Alternative titles; symbols
HGNC Approved Gene Symbol: DGCR8
Cytogenetic location: 22q11.21 Genomic coordinates (GRCh38) : 22:20,080,241-20,111,872 (from NCBI)
DGCR8 is a double-stranded RNA-binding protein that interacts with Drosha (608828) and facilitates microRNA (miRNA) maturation (summary by Chen et al., 2012).
By searching for genes within the DiGeorge syndrome (188400) critical region of chromosome 22, followed by PCR of a brain cDNA library and screening a fetal heart cDNA library, Shiohama et al. (2003) cloned DGCR8. The deduced 773-amino acid protein contains a WW motif in its N-terminal half and 2 double-stranded RNA-binding motifs in its C-terminal half. Northern blot analysis of human tissues detected a major transcript of 4.5 kb that was ubiquitously expressed and minor transcripts of 3.5 and 1.5 kb that were found only in testis. In situ hybridization of mouse embryos revealed Dgcr8 expression in neuroepithelium of primary brain, limb bud, vessels, thymus, and palate during various developmental stages.
RNase III proteins play key roles in microRNA (miRNA) biogenesis. The nuclear RNase III Drosha cleaves primary miRNAs (pri-miRNAs) to release hairpin-shaped pre-miRNAs that are subsequently cut to generate mature miRNAs. By immunoprecipitation of human embryonic kidney cell nuclear extracts, Han et al. (2004) found that DGCR8 interacted directly with Drosha, and the 2 proteins were present within a complex of about 650 kD. Both DGCR8 and Drosha could homodimerize in the absence of single-stranded RNA (ssRNA) in addition to interacting with each other. Depletion of DGCR8 from HeLa cells with small interfering RNA led to accumulation of pri-miRNA and loss of pre-miRNA and mature miRNA. Han et al. (2004) concluded that DGCR8 is critical for the processing of pri-miRNA into pre-miRNA.
Gregory et al. (2004) demonstrated that human Drosha is a component of 2 multiprotein complexes. The larger complex contains multiple classes of RNA-associated proteins including RNA helicases, proteins that bind double-stranded RNA, novel heterogeneous nuclear ribonucleoproteins, and the Ewing sarcoma family of proteins. The smaller complex is composed of Drosha and the double-stranded-RNA-binding protein DGCR8, the product of a gene deleted in DiGeorge syndrome. In vivo knockdown and in vitro reconstitution studies revealed that both components of this smaller complex, termed Microprocessor, are necessary and sufficient in mediating the genesis of miRNAs from the primary miRNA transcript.
Han et al. (2006) used computational and biochemical analyses to elucidate the molecular basis for pri-miRNA processing by Drosha-DGCR8. A typical metazoan pri-miRNA consists of an approximately 33-bp stem, with a terminal loop and basal ssRNA segments. Han et al. (2006) found that the basal ssRNA segments were essential for processing, whereas the terminal loop was dispensable. The cleavage site was determined mainly by the distance (about 11 bp) from the stem-ssRNA junction. DGCR8, but not Drosha, interacted with pri-miRNAs directly and specifically, and the basal ssRNA segments were critical for this interaction. Han et al. (2006) proposed that DGCR8 may function as the molecular anchor that measures the distance from the stem-ssRNA junction.
Wang et al. (2007) studied the role of miRNAs in embryonic stem (ES) cell differentiation by generating a Dgcr8 knockout model. Analysis of mouse knockout ES cells showed that DGCR8 is essential for biogenesis of miRNAs. Dgcr8-deficient mouse ES cells proliferated slowly and accumulated in G1 phase of the cell cycle. On the induction of differentiation, Dgcr8-deficient ES cells did not fully downregulate pluripotency markers and retained the ability to produce ES cell colonies; however, they did express some markers of differentiation. This phenotype differed from that reported for Dicer1 (606241) knockout cells, suggesting that Dicer has miRNA-independent roles in ES cell function. Wang et al. (2007) concluded that miRNAs function in the silencing of ES cell self-renewal that normally occurs with the induction of differentiation.
By screening mouse miRNAs for those that could rescue the growth defect in Dgcr8-knockout mouse ES cells, Wang et al. (2008) identified a group of ES cell-specific miRNAs with a shared seed sequence (AAGUGC), including several members of the miR290 cluster. Complementary target sequences were found in the 3-prime UTR of the Cdkn1a (116899) transcript. All 5 ES cell-specific miRNAs tested (miR291a-3p, miR291b-3p, miR294, miR295, and miR302d) directly targeted the 3-prime UTR of Cdkn1a and inhibited reporter gene expression. Target sites were also identified in the 3-prime UTRs of other inhibitors of the cyclin E (see CCNE1; 123837)-CDK2 (116953) pathway, including Rb1 (614041), Rbl1 (116957), Rbl2 (180203), and Lats2 (604861). Quantitative RT-PCR confirmed increased expression of these genes in Dgcr8-knockout mouse ES cells. Wang et al. (2008) concluded that ES cell-specific miRNAs have central roles in expediting the G1-S transition and promoting cellular proliferation.
