Alternative titles; symbols
HGNC Approved Gene Symbol: GMNN
Cytogenetic location: 6p22.3 Genomic coordinates (GRCh38) : 6:24,774,937-24,786,099 (from NCBI)
| Location | Phenotype |
Phenotype MIM number |
Inheritance |
Phenotype mapping key |
|---|---|---|---|---|
| 6p22.3 | Meier-Gorlin syndrome 6 | 616835 | Autosomal dominant | 3 |
The GMNN gene encodes geminin, a nuclear regulator protein that is an inhibitor of replication (summary by Burrage et al., 2015).
McGarry and Kirschner (1998) described a 25-kD protein, designated geminin, which inhibits DNA replication and is degraded during the mitotic phase of the cell cycle. Geminin contains 212 amino acids; it has a destruction box sequence (RRTLKVIQP) and is ubiquitinated by the anaphase-promoting complex in vitro.
Gross (2016) mapped the GMNN gene to chromosome 6p22.3 based on an alignment of the GMNN sequence (GenBank BC005389) with the genomic sequence (GRCh38).
Crystal Structure
Lee et al. (2004) described the crystal structure of the mouse geminin-Cdt1 (605525) complex using a truncated geminin involving residues 79-157 and a truncated Cdt1 including residues 172-368. The N-terminal region of a coiled-coil dimer of truncated geminin interacted with both N-terminal and C-terminal parts of truncated Cdt1. The primary interface relied on the steric complementarity between the truncated geminin dimer and hydrophobic face of the 2 short N-terminal helices of truncated Cdt1 and, in particular, pro181, ala182, tyr183, phe186, and leu189. Lee et al. (2004) concluded that the crystal structure, in conjunction with their biochemical data, indicated that the N-terminal region of truncated geminin might be required to anchor truncated Cdt1, and the C-terminal region of truncated geminin prevents access of the MCM complex to truncated Cdt1 through steric hindrance.
In synchronized HeLa cells, McGarry and Kirschner (1998) demonstrated that geminin is absent during G1 phase, accumulates during S, G2, and M phases, and disappears at the time of the metaphase-anaphase transition. Geminin inhibits DNA replication by preventing the incorporation of minichromosome maintenance (MCM) complex into prereplication complex. McGarry and Kirschner (1998) proposed that geminin inhibits DNA replication during S, G2, and M phases and that geminin destruction at the metaphase-anaphase transition permits replication in the succeeding cell cycle.
Wohlschlegel et al. (2000) demonstrated that geminin interacts tightly with CDT1 (605525), a replication initiation factor necessary for MCM loading. Inhibition of DNA replication by geminin in cell-free cDNA replication extracts could be reversed by the addition of excess CDT1. In the normal cell cycle, CDT1 is present only in G1 and S phases, whereas geminin is present in S and G2 phases. Wohlschlegel et al. (2000) concluded that their results suggest that geminin inhibits inappropriate origin firing by targeting CDT1.
In a yeast 2-hybrid screen, Del Bene et al. (2004) identified the DNA replication-inhibitor geminin as a partner of Six3 (603714). Geminin inhibits cell cycle progression by sequestering Cdt1, the key component for the assembly of the prereplication complex. Del Bene et al. (2004) showed that Six3 efficiently competes with Cdt1 directly to bind to geminin, which reveals how Six3 can promote cell proliferation without transcription. In common with Six3 inactivation, overexpression of the geminin gene in medaka induces specific forebrain and eye defects that are rescued by Six3. Conversely, loss of Gem (in common with gain of Six3) promotes retinal precursor-cell proliferation and results in expanded optic vesicles, markedly potentiating Six3 gain-of-function phenotypes. Del Bene et al. (2004) concluded that the transcription factor Six3 and the replication-initiation inhibitor geminin act antagonistically to control the balance between proliferation and differentiation during early vertebrate eye development.
Luo et al. (2004) showed that murine geminin associates transiently with members of the Hox-repressing polycomb complex, with the chromatin of Hox regulatory DNA elements, and with Hox proteins. Gain- and loss-of-function experiments in the chick neural tube demonstrated that geminin modulates the anterior boundary of Hoxb9 (142964) transcription, which suggests a polycomb-like activity for geminin. The interaction between geminin and Hox proteins prevents Hox proteins from binding to DNA, inhibits HOX-dependent transcriptional activation of reporter and endogenous downstream target genes, and displaces Cdt1 (605525) from its complex with geminin. By establishing competitive regulation, geminin functions as a coordinator of developmental and proliferative control.
