RESUMEN
Immotile cilia at the ventral node of mouse embryos are required for sensing leftward fluid flow that breaks left-right symmetry of the body. However, the flow-sensing mechanism has long remained elusive. In this work, we show that immotile cilia at the node undergo asymmetric deformation along the dorsoventral axis in response to the flow. Application of mechanical stimuli to immotile cilia by optical tweezers induced calcium ion transients and degradation of Dand5 messenger RNA (mRNA) in the targeted cells. The Pkd2 channel protein was preferentially localized to the dorsal side of immotile cilia, and calcium ion transients were preferentially induced by mechanical stimuli directed toward the ventral side. Our results uncover the biophysical mechanism by which immotile cilia at the node sense the direction of fluid flow.
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Señalización del Calcio , Calcio , Cilios , Mecanotransducción Celular , Animales , Ratones , Calcio/metabolismo , Cilios/fisiología , Embrión de MamíferosRESUMEN
Sexual reproduction is widespread in eukaryotes; however, only asexual reproduction has been observed in unicellular red algae, including Galdieria, which branched early in Archaeplastida. Galdieria possesses a small genome; it is polyextremophile, grows either photoautotrophically, mixotrophically, or heterotrophically, and is being developed as an industrial source of vitamins and pigments because of its high biomass productivity. Here, we show that Galdieria exhibits a sexual life cycle, alternating between cell-walled diploid and cell wall-less haploid, and that both phases can proliferate asexually. The haploid can move over surfaces and undergo self-diploidization or generate heterozygous diploids through mating. Further, we prepared the whole genome and a comparative transcriptome dataset between the diploid and haploid and developed genetic tools for the stable gene expression, gene disruption, and selectable marker recycling system using the cell wall-less haploid. The BELL/KNOX and MADS-box transcription factors, which function in haploid-to-diploid transition and development in plants, are specifically expressed in the haploid and diploid, respectively, and are involved in the haploid-to-diploid transition in Galdieria, providing information on the missing link of the sexual life cycle evolution in Archaeplastida. Four actin genes are differently involved in motility of the haploid and cytokinesis in the diploid, both of which are myosin independent and likely reflect ancestral roles of actin. We have also generated photosynthesis-deficient mutants, such as blue-colored cells, which were depleted in chlorophyll and carotenoids, for industrial pigment production. These features of Galdieria facilitate the understanding of the evolution of algae and plants and the industrial use of microalgae.
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Actinas , Rhodophyta , Actinas/genética , Animales , Carotenoides , Clorofila , Diploidia , Genómica , Haploidia , Estadios del Ciclo de Vida , Plantas/genética , Rhodophyta/genética , Factores de Transcripción/genética , VitaminasRESUMEN
Fibrous collagen imparts physical strength and flexibility to tissues by forming huge complexes. The density and orientation of collagen fibers must be correctly specified for the optimal physical property of the collagen complex. However, little is known about its underlying cellular mechanisms. Actinotrichia are collagen fibers aligned at the fin-tip of bony fish and are easily visible under the microscope due to their thick, linear structure. We used the actinotrichia as a model system to investigate how cells manipulate collagen fibers. The 3D image obtained by focused ion beam scanning electron microscopy (FIB-SEM) showed that the pseudopodia of mesenchymal cells encircle the multiple actinotrichia. We then co-incubated the mesenchymal cells and actinotrichia in vitro, and time-lapse analysis revealed how cells use pseudopods to align collagen fiber orientation. This in vitro behavior is dependent on actin polymerization in mesenchymal cells. Inhibition of actin polymerization in mesenchymal cells results in mis-orientation of actinotrichia in the fin. These results reveal how mesenchymal cells are involved in fin formation and have important implications for the physical interaction between cells and collagen fibers.
RESUMEN
Immotile cilia sense extracellular signals such as fluid flow, but whether Ca2+ plays a role in flow sensing has been unclear. Here, we examined the role of ciliary Ca2+ in the flow sensing that initiates the breaking of left-right (L-R) symmetry in the mouse embryo. Intraciliary and cytoplasmic Ca2+ transients were detected in the crown cells at the node. These Ca2+ transients showed L-R asymmetry, which was lost in the absence of fluid flow or the PKD2 channel. Further characterization allowed classification of the Ca2+ transients into two types: cilium-derived, L-R-asymmetric transients (type 1) and cilium-independent transients without an L-R bias (type 2). Type 1 intraciliary transients occurred preferentially at the left posterior region of the node, where L-R symmetry breaking takes place. Suppression of intraciliary Ca2+ transients delayed L-R symmetry breaking. Our results implicate cilium-derived Ca2+ transients in crown cells in initiation of L-R symmetry breaking in the mouse embryo.