In the absence of Dgcr8, a protein required for microRNA biogenesis, mouse embryonic stem (ES) cells are unable to suppress self-renewal. Melton et al. (2010) showed that the introduction of let7 (605386) microRNAs, a family of microRNAs highly expressed in somatic cells, can suppress self-renewal in Dgcr8-null but not wildtype ES cells. Introduction of ES cell cell-cycle-regulating (ESCC) microRNAs into the Dgcr8-null ES cells blocked the capacity of let7 to suppress self-renewal. Profiling and bioinformatic analyses showed that let7 inhibits, whereas ESCC microRNAs indirectly activate, numerous self-renewal genes. Furthermore, inhibition of the let7 family promoted dedifferentiation of somatic cells to induced pluripotent stem cells. Melton et al. (2010) concluded that ESCC and LET7 microRNAs act through common pathways to alternatively stabilize the self-renewing versus differentiated cell fates.
Chun et al. (2014) identified a specific disruption of synaptic transmission at thalamocortical glutamatergic projections in the auditory cortex in murine models of schizophrenia-associated 22q11 deletion syndrome (see 600850). This deficit is caused by an aberrant elevation of Drd2 (126450) in the thalamus, which renders 22q11 deletion syndrome thalamocortical projections sensitive to antipsychotics and causes a deficient acoustic startle response similar to that observed in schizophrenic patients. Haploinsufficiency of the miRNA-processing gene Dgcr8 is responsible for the Drd2 elevation and hypersensitivity of auditory thalamocortical projections to antipsychotics. Chun et al. (2014) concluded that this result suggested that DGCR8-miRNA-DRD2-dependent thalamocortical disruption is a pathogenic event underlying schizophrenia-associated psychosis.
Shiohama et al. (2003) determined that the DGCR8 gene contains 14 exons and spans more than 35 kb. The region just upstream of exon 1 shows a high GC and CpG content. The mouse Dgcr8 gene has the same gene structure and size as the human gene.
By genomic sequence analysis, Shiohama et al. (2003) mapped the DGCR8 gene to chromosome 22q11.2. They mapped the mouse Dgcr8 gene to a region of chromosome 16q that shows homology of synteny to human chromosome 22q11.2. However, the chromosomal segment is flipped in mouse as compared with human, so that the orientation of the human and mouse genes is opposite.
Individuals with 22q11.2 microdeletions show behavioral and cognitive deficits and are at high risk of developing schizophrenia. Stark et al. (2008) engineered a mouse strain carrying a hemizygous 1.3-Mb chromosomal deficiency spanning a segment syntenic to the human 22q11.2 locus. The hemizygous microdeletion, called Df(16)A +/-, encompassed 27 genes and represented most of the functional genes in the human segment. Behaviorally, Df(16)A +/- mice were hyperactive compared to wildtype littermates and showed deficits in the PPI task. Males, but not females, appeared fearful of exploring their environment. Stark et al. (2008) found that Df(16)A +/- mice had abnormal brain microarchitecture, although no gross brain abnormalities were present. In the hippocampus, Df(16)A +/- mice had reduced number and size of dendritic spines and decreased dendritic complexity of CA1 pyramidal neurons. Analysis of heterozygous Dgcr8-deficient mice revealed that altered miRNA biogenesis, dendritic complexity, and PPI performance in Df(16)A +/- mice was due to Dgcr8 haploinsufficiency. Stark et al. (2008) concluded that abnormal miRNA processing contributes to the behavioral and neuronal deficits associated with the human 22q11.2 deletion.
Chen et al. (2012) found that mice homozygous for vascular smooth muscle cell (VSMC)-specific deletion of Dgcr8 died by embryonic day-14.5, whereas mice heterozygous for the deletion were viable with no noticeable abnormalities. Examination of embryos showed that deletion of Dgcr8 in VSMCs resulted in growth delay, blood vessel dilation, and extensive liver hemorrhage. Examination of embryonic thoracic aorta revealed that loss of Dgcr8 reduced proliferation, enhanced apoptosis, and disrupted differentiation of VSMCs. Mechanistically, loss of Dgcr8 dysregulated the miRNA biogenesis in VSMCs, thereby affecting cellular survival pathways and contributing to reduced proliferation, enhanced apoptosis, and disrupted differentiation.
