The LINC (LInker of Nucleoskeleton and Cytoskeleton) complex is localized within the nuclear envelope and consists of SUN (Sad1/UNc84 homology domain-containing) proteins located in the inner nuclear membrane and KASH (Klarsicht/Anc1/Syne1 homology domain-containing) proteins located in the outer nuclear membrane, hence linking nuclear with cytoplasmic structures. While the nucleoplasm-facing side acts as a key player for correct pairing of homolog chromosomes and rapid chromosome movements during meiosis, the cytoplasm-facing side plays a pivotal role for sperm head development and proper acrosome formation during spermiogenesis. A further complex present in spermatozoa is involved in head-to-tail coupling. An intact LINC complex is crucial for the production of fertile sperm, as mutations in genes encoding for complex proteins are known to be associated with male subfertility in both mice and men. The present review provides a comprehensive overview on our current knowledge of LINC complex subtypes present in germ cells and its central role for male reproduction. Future studies on distinct LINC complex components are an absolute requirement to improve the diagnosis of idiopathic male factor infertility and the outcome of assisted reproduction.

Department of Urology Pediatric Urology and Andrology Molecular Andrology Justus Liebig University 35392 Giessen Germany

Department of Zoology Faculty of Science Charles University Vinicna 7 128 44 Prague 2 Czech Republic

Laboratory of Reproductive Biology Institute of Biotechnology of the Czech Academy of Sciences BIOCEV Prumyslova 595 252 50 Vestec Czech Republic

See more in PubMed

Ungricht R., Kutay U. Mechanisms and functions of nuclear envelope remodelling. Nat. Rev. Mol. Cell Biol. 2017;18:229–245. doi: 10.1038/nrm.2016.153. PubMed DOI

Lee Y.L., Burke B. LINC complexes and nuclear positioning. Semin. Cell Dev. Biol. 2018;82:67–76. doi: 10.1016/j.semcdb.2017.11.008. PubMed DOI

Pereira C.D., Serrano J.B., Martins F., da Cruz e Silva O.A.B., Rebelo S. Nuclear envelope dynamics during mammalian spermatogenesis: New insights on male fertility. Biol. Rev. 2019;94:1195–1219. doi: 10.1111/brv.12498. PubMed DOI

Ding X., Xu R., Yu J., Xu T., Zhuang Y., Han M. SUN1 Is Required for Telomere Attachment to Nuclear Envelope and Gametogenesis in Mice. Dev. Cell. 2007;12:863–872. doi: 10.1016/j.devcel.2007.03.018. PubMed DOI

Chi Y.H., Cheng L.I., Myers T., Ward J.M., Williams E., Su Q., Faucette L., Wang J.Y., Jeang K.T. Requirement for Sun1 in the expression of meiotic reproductive genes and piRNA. Development. 2009;136:965–973. doi: 10.1242/dev.029868. PubMed DOI PMC

Shibuya H., Hernández-Hernández A., Morimoto A., Negishi L., Höög C., Watanabe Y. MAJIN Links Telomeric DNA to the Nuclear Membrane by Exchanging Telomere Cap. Cell. 2015;163:1252–1266. doi: 10.1016/j.cell.2015.10.030. PubMed DOI

Link J., Leubner M., Schmitt J., Göb E., Benavente R., Jeang K.T., Xu R., Alsheimer M. Analysis of Meiosis in SUN1 Deficient Mice Reveals a Distinct Role of SUN2 in Mammalian Meiotic LINC Complex Formation and Function. PLoS Genet. 2014;10:e1004099. doi: 10.1371/journal.pgen.1004099. PubMed DOI PMC

Göb E., Schmitt J., Benavente R., Alsheimer M. Mammalian Sperm Head Formation Involves Different Polarization of Two Novel LINC Complexes. PLoS ONE. 2010;5:e12072. doi: 10.1371/journal.pone.0012072. PubMed DOI PMC

