Optogenetic Rescue of a Patterning Mutant

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数量性状发育遗传模型及其分析方法的研究进展

发育遗传模型是同时反映性状遗传和发育本质、提供影响遗传变异及调整发育进程的有关因素的信息的模型。建立在群体遗传学基础上的直接效应模型适用于单一基因控制的简单性状。渐成模型将遗传变异分解成直接分量和渐成分量(母体效应和互作效应),能更好地反映有机体遗传和发育的生物学机制。生长轨迹模型有效地综合了复杂性状各分量的发育动态,可获得连续的、综合的、详细的、动态的发育信息。条件遗传分析方法不仅可以估算特定时间段的净效应,且可将净效应分解为不同遗传分量,了解各效应分量的相对贡献。 Abstract：Developmental genetic models and analysis methods for quantitative traits are presented.Developmental genetic models should reflect the genetic and developmental essence,and provide the information of the factors influencing the genetic variation and the developmental process.Direct effect models,which based on the population genetics,may be suitable to analyze simple traits with single gene.Epigenetic models can decompose the whole genetic variation into direct and epigenetic components (maternal effects and epigenetic interaction effects),so that biological mechanism can be better understood.Growth trace models effectively synthesize the developmental dynamics of components of complex traits.With them,continuous,compositive,detailed,and dynamic information of development is available.Conditional analysis method can not only estimate the net effects in a specific time interval,but also depose them into genetic components and help to appreciate the contributions of different effects.     

Optogenetic manipulation identifies the roles of ERK and AKT dynamics in controlling mouse embryonic stem cell exit from pluripotency

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The benefits of local depletion: The centrosome as a scaffold for ubiquitin-proteasome-mediated degradation

The centrosome is the major microtubule-organizing center in animal cells but is dispensable for proper microtubule spindle formation in many biological contexts and is thus thought to fulfill additional functions. Recent observations suggest that the centrosome acts as a scaffold for proteasomal degradation in the cell to regulate a variety of biological processes including cell fate acquisition, cell cycle control, stress response, and cell morphogenesis. Here, we review the body of studies indicating a role for the centrosome in promoting proteasomal degradation of ubiquitin-proteasome substrates and explore the functional relevance of this system in different biological contexts. We discuss a potential role for the centrosome in coordinating local degradation of proteasomal substrates, allowing cells to achieve stringent spatiotemporal control over various signaling processes.     

Genetic reporter for live tracing fluid flow forces during cell fate segregation in mouse blastocyst development

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hlh-12, a gene that is necessary and sufficient to promote migration of gonadal regulatory cells in Caenorhabditis elegans,evolved within the Caenorhabditis clade

Specialized cells of the somatic gonad primordium of nematodes play important roles in the final form and function of the mature gonad. Caenorhabditis elegans hermaphrodites are somatic females that have a two-armed, U-shaped gonad that connects to the vulva at the midbody. The outgrowth of each gonad arm from the somatic gonad primordium is led by two female distal tip cells (fDTCs), while the anchor cell (AC) remains stationary and central to coordinate uterine and vulval development. The bHLH protein HLH-2 and its dimerization partners LIN-32 and HLH-12 had previously been shown to be required for fDTC specification. Here, we show that ectopic expression of both HLH-12 and LIN-32 in cells with AC potential transiently transforms them into fDTC-like cells. Furthermore, hlh-12 was known to be required for the fDTCs to sustain gonad arm outgrowth. Here, we show that ectopic expression of HLH-12 in the normally stationary AC causes displacement from its normal position and that displacement likely results from activation of the leader program of fDTCs because it requires genes necessary for gonad arm outgrowth. Thus, HLH-12 is both necessary and sufficient to promote gonadal regulatory cell migration. As differences in female gonadal morphology of different nematode species reflect differences in the fate or migratory properties of the fDTCs or of the AC, we hypothesized that evolutionary changes in the expression of hlh-12 may underlie the evolution of such morphological diversity. However, we were unable to identify an hlh-12 ortholog outside of Caenorhabditis. Instead, by performing a comprehensive phylogenetic analysis of all Class II bHLH proteins in multiple nematode species, we found that hlh-12 evolved within the Caenorhabditis clade, possibly by duplicative transposition of hlh-10. Our analysis suggests that control of gene regulatory hierarchies for gonadogenesis can be remarkably plastic during evolution without adverse phenotypic consequence.     

