Submitted Successfully!
To reward your contribution, here is a gift for you: A free trial for our video production service.
Thank you for your contribution! You can also upload a video entry or images related to this topic.
Version Summary Created by Modification Content Size Created at Operation
1 -- 1502 2023-03-29 12:13:26 |
2 format correct + 8 word(s) 1510 2023-03-31 04:41:08 |

Video Upload Options

Do you have a full video?


Are you sure to Delete?
If you have any further questions, please contact Encyclopedia Editorial Office.
Razuvaeva, A.V.; Graziadio, L.; Palumbo, V.; Pavlova, G.A.; Popova, J.V.; Pindyurin, A.V.; Bonaccorsi, S.; Somma, M.P.; Gatti, M. Subcellular Localization of the Asp/ASPM Proteins. Encyclopedia. Available online: (accessed on 14 June 2024).
Razuvaeva AV, Graziadio L, Palumbo V, Pavlova GA, Popova JV, Pindyurin AV, et al. Subcellular Localization of the Asp/ASPM Proteins. Encyclopedia. Available at: Accessed June 14, 2024.
Razuvaeva, Alyona V., Lucia Graziadio, Valeria Palumbo, Gera A. Pavlova, Julia V. Popova, Alexey V. Pindyurin, Silvia Bonaccorsi, Maria Patrizia Somma, Maurizio Gatti. "Subcellular Localization of the Asp/ASPM Proteins" Encyclopedia, (accessed June 14, 2024).
Razuvaeva, A.V., Graziadio, L., Palumbo, V., Pavlova, G.A., Popova, J.V., Pindyurin, A.V., Bonaccorsi, S., Somma, M.P., & Gatti, M. (2023, March 29). Subcellular Localization of the Asp/ASPM Proteins. In Encyclopedia.
Razuvaeva, Alyona V., et al. "Subcellular Localization of the Asp/ASPM Proteins." Encyclopedia. Web. 29 March, 2023.
Subcellular Localization of the Asp/ASPM Proteins

Investigations on different cell types showed that Asp (Drosophila abnormal spindle)/Aspm/ASPM (Abnormal Spindle-like Microcephaly-associated; or MCPH5) depletion disrupts one or more of the following mitotic processes: aster formation, spindle pole focusing, centrosome-spindle coupling, spindle orientation, metaphase-to-anaphase progression, chromosome segregation, and cytokinesis.

Drosophila Asp mouse Aspm human ASPM

1. Introduction

abnormal spindle (asp) was one of the first mitotic genes discovered in Drosophila asp mutants were shown to exhibit a strong mitotic phenotype in larval brain cells and morphologically abnormal spindles in male meiosis [1]. Molecular cloning of asp revealed that the gene encodes a large microtubule (MT)-binding protein that accumulates at the spindle poles [2]. The interest in asp was greatly heightened by the discovery that mutations in its human ortholog ASPM (Abnormal Spindle-like Microcephaly-associated) are the most common cause of autosomal recessive primary microcephaly (MCPH) [3][4][5]. MCPH is a rare and genetically heterogeneous disorder characterized by reduced head circumference of up to one-third of the normal volume at birth, resulting in mild-to-moderate intellectual disability. The principal cause of MCPH is a decreased production of neurons in the developing neocortex due to defects in progenitor cell proliferation and/or apoptosis (reviewed by [6][7][8]). To date (February 2023), 30 MCPH genes have been identified that are listed in the Online Mendelian Inheritance in Man (OMIM) database (, with ASPM designated as MCPH5. Most of these genes are involved in different aspects of mitotic division, including centriole biogenesis, centrosome-driven MT nucleation, kinetochore assembly and function, and spindle formation. However, a fraction of them are required for chromatin condensation and remodeling, DNA repair, and chromosome stability [7][8]. Remarkably, mutations in ASPM are responsible for more than 40% of MCPH cases [5].
Another reason for interest in the ASPM gene is its role in tumor development. ASPM expression is upregulated in several cancers, including prostate cancer, glioblastoma, and hepatocellular carcinoma, and increased ASPM expression is associated with tumor progression and poor clinical prognosis. It has also been shown that siRNA-mediated ASPM depletion strongly inhibits tumor cell proliferation ([9][10][11] and references therein). These and other studies suggested considering ASPM and the other MCPH genes as promising therapeutic targets in brain tumors (reviewed by [12][13]).
Although the Asp protein and its human (ASPM) and mouse (Aspm) orthologs have been studied for many years, a precise functional comparison between the three proteins has never been made.