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Primary cilia are antenna-like organelles on the surface of most mammalian cells that receive sonic hedgehog (Shh) signaling in embryogenesis and carcinogenesis. Cellular cholesterol functions as a direct activator of a seven-transmembrane oncoprotein called Smoothened (Smo) and thereby induces Smo accumulation on the ciliary membrane where it transduces the Shh signal. However, how cholesterol is supplied to the ciliary membrane remains unclear. Here, we report that peroxisomes are essential for the transport of cholesterol into the ciliary membrane. Zellweger syndrome (ZS) is a peroxisome-deficient hereditary disorder with several ciliopathy-related features and cells from these patients showed a reduced cholesterol level in the ciliary membrane. Reverse genetics approaches revealed that the GTP exchange factor Rabin8, the Rab GTPase Rab10, and the microtubule minus-end-directed kinesin KIFC3 form a peroxisome-associated complex to control the movement of peroxisomes along microtubules, enabling communication between peroxisomes and ciliary pocket membranes. Our findings suggest that insufficient ciliary cholesterol levels may underlie ciliopathies.
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Colesterol/metabolismo , Cilios/metabolismo , Síndrome de Zellweger/metabolismo , Células Cultivadas , Colesterol/genética , Cilios/genética , Cilios/patología , Quinasas del Centro Germinal/genética , Quinasas del Centro Germinal/metabolismo , Humanos , Cinesinas/genética , Cinesinas/metabolismo , Microtúbulos/genética , Microtúbulos/metabolismo , Microtúbulos/patología , Receptor Smoothened/genética , Receptor Smoothened/metabolismo , Síndrome de Zellweger/genética , Síndrome de Zellweger/patología , Proteínas de Unión al GTP rab/genética , Proteínas de Unión al GTP rab/metabolismoRESUMEN
Assessing the structure and function of organelles in living organisms of the primitive unicellular red algae Cyanidioschyzon merolae on three-dimensional sequential images demands a reliable automated technique in the class imbalance among various cellular structures during mitosis. Existing classification networks with commonly used loss functions were focused on larger numbers of cellular structures that lead to the unreliability of the system. Hence, we proposed a balanced deep regularized weighted compound dice loss (RWCDL) network for better localization of cell organelles. Specifically, we introduced two new loss functions, namely compound dice (CD) and RWCD by implementing multi-class variant dice and weighting mechanism, respectively for maximizing weights of peroxisome and nucleus among five classes as the main contribution of this study. We extended the Unet-like convolution neural network (CNN) architecture for evaluating the ability of our proposed loss functions for improved segmentation. The feasibility of the proposed approach is confirmed with three different large scale mitotic cycle data set with different number of occurrences of cell organelles. In addition, we compared the training behavior of our designed architectures with the ground truth segmentation using various performance measures. The proposed balanced RWCDL network generated the highest area under the curve (AUC) value in elevating the small and obscure peroxisome and nucleus, which is 30% higher than the network with commonly used mean square error (MSE) and dice loss (DL) functions. The experimental results indicated that the proposed approach can efficiently identify the cellular structures, even when the contour between the cells is obscure and thus convinced that the balanced deep RWCDL approach is reliable and can be helpful for biologist to accurately identify the relationship between the cell behavior and structures of cell organelles during mitosis.
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Procesamiento de Imagen Asistido por Computador/métodos , Redes Neurales de la Computación , Rhodophyta/ultraestructura , Algoritmos , Imagenología Tridimensional/métodos , Microscopía Electrónica de Rastreo/métodos , Mitosis , Orgánulos/ultraestructura , Rhodophyta/citologíaRESUMEN
The metaphase spindle is organized for accurate chromosome segregation. One of the fundamental features of the spindle across the species is its symmetrical shape; the spindle consists of two polar arrays of microtubules at both ends. Although it has been suggested that the formation of the bipolar shape requires force balance coordination by molecular motors, i.e., kinesins and dyneins, quantitative analysis for the pole mechanics has not been conducted. Here, we demonstrate that it is not only the shape but also the stiffness and microtubule density of the pairs of pole regions are symmetrically balanced in single spindles self-assembled in Xenopus egg extracts. We found that the inhibition of dynein functions dramatically reduced the stiffness and microtubule density in the pole region. By contrast, the inhibition of one of the kinesins, Eg5, which is the antagonistic motor protein of dynein, increased the value of these parameters. Moreover, the inhibition of both dynein and Eg5 recovered these parameter values to those of non-treated spindle poles. We also found that, when one pole structure was held widened with the use of two glass microneedles, the opposite pole structure spontaneously widened, resulting in the formation of the barrel-like shaped spindle. The values of stiffness and microtubule density in the manipulated pole region decreased, following the spontaneous decrement of those in the paired unmanipulated pole region. These results suggest that the spindle possesses a mechanism to dynamically maintain its symmetry in mechanical properties.