Schmitt J., Benavente R., Hodzic D., Höög C., Stewart C.L., Alsheimer M. Transmembrane protein Sun2 is involved in tethering mammalian meiotic telomeres to the nuclear envelope. Proc. Natl. Acad. Sci. USA. 2007;104:7426–7431. doi: 10.1073/pnas.0609198104. PubMed DOI PMC

Lei K., Zhang X., Ding X., Guo X., Chen M., Zhu B., Xu T., Zhuang Y., Xu R., Han M. SUN1 and SUN2 play critical but partially redundant roles in anchoring nuclei in skeletal muscle cells in mice. Proc. Natl. Acad. Sci. USA. 2009;106:10207–10212. doi: 10.1073/pnas.0812037106. PubMed DOI PMC

Calvi A., Wong A.S.W., Wright G., Wong E.S.M., Loo T.H., Stewart C.L., Burke B. SUN4 is essential for nuclear remodeling during mammalian spermiogenesis. Dev. Biol. 2015;407:321–330. doi: 10.1016/j.ydbio.2015.09.010. PubMed DOI

Gao Q., Khan R., Yu C., Alsheimer M., Jiang X., Ma H., Shi Q. The testis-specific LINC component SUN3 is essential for sperm head shaping during mouse spermiogenesis. J. Biol. Chem. 2020;295:6289–6298. doi: 10.1074/jbc.RA119.012375. PubMed DOI PMC

Pasch E., Link J., Beck C., Scheuerle S., Alsheimer M. The LINC complex component Sun4 plays a crucial role in sperm head formation and fertility. Biol. Open. 2015;4:1792–1802. doi: 10.1242/bio.015768. PubMed DOI PMC

Shao X., Tarnasky H.A., Lee J.P., Oko R., van der Hoorn F.A. Spag4, a Novel Sperm Protein, Binds Outer Dense-Fiber Protein Odf1 and Localizes to Microtubules of Manchette and Axoneme. Dev. Biol. 1999;211:109–123. doi: 10.1006/dbio.1999.9297. PubMed DOI

Yeh C.H., Kuo P.L., Wang Y.Y., Wu Y.Y., Chen M.F., Lin D.Y., Lai T.H., Chiang H.S., Lin Y.H. SEPT12/SPAG4/LAMINB1 complexes are required for maintaining the integrity of the nuclear envelope in postmeiotic male germ cells. PLoS ONE. 2015;10:e120722. doi: 10.1371/journal.pone.0120722. PubMed DOI PMC

Yang K., Adham I.M., Meinhardt A., Hoyer-Fender S. Ultra-structure of the sperm head-to-tail linkage complex in the absence of the spermatid-specific LINC component SPAG4. Histochem. Cell Biol. 2018;150:49–59. doi: 10.1007/s00418-018-1668-7. PubMed DOI

Jiang X.-Z., Yang M.-G., Huang L.-H., Li C.-Q., Xing X.-W. SPAG4L, a Novel Nuclear Envelope Protein Involved in the Meiotic Stage of Spermatogenesis. DNA Cell Biol. 2011;30:875–882. doi: 10.1089/dna.2010.1161. PubMed DOI

Yassine S., Escoffier J., Nahed R.A., Pierre V., Karaouzene T., Ray P.F., Arnoult C. Dynamics of Sun5 localization during spermatogenesis in wild type and Dpy19l2 knock-out mice indicates that Sun5 is not involved in acrosome attachment to the nuclear envelope. PLoS ONE. 2015;10:e118698. doi: 10.1371/journal.pone.0118698. PubMed DOI PMC

Shang Y., Zhu F., Wang L., Ouyang Y.-C., Dong M.-Z., Liu C., Zhao H., Cui X., Ma D., Zhang Z., et al. Essential role for SUN5 in anchoring sperm head to the tail. eLife. 2017;6:e28199. doi: 10.7554/eLife.28199. PubMed DOI PMC