2. Subcellular Localization of the Asp/ASPM Proteins

Early studies using antibodies against an Asp N terminal fragment of 512 amino acids showed that Asp localizes to the polar regions of the spindles and to the telophase central spindle in syncytial Drosophila embryos [2]. Subsequent studies expanded and refined these initial observations showing that Asp accumulates at the spindles poles of larval neuroblasts [14][15], epithelial cells [16], S2 tissue culture cells [17][18][19][20], and meiotic cells of both males and females [15][21][22]. Specifically, it has been reported that Asp accumulates at the transition region between the spindle and the centrosome, with Asp immunostaining partially overlapping the immunofluorescence signal elicited by γ-tubulin or Centrosomin (Cnn, the ortholog of the human centrosomal protein CDK5RAP2). However, a series of observations indicate that Asp localizes to the spindle poles independently of the centrosomes and that it is not an integral component of the centrosome. Namely, (i) Asp accumulates to the spindle poles of larval brain cells devoid of functional centrosomes, such as those of mutants in asterless (asl; encoding the ortholog of human CEP152), cnn or dd4 (encoding a γ-tubulin ring component) [15][18][23], (ii) the γ-tubulin and Cnn signals in asp mutant metaphases are of similar intensity to those of controls [15], and, most importantly, (iii) in colchicine-treated embryos and S2 cells with fully depolymerized spindle MTs Asp does not localize to the centrosome [15][20].
In addition to the spindle poles, Asp accumulates at the central spindle. The central spindle, or intercellular bridge, is a prominent MT bundle that forms during late telophase. It consists of antiparallel MTs with the plus ends interdigitating at the center of the bundle, where they associate with many different proteins generating a discrete structure currently called the midbody. These proteins form a dense cluster (midbody ring) that impedes the access of anti-tubulin antibodies, resulting in a dark zone after tubulin immunostaining [24]. Asp associates with the sides of the MT bundle that face the telophase nuclei. This peculiar localization has been observed in different cell types, including larval neuroblasts, S2 tissue culture cells, and male meiotic cells [15][20][21]. Asp also accumulates at the extremities of the central spindle of embryonic telophases. In these syncytial divisions, where cytokinesis does not occur, the central spindle is not hourglass-shaped as in cells with a contractile ring; it is instead diamond-shaped with sharply focused extremities that are highly enriched in Asp [15]. The localization of Asp at the spindle poles and at the outer sides of the central spindle suggests that Asp binds and crosslinks the minus ends of the spindle MTs [15][18][19][21]. This suggestion was recently corroborated by in vitro studies showing that Asp accumulates at the MT minus ends [25].
Besides its accumulation at the spindle poles and central spindle extremities, antibody staining revealed a weak Asp signal along the spindle MTs of different cell types, including larval neuroblasts, spermatocytes, and S2 cells [15][19][21]. In addition, the prometaphase and metaphase spindles of live larval neuroblasts and S2 cells, both expressing Asp-GFP, displayed discrete fluorescent signals along the spindle MTs. Imaging of these Asp-GFP particles revealed that they stream towards the spindle poles and are eventually incorporated into the polar Asp pool [17][18]. A poleward flow of Asp-GFP particles was also observed in the epithelial cell spindles of Drosophila pupal notum [16].