RESUMEN
Collective behaviors of motile units through hydrodynamic interactions induce directed fluid flow on a larger length scale than individual units. In cells, active cytoskeletal systems composed of polar filaments and molecular motors drive fluid flow, a process known as cytoplasmic streaming. The motor-driven elongation of microtubule bundles generates turbulent-like flow in purified systems; however, it remains unclear whether and how microtubule bundles induce large-scale directed flow like the cytoplasmic streaming observed in cells. Here, we adopted Xenopus egg extracts as a model system of the cytoplasm and found that microtubule bundle elongation induces directed flow for which the length scale and timescale depend on the existence of geometrical constraints. At the lower activity of dynein, kinesins bundle and slide microtubules, organizing extensile microtubule bundles. In bulk extracts, the extensile bundles connected with each other and formed a random network, and vortex flows with a length scale comparable to the bundle length continually emerged and persisted for 1 min at multiple places. When the extracts were encapsulated in droplets, the extensile bundles pushed the droplet boundary. This pushing force initiated symmetry breaking of the randomly oriented bundle network, leading to bundles aligning into a rotating vortex structure. This vortex induced rotational cytoplasmic flows on the length scale and timescale that were 10- to 100-fold longer than the vortex flows emerging in bulk extracts. Our results suggest that microtubule systems use not only hydrodynamic interactions but also mechanical interactions to induce large-scale temporally stable cytoplasmic flow.
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Microtúbulos/química , Microtúbulos/metabolismo , Animales , Citoplasma , Citoesqueleto/química , Citoesqueleto/metabolismo , Dineínas/química , Dineínas/metabolismo , Cinesinas/química , Cinesinas/metabolismo , Microscopía Confocal , Xenopus laevisRESUMEN
Seven novel spiromeroterpenoids, asnovolins A-G (1-7), one of which was shown to suppress fibronectin expression, were isolated from Aspergillus novofumigatus CBS117520 along with a known compound, novofumigatonin (8). The structures of asnovolins A-G were elucidated using MS and 2D-NMR data. Asnovolin E (5) suppressed fibronectin expression by normal human neonatal dermal fibroblast cells.
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Compuestos de Espiro/aislamiento & purificación , Compuestos de Espiro/farmacología , Terpenos/aislamiento & purificación , Terpenos/farmacología , Aspergillus/química , Ensayos de Selección de Medicamentos Antitumorales , Fibronectinas , Humanos , Estructura Molecular , Resonancia Magnética Nuclear Biomolecular , Compuestos de Espiro/química , Terpenos/químicaRESUMEN
Growth inhibitors were isolated from an arctic strain of Trichoderma polysporum, and the structures were elucidated and the in vitro inhibitory effects of these compounds against Pythium iwayamai were investigated. Eleven compounds were isolated; four showed a concentration-dependent growth-inhibitory effect against P. iwayamai. None of these compounds have been reported previously as substances with antimicrobial activity against P. iwayamai. One of these four compounds inhibited the growth of the pathogen at 33 µg ml(-1) concentration during a 15-day incubation at 20 °C. This effect was comparable to that of chloroneb (1: 1,4-dichloro-2,5-dimethoxybenzene), a fungicide with activity against P. iwayamai. Thus, the results of the present study show that the arctic strain of T. polysporum can be an effective source of antibiotics with activity against the snow rot pathogen, P. iwayamai.
