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HGNC Approved Gene Symbol: SCRIB
Cytogenetic location: 8q24.3 Genomic coordinates (GRCh38) : 8:143,790,925-143,815,773 (from NCBI)
SCRIB is a cytoplasmic multimodular scaffold protein targeted to epithelial adherens junctions and neuronal presynaptic compartments. SCRIB and its orthologs in vertebrates and invertebrates participate in cell polarization (summary by Nola et al., 2008).
EMBOW, or oSCRIB, is a microprotein encoded by an upstream ORF (uORF) of SCRIB that regulates the interactions and chromatin and mitotic functions of WDR5 (609012) (Chen et al., 2023).
By sequencing clones obtained from a size-fractionated myeloid leukemia cell line cDNA library, Nagase et al. (1995) cloned SCRIB, which they designated KIAA0147. The nucleotide sequence contains a central GAG repeat that occurs 19 times within a 36-triplet stretch, creating a glutamine-rich region in the deduced 1,551-amino acid protein. KIAA0147 shares 32% amino acid identity with yeast adenylyl cyclase over a 302-amino acid region. Northern blot analysis revealed expression in all tissues examined, with highest expression in skeletal muscle.
Nakagawa and Huibregtse (2000) identified a 220-kD protein within the lysate of a cervical carcinoma cell line that interacts with human papillomavirus E6 protein. By mass spectrometry of tryptic fragments, followed by searching an EST database, they determined that the E6-interacting protein is KIAA0147, the human homolog of Drosophila Scrib, with which it shares 35% amino acid identity. SCRIB contains a series of N-terminal leucine-rich repeats and 4 central PDZ domains. Comparison with the Drosophila protein suggested that the KIAA0147 cDNA lacks 5-prime sequences specifying approximately 67 amino acids.
Using a positional cloning approach, Murdoch et al. (2003) identified Scrb1 as the mouse gene mutated in the 'circletail' (crc) phenotype, which is characterized by craniorachischisis, a severe neural tube defect. RT-PCR detected several Scrb1 alternative transcripts resulting from inclusion or exclusion of exons 16, 29, or 36. During mouse development, expression of Scrb1 showed a dynamic pattern of expression in a wide variety of organ systems, as well as in neuroepithelium during initiation of neural tube closure. Expression of Scrb1 overlapped with expression of Vangl2 (600533), the gene mutated in 'loop-tail,' a similar defect of neural tube closure. Coexpression was found in neuroepithelium, ventricular myocardium, eyelid, lung epithelium, whisker follicles, and the epithelial lining of the stomach.
EMBOW
Chen et al. (2023) characterized the microprotein oSCRIB, which they renamed EMBOW based on its cellular role. EMBOW is encoded by a uORF of SCRIB variant-1 that extends into the SCRIB coding sequence by 284 nucleotides in the -1 reading frame. The 120-amino acid EMBOW microprotein is completely different from SCRIB due to the alternative reading frame. Database analysis revealed EMBOW orthologs in mouse, cow, pig, and primates. The authors confirmed the presence of endogenous EMBOW in HEK293T cells by immunoblot analysis. EMBOW was ubiquitously expressed in immortalized and primary human cells from various tissues and in cancer. Moreover, EMBOW expression was cell cycle regulated, with a global maximum at late G1 phase and a smaller increase at G2/M. SCRIB expression did not change during the cell cycle, suggesting that EMBOW and SCRIB protein expression is decoupled despite their synthesis from the same mRNA. Immunofluorescence analysis demonstrated that EMBOW localized to nuclei of knockin HEK293T cells during interphase.
Murdoch et al. (2003) determined that the mouse Scrb1 gene contains 38 exons and spans about 23 kb.
By database analysis, Dauber et al. (2013) mapped the SCRIB gene to chromosome 8q24.3.
Nakagawa and Huibregtse (2000) determined that SCRIB binds directly to the human papillomavirus E6 protein. They showed that the binding is mediated by the PDZ domain of SCRIB and a C-terminal epitope of E6. Fluorescence-labeled SCRIB localized to the periphery of canine kidney cells, where it colocalized with ZO1 (TJP1; 601009) in tight junctions. Nakagawa and Huibregtse (2000) determined that SCRIB is targeted for ubiquitination by a complex of E6 and UBE3A (601623) in vitro and that expression of E6 induces degradation of SCRIB and DLG (601014) in vivo. E6 coexpression resulted in loss of integrity of tight junctions, as measured by ZO1 localization, and this effect was dependent on the PDZ-binding epitope of E6.
