Development Growth & Differentiation最新文献

Research in neuroscience has greatly benefited from the development of genetic approaches that enable lineage tracing, cell type targeting, and conditional gene regulation. Recent advances in combinatorial strategies, which integrate multiple cellular features, have significantly enhanced the spatiotemporal precision and flexibility of these manipulations. In this minireview, we introduce the concept and design of these strategies and provide a few examples of their application in genetic fate mapping, cell type targeting, and reversible conditional gene regulation. These advancements have facilitated in-depth investigation into the developmental principles underlying the assembly of brain circuits, granting experimental access to highly specific cell lineages and subtypes, as well as offering valuable new tools for modeling and studying neurological diseases. Additionally, we discuss future directions aimed at expanding and improving the existing genetic toolkit for a better understanding of the development, structure, and function of healthy and diseased brains.

We previously identified Xenopus tudor domain containing 6/Xenopus tudor repeat (Xtdrd6/Xtr), which was exclusively expressed in the germ cells of adult Xenopus laevis. Western blot analysis showed that the XTdrd6/Xtr protein was translated in St. I/II oocytes and persisted as a maternal factor until the tailbud stage. XTdrd6/Xtr has been reported to be essential for the translation of maternal mRNA involved in oocyte meiosis. In the present study, we examined the distribution of the XTdrd6/Xtr protein during oogenesis and early development, to predict the time point of its action during development. First, we showed that XTdrd6/Xtr is localized to germinal granules in the germplasm by electron microscopy. XTdrd6/Xtr was found to be localized to the origin of the germplasm, the mitochondrial cloud of St. I oocytes, during oogenesis. Notably, XTdrd6/Xtr was also found to be localized around the nuclear membrane of St. I oocytes. This suggests that XTdrd6/Xtr may immediately interact with some mRNAs that emerge from the nucleus and translocate to the mitochondrial cloud. XTdrd6/Xtr was also detected in primordial germ cells and germ cells throughout development. Using transgenic Xenopus expressing XTdrd6/Xtr with a C-terminal FLAG tag produced by homology-directed repair, we found that the zygotic translation of the XTdrd6/Xtr protein began at St. 47/48. As germ cells are surrounded by gonadal somatic cells and are considered to enter a new differentiation stage at this phase, the newly synthesized XTdrd6/Xtr protein may regulate the translation of mRNAs involved in the new steps of germ cell differentiation.

Abnormal expression of the transcriptional regulator and hedgehog (Hh) signaling pathway effector Gli3 is known to trigger congenital disease, most frequently affecting the central nervous system (CNS) and the limbs. Accurate delineation of the genomic cis-regulatory landscape controlling Gli3 transcription during embryonic development is critical for the interpretation of noncoding variants associated with congenital defects. Here, we employed a comparative genomic analysis on fish species with a slow rate of molecular evolution to identify seven previously unknown conserved noncoding elements (CNEs) in Gli3 intronic intervals (CNE15–21). Transgenic assays in zebrafish revealed that most of these elements drive activities in Gli3 expressing tissues, predominantly the fins, CNS, and the heart. Intersection of these CNEs with human disease associated SNPs identified CNE15 as a putative mammalian craniofacial enhancer, with conserved activity in vertebrates and potentially affected by mutation associated with human craniofacial morphology. Finally, comparative functional dissection of an appendage-specific CNE conserved in slowly evolving fish (elephant shark), but not in teleost (CNE14/hs1586) indicates co-option of limb specificity from other tissues prior to the divergence of amniotes and lobe-finned fish. These results uncover a novel subset of intronic Gli3 enhancers that arose in the common ancestor of gnathostomes and whose sequence components were likely gradually modified in other species during the process of evolutionary diversification.

Neural stem cells are multipotent stem cells that generate functional newborn neurons through a process called neurogenesis. Neurogenesis in the adult brain is tightly regulated and plays a pivotal role in the maintenance of brain function. Disruption of adult neurogenesis impairs cognitive function and is correlated with numerous neurologic disorders. Deciphering the mechanisms underlying adult neurogenesis not only advances our understanding of how the brain functions, but also offers new insight into neurologic diseases and potentially contributes to the development of effective treatments. The field of adult neurogenesis is experiencing significant growth in China. Chinese researchers have demonstrated a multitude of factors governing adult neurogenesis and revealed the underlying mechanisms of and correlations between adult neurogenesis and neurologic disorders. Here, we provide an overview of recent advancements in the field of adult neurogenesis due to Chinese scientists.

