Alternative titles; symbols
HGNC Approved Gene Symbol: NR2F1
SNOMEDCT: 770723007;
Cytogenetic location: 5q15 Genomic coordinates (GRCh38): 5:93,583,222-93,594,611 (from NCBI)
| Location | Phenotype |
Phenotype MIM number |
Inheritance |
Phenotype mapping key |
|---|---|---|---|---|
| 5q15 | Bosch-Boonstra-Schaaf optic atrophy syndrome | 615722 | Autosomal dominant | 3 |
The NR2F1 gene encodes a conserved nuclear receptor protein that regulates transcription (summary by Bosch et al., 2014).
Miyajima et al. (1988) identified the ERBA-related gene EAR3. The predicted EAR3 protein was very similar in primary structure to receptors for steroid hormones and thyroid hormone. The EAR3 and EAR2 (132880) amino acid sequences share 86% homology in the DNA-binding domain and 76% homology in the putative ligand-binding domain. Northern blot analysis of human fetal tissue showed ubiquitous expression of EAR3.
Chicken ovalbumin upstream promoter transcription factors (COUP-TFs) are members of the steroid/thyroid hormone receptor superfamily. Qiu et al. (1995) noted that, like other members of the family, COUP-TFs contain a DNA-binding domain and a putative ligand-binding domain. They are also response elements for several other members of the superfamily, namely, the vitamin D receptor (277440), the thyroid hormone receptor (see 190120), the retinoic acid receptor (see RARA; 180240), and the retinoid X receptor (see 180245). COUP-TFs are expressed in many tissues and in various cell lines. Furthermore, in situ hybridization experiments demonstrated that COUP-TFs are highly expressed during mouse embryonic development. Their expression patterns are spatially and temporally regulated, suggesting that COUP-TFs may be involved in organogenesis.
At mouse embryonic day 11.5 (E11.5), at the onset of cerebral corticogenesis, Zhou et al. (2001) found that Coup-Tfi showed a graded pattern of expression in neocortex. Coup-Tfi expression was higher in caudolateral regions and lower in rostromedial areas. This gradient of expression was maintained in the cortical plate after birth.
By immunohistochemical analysis, Armentano et al. (2006) found that Couptf1 localized to regions of developing mouse brain from which major forebrain neuronal tracts originated.
By immunohistochemical analysis of mature mouse retina, Inoue et al. (2010) found that Coup-Tfi was expressed in more cell types than Coup-Tfii (NR2F2; 107773) in the inner nuclear layer.
Tang et al. (2010) found that both Coup-Tfi and Coup-Tfii were expressed in dorso-distal optic vesicles and in a 'ventral high-dorsal low' gradient in the presumptive retinal pigment epithelium (RPE) in mouse at E9.5. The 2 proteins showed differences in expression in some early eye structures, and Coup-Tfii was generally more abundant than Coup-Tfi.
Two COUP-TF genes have been identified in the human: COUP-TFI, also referred to as EAR3 and NR2F1, and COUP-TFII, also called ARP1. To determine whether the genomic organization is conserved between human and mouse, Qiu et al. (1995) isolated these 2 genes in the mouse and characterized their structure. Both genes have relatively simple structures, with 3 coding exons, that are similar to those of their human counterparts.
Miyajima et al. (1988) mapped the EAR3 gene to chromosome 5 by hybridization analysis of DNAs from sorted chromosomes.
Qiu et al. (1995) mapped the mouse COUP-TFI gene to the distal region of chromosome 13 and COUP-TFII to the central region of chromosome 7. Furthermore, they mapped human COUP-TFI to 5q14 and COUP-TFII to 15q26 (where the gene designated ARP1 had been localized). The human chromosomal localization was achieved by isotopic in situ hybridization; the murine assignments by interspecific backcross analysis.
Inoue et al. (2010) found that forced expression of Coup-Tfi or Coup-Tfii in embryonic mouse retinal explant cultures reduced the number of cells expressing markers of rod photoreceptors. In contrast, the Coup-Tfs increased the number of cells expressing markers of cone photoreceptors and increased the number of glycinergic amacrine cells.