Montcouquiol et al. (2003) showed that a mutation in the Vangl2 gene results in significant disruptions in the polarization of stereociliary bundles in mouse cochlea as a result of defects in the direction of movement and/or anchoring of the kinocilium within each hair cell. Similar but less severe defects are observed in animals containing a mutation in the LAP protein family gene Scrb1. Polarization defects in animals heterozygous for Vangl2 and Scrb1 are comparable with Vangl2 homozygotes, demonstrating genetic interactions between these genes in the regulation of planar cell polarity in mammals.
Zhan et al. (2008) showed that depletion of Scribble in mammary epithelia disrupted cell polarity, blocked 3-dimensional morphogenesis, inhibited apoptosis, and induced dysplasia in vivo that progressed to tumors after long latency. Like depletion, mislocalization of Scribble from cell-cell junctions was sufficient to promote cell transformation. Spontaneous mammary tumors in mice and humans showed both downregulated and mislocalized Scribble. Zhan et al. (2008) concluded that Scribble has a role as a tumor suppressor.
Using immunoprecipitation analysis, Nola et al. (2008) showed that SCRIB interacted with PAK1 (602590) and PAK2 (605022), serine/threonine kinases crucial for cell migration. Immunohistochemical analysis showed that SCRIB and PAK colocalized at the leading edge of migrating human epithelial cells and mouse embryonic fibroblasts in response to chemoattractants. Knockdown studies with human breast epithelial cells showed that SCRIB was required for localization of PAK and beta-PIX (ARHGEF7; 605477) at the leading edge of migrating cells, PAK activation, formation of membrane protrusions at the leading edge, and cell motility. Circletail mouse fibroblasts also showed reduced motility in response to serum stimulation compared with wildtype fibroblasts. The cell migration defect of SCRIB-deficient cells appeared to be due to loss of PAK activation, since constitutively active PAK rescued chemotaxis in SCRIB-deficient cells. Depletion of beta-PIX or SCRIB caused comparable defects in cell migration and PAK activation. Nola et al. (2008) concluded that SCRIB participates in lamellipodia formation through activation of PAK at the leading edge of migratory cells.
Dow et al. (2008) found that knockdown of SCRIB via small hairpin RNA cooperated with oncogenic RAS (HRAS; 190020) or RAF (RAF1; 164760) mutants to promote an invasive phenotype in MCF10A breast epithelia cells. The invasive phenotype was predominantly due to loss of SCRIB-dependent suppression of MAP kinase signaling.
Khalil et al. (2018) identified surface modulation of erythropoietin receptor (EPOR; 133171) as a critical component of the erythroid iron deprivation response. Iron deprivation significantly decreased surface EPOR levels and affected capacity for downstream signaling in human cells, and knockin mice with enforced surface retention of Epor failed to develop anemia with iron deprivation. Further investigation identified SCRIB as an iron response factor regulated by the erythroid iron-deprivation response that influenced surface EPOR display. In cytosolic and membrane fractions of human erythroblasts, SCRIB appeared as 3 to 4 species ranging from approximately 180 to 250 kD, with the largest form predominating in cytosolic and whole-cell lysate preparations. The presence of multiple species appeared to be caused by differential ubiquitylation of SCRIB. Immunofluorescence analysis of iron-replete erythroblasts revealed that SCRIB was concentrated at the cell periphery, but it also distributed throughout the cytoplasm in a vesicular pattern. Erythroid iron deprivation caused downregulation of SCRIB through mediation of cathepsin (see 613111) and the iron-sensing transferrin receptor-2 (TFR2; 604720). SCRIB deficiency in turn reduced surface expression of EPOR but selectively retained survival signaling via AKT (164730), thereby providing a means for integration of iron sensing with receptor function to permit modulation of progenitor expansion without compromising survival.
Metais et al. (2005) demonstrated that SCRIB interacted with ZO2 (607709), mediated by the PDZ domains of SCRIB and the C-terminal motif of ZO2. Immunostaining showed partial colocalization of the 2 proteins at cell-cell junctions, suggesting that their interaction takes place there. Tyrosine phosphorylation of SCRIB did not affect its interaction with ZO2.
Using mammalian 2-hybrid assays and GST pull-down experiments, Petit et al. (2005) demonstrated that the PDZ domains of SCRIB directly bind the C terminus of TRIP6 (602933). Mutation analysis showed that, among the 4 PDZ domains of SCRIB, the third PDZ domain was required for an efficient interaction with TRIP6. However, interaction with SCRIB was not essential for targeting TRIP6 to cell-cell contacts and to focal adhesions.