Modeling neurodevelopment in a dish with pluripotent stem cells

Pluripotent stem cells (PSCs) can differentiate into all cell types in the body, and their differentiation procedures recapitulate the developmental processes of embryogenesis. Focusing on neurodevelopment, we describe here the application of knowledge gained from embryology to the neural induction of PSCs. Furthermore, PSC‐based neural modeling provides novel insights into neurodevelopmental processes. In particular, human PSC cultures are a powerful tool for the study of human‐specific neurodevelopmental processes and could even enable the elucidation of the mechanisms of human brain evolution. We also discuss challenges and potential future directions in further improving PSC‐based neural modeling.     

果蝇蜕皮激素诱导程序性细胞死亡的遗传调控因子

近年来关于果蝇程序性细胞死亡（programmed cell death, PCD）的研究结果表明,在果蝇的变态发育过程中,蜕皮激素与受体结合后诱导转录因子的表达。这些转录因子作为程序性细胞死亡调控网络中的初、次级应答信号,激活凋亡诱导因子Reaper、Hid和Grim的表达。Reaper、Hid和Grim进而阻止凋亡蛋白抑制因子的活性,从而启动半胱氨酸蛋白酶caspase途径,引起细胞凋亡（apoptosis）。该文综述了蜕皮激素诱导的果蝇程序性细胞死亡中各遗传调控因子之间的关系。     

21三体综合症植入前诊断的临床前运用研究

探讨建立一个高效、稳定的21三体遗传病植入前诊断的方法,以染色体G显带核型分析为对照,取正常成人外周血单个淋巴细胞40枚、21三体患者外周血单个淋巴细胞40枚及单卵裂球20枚,采用荧光定量PCR技术同时扩增21号染色体上特异区域基因片段(DSCR)和12号染色体上管家基因(GAPDH)片断作内对照,结果在正常组织同时扩增二片断的有效率为95%(38/40),扩增产物的荧光强度比值为1.00±0.05;21三体患者单个淋巴细胞同时扩增二片断的有效扩增率为92.5%(37/40),DSCR/GAPDH荧光强度的比值约为1.58±0.17;单卵裂球的扩增效率为80.0%(16/20).三者实验结果与染色体核型分析结果完全一致,准确率100%.研究结果表明荧光定量PCR技术产前检测21三体综合征具有准确、快速、安全、实用等特点,有较高的临床推广应用价值.     

Change in the developmental fate of the chick optic vesicle from the neural retina to the telencephalon

The forebrain develops into the telencephalon, diencephalon, and optic vesicle (OV). The OV further develops into the optic cup, the inner and outer layers of which develop into the neural retina and retinal pigmented epithelium (RPE), respectively. We studied the change in fate of the OV by using embryonic transplantation and explant culture methods. OVs excised from 10-somite stage chick embryos were freed from surrounding tissues (the surface ectoderm and mesenchyme) and were transplanted back to their original position in host embryos. Expression of neural retina-specific genes, such as Rax and Vsx2 (Chx10), was downregulated in the transplants. Instead, expression of the telencephalon-specific gene Emx1 emerged in the proximal region of the transplants, and in the distal part of the transplants close to the epidermis, expression of an RPE-specific gene Mitf was observed. Explant culture studies showed that when OVs were cultured alone, Rax was continuously expressed regardless of surrounding tissues (mesenchyme and epidermis). When OVs without surrounding tissues were cultured in close contact with the anterior forebrain, Rax expression became downregulated in the explants, and Emx1 expression became upregulated. These findings indicate that chick OVs at stage 10 are bi-potential with respect to their developmental fates, either for the neural retina or for the telencephalon, and that the surrounding tissues have a pivotal role in their actual fates. An in vitro tissue culture model suggests that under the influence of the anterior forebrain and/or its surrounding tissues, the OV changes its fate from the retina to the telencephalon.     

