Development Growth & Differentiation最新文献

The mammalian neocortex is characterized by tangential surface expansion and a six-layer layered structure. However, developmental mechanisms underlying the evolution of the neocortex remain to be elucidated. We hold the symposium entitled “Genetic and developmental bases for mammalian neocortical evolution” was held on June 22, 2024, at Kyoto as an official symposium in the annual meeting of Japanese Society for Developmental Biologists. Selected speakers presented their recent findings on mammalian neocortical development and evolution, sharing exciting results with the audience.

As skin ages, its structure and function undergo significant transformations driven by complex cellular and molecular processes. In this study, we explore these changes using the axolotl, an amphibian model known for its transparent skin, allowing detailed observation of both epidermal and dermal layers. We found that axolotl skin, composed of an epidermis and a collagen-rich dermis with three distinct layers (stratum baladachinum, spongiosum, and compactum), shows clear age-related alterations. These changes include reduced fibroblast numbers, altered lattice-patterned cell morphology, disruption of the lattice patterned collagen fiber pattern, thickening the stratum spongiosum, and thinning of the stratum compactum. Notably, fibroblasts, which play a crucial role in collagen braiding, displayed diminished functionality in older axolotls. This study highlights how aging affects both the structural integrity of dermal collagen and cellular dynamics. Given the similarity between axolotl and mammalian skin, these findings may provide valuable insights into the mechanisms of skin aging and potential avenues for anti-aging therapies. This research offers a foundation for future studies aimed at understanding skin aging and regeneration.

The adap1 (ADP-ribosylation factor GTPase-activating protein [ArfGAP] with dual pleckstrin homology [PH] domains 1) gene is predominantly expressed in the mouse brain and is important in neural differentiation and development. However, the functions of adap1 in morphogenesis, locomotor activity, and behaviors in vertebrates are not fully understood. Whole-mount in situ hybridization (WISH) analysis revealed that adap1 was widely expressed in the zebrafish brain, including the forebrain, midbrain, and hindbrain, during early embryogenesis. To investigate the physiological function of the adap1 gene, we generated zebrafish adap1 mutants harboring frameshift mutations around codon 120 of adap1. The adap1 mutants containing homozygous mutant alleles exhibited no apparent morphological abnormalities at 1 day postfertilization (dpf), and the spontaneous coiling and touch response of the adap1 mutants were comparable to those of the wild-type fish. In addition, the expression of neural genes, such as emx1, mbx, and huC, was comparable between the wild-type fish and the adap1 mutants at 1 dpf. The adap1 mutants grew to adulthood without exhibiting any apparent swimming defects. The adult adap1 mutants spent more time than the wild type in the center region of the open field test. In the social behavior test, zebrafish containing the adap1 mutant alleles spent more time than the wild type in the regions near the chambers where novel conspecifics swam. These results imply the involvement of the adap1 gene in regulating approach behavior to visual cues from conspecifics.

Granule cells in the cerebellum are the most numerous neurons in the vertebrate brain. They are derived from neural progenitor cells that express the proneural gene atoh1 (atoh1a, b, c in zebrafish) during early neurogenesis. In zebrafish, unlike in mammals, granule cells are continuously produced throughout life, from the larval stage to adulthood. Additionally, granule cells regenerate and replace damaged areas following injury in the adult cerebellum. However, the mechanisms underlying granule cell generation and their role in adult cerebellar regeneration remain largely unclear. In this study, using lineage tracing with the inducible DNA recombinase CreERT2, we found that granule cells differentiated from atoh1c-expressing neural progenitor cells and migrated to their appropriate locations in the adult stage, similar to the processes observed during early embryogenesis. Granule cells that differentiated from atoh1c-expressing neural progenitor cells in adulthood also contributed to cerebellar regeneration. Furthermore, inhibition of transforming growth factor-β (TGF-β) signaling, either via chemical inhibitors or CRISPR/Cas9, suppressed atoh1a/c expression and reduced granule cell numbers in larvae. Chemical inhibition of TGF-β signaling also suppressed neural progenitor cell proliferation, atoh1c expression, and granule cell neurogenesis in the adult cerebellum. These findings demonstrate that TGF-β signaling is essential for granule cell production from progenitor cells throughout the lifespan of zebrafish.

In previous studies, we have established approximately 15 cultured cell-lines derived from planula larvae of Acropora tenuis. Based on their morphology and behavior, these cells were classified into three types, flattened amorphous cells (FAmCs), vacuolated adherent cells (VAdCs), and small smooth cells (SSmCs). FAmCs include fibroblast-like cells and spherical, brilliant brown cells (BBrCs), which are transformable to each other. To examine the larval origin of the three cell types, we raised antibodies: anti-AtMLRP2 that appears to recognize FAmC, anti-AtAHNAK for BBrC, anti-AtSOMP5 and anti-AtEndoG for SSmC, and anti-AtGal and anti-AtFat4 for VAdC, respectively. Anti-AtMLRP2 antibody stained in vivo stomodeum and neuroblast-like cells embedded in larval ectoderm around the aboral pole. Anti-AtAHNAK antibody stained neuron-like and neuroblast-like cells, both of which were also stained with neuron-specific tubulin β-3 antibody. These results suggest that in vitro BBrCs and in vivo neuroblast-like cells share neuronal properties in common. Two antibodies for SSmCs, anti-AtSOMP5 and anti-AtEndoG, stained larval ectoderm cells, suggesting that SSmCs have larval ectoderm properties. Two antibodies for VAdCs, anti-AtGal and anti-AtFat4, stained larval endoderm cells, suggesting that VAdCs have larval endoderm properties. Therefore, the in vitro cell lines appear to retain properties of the stomodeum, neuroblast, ectoderm, or endoderm. Each of them may be used in future investigations to reveal cellular and molecular properties of cell types of coral larvae, such as the potential for symbiosis.

