate these genes as direct DLX targets, we identified conserved non-coding sequences containing candidate DLX binding motifs and demonstrated DLX-responsiveness in vitro.

Conclusions: The evidence presented in this study combines to support the hypothesis that these four genes are direct targets of DLX transcription factors in the lower jaw-forming tissue.

Background: The FOXOs regulate the transcription of many genes, including ones directly linked to pathways required for lens development. However, this transcription factor family has rarely been studied in the context of development, including the development of the lens. FOXO expression, regulation, and function during lens development remained unexplored.

Results: In studies of the embryonic lens, we showed that both FOXO1 and FOXO4, which share many downstream targets, are expressed in a differentiation-state-specific manner, most highly in lens epithelial and differentiating cortical fiber cells. Their expression patterns and subcellular distributions suggest both shared and distinct functions. Stabilization of FOXO cytoplasmic pools involved their binding to the chaperone protein 14-3-3. FOXO association with β-catenin linked this transcription complex to fiber cell-specific gene activation. Inhibition of PI3K/Akt signaling promoted FOXO1/FOXO4 nuclear localization in lens epithelial and fiber cells and expression of the CDKi p27 in the lens epithelium where it has been linked to lens cell withdrawal from the cell cycle and initiation of the lens differentiation program. We showed that FOXO1 transcriptional activation is required for the induction of p27 when Akt signaling is blocked, demonstrating the linearity of the PI3K/Akt/FOXO1/p27 pathway.

Conclusions: PI3K/Akt signaling regulates FOXO-dependent lens cell differentiation.

Background: Perfluoroalkyl substances (PFAS) are persistent environmental contaminants previously used for industrial purposes as a non-stick coating and flame retardant. The stability of these molecules prevents their breakdown, which results in ground water contamination across the globe. Perfluoroalkyl substances molecules are known to bioaccumulate in various organisms. However, the health consequences remain unclear due to the large number of molecules in the PFAS family and different effects on various tissues. Here, we use the frog Xenopus laevis to investigate the developmental consequences of exposure to the PFAS molecule perfluoro-octanoic sulfonate (PFOS).

Results: We find that exposure to high levels of PFOS results in significant axial shortening of developing tadpoles. Further, we find that PFOS exposure results in a dose-dependent formation of a cellular mass in the dorsal fin. Unexpectedly, we found that these developmental phenotypes are exacerbated upon co-exposure with commonly used antibiotics. Specifically, PFOS and gentamicin co-treatment results in increased apoptosis, loss of cellular integrity, and increased overall lethality.

Conclusions: Our results suggest a mechanism whereby gentamicin reaches levels that are toxic to mitochondria only in the presence of PFOS. These findings add to our understanding of PFOS exposure to vertebrate development and present an added concern with potential interactions with antibiotics.

Background: The pancreas exhibits diverse structures and roles across vertebrates. The pancreas has evolved to include both endocrine and exocrine cells, a change that occurred during the transition from fish to amphibian. This event emphasizes the evolutionary significance of amphibians. However, research has focused predominantly on anuran amphibians, with urodeles, such as newts, remaining underexplored. In this study, we investigated the development of the pancreas using Pleurodeles waltl as a model species of urodele.

Results: The newt pancreas consists of a single organ with exocrine tissue characterized by acinar structures and endocrine tissue forming islets. Notably, the newt possesses unique pancreas-like tissues on their intestines. We found that disruption of the newt Pancreatic and Duodenal Homeobox (Pdx) 1 gene resulted in an underdeveloped pancreas. Conversely, disruption of the Pdx2 paralog in newt had no significant impact on pancreatic development.

Conclusion: The newt pancreas shows a morphology similar to that of the mammalian pancreas, which includes both exocrine and endocrine tissues. These results highlight the intermediate evolutionary position of the newt in the context of the evolution of pancreatic development. Our findings indicate that characterization of the newt pancreas will be crucial for understanding the evolutionary progression of pancreatic function in vertebrates.

Background: Conjunctival placodes are a series of placodes that develop into the conjunctival (scleral) papillae and ultimately induce a series of scleral ossicles in the eyes of many vertebrates. This study establishes a hydrocortisone injection procedure (incl. dosage) that consistently inhibits all conjunctival papillae in the embryonic chicken eye. The effects of this hydrocortisone treatment on apoptosis, vasculature, and placode-related gene expression were assessed.

Results: Hydrocortisone treatment does not increase apoptotic cell death or have a major effect on the ciliary artery or vascular plexus in the eye. β-catenin and Eda expression levels were not significantly altered following hydrocortisone treatment, despite the absence of conjunctival papillae. Notably, Fgf20 expression was significantly reduced following hydrocortisone treatment, and the distribution of β-catenin was altered.

Conclusions: Our study showed that conjunctival papillae induction begins as early as HH27.5 (E5.5). Hydrocortisone treatment reduces Fgf20 expression independently of β-catenin and Eda and may instead affect other members of the Wnt/β-catenin or Eda/Edar pathways, or it may affect the ability of morphogens to diffuse through the extracellular matrix. This study contributes to a growing profile of gene expression data during placode development and enhances our understanding of how some vertebrate eyes develop these fascinating bones.

Background: Theory predicts that drought-resistant embryos with extended incubations are evolutionarily favored in environments with high mortality of larvae but safe for eggs. Here, we experimentally test, under common garden conditions, the effect of three incubation temperatures and media on embryonic developmental length, extended incubation out of the water, survival, metabolic rate, and hatching dynamics in the estuarine pupfish Garmanella pulchra. We also described the morphological changes of embryonic cortical structures related to air exposure.

Results: We found that embryos incubated out of water in low and medium temperatures present an extended incubation period beyond their hatching capability with a deep metabolic depression. Also, these embryos exhibited a hatching asynchrony not related to water availability. Embryos incubated at high temperatures did not show extended incubation, with decreased probability of survival out of water. Our morphological observations of the embryonic cortical structures reveal that the perivitelline space and hair-like filaments buffer the deleterious drought effects.

Conclusions: Our results reveal that G. pulchra possesses life-history traits typical of two separate phenomena: delay hatching and diapause; supporting a true continuum between them, rather than a dichotomy. The evolution of these traits may respond to aerial exposure during low tides in the estuaries of Yucatán they inhabit.