Lin et al. (2015) found that mice with Schwann cell (SC)-specific deletion of Dgcr8 developed normally during the first postnatal week, but they developed severe limb defects with reduced peripheral nerve myelination, similar to mouse models of congenital hypomyelination. Immunofluorescence analysis showed that SCs lacking Dgcr8 continued to proliferate, but they failed to downregulate Sox2 (184429) and upregulate Egr2 (129010), lacked myelin gene expression, and displayed increased proliferation and reduced differentiation. Correspondingly, mutant nerves lacking Dgcr8 displayed altered gene expression profiles, with expression of denervation-associated genes. Analysis of gene expression in mutant nerves confirmed that Shh (600725) was a denervation-specific gene. In addition, Dgcr8 was required for myelin maintenance, as Dgcr8 ablation in mature SCs led to dysregulated gene expression and increased macrophage infiltration.
Chen, Z., Wu, J., Yang, C., Fan, P., Balazs, L., Jiao, Y., Lu, M., Gu, W., Li, C., Pfeffer, L. M., Tigyi, G., Yue, J. DiGeorge syndrome critical region 8 (DGCR8) protein-mediated microRNA biogenesis is essential for vascular smooth muscle cell development in mice. J. Biol. Chem. 287: 19018-19028, 2012. [PubMed: 22511778] [Full Text: https://doi.org/10.1074/jbc.M112.351791]
Chun, S., Westmoreland, J. J., Bayazitov, I. T., Eddins, D., Pani, A. K., Smeyne, R. J., Yu, J., Blundon, J. A., Zakharenko, S. S. Specific disruption of thalamic inputs to the auditory cortex in schizophrenia models. Science 344: 1178-1182, 2014. [PubMed: 24904170] [Full Text: https://doi.org/10.1126/science.1253895]
Gregory, R. I., Yan, K., Amuthan, G., Chendrimada, T., Doratotaj, B., Cooch, N., Shiekhattar, R. The Microprocessor complex mediates the genesis of microRNAs. Nature 432: 235-240, 2004. [PubMed: 15531877] [Full Text: https://doi.org/10.1038/nature03120]
Han, J., Lee, Y., Yeom, K.-H., Kim, Y.-K., Jin, H., Kim, V. N. The Drosha-DGCR8 complex in primary microRNA processing. Genes Dev. 18: 3016-3027, 2004. [PubMed: 15574589] [Full Text: https://doi.org/10.1101/gad.1262504]
Han, J., Lee, Y., Yeom, K.-H., Nam, J.-W., Heo, I., Rhee, J.-K., Sohn, S. Y., Cho, Y., Zhang, B.-T., Kim, V. N. Molecular basis for the recognition of primary microRNAs by the Drosha-DGCR8 complex. Cell 125: 887-901, 2006. [PubMed: 16751099] [Full Text: https://doi.org/10.1016/j.cell.2006.03.043]
Lin, H. P., Oksuz, I., Hurley, E., Wrabetz, L., Awatramani, R. Microprocessor complex subunit DiGeorge syndrome critical region gene 8 (Dgcr8) is required for schwann cell myelination and myelin maintenance. J. Biol. Chem. 290: 24294-24307, 2015. [PubMed: 26272614] [Full Text: https://doi.org/10.1074/jbc.M115.636407]
Melton, C., Judson, R. L., Blelloch, R. Opposing microRNA families regulate self-renewal in mouse embryonic stem cells. Nature 463: 621-626, 2010. Note: Erratum: Nature 464: 126 only, 2010. [PubMed: 20054295] [Full Text: https://doi.org/10.1038/nature08725]
Shiohama, A., Sasaki, T., Noda, S., Minoshima, S., Shimizu, N. Molecular cloning and expression analysis of a novel gene DGCR8 located in the DiGeorge syndrome chromosomal region. Biochem. Biophys. Res. Commun. 304: 184-190, 2003. [PubMed: 12705904] [Full Text: https://doi.org/10.1016/s0006-291x(03)00554-0]
Stark, K. L., Xu, B., Bagchi, A., Lai, W.-S., Liu, H., Hsu, R., Wan, X., Pavlidis, P., Mills, A. A., Karayiorgou, M., Gogos, J. A. Altered brain microRNA biogenesis contributes to phenotypic deficits in a 22q11-deletion mouse model. Nature Genet. 40: 751-760, 2008. [PubMed: 18469815] [Full Text: https://doi.org/10.1038/ng.138]
Wang, Y., Baskerville, S., Shenoy, A., Babiarz, J. E., Baehner, L., Blelloch, R. Embryonic stem cell-specific microRNAs regulate the G1-S transition and promote rapid proliferation. Nature Genet. 40: 1478-1483, 2008. [PubMed: 18978791] [Full Text: https://doi.org/10.1038/ng.250]
Wang, Y., Medvid, R., Melton, C., Jaenisch, R., Blelloch, R. DGCR8 is essential for microRNA biogenesis and silencing of embryonic stem cell self-renewal. Nature Genet. 39: 380-385, 2007. [PubMed: 17259983] [Full Text: https://doi.org/10.1038/ng1969]