Using yeast 1-hybrid and chromatin immunoprecipitation assays, Kim et al. (2006) showed that the C-terminal domain of mouse Gem bound to the leucine repeats of mouse Ap4 (REPIN1; 619039) to form a transcription complex that repressed the promoter of mouse Pahxap1 (PHYHIP; 608511), a neuronal gene, in transfected mouse and human nonneuronal cells. Gem interacted with the corepressor Smrt (NCOR2; 600848) to form an Ap4-Gem-Smrt complex that recruited Hdac3 (605166) to establish and maintain trichostatin A (TSA)-dependent repression of Pahxap1 in nonneuronal cells through histone deacetylation, thereby regulating developmental expression of Pahxap1 in brain. The Ap4-Gem complex also repressed mouse and human DYRK1A (600855), a candidate gene for Down syndrome (DS; 190685). Immunohistochemical analysis confirmed decreased expression of AP4 and GEM and overexpression of DYRK1A in cerebral cortex of DS fetal brain. Restoration of Gem expression in brains of adult mice that expressed little Gem, similar to DS fetal brain, suppressed elevated expression of a reporter gene driven by exogenous Pahxap1 promoter.
Using mouse fetal liver cells and transfected human cells, Ohtsubo et al. (2008) showed that Rae28 (PHC1; 602978) deficiency impaired ubiquitin-proteasome-mediated degradation of geminin and increased geminin protein stability. Retroviral transduction experiments suggested that the resultant accumulation of geminin eliminated hematopoietic stem cell activity in Rae28-deficient mice. Using purified recombinant Polycomb group (PcG) complex-1 reconstituted in insect cells, Ohtsubo et al. (2008) confirmed that Rae28 mediated recruitment of Scmh1 (616396), which provided an interaction domain for geminin, and demonstrated that PcG complex-1 acted as the E3 ubiquitin ligase for geminin in vitro and in vivo. They concluded that PcG complex-1 supports hematopoietic stem cell activity through direct regulation of geminin.
Initiation of DNA replication requires the assembly of a prereplication complex (pre-RC) in late mitosis and G1, with sequential loading of the origin recognition complex (see ORC1; 601902), CDC6 (602627), CDT1, and the MCM2-7 complex (see MCM2; 116945) onto replication origins. Upon initiation of DNA replication, the pre-RC is disassembled, and CDT1 and CDC6 are released from the origins to prevent rereplication. Using human cell lines, Shen et al. (2012) showed that ORCA (LRWD1; 615167) was required for pre-RC assembly and replication initiation. Knockdown of ORCA via small interfering RNA reduced association of ORC and MCM2-7 with chromatin and caused failure of cell cycle progression through S phase. ORCA associated dynamically with different pre-RC components during the cell cycle: it associated with ORC and CDT1 at G1, with ORC(2-5) and geminin in S phase, and with ORC(2-5), phosphorylated CDT1, and phosphorylated geminin during mitosis. ORCA interacted directly with ORC2 (601182), CDT1, and geminin, and ORC2 was required for ORCA stability. Overexpression of geminin reduced the affinity of CDT1 for ORCA, and loss of association between ORCA and CDT1 appeared to be a key step in disassembling the pre-RC at the end of G1 phase.
Ortiz-Alvarez et al. (2019) found that overexpression of Gemc1 (GMNC; 614448) through in utero electroporation in mouse embryos favored formation of pure ependymal cells at the expense of type B1 astrocytes. In contrast, overexpression of geminin favored generation of type B1 cells. The authors concluded that the balance of these 2 sister cells produced through symmetric or asymmetric divisions in mouse embryos was modulated by the expression levels of geminin family genes.
By whole-exome and/or Sanger sequencing in 3 unrelated patients with Meier-Gorlin syndrome (see MGORS6, 616835) in whom no mutations were found in previously identified MGORS-causing genes, Burrage et al. (2015) identified heterozygous de novo mutations in the 5-prime end of the GMNN gene (602842.0001-602842.0003). The mutations were not found in the 1000 Genomes Project or ExAC databases. Functional studies in patient lymphocyte-derived cell lines suggested a gain-of-function mechanism in which the mutation results in a protein lacking the destruction box and hence having increased stability and prolonged inhibition of replication.