Aspm localization in neuroepithelial (NE) mouse cells is very similar to the Asp localization in Drosophila cells. Aspm localizes to the spindle poles throughout mitosis, accumulating in the immediate vicinity of the γ-tubulin signal of centrosomes. Aspm staining does not overlap the γ-tubulin immunoreactivity, and Aspm is absent from centrosomes during interphase [26]. In addition, Aspm localizes to the outer regions of the central spindle, but it is excluded from the midzone/midbody [27]. Thus, like its Drosophila ortholog, mouse Aspm appears to localize to spindle regions enriched in MT minus ends, consistent with the observation that Aspm preferentially associates with the MT minus ends in vitro [25].
Early studies on U2OS tissue culture cells suggested that human ASPM co-localizes with the centrosomes at the spindle poles and is enriched at the centrosomes in interphase nuclei [28]. Similar conclusions were reached in analyses performed in HeLa cells [29]. However, subsequent studies in U2OS cells showed that ASPM forms a ring around the centrosomes at the spindle poles, with little overlap with the γ-tubulin staining [30]. These studies did not provide evidence for ASPM localization at the interphase centrosomes. They also showed that after tubulin depolymerization with nocodazole, ASPM immunostaining at the spindle poles is lost, while γ-tubulin staining is unaffected [30]. However, in another investigation, antibody staining showed discrete ASPM signals located next to centrin (a centriolar marker) signals in interphase cells [31]. Thus, while it is clear that ASPM localization at the spindle poles is MT-dependent and centrosome-independent, the relationships between ASPM and the centrosome are not fully clarified.
ASPM localizes to the central spindle like its Drosophila and mouse counterparts, but there are some conflicting results about its precise localization to this structure. Using a commercial anti-human ASPM antibody and an antibody raised against amino acids 1-418 of rat ASPM, Paramasivam et al. [29] showed that both antibodies stain the midbody (dark zone) of HeLa cells. In a subsequent study, Higgins et al. [30] showed that an antibody directed to an ASPM N terminal peptide (aa 363–386) associates with the extremities of the central spindle but not with the midbody. In contrast, the same study showed that another antibody raised against a C terminal peptide (aa 3443–3458) of ASPM specifically decorates the midbody but fails to stain the lateral regions of the central spindle. This discrepancy was not addressed, and the authors focused on the relationships between ASPM and the centrosomes [30].
More recently, Jiang et al. [25] analyzed the properties and the mitotic behavior of a complete GFP-ASPM protein generated by the insertion of a GFP coding sequence just upstream of the first ASPM exon. In HeLa cells, GFP-ASPM accumulated to the spindle poles throughout mitosis; it also accumulated at central spindle extremities but was absent from the midbody. Importantly, Jiang et al. [25] also showed that ASPM binds the MT minus ends both in vitro and in living cells.
Collectively the extant results indicate that the orthologous Asp/ASPM proteins exhibit very similar, if not identical, localization patterns. They do not appear to be integral centrosome components but accumulate to the spindle poles, where they are likely to bind and crosslink the minus ends of the MTs that detach from the centrosomes ([32]; reviewed by [33]). In addition, Asp and its orthologues accumulate at the extremities of the central spindle that are enriched in MT minus ends. It is unlikely that they are also part of the midbody, as this structure is thought to contain little to no MT minus ends [24][34][35]. The detection of ASPM at the midbody with some specific antibodies might reflect a cross-reaction with one of the many proteins that compose this structure [36].