Neurons born during the fetal period have extreme longevity and survive until the death of the individual because the human brain has highly limited tissue regeneration. The brain is comprised of an enormous variety of neurons each exhibiting different morphological and physiological characteristics and recent studies have further reported variations in their genome including chromosomal abnormalities, copy number variations, and single nucleotide mutations. During the early stages of brain development, the increasing number of neurons generated at high speeds has been proposed to lead to chromosomal instability. Additionally, mutations in the neuronal genome can occur in the mature brain. This observed genomic mosaicism in the brain can be produced by multiple endogenous and environmental factors and careful analyses of these observed variations in the neuronal genome remain central for our understanding of the genetic basis of neurological disorders.

With advances in high-throughput, large-scale in vivo measurement and genome modification techniques at the single-nucleotide level, there is an increasing demand for the development of new technologies for the flexible design and control of cellular systems. Computer-aided design is a powerful tool to design new cells. Whole-cell modeling aims to integrate various cellular subsystems, determine their interactions and cooperative mechanisms, and predict comprehensive cellular behaviors by computational simulations on a genome-wide scale. It has been applied to prokaryotes, yeasts, and higher eukaryotic cells, and utilized in a wide range of applications, including production of valuable substances, drug discovery, and controlled differentiation. Whole-cell modeling, consisting of several thousand elements with diverse scales and properties, requires innovative model construction, simulation, and analysis techniques. Furthermore, whole-cell modeling has been extended to multiple scales, including high-resolution modeling at the single-nucleotide and single-amino acid levels and multicellular modeling of tissues and organs. This review presents an overview of the current state of whole-cell modeling, discusses the novel computational and experimental technologies driving it, and introduces further developments toward multihierarchical modeling on a whole-genome scale.

Monoaminergic systems are conserved in vertebrates, yet they present variations in neuroanatomy, genetic components and functions across species. MonoAmine Oxidase, or MAO, is the enzyme responsible for monoamine degradation. While mammals possess two genes, MAO-A and MAO-B, fish possess one single mao gene. To study the function of MAO and monoamine homeostasis on fish brain development and physiology, here we have generated a mao knockout line in Astyanax mexicanus (surface fish), by CRISPR/Cas9 technology. Homozygote mao knockout larvae died at 13 days post-fertilization. Through a time-course analysis, we report that hypothalamic serotonergic neurons undergo fine and dynamic regulation of serotonin level upon loss of mao function, in contrast to those in the raphe, which showed continuously increased serotonin levels – as expected. Dopaminergic neurons were not affected by mao loss-of-function. At behavioral level, knockout fry showed a transient decrease in locomotion that followed the variations in the hypothalamus serotonin neuronal levels. Finally, we discovered a drastic effect of mao knockout on brain progenitors proliferation in the telencephalon and hypothalamus, including a reduction in the number of proliferative cells and an increase of the cell cycle length. Altogether, our results show that MAO has multiple and varied effects on Astyanax mexicanus brain development. Mostly, they bring novel support to the idea that serotonergic neurons in the hypothalamus and raphe of the fish brain are different in nature and identity, and they unravel a link between monoaminergic homeostasis and brain growth.

In birds, primordial germ cells (PGCs) use the bloodstream to travel to a specific region, where the cells undergo extravasation followed by intrastromal migration to the gonadal crest for further colonization. Currently, DDX4, SSEA1, and Oct4 are used to identify germ cells. Other germline cell-associated molecules are N-cadherin, GnRHR, and 3β hydroxysteroid dehydrogenase (3βHSD), which have been used in mice and birds during gonadal development; however, its role in early gonadogenesis in birds is poorly described. This study aimed to evaluate the differential immunodetection of N-cadherin binding molecule, Oct4 pluripotency protein, GnRHR receptor, and 3βHSD enzyme in Columba livia embryos during migration colonization of PGCs in the gonadal crest and early gonadogenesis. These markers were revealed by immunohistochemistry in histological preparations of C. livia corresponding to stages (S)15 to S40. Immunodetection of N-cadherin, Oct4, GnRHR, and 3βHSD in the germ line of C. livia allowed the identification of PGCs in the yolk sac membrane at the level of the splanchnic mesoderm during migration to the genital crest and its colonization. In the same way, it was possible to characterize and localize PGCs during early gonadogenesis. This study in C. livia demonstrates that Oct4, N-cadherin, GNRHR, and 3βHSD are immunodetected in PGCs and could be used as potential germline cell markers during cell migration out of blood vessels, colonization in the genital crest, and early gonadogenesis. Furthermore, this study could be used as a novel general model to understand the early gonadogenesis in altricial species.