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Antifúngicos/farmacología , Inhibidores de Crecimiento/farmacología , Pythium/efectos de los fármacos , Trichoderma/metabolismo , Antifúngicos/aislamiento & purificación , Clorobencenos/farmacología , Relación Dosis-Respuesta a Droga , Inhibidores de Crecimiento/química , Inhibidores de Crecimiento/aislamiento & purificación , Pythium/crecimiento & desarrollo , Factores de TiempoRESUMEN
Three new phthalide derivatives, emefuranones A1, A2 and B (1-3); six new phthalane derivatives, emefuran A, B1, B2, C1, C2 and D (4-9); three new farnesylated phthalide derivatives, farnesylemefuranones A-C (10-12); xylarinol C (13); and emericelloxide (14), along with four known compounds (dustanin, sorbicillin, aspergillodiol and xylarinol A), were isolated from the culture extracts of Emericella sp. IFM57991. Structures of 1-14 were elucidated on the basis of spectroscopic analysis and chemical evidence. Compounds 4-7 and 13 showed moderate antibacterial activities against Bacillus subtilis.
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Antiinfecciosos/farmacología , Bacillus subtilis/efectos de los fármacos , Benzofuranos/farmacología , Medios de Cultivo/química , Emericella/metabolismo , Ftalimidas/farmacología , Antiinfecciosos/química , Antiinfecciosos/aislamiento & purificación , Benzofuranos/química , Benzofuranos/aislamiento & purificación , Pruebas Antimicrobianas de Difusión por Disco , Emericella/crecimiento & desarrollo , Humanos , Espectroscopía de Resonancia Magnética , Modelos Moleculares , Estructura Molecular , Ftalimidas/química , Ftalimidas/aislamiento & purificaciónRESUMEN
Optical microheating is a powerful non-invasive method for manipulating biological functions such as gene expression, muscle contraction, and cell excitation. Here, we demonstrate its potential usage for regulating neurite outgrowth. We found that optical microheating with a water-absorbable 1,455-nm laser beam triggers directional and explosive neurite outgrowth and branching in rat hippocampal neurons. The focused laser beam under a microscope rapidly increases the local temperature from 36 °C to 41 °C (stabilized within 2 s), resulting in the elongation of neurites by more than 10 µm within 1 min. This high-speed, persistent elongation of neurites was suppressed by inhibitors of both microtubule and actin polymerization, indicating that the thermosensitive dynamics of these cytoskeletons play crucial roles in this heat-induced neurite outgrowth. Furthermore, we showed that microheating induced the regrowth of injured neurites and the interconnection of neurites. These results demonstrate the efficacy of optical microheating methods for the construction of arbitrary neural networks.
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Neuritas/fisiología , Animales , Señalización del Calcio , Técnicas de Cultivo de Célula , Aumento de la Célula/efectos de la radiación , Células Cultivadas , Hipocampo/citología , Calor , Rayos Infrarrojos , Microtúbulos/metabolismo , RatasRESUMEN
Living cells sense absolute temperature and temporal changes in temperature using biological thermosensors such as ion channels. Here, we reveal, to our knowledge, a novel mechanism of sensing spatial temperature gradients within single cells. Spherical mitotic cells form directional membrane extensions (polar blebs) under sharp temperature gradients (≥â¼0.065°C µm(-1); 1.3°C temperature difference within a cell), which are created by local heating with a focused 1455-nm laser beam under an optical microscope. On the other hand, multiple nondirectional blebs are formed under gradual temperature gradients or uniform heating. During heating, the distribution of actomyosin complexes becomes inhomogeneous due to a break in the symmetry of its contractile force, highlighting the role of the actomyosin complex as a sensor of local temperature gradients.