Gonzalez et al. (2006) did not find Gmnn-null mouse embryos at any postimplantation stages of development. Ablation of Gmnn prevented formation of the inner cell mass and caused premature endoreduplication at 8 cells, rather than 32 cells. All cells in Gmnn-deficient embryos committed to the trophoblast cell lineage and consisted of trophoblast giant cells only. Gonzalez et al. (2006) concluded that degradation of geminin during S and gap-like phases by proteasome-mediated degradation is part of the mechanism regulating endoreduplication.
By whole-exome sequencing in a patient with Meier-Gorlin syndrome (MGORS6; 616835) in whom no mutations were found in previously identified MGORS-causing genes, Burrage et al. (2015) identified a de novo heterozygous c.16A-T transversion (c.16A-T, NM_015895.4) in exon 2 (the first coding exon) of the GMNN gene, resulting in a lys6-to-ter (L6X) substitution. The mutation, which was confirmed by Sanger sequencing, was not found in the 1000 Genomes Project or ExAC databases. Functional studies in patient lymphocyte-derived cell lines suggested a gain-of-function mechanism in which the mutation results in a protein lacking the destruction box and hence having increased stability and prolonged inhibition of replication.
By whole-exome sequencing in a patient with Meier-Gorlin syndrome (MGORS1; 616835) in whom no mutations were found in previously identified MGORS-causing genes, Burrage et al. (2015) identified a de novo heterozygous 4-bp deletion (c.35_38delTCAA, NM_015895.4) in exon 2 (the first coding exon) of the GMNN gene, resulting in a frameshift (Ile12LysfsTer4) that was predicted to cause premature termination 4 positions downstream. The mutation, which was confirmed by Sanger sequencing, was not found in the 1000 Genomes Project or ExAC databases. Functional studies in patient lymphocyte-derived cell lines suggested a gain-of-function mechanism in which the mutation results in a protein lacking the destruction box and hence having increased stability and prolonged inhibition of replication. This patient had previously been reported by Bongers et al. (2001) (patient 2) and de Munnik et al. (2012) (patient 43).
By Sanger sequencing in a patient with Meier-Gorlin syndrome (MGORS6; 616835) in whom no mutations were found in previously identified MGORS-causing genes, Burrage et al. (2015) identified a de novo heterozygous c.50A-G transition (c.50A-G, NM_015895.4) in the second to last nucleotide of exon 2 (the first coding exon) in the GMNN gene, resulting in a lys17-to-arg (K17R) substitution. The mutation was not found in the 1000 Genomes Project or ExAC databases.
Bongers, E. M. H. F., Opitz, J. M., Fryer, A., Sarda, P., Hennekam, R. C. M., Hall, B. D., Superneau, D. W., Harbison, M., Poss, A., van Bokhoven, H., Hamel, B. C. J., Knoers, N. V. A. M. Meier-Gorlin syndrome: report of eight additional cases and review. Am. J. Med. Genet. 102: 115-124, 2001. [PubMed: 11477602] [Full Text: https://doi.org/10.1002/ajmg.1452]
Burrage, L. C., Charng, W.-L., Eldomery, M. K., Willer, J. R., Davis, E. E., Lugtenberg, D., Zhu, W., Leduc, M. S., Akdemir, Z. C., Azamian, M., Zapata, G., Hernandez, P. P., and 18 others. De novo GMNN mutations cause autosomal-dominant primordial dwarfism associated with Meier-Gorlin syndrome. Am. J. Hum. Genet. 97: 904-913, 2015. [PubMed: 26637980] [Full Text: https://doi.org/10.1016/j.ajhg.2015.11.006]
de Munnik, S. A., Bicknell, L. S., Aftimos, S., Al-Aama, J. Y., van Bever, Y., Bober, M. B., Clayton-Smith, J., Edrees, A. Y., Feingold, M., Fryer, A., van Hagen, J. M., Hennekam, R. C., and 22 others. Meier-Gorlin syndrome genotype-phenotype studies: 35 individuals with pre-replication complex gene mutations and 10 without molecular diagnosis. Europ. J. Hum. Genet. 20: 598-606, 2012. [PubMed: 22333897] [Full Text: https://doi.org/10.1038/ejhg.2011.269]
Del Bene, F., Tessmar-Raible, K., Wittbrodt, J. Direct interaction of geminin and Six3 in eye development. Nature 427: 745-749, 2004. [PubMed: 14973488] [Full Text: https://doi.org/10.1038/nature02292]
Gonzalez, M. A., Tachibana, K. K., Adams, D. J., van der Weyden, L., Hemberger, M., Coleman, N., Bradley, A., Laskey, R. A. Geminin is essential to prevent endoreduplication and to form pluripotent cells during mammalian development. Genes Dev. 20: 1880-1884, 2006. [PubMed: 16847348] [Full Text: https://doi.org/10.1101/gad.379706]
Gross, M. B. Personal Communication. Baltimore, Md. 2/29/2016.