Tang et al. (2010) found that knockdown of both COUP-TFI and COUP-TFII in ARPE-19 human RPE cells via small interfering RNA increased expression of PAX6 (607108) and reduced expression of OTX2 (600037) and MITF (156845), which are key RPE genes, as well as VAX2 (604295), a negative regulator of PAX6. In contrast, overexpression of COUP-TFs repressed PAX6 expression. Chromatin immunoprecipitation experiments and reporter gene assays showed that both COUP-TFs bound a direct repeat element in the PAX6 promoter and downregulated PAX6 and OTX2 expression.
Bovetti et al. (2013) reported that Couptf1 regulated tyrosine hydroxylase (TH; 191290) expression in adult mouse olfactory bulb cells through activity-dependent induction of Zif268 (EGR1; 128990). They concluded that Couptf1 has a role in regulating sensory-dependent plasticity in olfactory dopaminergic neurons in adult mouse.
In 2 patients with Bosch-Boonstra-Schaaf optic atrophy syndrome (BBSOAS; 615722), Bosch et al. (2014) identified heterozygous deletions of chromosome 5q (0.83 Mb and 2.85 Mb, respectively) encompassing the NR2F1 gene.
In 5 patients with BBSOAS, including an affected father and son (individuals 17 and 18, respectively), Chen et al. (2016) identified large heterozygous deletions on chromosome 5, ranging from 0.2 to 5.0 Mb and encompassing the NR2F1 gene.
In 4 patients with Bosch-Boonstra-Schaaf optic atrophy syndrome (BBSOAS; 615722), Bosch et al. (2014) identified 4 different de novo heterozygous missense mutations in the NR2F1 gene (132890.0001-132890.0004). Mutations in the first 2 patients were found by whole-exome sequencing of 12 patients with a similar phenotype. In vitro functional expression assays with a luciferase reporter in HEK293 cells showed that all the mutant proteins had significantly decreased transcriptional activity compared to wildtype. The findings suggested haploinsufficiency as the pathogenetic mechanism for the disorder. The patients had delayed development, moderately impaired intellectual development, and optic atrophy. Most patients also had evidence of cerebral visual impairment. Dysmorphic facial features were variable and nonspecific.
In 15 patients with BBSOAS, Chen et al. (2016) identified 15 de novo heterozygous mutations in the NR2F1 gene, including 7 missense mutations, 5 mutations that disrupted translation initiation (see, e.g., 132890.0005), 2 indels resulting in a frameshift, and an in-frame indel. The mutations were identified by whole-exome sequencing and confirmed by Sanger sequencing, or by chromosome microarray analysis in the case of deletions. Five of the missense mutations were located in the DNA-binding domain (DBD), 1 was located adjacent to the DBD domain, and 1 was located in the ligand-binding domain (LBD).
Martin-Hernandez et al. (2018) identified a de novo heterozygous mutation in the DBD of the NR2F1 gene (K96E; 132890.0006) in a 17-year-old Spanish patient with BBSOAS. The mutation was found by whole-exome sequencing and confirmed by Sanger sequencing.
In a 7-year-old Korean boy with BBSOAS, Park et al. (2019) identified a heterozygous nonsense mutation in the NR2F1 gene (Y171X; 132890.0007). Parental testing was not performed. The mutation was identified using a next-generation sequencing panel of 429 genes associated with hereditary optic neuropathy.
By whole-exome sequencing, Starosta et al. (2020) identified a de novo heterozygous Y171X mutation in the NR2F1 gene in a woman with BBSOAS who had previously been diagnosed with congenital disorder of glycosylation type Ic (see 604566.0007).
In a 30-year-old man with BBSOAS, Bojanek et al. (2020) identified a de novo heterozygous nonsense mutation in the NR2F1 gene (Q28X; 132890.0008). The mutation was identified by trio whole-exome sequencing.
In a boy with severe BBSOAS, Walsh et al. (2020) identified a de novo heterozygous frameshift mutation in the LBD of the NR2F1 gene (c.1080del; 132890.0009). Because the mutation occurred in the last exon of N2RF1, Walsh et al. (2020) speculated that the resultant mRNA might not be subject to nonsense-mediated decay, raising the question of whether there may be a dominant-negative effect in this case as has been considered for missense mutations affecting the DBD.