Qin et al. (2005) found that SCRIB knockdown caused a delay in tight junction assembly in MDCK II cells. MDCK II cells with SCRIB knockdown also lost their epithelial morphology at low density and displayed increased cell motility with attenuated orientated migration, suggesting that SCRIB might regulate epithelial cell adhesion and/or migration. These effects by SCRIB on MDCK II cells were independent of beta-PIX (ARHGEF7; 605477) binding, indicating that SCRIB did not regulate the HGF (142409) signaling pathway. Instead, SCRIB was found to be required for E-cadherin (192090)-mediated adhesion, as loss of SCRIB in MDCK II cells caused a defect in adherens junction structure and compromised E-cadherin-mediated cell-cell adhesion without affecting the exocytosis or endocytosis of E-cadherin. Depletion of E-cadherin phenocopied the effects of SCRIB loss, and expression of an E-cadherin-alpha-catenin (116805) fusion protein reversed the effects of SCRIB loss, further confirming the SCRIB regulation of epithelial cell adhesion and migration through E-cadherin.
Takizawa et al. (2006) demonstrated that SCRIB interacted with APC (175100), mediated by the PDZ domains 1 and 4 of SCRIB and the C-terminal PDZ domain-binding motif of APC. In support, SCRIB and APC were found to colocalize in cultured MDCK cells and cultured rat hippocampal neurons. APC and high-risk HPV E6 proteins contain the class 1 PDZ-binding motif threonine/serine-X-leucine/valine at their C termini, and overexpression of the C-terminal PDZ domain-binding motif of APC and high-risk HPV E6 disrupted the junctional integrity of epithelial cells, suggesting the functional importance of the association between SCRIB and APC. In addition, knockdown of SCRIB disrupted proper localization of APC at the adherens junction, indicating that complex formation between SCRIB and APC was required for normal localization of APC.
Stewart et al. (2023) demonstrated that Scribble directly interacted and colocalized with the G protein-coupled receptor PTHR (PTH1R; 168468) in MDCK cells. Analysis with purified recombinant proteins showed that PDZ domains 1 and 3 of Scribble specifically bound the C-terminal PDZ-binding motif (PBM) of PTHR. Moreover, the crystal structure of Scribble PDZ1 and PDZ3 in complex with PTHR PBM provided conformational bases and defined the key residues involved in the binding. Mice with renal proximal tubule-specific deletion of Scribble showed increased plasma phosphate and decreased vitamin D, indicating a role for Scribble in renal phosphate homeostasis.
EMBOW
Chen et al. (2023) found that mouse and human EMBOW interacted directly with WDR5 via the WIN site of WDR5. EMBOW knockout in HEK293T cells showed that EMBOW specifically regulated the WIN-site interactome of WDR5 through its interaction with WDR5. Loss of EMBOW decreased WDR5 on the spindle pole during mitosis, shortened mitotic spindle length, prolonged G2/M phase, and delayed proliferation. Furthermore, loss of EMBOW increased WDR5 and H3K4me3 levels of de novo genes and dysregulated WDR5 binding to off-target genes and the mitotic spindle.
Based on findings in mouse models (e.g., Murdoch et al., 2003), Robinson et al. (2012) sequenced the SCRIB gene in 36 fetuses with craniorachischisis (CRN), the most severe type of neural tube defect (see 182940) in which the neural tube remains open from the midbrain or rostral hindbrain to the base of the spine. Two of 36 fetuses with CRN were found to carry heterozygous missense variations: P454S and R1535Q, respectively. Cellular transfection of the R1535Q mutation resulted in increased abnormal localization of the mutant protein in the cytoplasm rather than at the membrane, but it showed normal interaction with VANGL2 (600533). The P454S variant protein, which was not conserved between species, showed localization similar to wildtype, suggesting that it is not pathogenic.
Lei et al. (2013) identified 3 heterozygous putatively pathogenic missense variants in the SCRIB gene in 3 (1.6%) of 192 infants with spina bifida (see 182940). All mutations, P1043L, P1332L, and L1520R, occurred at highly conserved residues and were demonstrated to have increased cytoplasmic localization compared to wildtype, but none lost the physical interaction with VANGL2. None of the mutations were found in the dbSNP or 1000 Genomes Project databases or in 190 control infants, but P1332L was found in the Exome Variant Server database with a minor allele frequency of 0.007 among European American populations. Lei et al. (2013) suggested that variation in the SCRIB gene may contribute to the multifactorial etiology of neural tube defects.