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Forma de la Célula/fisiología , Temperatura , Actomiosina/metabolismo , Calcio/metabolismo , Membrana Celular/efectos de los fármacos , Membrana Celular/fisiología , Forma de la Célula/efectos de los fármacos , Células HeLa , Humanos , Rayos Infrarrojos , Rayos Láser , Grabación en VideoRESUMEN
Dry age-related macular degeneration (AMD) accounts for over 85% of AMD cases in the United States, whereas Japanese AMD patients predominantly progress to wet AMD or polypoidal choroidal vasculopathy. Recent genome-wide association studies have revealed a strong association between AMD and an insertion/deletion sequence between the ARMS2 (age-related maculopathy susceptibility 2) and HTRA1 (high temperature requirement A serine peptidase 1) genes. Transcription regulator activity was localized in mouse retinas using heterozygous HtrA1 knock-out mice in which HtrA1 exon 1 was replaced with ß-galactosidase cDNA, thereby resulting in dominant expression of the photoreceptors. The insertion/deletion sequence significantly induced HTRA1 transcription regulator activity in photoreceptor cell lines but not in retinal pigmented epithelium or other cell types. A deletion construct of the HTRA1 regulatory region indicated that potential transcriptional suppressors and activators surround the insertion/deletion sequence. Ten double-stranded DNA probes for this region were designed, three of which interacted with nuclear extracts from 661W cells in EMSA. Liquid chromatography-mass spectrometry (LC-MS/MS) of these EMSA bands subsequently identified a protein that bound the insertion/deletion sequence, LYRIC (lysine-rich CEACAM1 co-isolated) protein. In addition, induced pluripotent stem cells from wet AMD patients carrying the insertion/deletion sequence showed significant up-regulation of the HTRA1 transcript compared with controls. These data suggest that the insertion/deletion sequence alters the suppressor and activator cis-elements of HTRA1 and triggers sustained up-regulation of HTRA1. These results are consistent with a transgenic mouse model that ubiquitously overexpresses HtrA1 and exhibits characteristics similar to those of wet AMD patients.
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Células Madre Pluripotentes Inducidas/metabolismo , Proteínas/metabolismo , Serina Endopeptidasas/metabolismo , Anciano , Animales , Western Blotting , Línea Celular , Cromatografía Liquida , Ensayo de Cambio de Movilidad Electroforética , Femenino , Serina Peptidasa A1 que Requiere Temperaturas Altas , Humanos , Inmunohistoquímica , Hibridación in Situ , Masculino , Ratones , Ratones Noqueados , Mutación , Ratas , Retina/metabolismo , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Espectrometría de Masas en TándemRESUMEN
PURPOSE: A possible association has been reported between exfoliation syndrome (EX) and various ocular and systemic vascular disorders; however, it is unclear if there is an association between EX and central retinal vein occlusion (CRVO). Because latent deposits of exfoliation materials might not be recognized during slit-lamp examination, an ocular biopsy is required to establish a precise diagnosis. We evaluated a possible association between EX and CRVO using lysyl oxidase-like 1 (LOXL1) gene variants as alternative markers for EX. METHODS: The allelic and genotypic frequencies of three LOXL1 variants (rs1048661, rs3825942, and rs2165241) were determined in 68 consecutive Japanese patients with CRVO [15 with exfoliation syndrome (EX+) and 53 without exfoliation syndrome (EX-)] and 90 control patients with cataract without EX (CT). RESULTS: The frequencies of the rs1048661 and rs3825942 variants showed borderline difference between the CRVO and CT groups (p = 0.04085 and p = 0.06088, respectively, for allelic frequencies, and p = 0.06838 and p = 0.03482, respectively, for genotypic frequencies). Compared with the CT group, subgroup analysis showed that the CRVO EX+ group had significant differences in the allelic and genotypic frequencies of rs1048661 (p = 0.0006447 and p = 0.0001392, respectively) and had borderline differences in the allelic and genotypic frequencies of rs3825942 (p = 0.03403 and p = 0.07341, respectively), while the CRVO EX- group did not (p = 0.1324-0.6306). Subgroup analysis showed that the frequencies of rs2165241 did not differ between the CRVO and CT groups. CONCLUSIONS: When the LOXL1 variants were used as disease markers for clinically undetectable EX, there was no association between CRVO and EX. The results suggested that the LOXL1 variants, which are well-established markers for EX, are not likely genetic markers for CRVO in Japanese subjects.
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Aminoácido Oxidorreductasas/genética , Pueblo Asiatico/genética , Síndrome de Exfoliación/genética , Polimorfismo de Nucleótido Simple , Oclusión de la Vena Retiniana/genética , Adulto , Anciano , Anciano de 80 o más Años , Catarata/genética , Femenino , Frecuencia de los Genes , Marcadores Genéticos , Técnicas de Genotipaje , Humanos , Japón/epidemiología , Masculino , Persona de Mediana Edad , Reacción en Cadena de la PolimerasaRESUMEN
Purpose. To investigate genetic and clinical features of patients with rhodopsin (RHO) mutations in two Japanese families with autosomal dominant retinitis pigmentosa (adRP). Methods. Whole-exome sequence analysis was performed in ten adRP families. Identified RHO mutations for the cosegregation analysis were confirmed by Sanger sequencing. Ophthalmic examinations were performed to evaluate the RP phenotypes. The impact of the RHO mutation on the rhodopsin conformation was examined by molecular modeling analysis. Results. In two adRP families, we identified two RHO mutations (c.377G>T (p.W126L) and c.1036G>C (p.A346P)), one of which was novel. Complete cosegregation was confirmed for each mutation exhibiting the RP phenotype in both families. Molecular modeling predicted that the novel mutation (p.W126L) might impair rhodopsin function by affecting its conformational transition in the light-adapted form. Clinical phenotypes showed that patients with p.W126L exhibited sector RP, whereas patients with p.A346P exhibited classic RP. Conclusions. Our findings demonstrated that the novel mutation (p.W126L) may be associated with the phenotype of sector RP. Identification of RHO mutations is a very useful tool for predicting disease severity and providing precise genetic counseling.