Kim, M.-Y., Jeong, B. C., Lee, J. H., Kee, H. J., Kook, H., Kim, N. S., Kim, Y. H., Kim, J.-K., Ahn, K. Y., Kim, K. K. A repressor complex, AP4 transcription factor and geminin, negatively regulates expression of target genes in nonneuronal cells. Proc. Nat. Acad. Sci. 103: 13074-13079, 2006. [PubMed: 16924111] [Full Text: https://doi.org/10.1073/pnas.0601915103]
Lee, C., Hong, B., Choi, J. M., Kim, Y., Watanabe, S., Ishimi, Y., Enomoto, T., Tada, S., Kim, Y., Cho, Y. Structural basis for inhibition of the replication licensing factor Cdt1 by geminin. Nature 430: 913-917, 2004. [PubMed: 15286659] [Full Text: https://doi.org/10.1038/nature02813]
Luo, L., Yang, X., Takihara, Y., Knoetgen, H., Kessel, M. The cell-cycle regulator geminin inhibits Hox function through direct and polycomb-mediated interactions. Nature 427: 749-753, 2004. [PubMed: 14973489] [Full Text: https://doi.org/10.1038/nature02305]
McGarry, T. J., Kirschner, M. W. Geminin, an inhibitor of DNA replication, is degraded during mitosis. Cell 93: 1043-1053, 1998. [PubMed: 9635433] [Full Text: https://doi.org/10.1016/s0092-8674(00)81209-x]
Ohtsubo, M., Yasunaga, S., Ohno, Y., Tsumura, M., Okada, S., Ishikawa, N., Shirao, K., Kikuchi, A., Nishitani, H., Kobayashi, M., Takihara, Y. Polycomb-group complex 1 acts as an E3 ubiquitin ligase for Geminin to sustain hematopoietic stem cell activity. Proc. Nat. Acad. Sci. 105: 10396-10401, 2008. [PubMed: 18650381] [Full Text: https://doi.org/10.1073/pnas.0800672105]
Ortiz-Alvarez, G., Daclin, M., Shihavuddin, A., Lansade, P., Fortoul, A., Faucourt, M., Clavreul, S., Lalioti, M.-E., Taraviras, S., Hippenmeyer, S., Livet, J., Meunier, A., Genovesio, A., Spassky, N. Adult neural stem cells and multiciliated ependymal cells share a common lineage regulated by the Geminin family members. Neuron 102: 159-172, 2019. [PubMed: 30824354] [Full Text: https://doi.org/10.1016/j.neuron.2019.01.051]
Shen, Z., Chakraborty, A., Jain, A., Giri, S., Ha, T., Prasanth, K. V., Prasanth, S. G. Dynamic association of ORCA with prereplicative complex components regulates DNA replication initiation. Molec. Cell. Biol. 32: 3107-3120, 2012. [PubMed: 22645314] [Full Text: https://doi.org/10.1128/MCB.00362-12]
Wohlschlegel, J. A., Dwyer, B. T., Dhar, S. K., Cvetic, C., Walter, J. C., Dutta, A. Inhibition of eukaryotic DNA replication by geminin binding to Cdt1. Science 290: 2309-2312, 2000. [PubMed: 11125146] [Full Text: https://doi.org/10.1126/science.290.5500.2309]