Alternative titles; symbols
HGNC Approved Gene Symbol: STIL
Cytogenetic location: 1p33 Genomic coordinates (GRCh38): 1:47,250,139-47,314,896 (from NCBI)
| Location | Phenotype |
Phenotype MIM number |
Inheritance |
Phenotype mapping key |
|---|---|---|---|---|
| 1p33 | Microcephaly 7, primary, autosomal recessive | 612703 | Autosomal recessive | 3 |
STIL1 localizes to pericentriolar material surrounding parental centrioles and is essential for centriole duplication during the cell cycle (Vulprecht et al., 2012).
While studying the transcript of the SCL gene (TAL1; 187040), Aplan et al. (1990) identified STIL, which they termed SIL. SIL was identified through a fusion cDNA in a T-cell line resulting from an interstitial deletion between SIL and the 5-prime UTR of SCL (see CYTOGENETICS). As with SCL, SIL showed cross-species conservation. Northern blot analysis detected a 5.5-kb SIL transcript in thymus and T-cell line mRNA.
By Southern blot analysis using a human SIL probe, Collazo-Garcia et al. (1995) detected SIL orthologs in cow and mouse, but not in chicken, shark, fruit fly, or yeast. They cloned mouse Sil, which encodes a deduced 1,262-amino acid protein with numerous potential phosphorylation and N-glycosylation sites. The mouse protein shares 75% identity with the 1,287-amino acid human SIL protein. RT-PCR detected Sil expression in all mouse tissues examined, with highest levels in bone marrow, thymus, spleen, colon, and stomach.
Karkera et al. (2002) found that the human SIL protein contains a putative nuclear localization signal and a cysteine-terminal domain similar to the C-terminal domain of TGF-beta (TGFB1; 190180).
By RT-PCR, Kumar et al. (2009) detected expression of the STIL gene in human fetal brain and suggested that it may be involved in neuronal cell proliferation.
Vulprecht et al. (2012) reported that STIL has a central coiled-coil domain and a STAN domain domain near the C terminus. They found that fluorescence-tagged STIL localized to centrosomes during mitosis in human U2OS osteosarcoma cells. STIL expression at centrosomes began in early G1 phase, gradually increased during late G1 through S to G2 phase, and diminished in anaphase. Immunoelectron microscopy localized STIL to the pericentriolar material surrounding the mother centriole. Fluorescence recovery after photobleaching revealed that a fraction of STIL continuously shuttled between the cytoplasm and centrosomes in U2OS cells.
By quantitative RT-PCR, Li et al. (2013) found that stil was expressed in all adult zebrafish tissues and organs examined. Stil expression was higher in zebrafish embryos than in adult. In situ hybridization of embryos detected high stil mRNA in brain and spinal cord.
Karkera et al. (2002) determined that the STIL gene contains 20 exons, including alternatively spliced exons 13A and 13B and 18A and 18B. The coding region begins in exon 3.
Colaizzo-Anas and Aplan (2003) identified 3 consensus CCAAT boxes, 3 potential SP1 (189906) sites, a potential E2F (see 189971) site, and 2 potential GATA1 (305371) sites in the upstream region of the STIL gene. A region around the major transcription initiation site is highly GC rich, with 34 copies of the CpG dinucleotide. Colaizzo-Anas and Aplan (2003) identified a minimal promoter region between nucleotides -193 and -80 that included all 3 CCAAT boxes.
Using FISH, Karkera et al. (2002) confirmed that the STIL gene maps to chromosome 1p32.
Gross (2013) mapped the STIL gene to chromosome 1p33 based on an alignment of the STIL sequence (GenBank AF349657) with the genomic sequence (GRCh37).
Using Northern blot analysis, Collazo-Garcia et al. (1995) found that the expression of Sil decreased following DMSO-induced differentiation in a mouse erythroleukemia cell line.
Aplan et al. (1997) demonstrated that transgenic mice in which inappropriately expressed human SCL protein, driven by human SIL regulatory elements, developed aggressive T-cell malignancies in collaboration with a misexpressed LMO1 (186921) protein, thus recapitulating the situation seen in a subset of human T-cell ALL. Aplan et al. (1997) also demonstrated that inappropriately expressed SCL could interfere with the development of other tissues derived from mesoderm. Finally, Aplan et al. (1997) demonstrated that an SCL construct lacking the SCL transactivation domain collaborated with misexpressed LMO1, demonstrating that the SCL transactivation domain is dispensable for oncogenesis and supporting the hypothesis that the SCL gene product exerts its oncogenic action through a dominant-negative mechanism.