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Antineoplásicos/farmacología , Ascomicetos/metabolismo , Glicósidos/farmacología , Péptidos/farmacología , Esteroides/farmacología , Antineoplásicos/química , Antineoplásicos/metabolismo , Ascomicetos/química , Glicósidos/química , Glicósidos/metabolismo , Estructura Molecular , Péptidos/química , Péptidos/metabolismo , Esteroides/química , Esteroides/metabolismoRESUMEN
The meiotic spindle is a bipolar molecular machine that is designed to segregate duplicated chromosomes toward the opposite poles of the cell. The size and shape of the spindle are considered to be maintained by a balance of forces produced by molecular motors and microtubule assembly dynamics. Several studies have probed how mechanical perturbations of the force balance affect the spindle structure. However, the spindle's response to a stretching force acting at the spindle pole and along its long axis, i.e., the direction in which chromosomes are segregated, has not been examined. Here, we describe a method to apply a stretching force to the metaphase spindle assembled in Xenopus egg extracts and measure the relationship between the force and the three-dimensional deformation of the spindle. We found that the spindle behaves as a Zener-type viscoelastic body when forces are applied at the spindle pole, generating a restoring force for several minutes. In addition, both the volume of the spindle and the tubulin density are conserved under the stretching force. These results provide insight into how the spindle size is maintained at metaphase.
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Elasticidad , Huso Acromático/metabolismo , Animales , Oocitos/metabolismo , Huso Acromático/química , Estrés Mecánico , XenopusRESUMEN
BACKGROUND: The purpose of this study was to investigate the association between ARMS2/HTRA1, CFH, and C3 gene polymorphisms and retinal angiomatous proliferation (RAP), an infrequent and severe form of exudative age-related macular degeneration, which is characterized by intraretinal neovascularization. METHODS: Diagnosis of RAP was based on fundus photographs, images of fluorescein and indocyanine green angiographies, and optical coherence tomography findings. Six single nucleotide polymorphisms (SNPs), A69S (rs10490924) in ARMS2, rs11200638 in HTRA1, I62V (rs800292) in CFH, Y402H (rs1061170) in CFH, R80G (rs2230199) in C3, and rs2241394 in C3, were genotyped in eight Japanese patients with RAP. RESULTS: The two SNPs in the ARMS2/HTRA1 were in complete linkage disequilibrium. The frequency of the risk T allele in ARMS2 (the risk A allele in HTRA1) was 93.8% in the RAP patients. The frequency of homozygosity for the risk genotype TT of ARMS2 (the risk genotype AA of HTRA1) was 87.5%. The frequency of the non-risk allele (A) of I62V was 100%. The frequencies of risk alleles of Y402H, R80G, and rs2241394 were 12.5%, 0%, and 18.8%, respectively. CONCLUSION: Our results suggest that the risk alleles of the ARMS2/HTRA1 SNPs may be associated with development of RAP and play a major role in the pathogenesis of intraretinal angiogenesis.
RESUMEN
The polymerization/depolymerization dynamics of microtubules (MTs) have been reported to contribute to control of the size and shape of spindles, but quantitative analysis of how the size and shape correlate with the amount and density of MTs in the spindle remains incomplete. Here, we measured these parameters using 3D microscopy of meiotic spindles that self-organized in Xenopus egg extracts and presented a simple equation describing the relationship among these parameters. To examine the validity of the equation, we cut the spindle into two fragments along the pole-to-pole axis by micromanipulation techniques that rapidly decrease the amount of MTs. The spheroidal shape spontaneously recovered within 5 min, but the size of each fragment remained small. The equation we obtained quantitatively describes how the spindle size correlates with the amount of MTs while maintaining the shape and the MT density.