中枢神经系统发育的不对称细胞分裂机制

无论在无脊椎动物还是脊椎动物中,组成中枢神经系统（CNS）的大多数细胞都是由极性神经祖细胞不对称分裂而来。通过简要综述果蝇（Drosophila melanogaste）成神经母细胞（NB）不对称分裂机制,并与近年来在脊椎动物不对称细胞分裂上取得的研究成果相比较,尝试找出两个系统的相似性和相异性。     

Temporally- and spatially regulated generation of distinct descendants by sonic hedgehog-expressing progenitors in the forebrain

The generation of distinct neural subtypes depends on the activities of cell-extrinsic and -intrinsic factors during the development of the vertebrate CNS. Previous studies have provided a molecular basis for how neural progenitors are patterned and generate distinct descendants that are spatially and temporally regulated by inductive signals secreted by polarized sources. However, it still remains unknown how the generation of neural descendants by progenitors located at polarized sources of inductive signals is controlled. Sonic hedgehog (Shh), which is expressed at the ventral midline in the forebrain, has been shown to play a critical role for the patterning and specification of distinct neural subtypes in the forebrain. Here, we analyzed the identities and distributions of Shh-descendants generated at discrete time points in the forebrain by using a ShhcreER(T2) mouse driver line in which a tamoxifen-inducible Cre cassette was inserted into the Shh locus together with a Z/EG mouse reporter line. Our results showed that Shh-expressing neural progenitors generated neuronal and glial descendants distributed throughout the telencephalon and diencephalon in a temporally distinct manner. Furthermore, our results showed that Shh-progenitors are located at two spatially distinct sub-domains that can be characterized by their temporally distinct patterns of Shh expression. These results suggest that temporally- and spatially controlled mechanisms that specify neural subtypes operate in the Shh-expressing progenitor domain, and raise the possibility that the distinct temporal gradient of Shh activity might be responsible for the generation of distinct neural subtypes in the telencephalon.     

Cellular sociology regulates the hierarchical spatial patterning and organization of cells in organisms

Advances in single-cell biotechnology have increasingly revealed interactions of cells with their surroundings, suggesting a cellular society at the microscale. Similarities between cells and humans across multiple hierarchical levels have quantitative inference potential for reaching insights about phenotypic interactions that lead to morphological forms across multiple scales of cellular organization, namely cells, tissues and organs. Here, the functional and structural comparisons between how cells and individuals fundamentally socialize to give rise to the spatial organization are investigated. Integrative experimental cell interaction assays and computational predictive methods shape the understanding of societal perspective in the determination of the cellular interactions that create spatially coordinated forms in biological systems. Emerging quantifiable models from a simpler biological microworld such as bacterial interactions and single-cell organisms are explored, providing a route to model spatio-temporal patterning of morphological structures in humans. This analogical reasoning framework sheds light on structural patterning principles as a result of biological interactions across the cellular scale and up.     

果蝇心脏发育基因调控的研究进展

果蝇心脏的发育是一个受到一系列基因共同调控的复杂过程,这些基因在脊椎动物和无脊椎动物果蝇中具有惊人的相似性,对于它们功能的研究将有助于揭示人类心脏发育的过程及分子控制机理.通过将果蝇作为一种重要的模式动物,对心脏发育基因调控的研究进展作一综述.     

Acclimation of thermal physiology in natural populations of Drosophila melanogaster : a test of an optimality model

Many organisms modify their physiological functions by acclimating to changes in their environment. Recent studies of thermal physiology have been influenced by verbal models that fail to consider the selective advantage of acclimation and thus make no predictions about variation in acclimation capacity. We used a quantitative model of optimal plasticity to generate predictions about the capacity of Drosophila melanogaster to acclimate to developmental temperature. This model predicts that the ability to acclimate thermal sensitivity should evolve when temperature varies greatly among generations. Based on the model, we expected that flies from the highly seasonal environment of New Jersey would acclimate thermal sensitivity more than would flies from the less seasonal environment of Florida. When raised at constant and fluctuating temperatures, flies from these populations failed to adjust their thermal optima in the way predicted by the model, suggesting that current assumptions about functional and genetic constraints should be reconsidered.     