Colaizzo-Anas and Aplan (2003) found that the promoter regions of the mouse and human SIL genes share a high degree of sequence conservation. Either promoter activated translation of a reporter gene in mouse and human cells, consistent with a high degree of sequence conservation. Expression of both SIL and a SIL/SCL construct that mimicked the SIL/SCL rearrangement were downregulated by DMSO following expression in mouse erythroleukemia cells. The CpG region of the mouse Sil promoter was partially unmethylated in bone marrow DNA, in which the Sil gene is highly expressed, and was more highly methylated in skeletal muscle, liver, and brain DNA, in which Sil is not expressed.
Vulprecht et al. (2012) found that overexpression of PLK4 (605031) in centrin-2 (CETN2; 300006)-expressing HeLa cells induced formation of multiple procentrioles on the parental centriole and accumulation of STIL around the parental centriole. Knockdown of STIL in PLK4-overexpressing cells abrogated centriole overduplication. Stil -/- mouse embryonic fibroblasts (MEFs) lacked centrosomes and primary cilia. Expression of human STIL in Stil -/- MEFs induced reappearance of centrosomes and primary cilia. Overexpression of STIL in U2OS cells resulted in appearance of multiple centriole-like structures, but it did not cause multinucleation. Knockdown of STIL in U2OS cells caused progressive reduction in centrosome number and loss of primary cilia. Knockdown of STIL also diminished centrosomal content of SAS6 (SSAS6; 609321), but not centrin, gamma-tubulin (TUBG1; 191135), or pericentrin (PCNT; 605925). Immunoprecipitation analysis revealed that STIL interacted with CPAP (CENPJ; 609279) in transfected HEK293 cells, suggesting that STIL is part of the centriole duplication machinery. Deletion analysis revealed that the N-terminal half of STIL interacted with CPAP and that the STAN domain of STIL was required for centrosomal localization and duplication.
Moyer et al. (2015) stated that PLK4-dependent phosphorylation of the STAN domain of STIL creates a binding site for SAS6 that is required for SAS6 recruitment to the site of procentriole assembly. They found that the central coiled-coil domain of STIL interacted with both active and inactive PLK4. Interaction with STIL stimulated PLK4 kinase activity, resulting in phosphorylation of STIL on ser1108 and ser1116 within the STAN domain and autophosphorylation of PLK4 on thr170 in the activation loop of the kinase domain. Autophosphorylation of PLK4 stimulated its degradation via the proteasome, and knockdown of STIL stabilized PLK4 at the centrosome. Alanine substitution revealed that phosphorylation of STIL on the STAN domain serines was required for interaction of STIL with centrioles and for centriole duplication. Preventing phosphorylation of STIL reduced SAS6 recruitment to centrioles. Moyer et al. (2015) concluded that PLK4-mediated phosphorylation of STIL increases efficiency of STIL targeting to centrioles, leading to recruitment of SAS6 and centriole duplication.
Liu et al. (2018) found that CEP85 (618898) positively regulated centriole duplication by interacting directly with STIL. Interaction with CEP85 was essential for recruitment and stability of STIL at centrosomes, as well as for subsequent activation of PLK4 during centriole duplication. Interaction of CEP85 and STIL was facilitated through the N-terminal domain of STIL and the C-terminal coiled-coil domain of CEP85. X-ray crystallography and mutation analyses revealed that the proteins interacted through a highly conserved interface, showing a 2:2 binding ratio with 1 N-terminal domain of STIL bound to each of the 2 coiled-coil strands of the parallel CEP85 dimer.
Aplan et al. (1990) identified a fusion cDNA in a T-cell line resulting from an interstitial deletion between SIL and the 5-prime UTR of SCL. They thought it unlikely that a chimeric SIL/SCL protein would be formed, because SIL joined SCL in the SCL 5-prime UTR upstream of an in-frame TAA stop codon preceding the initiation ATG in the SCL message. Similar to 1;14 translocations, the deletion brought SIL and SCL close together and disrupted the 5-prime regulatory region of SCL. Essentially identical deletions were found in 2 other T-cell lines. Aplan et al. (1990) suspected that the rearrangement was mediated by a V-(D)-J recombinase activity, although neither gene encodes an immunoglobulin or T-cell receptor. By pulsed-field gel analysis of NotI-digested genomic DNA, they concluded that the rearrangement was an interstitial deletion of less than 260 kb of chromosome 1.
Brown et al. (1990) reported genomic rearrangement consistent with SIL/SCL fusion in 13 of 50 children with T-cell acute lymphoblastic leukemia. This work showed that growth-affecting genes other than immune receptors risk rearrangements.
Aplan et al. (1992) found the SIL/SCL rearrangement to be several times more frequent than the t(11;14) translocation and specific for T-cell ALL. Leukemic blasts from 30 patients with B-cell precursor ALL failed to show the change. The fusion occurred in the 5-prime UTRs of both genes, preserving the SCL coding region. The net result of this rearrangement was that SCL mRNA expression became regulated by the SIL promoter, leading to inappropriate SCL expression.