In the M-phase, the nuclear membrane is broken down, nucleosomes are condensed as mitotic chromosomes, and transcription factors are generally known to be dislocated from their recognition sequences and dispersed to the cytoplasm. However, some transcription factors have recently been reported to remain on mitotic chromosomes and facilitate the rapid re-activation of the target genes in early G1-phase. Paired-like homeobox 2B (PHOX2B) is a transcription factor exhibiting chromosomal localization during M-phase. PHOX2B mutations are associated with congenital central hypoventilation syndrome, Hirschsprung disease, and neuroblastoma. In this study, we investigated PHOX2B chromosomal localization during M-phase through immunostaining and fluorescence recovery after photobleaching analysis to determine whether the chromosomal localization of disease-associated PHOX2B mutants is altered during M-phase. Missense mutations in the homeodomain and the frameshift mutation in the C-terminal domain disrupted the chromosomal localization of PHOX2B in M-phase, leading to its dispersion in the cell. Furthermore, a PHOX2B mutant with polyalanine expansion showed a line-shaped localization to the restricted region of mitotic chromosomes. Our findings suggest an association between the disease-associated mutations and defective chromosomal localization of transcription factors during M-phase. Further investigations of PHOX2B chromosomal localization during M-phase could reveal pathogenic mechanisms of such diseases.

Previous studies have shown that tissue regeneration induces expression of genes that play important roles in regeneration. Recently, several studies have identified regeneration-response enhancers (RREs) that activate gene expression by tissue injury. Particularly, we showed that RREs contain two transcription factor-binding motifs: a bHLH transcription factor-binding motif, an E-box, and an AP-1/bZIP transcription factor-binding motif, a 12-O-Tetradecanoylphorbol 13-acetate response element (TRE). However, the triggers and subsequent signals generated by injury are still unclear. In this study, we analyzed RRE activation using various injury models. Although inter-ray incisions and skin exfoliation injuries did not activate RREs or regeneration genes, the fin puncture injury activated RREs and several regeneration-response genes. After fin puncture injury, msxc was activated only on the proximal side of the hole where blastema-like tissue was formed, whereas RREs, junbb, and fibronectin 1b (fn1b) were activated on both the proximal and distal sides, implying that activation of RREs, junbb, and fn1b is independent of blastema formation. Here, we also established a mild cryoinjury method. After this injury, transient vascular destruction, an increase in cell death, and an accumulation of myeloid cells were observed; however, no major morphological damage was observed. Importantly, msxc was not induced by cryoinjury, whereas fn1b, junbb, and 1.8 k RRE (−1.8 kb promoter of fn1b) were activated, suggesting that cryoinjury induces the responses of fn1b, junbb, and 1.8 k RRE without forming the blastema. Thus, our study shows that the cryoinjury model and the RRE transgenic (Tg) zebrafish may provide a useful platform for exploring injury signals.

The usefulness of zebrafish for understanding the human nervous system is exemplified by the articles in part 1. The virtual special issue part 2 not only covers more work using this well-established species, but also highlights that other fish species may serve as alternative or more appropriate models, due to unique biological or evolutionary characteristics, to explore genetic and molecular mechanisms of neurological and psychiatric disorders.

Animals vary in their ability to replace body parts lost to injury, a phenomenon known as restorative regeneration. Uncovering conserved signaling steps required for regeneration may aid regenerative medicine. Reactive oxygen species (ROS) are necessary for proper regeneration in species across a wide range of taxa, but it is unknown whether ROS are essential for annelid regeneration. As annelids are a widely used and excellent model for regeneration, we sought to determine whether ROS play a role in the regeneration of the highly regenerative annelid, Lumbriculus variegatus. Using a ROS-sensitive fluorescent probe we observed ROS accumulation at the wound site within 15 min after amputation; this ROS burst lessened by 6 h post-amputation. Chemical inhibition of this ROS burst delayed regeneration, an impairment that was partially rescued with exogenous ROS. Our results suggest that similar to other animals, annelid regeneration depends upon ROS signaling, implying a phylogenetically ancient requirement for ROS in regeneration.

The 16th Japanese Drosophila Research Conference (JDRC16) was held at the Sendai International Center from September 17 to 19 2024. It had been 2 years since the last JDRC15 held in Nagoya. The conference brought together 231 researchers, including 22 researchers from overseas, creating a vibrant and diverse platform for scientific exchange. Prof. Shigeo Hayashi of RIKEN BDR delivered a keynote lecture, and his groundbreaking ideas and research captivated the audience. Over the 3 days, the conference featured 53 oral presentations across 11 sessions and 2 special sessions, as well as 128 poster presentations, all of which fostered stimulating discussions and the exchange of innovative ideas. The reception provided an additional opportunity for researchers to engage in meaningful dialogue while enjoying Sendai's renowned specialties. Held under clear autumn skies in a great nature along the river, this conference painted a beautiful contrast to the heated discussions in the venue. Consequently, this conference fully contributed to the mission proffered by Prof. Hayashi, “Fly to New World,” expanding the insights gained from flies into new and unexplored scientific areas.