Zhang J., Felder A., Liu Y., Guo L.T., Lange S., Dalton N.D., Gu Y., Peterson K.L., Mizisin A.P., Shelton G.D., et al. Nesprin 1 is critical for nuclear positioning and anchorage. Hum. Mol. Genet. 2010;19:329–341. doi: 10.1093/hmg/ddp499. PubMed DOI PMC

Ketema M., Kreft M., Secades P., Janssen H., Sonnenberg A. Nesprin-3 connects plectin and vimentin to the nuclear envelope of Sertoli cells but is not required for Sertoli cell function in spermatogenesis. Mol. Biol. Cell. 2013;24:2454–2466. doi: 10.1091/mbc.e13-02-0100. PubMed DOI PMC

Horn H.F., Kim D.I., Wright G.D., Wong E.S.M., Stewart C.L., Burke B., Roux K.J. A mammalian KASH domain protein coupling meiotic chromosomes to the cytoskeleton. J. Cell Biol. 2013;202:1023–1039. doi: 10.1083/jcb.201304004. PubMed DOI PMC

Morimoto A., Shibuya H., Zhu X., Kim J., Ishiguro K., Han M., Watanabe Y. A conserved KASH domain protein associates with telomeres, SUN1, and dynactin during mammalian meiosis. J. Cell Biol. 2012;198:165–172. doi: 10.1083/jcb.201204085. PubMed DOI PMC

Crisp M., Liu Q., Roux K., Rattner J.B., Shanahan C., Burke B., Stahl P.D., Hodzic D. Coupling of the nucleus and cytoplasm: Role of the LINC complex. J. Cell Biol. 2006;172:41–53. doi: 10.1083/jcb.200509124. PubMed DOI PMC

Hao H., Starr D.A. SUN/KASH interactions facilitate force transmission across the nuclear envelope. Nucleus. 2019;10:73–80. doi: 10.1080/19491034.2019.1595313. PubMed DOI PMC

Haque F., Lloyd D.J., Smallwood D.T., Dent C.L., Shanahan C.M., Fry A.M., Trembath R.C., Shackleton S. SUN1 Interacts with Nuclear Lamin A and Cytoplasmic Nesprins To Provide a Physical Connection between the Nuclear Lamina and the Cytoskeleton. Mol. Cell. Biol. 2006;26:3738–3751. doi: 10.1128/MCB.26.10.3738-3751.2006. PubMed DOI PMC

Starr D.A., Fridolfsson H.N. Interactions Between Nuclei and the Cytoskeleton Are Mediated by SUN-KASH Nuclear-Envelope Bridges. Annu. Rev. Cell Dev. Biol. 2010;26:421–444. doi: 10.1146/annurev-cellbio-100109-104037. PubMed DOI PMC

Wang W., Shi Z., Jiao S., Chen C., Wang H., Liu G., Wang Q., Zhao Y., Greene M.I., Zhou Z. Structural insights into SUN-KASH complexes across the nuclear envelope. Cell Res. 2012;22:1440–1452. doi: 10.1038/cr.2012.126. PubMed DOI PMC

Zhou Z., Du X., Cai Z., Song X., Zhang H., Mizuno T., Suzuki E., Yee M.R., Berezov A., Murali R., et al. Structure of Sad1-UNC84 homology (SUN) domain defines features of molecular bridge in nuclear envelope. J. Biol. Chem. 2012;287:5317–5326. doi: 10.1074/jbc.M111.304543. PubMed DOI PMC

Nie S., Ke H., Gao F., Ren J., Wang M., Huo L., Gong W., Feng W. Coiled-Coil Domains of SUN Proteins as Intrinsic Dynamic Regulators. Structure. 2016;24:80–91. doi: 10.1016/j.str.2015.10.024. PubMed DOI

Sosa B.A., Rothballer A., Kutay U., Schwartz T.U. LINC complexes form by binding of three KASH peptides to domain interfaces of trimeric SUN proteins. Cell. 2012;149:1035–1047. doi: 10.1016/j.cell.2012.03.046. PubMed DOI PMC