Kumar et al. (2009) identified 3 different homozygous mutations in the STIL gene (181590.0001-181590.0003) in affected members of 4 Indian families with primary microcephaly-7 (MCPH7; 612703).
In affected members of a large consanguineous kindred from the Bushehr province of Iran with primary microcephaly-7, Papari et al. (2013) identified a homozygous mutation in the STIL gene (L798W; 181590.0004). The mutation was found by linkage analysis and candidate gene sequencing. This family was ascertained from a larger cohort of 14 families from the same region in Iran with autosomal recessive primary microcephaly. One additional family had a mutation in the ASPM gene (605481), consistent with MCPH5 (608716), but no mutations were found in the other 12 families.
In affected members of a highly consanguineous Pakistani family with MCPH7, Kakar et al. (2015) identified a homozygous truncating mutation in the STIL gene (181590.0005). The mutation, which was found by a combination of homozygosity mapping and whole-exome sequencing, segregated with the disorder in the family.
Izraeli et al. (1999) disrupted the Sil gene in mouse by homologous recombination. Heterozygotes were normal, but mutant homozygotes died in utero after embryonic day 10.5. Between embryonic days 7.5 and 8.5, striking developmental anomalies appeared in Sil -/- embryos. In addition to reduced size and limited developmental progress compared with wildtype embryos, Sil mutants displayed prominent midline neural tube defects, including delay or failure of neural tube closure and holoprosencephaly (236100). In addition, left-right development was abnormal. In heterozygous and wildtype embryos, the embryonic heart tube always looped to the right, whereas in Sil mutants the direction of heart looping was randomized. Nodal (601265), Lefty2 (601877), and Pitx2 (601542) are normally expressed only in the left lateral-plate mesoderm before heart looping, with continued expression of Pitx2 on the left side of the looping heart tube. In contrast, Sil mutants showed bilaterally symmetric expression of Nodal and Pitx2 at all stages examined. For Lefty2, most Sil -/- embryos also showed bilaterally symmetric expression. However, a small number of mutants expressed Lefty2 only on the right. Expression of both Patched (601309) and Gli1 (165220) was greatly reduced in Sil -/- embryos. Shh (600725) and Hnf3b (600288) were expressed in the notochord of Sil mutants. However, the markedly reduced expression of their target genes indicated that Shh signaling in the midline may have been blocked in Sil -/- embryos. Comparison with Shh mutant embryos, which have axial defects but normal cardiac looping, indicated that the consequences of abnormal midline development for left-right patterning depend on the time of onset, duration, and severity of disruption of the normal asymmetric patterns of expression of Nodal, Lefty2, and Pitx2.
The 'night blindness b' (nbb) mutation causes late-onset degeneration of zebrafish retinal dopaminergic interplexiform cells (DA-IPCs). After 4 months of age, heterozygous mutants show decreased visual sensitivity during prolonged dark adaptation and decreased numbers of retinal DA-IPCs. The nbb mutation in homozygosity is embryonic lethal. Li et al. (2013) found that the nbb phenotype is caused by a G-to-A transition in the zebrafish stil gene that alters a donor splice site in intron 8, resulting in an insertion of a 37-bp fragment and introduction of a stop codon. Morpholino-mediated knockdown of stil expression increased DA-IPC susceptibility to neurotoxins. Inhibition of shh (600725) signaling increased the susceptibility of mutant and wildtype DA-IPCs to neurotoxic insult, and elevated shh signaling protected nbb mutant DA-IPCs from neurotoxic insult.
In 3 Indian sibs with primary microcephaly-7 (MCPH7; 612703), Kumar et al. (2009) identified a homozygous 3715C-T transition in exon 18 of the STIL gene, resulting in a gln1239-to-ter (Q1239X) substitution. Each unaffected parent was heterozygous for the mutation, and it was not identified in 202 control chromosomes.
In affected members of 2 Indian families with primary microcephaly-7 (MCPH7; 612703), Kumar et al. (2009) identified a homozygous 1-bp deletion (3655delG) in exon 18 of the STIL gene, predicted to result in a frameshift and premature termination. Haplotype analysis did not suggest a founder effect.
In an Indian patient with primary microcephaly-7 (MCPH7; 612703), born of consanguineous parents, Kumar et al. (2009) identified a homozygous G-to-A transition in intron 16 of the STIL gene, predicted to result in a truncated protein. The mutation was not found in 208 control chromosomes.
In affected members of a large consanguineous family from the Bushehr province of Iran with primary microcephaly-7 (MCPH7; 612703), Papari et al. (2013) identified a homozygous c.2392T-G transversion in exon 14 of the STIL gene, resulting in a leu798-to-trp (L798W) substitution at a conserved residue. The mutation, which was found by linkage analysis and candidate gene sequencing, was not found in 100 Iranian controls. Functional studies were not performed.