  1. Ripoll, P.; Pimpinelli, S.; Valdivia, M.M.; Avila, J. A cell division mutant of Drosophila with a functionally abnormal spindle. Cell 1985, 41, 907–912.
  2. Saunders, R.D.C.; do Carmo Avides, M.; Howard, T.; Gonzalez, C.; Glover, D.M. The Drosophila gene abnormal spindle encodes a novel microtubule-associated protein that associates with the polar regions of the mitotic spindle. J. Cell Biol. 1997, 137, 881–890.
  3. Bond, J.; Roberts, E.; Mochida, G.H.; Hampshire, D.J.; Scott, S.; Askham, J.M.; Springell, K.; Mahadevan, M.; Crow, Y.J.; Markham, A.F.; et al. ASPM is a major determinant of cerebral cortical size. Nat. Genet. 2002, 32, 316–320.
  4. Bond, J.; Scott, S.; Hampshire, D.J.; Springell, K.; Corry, P.; Abramowicz, M.J.; Mochida, G.H.; Hennekam, R.C.M.; Maher, E.R.; Fryns, J.-P.; et al. Protein-truncating mutations in ASPM cause variable reduction in brain size. Am. J. Hum. Genet. 2003, 73, 1170–1177.
  5. Létard, P.; Drunat, S.; Vial, Y.; Duerinckx, S.; Ernault, A.; Amram, D.; Arpin, S.; Bertoli, M.; Busa, T.; Ceulemans, B.; et al. Autosomal recessive primary microcephaly due to ASPM mutations: An update. Hum. Mutat. 2018, 39, 319–332.
  6. Jayaraman, D.; Bae, B.-I.; Walsh, C.A. The genetics of primary microcephaly. Annu. Rev. Genom. Hum. Genet. 2018, 19, 177–200.
  7. Jean, F.; Stuart, A.; Tarailo-Graovac, M. Dissecting the genetic and etiological causes of primary microcephaly. Front. Neurol. 2020, 11, 570830.
  8. Siskos, N.; Stylianopoulou, E.; Skavdis, G.; Grigoriou, M.E. Molecular genetics of microcephaly primary hereditary: An overview. Brain Sci. 2021, 11, 581.
  9. Horvath, S.; Zhang, B.; Carlson, M.; Lu, K.V.; Zhu, S.; Felciano, R.M.; Laurance, M.F.; Zhao, W.; Qi, S.; Chen, Z.; et al. Analysis of oncogenic signaling networks in glioblastoma identifies ASPM as a molecular target. Proc. Natl. Acad. Sci. USA 2006, 103, 17402–17407.
  10. Bikeye, S.-N.N.; Colin, C.; Marie, Y.; Vampouille, R.; Ravassard, P.; Rousseau, A.; Boisselier, B.; Idbaih, A.; Calvo, C.F.; Leuraud, P.; et al. ASPM-associated stem cell proliferation is involved in malignant progression of gliomas and constitutes an attractive therapeutic target. Cancer Cell Int. 2010, 10, 1.
  11. Zhang, H.; Yang, X.; Zhu, L.; Li, Z.; Zuo, P.; Wang, P.; Feng, J.; Mi, Y.; Zhang, C.; Xu, Y.; et al. ASPM promotes hepatocellular carcinoma progression by activating Wnt/β-Catenin signaling through antagonizing autophagy-mediated Dvl2 degradation. FEBS Open Bio 2021, 11, 2784–2799.
  12. Lang, P.Y.; Gershon, T.R. A new way to treat brain tumors: Targeting proteins coded by microcephaly genes?: Brain tumors and microcephaly arise from opposing derangements regulating progenitor growth. Drivers of microcephaly could be attractive brain tumor t. BioEssays 2018, 40, 1700243.
  13. Iegiani, G.; Di Cunto, F.; Pallavicini, G. Inhibiting microcephaly genes as alternative to microtubule targeting agents to treat brain tumors. Cell Death Dis. 2021, 12, 956.
  14. do Carmo Avides, M.; Glover, D.M. Abnormal spindle protein, Asp, and the integrity of mitotic centrosomal microtubule organizing centers. Science 1999, 283, 1733–1735.
  15. Wakefield, J.G.; Bonaccorsi, S.; Gatti, M. The Drosophila protein Asp is involved in microtubule organization during spindle formation and cytokinesis. J. Cell Biol. 2001, 153, 637–648.
  16. Bosveld, F.; Ainslie, A.; Bellaïche, Y. Sequential activities of dynein, Mud and Asp in centrosome-spindle coupling maintain centrosome number upon mitosis. J. Cell Sci. 2017, 130, 3557–3567.
  17. Schoborg, T.; Zajac, A.L.; Fagerstrom, C.J.; Guillen, R.X.; Rusan, N.M. An Asp-CaM complex is required for centrosome-pole cohesion and centrosome inheritance in neural stem cells. J. Cell Biol. 2015, 211, 987–998.
  18. Ito, A.; Goshima, G. Microcephaly protein Asp focuses the minus ends of spindle microtubules at the pole and within the spindle. J. Cell Biol. 2015, 211, 999–1009.