Dauber et al. (2013) reported 5 unrelated children with 5 different heterozygous de novo interstitial deletions of chromosome 8q24.3 (615583); the children were identified from a cohort of patients who underwent array comparative genomic hybridization (aCGH). The deletions ranged from 78 kb to 1 Mb, and none of the breakpoints were the same. The minimal common deletion encompassed 3 genes: SCRIB, NRBP2 (615563), and PUF60 (604819). Morpholino knockout of these genes in zebrafish suggested that haploinsufficiency for SCRIB and PUF60 was responsible for the phenotype, whereas loss of NRBP2 was considered unlikely to contribute to the clinical features. The patients had facial dysmorphism and global growth retardation, including 3 with microcephaly; all but 1 had developmental delay. Common dysmorphic facial features included long philtrum, anteverted nares, short nose, thin upper lip, and broad nasal root. More variable features included microretrognathia, coloboma, short neck, preauricular pits, and bitemporal narrowing. All but 1 patient had renal abnormalities, including unilateral renal agenesis, renal hypoplasia, polycystic kidneys, and ectopic renal fusion. Three patients had vertebral abnormalities, such as sacral dysplasia, coccyx agenesis, vertebral fusion, or hemivertebrae, and 4 had joint laxity or hip dislocation. Two patients had cardiac ventricular defects.
Circletail (crc) is a mouse phenotype characterized by craniorachischisis, a severe neural tube defect. Murdoch et al. (2003) determined that the circletail mutation is a 1-bp insertion in the Scrb1 gene, resulting in a frameshift that leads to premature termination of the protein.
Phillips et al. (2007) found that crc mouse mutants developed heart malformation and cardiomyopathy attributable to abnormalities in cardiomyocyte organization within the early heart tube. N-cadherin (CDH2; 114020) was lost from the cardiomyocyte cell membrane and cell-cell adhesion was disrupted. This resulted in abnormalities in heart looping and in formation of both the trabeculae and compact myocardium, which ultimately resulted in cardiac misalignment defects and ventricular noncompaction. Mislocalization of Vangl2 (600533) in crc/crc cardiomyocytes suggested that wildtype Scrib acts in the planar cell polarity pathway in the heart. Moreover, heterozygosity for mutations in both Scrib and Vangl2 caused cardiac defects similar to those found in homozygous mutants for each gene but without other major defects.
In humans, the PUF60 (604819) and SCRIB genes map to a region of chromosome 8q24.3 subject to copy number variation associated with coloboma, microcephaly, developmental delay, short stature, and craniofacial, cardiac, and renal defects (615583). Dauber et al. (2013) found that morpholino-mediated knockdown of either Puf60 or Scrib in zebrafish recapitulated some of these phenotypes, including reduced body length, microcephaly, and retrognathia. Knockdown of Scrib, but not Puf60, also resulted in coloboma and gross edema. Knockdown of both genes exacerbated the short stature phenotype.
Chen, Y., Su, H., Zhao, J., Na, Z., Jiang, K., Bacchiocchi, A., Loh, K. H., Halaban, R., Wang, Z., Cao, X., Slavoff, S. A. Unannotated microprotein EMBOW regulates the interactome and chromatin and mitotic functions of WDR5. Cell Rep. 42: 113145, 2023. [PubMed: 37725512] [Full Text: https://doi.org/10.1016/j.celrep.2023.113145]
Dauber, A., Golzio, C., Guenot, C., Jodelka, F. M., Kibaek, M., Kjaergaard, S., Leheup, B., Martinet, D., Nowaczyk, M. J. M., Rosenfeld, J. A., Zeesman, S., Zunich, J., Beckmann, J. S., Hirschhorn, J. N., Hastings, M. L., Jacquemont, S., Katsanis, N. SCRIB and PUF60 are primary drivers of the multisystemic phenotypes of the 8q24.3 copy-number variant. Am. J. Hum. Genet. 93: 798-811, 2013. Note: Erratum: Am. J. Hum. Genet. 93: 994 only, 2013. [PubMed: 24140112] [Full Text: https://doi.org/10.1016/j.ajhg.2013.09.010]
Dow, L. E., Elsum, I. A., King, C. L., Kinross, K. M., Richardson, H. E., Humbert, P. O. Loss of human Scribble cooperates with H-Ras to promote cell invasion through deregulation of MAPK signalling. Oncogene 27: 5988-6001, 2008. [PubMed: 18641685] [Full Text: https://doi.org/10.1038/onc.2008.219]
Khalil, S., Delehanty, L., Grado, S., Holy, M., White, Z., III, Freeman, K., Kurita, R., Nakamura, Y., Bullock, G., Goldfarb, A. Iron modulation of erythropoiesis is associated with Scribble-mediated control of the erythropoietin receptor. J. Exp. Med. 215: 661-679, 2018. [PubMed: 29282252] [Full Text: https://doi.org/10.1084/jem.20170396]
Lei, Y., Zhu, H., Duhon, C., Yang, W., Ross, M. E., Shaw, G. M., Finnell, R. H. Mutations in planar cell polarity gene SCRIB are associated with spina bifida. PLoS One 8: e69262, 2013. Note: Electronic Article. [PubMed: 23922697] [Full Text: https://doi.org/10.1371/journal.pone.0069262]
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