Hodzic D.M., Yeater D.B., Bengtsson L., Otto H., Stahl P.D. Sun2 is a novel mammalian inner nuclear membrane protein. J. Biol. Chem. 2004;279:25805–25812. doi: 10.1074/jbc.M313157200. PubMed DOI

Kim D.I., Kc B., Roux K.J. Making the LINC: SUN and KASH protein interactions. Biol. Chem. 2015;396:295–310. doi: 10.1515/hsz-2014-0267. PubMed DOI PMC

Yang K., Meinhardt A., Zhang B., Grzmil P., Adham I.M., Hoyer-Fender S. The Small Heat Shock Protein ODF1/HSPB10 Is Essential for Tight Linkage of Sperm Head to Tail and Male Fertility in Mice. Mol. Cell. Biol. 2012;32:216–225. doi: 10.1128/MCB.06158-11. PubMed DOI PMC

Padmakumar V.C., Libotte T., Lu W., Zaim H., Abraham S., Noegel A.A., Gotzmann J., Foisner R., Karakesisoglou I. The inner nuclear membrane protein Sun1 mediates the anchorage of Nesprin-2 to the nuclear envelope. J. Cell Sci. 2005;118:3419–3430. doi: 10.1242/jcs.02471. PubMed DOI

Lee C.-Y., Horn H.F., Stewart C.L., Burke B., Bolcun-Filas E., Schimenti J.C., Dresser M.E., Pezza R.J. Mechanism and Regulation of Rapid Telomere Prophase Movements in Mouse Meiotic Chromosomes. Cell Rep. 2015;11:551–563. doi: 10.1016/j.celrep.2015.03.045. PubMed DOI PMC

Haque F., Mazzeo D., Patel J.T., Smallwood D.T., Ellis J.A., Shanahan C.M., Shackleton S. Mammalian SUN protein interaction networks at the inner nuclear membrane and their role in laminopathy disease processes. J. Biol. Chem. 2010;285:3487–3498. doi: 10.1074/jbc.M109.071910. PubMed DOI PMC

Liu Q., Pante N., Misteli T., Elsagga M., Crisp M., Hodzic D., Burke B., Roux K.J. Functional association of Sun1 with nuclear pore complexes. J. Cell Biol. 2007;178:785–798. doi: 10.1083/jcb.200704108. PubMed DOI PMC

Frohnert C., Schweizer S., Hoyer-Fender S. SPAG4L/SPAG4L-2 are testis-specific SUN domain proteins restricted to the apical nuclear envelope of round spermatids facing the acrosome. Mol. Hum. Reprod. 2011;17:207–218. doi: 10.1093/molehr/gaq099. PubMed DOI

Starr D.A., Han M. Role of ANC-1 in tethering nuclei to the actin cytoskeleton. Science. 2002;298:406–409. doi: 10.1126/science.1075119. PubMed DOI

Gurusaran M., Davies O.R. LINC complex branching through structurally diverse SUN-KASH 6:6 assemblies. bioRxiv. 2020 doi: 10.1101/2020.03.21.001867. PubMed DOI PMC

Zhang Q., Skepper J.N., Yang F., Davies J.D., Hegyi L., Roberts R.G., Weissberg P.L., Ellis J.A., Shanahan C.M. Nesprins: A novel family of spectrin-repeat-containing proteins that localize to the nuclear membrane in multiple tissues. J. Cell Sci. 2001;114:4485–4498. PubMed

Taranum S., Sur I., Müller R., Lu W., Rashmi R.N., Munck M., Neumann S., Karakesisoglou I., Noegel A.A. Cytoskeletal Interactions at the Nuclear Envelope Mediated by Nesprins. Int. J. Cell Biol. 2012;2012:1–11. doi: 10.1155/2012/736524. PubMed DOI PMC