Genetic loads and coadaptivity of chromosomal inversions I. Inversion polymorphism and genetic load on chromosome O in a Drosophila subobscura population from Petnica

Inversion polymorphism on chromosome O and polymorphism for the viability of determining genes have been studied in a natural population of Drosophila subobscura from Petnica (Serbia). The range of inversion polymorphism and the abundance of particular gene arrangements in the study population agree with a general pattern of inversion polymorphism of D. subobscura in Europe. The data obtained on the amount of genetic loads show that the D. subobscura population from Petnica displays a moderate degree of that polymorphism, compared to the other studied populations of these species. Therefore, the D. subobscura population from Petnica could be tentatively classified as an ecologically central population. Examination association of chromosomal, thus, inversion polymorphism with gene polymorphism, in the form of genetic loads show that differences exist in the mean viability among certain gene arrangements. The distribution of deleterious genes among chromosome O gene arrangements were non-random.     

Novel Genes Involved in Controlling Specification of Drosophila FMRFamide Neuropeptide Cells

The expression of neuropeptides is often extremely restricted in the nervous system, making them powerful markers for addressing cell specification . In the developing Drosophila ventral nerve cord, only six cells, the Ap4 neurons, of some 10,000 neurons, express the neuropeptide FMRFamide (FMRFa). Each Ap4/FMRFa neuron is the last-born cell generated by an identifiable and well-studied progenitor cell, neuroblast 5-6 (NB5-6T). The restricted expression of FMRFa and the wealth of information regarding its gene regulation and Ap4 neuron specification makes FMRFa a valuable readout for addressing many aspects of neural development, i.e., spatial and temporal patterning cues, cell cycle control, cell specification, axon transport, and retrograde signaling. To this end, we have conducted a forward genetic screen utilizing an Ap4-specific FMRFa-eGFP transgenic reporter as our readout. A total of 9781 EMS-mutated chromosomes were screened for perturbations in FMRFa-eGFP expression, and 611 mutants were identified. Seventy-nine of the strongest mutants were mapped down to the affected gene by deficiency mapping or whole-genome sequencing. We isolated novel alleles for previously known FMRFa regulators, confirming the validity of the screen. In addition, we identified novel essential genes, including several with previously undefined functions in neural development. Our identification of genes affecting most major steps required for successful terminal differentiation of Ap4 neurons provides a comprehensive view of the genetic flow controlling the generation of highly unique neuronal cell types in the developing nervous system.     

Development of anterior gustatory epithelia in the palate and tongue requires epidermal growth factor receptor.

We characterized the gustatory phenotypes of neonatal mice having null mutations for epidermal growth factor receptor (egfr(-/-)), brain-derived neurotrophic factor (bdnf(-/-)), or both. We counted the number and diameter of fungiform taste buds, the prevalence of poorly differentiated or missing taste cells, and the incidence of ectopic filiform-like spines, each as a function of postnatal age and anterior/posterior location. Egfr(-/-) mice and bdnf(-/-) mice had similar reductions in the total number of taste buds on the anterior portions of the tongue and palate. Nonetheless, there were significant differences in their gustatory phenotypes. EGFR deficiency selectively impaired the development of anterior gustatory epithelia in the mouth. Only bdnf(-/-) mice had numerous taste buds missing from the foliate, vallate, and posterior fungiform papillae. Only egfr(-/-) fungiform taste papillae had robust gustatory innervation, markedly reduced cytokeratin 8 expression in taste cells, and a high incidence of a filiform-like spine. Egfr/bdnf double-null mutant mice had a higher frequency of failed fungiform taste bud differentiation. In bdnf(-/-) mice taste cell development failed because of sparse gustatory innervation. In contrast, in young egfr(-/-) mice the abundance of axons innervating fungiform papillae and the normal numbers of geniculate ganglion neurons implicate gustatory epithelial defects rather than neural defects.