  19. Morales-Mulia, S.; Scholey, J.M. Spindle pole organization in Drosophila S2 cells by dynein, abnormal spindle protein (Asp), and KLP10A. Mol. Biol. Cell 2005, 16, 3176–3186.
  20. Popova, J.V.; Pavlova, G.A.; Razuvaeva, A.V.; Yarinich, L.A.; Andreyeva, E.N.; Anders, A.F.; Galimova, Y.A.; Renda, F.; Somma, M.P.; Pindyurin, A.V.; et al. Genetic control of kinetochore-driven microtubule growth in Drosophila mitosis. Cells 2022, 11, 2127.
  21. Riparbelli, M.G.; Callaini, G.; Glover, D.M.; do Carmo Avides, M. A Requirement for the abnormal spindle protein to organise microtubules of the central spindle for cytokinesis in Drosophila. J. Cell Sci. 2002, 115, 913–922.
  22. Riparbelli, M.G.; Massarelli, C.; Robbins, L.G.; Callaini, G. The abnormal spindle protein is required for germ cell mitosis and oocyte differentiation during Drosophila oogenesis. Exp. Cell Res. 2004, 298, 96–106.
  23. Barbosa, V.; Yamamoto, R.R.; Henderson, D.S.; Glover, D.M. Mutation of a Drosophila gamma tubulin ring complex subunit encoded by discs degenerate-4 differentially disrupts centrosomal protein localization. Genes Dev. 2000, 14, 3126–3139.
  24. D’Avino, P.P.; Giansanti, M.G.; Petronczki, M. Cytokinesis in animal cells. Cold Spring Harb. Perspect. Biol. 2015, 7, a015834.
  25. Jiang, K.; Rezabkova, L.; Hua, S.; Liu, Q.; Capitani, G.; Altelaar, A.F.M.; Heck, A.J.R.; Kammerer, R.A.; Steinmetz, M.O.; Akhmanova, A. Microtubule minus-end regulation at spindle poles by an ASPM-katanin complex. Nat. Cell Biol. 2017, 19, 480–492.
  26. Fish, J.L.; Kosodo, Y.; Enard, W.; Pääbo, S.; Huttner, W.B. Aspm specifically maintains symmetric proliferative divisions of neuroepithelial cells. Proc. Natl. Acad. Sci. USA 2006, 103, 10438–10443.
  27. Pulvers, J.N.; Bryk, J.; Fish, J.L.; Wilsch-Brauninger, M.; Arai, Y.; Schreier, D.; Naumann, R.; Helppi, J.; Habermann, B.; Vogt, J.; et al. Mutations in mouse Aspm (abnormal spindle-like microcephaly associated) cause not only microcephaly but also major defects in the germline. Proc. Natl. Acad. Sci. USA 2010, 107, 16595–16600.
  28. Zhong, X.; Liu, L.; Zhao, A.; Pfeifer, G.P.; Xu, X. The abnormal spindle-like, microcephaly-associated (ASPM) gene encodes a centrosomal protein. Cell Cycle Georget. Tex 2005, 4, 1227–1229.
  29. Paramasivam, M.; Chang, Y.J.; LoTurco, J.J. ASPM and Citron kinase co-localize to the midbody ring during cytokinesis. Cell Cycle Georget. Tex 2007, 6, 1605–1612.
  30. Higgins, J.; Midgley, C.; Bergh, A.-M.; Bell, S.M.; Askham, J.M.; Roberts, E.; Binns, R.K.; Sharif, S.M.; Bennett, C.; Glover, D.M.; et al. Human ASPM participates in spindle organisation, spindle orientation and cytokinesis. BMC Cell Biol. 2010, 11, 85.
  31. Jayaraman, D.; Kodani, A.; Gonzalez, D.M.; Mancias, J.D.; Mochida, G.H.; Vagnoni, C.; Johnson, J.; Krogan, N.; Harper, J.W.; Reiter, J.F.; et al. Microcephaly proteins Wdr62 and Aspm define a mother centriole complex regulating centriole biogenesis, apical complex, and cell fate. Neuron 2016, 92, 813–828.
  32. Mastronarde, D.N.; McDonald, K.L.; Ding, R.; McIntosh, J.R. Interpolar spindle microtubules in PTK Cells. J. Cell Biol. 1993, 123, 1475–1489.
  33. Borgal, L.; Wakefield, J.G. Context-dependent spindle pole focusing. Essays Biochem. 2018, 62, 803–813.
  34. Eggert, U.S.; Mitchison, T.J.; Field, C.M. Animal cytokinesis: From parts list to mechanisms. Annu. Rev. Biochem. 2006, 75, 543–566.
  35. She, Z.-Y.; Wei, Y.-L.; Lin, Y.; Li, Y.-L.; Lu, M.-H. Mechanisms of the Ase1/PRC1/MAP65 family in central spindle assembly. Biol. Rev. Camb. Philos. Soc. 2019, 94, 2033–2048.
  36. Chen, C.-T.; Ettinger, A.W.; Huttner, W.B.; Doxsey, S.J. Resurrecting remnants: The lives of post-mitotic midbodies. Trends Cell Biol. 2013, 23, 118–128.
Contributors MDPI registered users' name will be linked to their SciProfiles pages. To register with us, please refer to : , , , , , , , ,
View Times: 338
Revisions: 2 times (View History)
Update Date: 31 Mar 2023
Video Production Service