Horn H.F., Brownstein Z., Lenz D.R., Shivatzki S., Dror A.A., Dagan-Rosenfeld O., Friedman L.M., Roux K.J., Kozlov S., Jeang K.-T., et al. The LINC complex is essential for hearing. J. Clin. Investig. 2013;123:740–750. doi: 10.1172/JCI66911. PubMed DOI PMC

Shibuya H., Ishiguro K., Watanabe Y. The TRF1-binding protein TERB1 promotes chromosome movement and telomere rigidity in meiosis. Nat. Cell Biol. 2014;16:145–156. doi: 10.1038/ncb2896. PubMed DOI

Zhang J., Tu Z., Watanabe Y., Shibuya H. Distinct TERB1 Domains Regulate Different Protein Interactions in Meiotic Telomere Movement. Cell Rep. 2017;21:1715–1726. doi: 10.1016/j.celrep.2017.10.061. PubMed DOI

Wang Y., Chen Y., Chen J., Wang L., Nie L., Long J., Chang H., Wu J., Huang C., Lei M. The meiotic TERB1-TERB2-MAJIN complex tethers telomeres to the nuclear envelope. Nat. Commun. 2019;10:1–19. doi: 10.1038/s41467-019-08437-1. PubMed DOI PMC

Schroer T.A. Dynactin. Annu. Rev. Cell Dev. Biol. 2004;20:759–779. doi: 10.1146/annurev.cellbio.20.012103.094623. PubMed DOI

Spindler M.-C., Redolfi J., Helmprobst F., Kollmannsberger P., Stigloher C., Benavente R. Electron tomography of mouse LINC complexes at meiotic telomere attachment sites with and without microtubules. Commun. Biol. 2019;2:376. doi: 10.1038/s42003-019-0621-1. PubMed DOI PMC

Stewart C.L., Burke B. The missing LINC: A mammalian KASH-domain protein coupling meiotic chromosomes to the cytoskeleton. Nucleus. 2014;5:3–10. doi: 10.4161/nucl.27819. PubMed DOI PMC

Kierszenbaum A.L., Rivkin E., Tres L.L. Acroplaxome, an F-Actin–Keratin-containing Plate, Anchors the Acrosome to the Nucleus during Shaping of the Spermatid Head. Mol. Biol. Cell. 2003;14:4628–4640. doi: 10.1091/mbc.e03-04-0226. PubMed DOI PMC

Ketema M., Wilhelmsen K., Kuikman I., Janssen H., Hodzic D., Sonnenberg A. Requirements for the localization of nesprin-3 at the nuclear envelope and its interaction with plectin. J. Cell Sci. 2007;120:3384–3394. doi: 10.1242/jcs.014191. PubMed DOI

Wilhelmsen K., Litjens S.H.M., Kuikman I., Tshimbalanga N., Janssen H., Van Bout I.D., Raymond K., Sonnenberg A. Nesprin-3, a novel outer nuclear membrane protein, associates with the cytoskeletal linker protein plectin. J. Cell Biol. 2005;171:799–810. doi: 10.1083/jcb.200506083. PubMed DOI PMC

Rattner J.B., Brinkley B.R. Ultrastructure of mammalian spermiogenesis. J. Ultrastruct. Res. 1972;41:209–218. doi: 10.1016/S0022-5320(72)90065-2. PubMed DOI

Russell L.D., Russell J.A., MacGregor G.R., Meistrich M.L. Linkage of manchette microtubules to the nuclear envelope and observations of the role of the manchette in nuclear shaping during spermiogenesis in rodents. Am. J. Anat. 1991;192:97–120. doi: 10.1002/aja.1001920202. PubMed DOI

Kierszenbaum A.L. Intramanchette transport (IMT): Managing the making of the spermatid head, centrosome, and tail. Mol. Reprod. Dev. 2002;63:1–4. doi: 10.1002/mrd.10179. PubMed DOI