In 6 affected members of a highly consanguineous Pakistani family with autosomal recessive primary microcephaly-7 (MCPH7; 612703), Kakar et al. (2015) identified a homozygous G-to-A transition (c.453+5G-A) in intron 5 of the STIL gene, resulting in the skipping of exon 5 and premature termination (Asp89GlyfsTer8). The mutation, which was found by a combination of homozygosity mapping and whole-exome sequencing and confirmed by Sanger sequencing, segregated with the disorder in the family and was not found in the dbSNP or Exome Variant Server databases, in 511 in-house control exomes, or in 90 Pakistani controls. Analysis of patient cells showed that the mutation resulted in a leaky splicing defect in which the majority of transcripts showed aberrant splicing. Brain imaging of 2 of the patients showed features consistent with lobar holoprosencephaly.
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Izraeli, S., Lowe, L. A., Bertness, V. L., Good, D. J., Dorward, D. W., Kirsch, I. R., Kuehn, M. R. The SIL gene is required for mouse embryonic axial development and left-right specification. Nature 399: 691-694, 1999. [PubMed: 10385121] [Full Text: https://doi.org/10.1038/21429]
Kakar, N., Ahmad, J., Morris-Rosendahl, D. J., Altmuller, J., Friedrich, K., Barbi, G., Nurnberg, P., Kubisch, C., Dobyns, W. B., Borck, G. STIL mutation causes autosomal recessive microcephalic lobar holoprosencephaly. Hum. Genet. 134: 45-51, 2015. [PubMed: 25218063] [Full Text: https://doi.org/10.1007/s00439-014-1487-4]
Karkera, J. D., Izraeli, S., Roessler, E., Dutra, A., Kirsch, I., Muenke, M. The genomic structure, chromosomal localization, and analysis of SIL as a candidate gene for holoprosencephaly. Cytogenet. Genome Res. 97: 62-67, 2002. [PubMed: 12438740] [Full Text: https://doi.org/10.1159/000064057]
Kumar, A., Girimaji, S. C., Duvvari, M. R., Blanton, S. H. Mutations in STIL, encoding a pericentriolar and centrosomal protein, cause primary microcephaly. Am. J. Hum. Genet. 84: 286-290, 2009. [PubMed: 19215732] [Full Text: https://doi.org/10.1016/j.ajhg.2009.01.017]
Li, J., Li, P., Carr, A., Wang, X., DeLaPaz, A., Sun, L., Lee, E., Tomei, E., Li, L. Functional expression of SCL/TAL1 interrupting locus (Stil) protects retinal dopaminergic cells from neurotoxin-induced degeneration. J. Biol. Chem. 288: 886-893, 2013. [PubMed: 23166330] [Full Text: https://doi.org/10.1074/jbc.M112.417089]
Liu, Y., Gupta, G. D., Barnabas, D. D., Agircan, F. G., Mehmood, S., Wu, D., Coyaud, E., Johnson, C. M., McLaughlin, S. H., Andreeva, A., Freund, S. M. V., Robinson, C. V., Cheung, S. W. T., Raught, B., Pelletier, L., van Breugel, M. Direct binding of CEP85 to STIL ensures robust PLK4 activation and efficient centriole assembly. Nature Commun. 9: 1731, 2018. Note: Electronic Article. [PubMed: 29712910] [Full Text: https://doi.org/10.1038/s41467-018-04122-x]
Moyer, T. C., Clutario, K. M., Lambrus, B. G., Daggubati, V., Holland, A. J. Binding of STIL to Plk4 activates kinase activity to promote centriole assembly. J. Cell Biol. 209: 863-878, 2015. [PubMed: 26101219] [Full Text: https://doi.org/10.1083/jcb.201502088]
Papari, E., Bastami, M., Farhadi, A., Abedini, S. S., Hosseini, M., Bahman, I., Mohseni, M., Garshasbi, M., Moheb, L. A., Behjati, F., Kahrizi, K., Ropers, H.-H., Najmabadi, H. Investigation of primary microcephaly in Bushehr province of Iran: novel STIL and ASPM mutations. (Letter) Clin. Genet. 83: 488-490, 2013. [PubMed: 22989186] [Full Text: https://doi.org/10.1111/j.1399-0004.2012.01949.x]
Vulprecht, J., David, A., Tibelius, A., Castiel, A., Konotop, G., Liu, F., Bestvater, F., Raab, M. S., Zentgraf, H., Izraeli, S., Kramer, A. STIL is required for centriole duplication in human cells. J. Cell Sci. 125: 1353-1362, 2012. [PubMed: 22349705] [Full Text: https://doi.org/10.1242/jcs.104109]