Zhang X., Lei K., Yuan X., Wu X., Zhuang Y., Xu T., Xu R., Han M. SUN1/2 and Syne/Nesprin-1/2 Complexes Connect Centrosome to the Nucleus during Neurogenesis and Neuronal Migration in Mice. Neuron. 2009;64:173–187. doi: 10.1016/j.neuron.2009.08.018. PubMed DOI PMC

Fan J. A role for the spectrin superfamily member Syne-1 and kinesin II in cytokinesis. J. Cell Sci. 2004;117:619–629. doi: 10.1242/jcs.00892. PubMed DOI

Lin Y.H., Lin Y.M., Wang Y.Y., Yu I.S., Lin Y.W., Wang Y.H., Wu C.M., Pan H.A., Chao S.C., Yen P.H., et al. The expression level of septin12 is critical for spermiogenesis. Am. J. Pathol. 2009;174:1857–1868. doi: 10.2353/ajpath.2009.080955. PubMed DOI PMC

Lin Y.H., Lin Y.M., Teng Y.N., Hsieh T.Y.T., Lin Y.S., Kuo P.L. Identification of ten novel genes involved in human spermatogenesis by microarray analysis of testicular tissue. Fertil. Steril. 2006;86:1650–1658. doi: 10.1016/j.fertnstert.2006.04.039. PubMed DOI

Elkhatib R., Longepied G., Paci M., Achard V., Grillo J.-M., Levy N., Mitchell M.J., Metzler-Guillemain C. Nuclear envelope remodelling during human spermiogenesis involves somatic B-type lamins and a spermatid-specific B3 lamin isoform. MHR Basic Sci. Reprod. Med. 2015;21:225–236. doi: 10.1093/molehr/gau111. PubMed DOI

Fawcett D.W., Phillips D.M. The fine structure and development of the neck region of the mammalian spermatozoon. Anat. Rec. 1969;165:153–183. doi: 10.1002/ar.1091650204. PubMed DOI

Shang Y., Yan J., Tang W., Liu C., Xiao S., Guo Y., Yuan L., Chen L., Jiang H., Guo X., et al. Mechanistic insights into acephalic spermatozoa syndrome–associated mutations in the human SUN5 gene. J. Biol. Chem. 2018;293:2395–2407. doi: 10.1074/jbc.RA117.000861. PubMed DOI PMC

Pierre V., Martinez G., Coutton C., Delaroche J., Yassine S., Novella C., Pernet-Gallay K., Hennebicq S., Ray P.F., Arnoult C. Absence of Dpy19l2, a new inner nuclear membrane protein, causes globozoospermia in mice by preventing the anchoring of the acrosome to the nucleus. Development. 2012;139:2955–2965. doi: 10.1242/dev.077982. PubMed DOI

Méjat A., Misteli T. LINC complexes in health and disease. Nucleus. 2010;1:40–52. doi: 10.4161/nucl.1.1.10530. PubMed DOI PMC

Inhorn M.C., Patrizio P. Infertility around the globe: New thinking on gender, reproductive technologies and global movements in the 21st century. Hum. Reprod. Update. 2015;21:411–426. doi: 10.1093/humupd/dmv016. PubMed DOI

Zhu F., Wang F., Yang X., Zhang J., Wu H., Zhang Z., Zhang Z., He X., Zhou P., Wei Z., et al. Biallelic SUN5 Mutations Cause Autosomal-Recessive Acephalic Spermatozoa Syndrome. Am. J. Hum. Genet. 2016;99:942–949. doi: 10.1016/j.ajhg.2016.08.004. PubMed DOI PMC

Fang J., Zhang J., Zhu F., Yang X., Cui Y., Liu J. Patients with acephalic spermatozoa syndrome linked to SUN5 mutations have a favorable pregnancy outcome from ICSI. Hum. Reprod. 2018;33:372–377. doi: 10.1093/humrep/dex382. PubMed DOI

Protamine 2 deficiency results in Septin 12 abnormalities