Chen et al. (2016) assessed molecular and clinical features in 20 patients with BBSOAS. The 5 patients with microdeletions encompassing the NR2F1 gene had a lower prevalence of several clinical features when compared to 5 patients with missense mutations that completely abolish transcriptional activity, including hypotonia, oromotor dysfunction, thin corpus callosum, repetitive behaviors, autism spectrum disorder, seizures, and hearing defects. These findings led Chen et al. (2016) to consider whether a dominant-negative effect plays a role in BBSOAS.
Rech et al. (2020) compared the prevalence of clinical features between 22 patients with BBSOAS and point mutations or in-frame deletions in the DNA-binding domain (DBD) of the NR2F gene and 32 patients with BBSOAS and whole-gene deletions, nonsense mutations, frameshift mutations, or point mutations outside of the DBD. Rech et al. (2020) found that mutations in the DBD were associated with a higher prevalence of motor delay, the inability to walk unassisted, the absence of speech, seizures, and sensitivity to touch compared to other types of mutations.
Using Coup-Tfi-null mice, Zhou et al. (2001) showed that Coup-Tfi was required for regional and graded expression of several neocortical markers, including Id2 (600386), Ror-beta (RORB; 601972), and cadherin-8 (CDH8; 603008). Graded expression of the limbic system-associated protein Lamp (LSAMP; 603241) was also lost in Coup-Tfi-null mice, concomitant with misguided thalamocortic projection neurons. Coup-Tfi appeared to act through a pathway that differed from that of Pax6 and Emx2 (600035).
Armentano et al. (2006) found that all homozygous Couptf1-null mice died at perinatal stages prior to weaning. Absence of Couptf1 in mouse brain resulted in callosal axons that arrived at the midline but were unable to cross and swirled into longitudinal neuromas called Probst bundles. Aberrant fibers also projected abnormally along the anterior-posterior axis. Similarly, Couptf1-null hippocampal axons stopped at the midline and projected abnormally toward the anterior commissure (AC), while some mutant AC fibers misrouted toward the hippocampal commissure. Microarray, real-time PCR, and immunohistochemical analyses of cultured hippocampal neurons revealed that loss of Couptf1 perturbed expression of cytoskeletal molecules involved in axon guidance and neuronal migration. Expression of the microtubule-associated protein Map1b (157129) was reduced, whereas expression of the Rho-GTPase Rnd2 (601555) was elevated, in Couptf1-null neurons.
By comparing transgenic Couptf1-overexpressing mice and Couptf1-null mice, Faedo et al. (2008) found that Couptf1 dosage regulated patterning of cortical progenitor cells. Couptf1 promoted ventral cortical fate, cell cycle exit, and neural differentiation and regulated the balance of early- and late-born neurons and the balanced production of different types of layer V cortical projection neurons. Couptf1 controlled these processes by repressing Map kinase (see 176948) and Wnt (see 164820) signaling pathways.
Tang et al. (2010) noted that both Coup-Tfi-null mice and Coup-Tfii-null mice die early during development. Using conditional deletion of Coup-Tfi and Coup-Tfii in mouse eye and ventral forebrain, Tang et al. (2010) found that the Coup-Tf genes compensated for each other, resulting in mice lacking major eye abnormalities. When all 4 alleles of the Coup-Tf genes were deleted, mutant mice displayed severe coloboma and microphthalmia, which persisted after birth. Examination of double-knockout mice revealed that Coup-Tfi and Coup-Tfii were required for differentiation of the neural retina and ventral and dorsal optic stalk. Double mutants showed increased expression of Pax6 in prospective RPE, followed by transformation of RPE cells into neural retina.
Alfano et al. (2011) reported that loss of Couptf1 in mice affected neuronal radial migration in presumptive somatosensory cortex, concomitant with elevated Rnd2 expression and loss of the Rnd2 expression gradient. Chromatin immunoprecipitation analysis showed that Couptf1 directly bound to 5 sites in and near the Rnd2 gene. Lowering Rnd2 expression in Couptf1-null mice via short hairpin RNA largely rescued the distribution and morphologic defects in Couptf1-deficient neurons.
In a 12-year-old boy with Bosch-Boonstra-Schaaf optic atrophy syndrome (BBSOAS; 615722), Bosch et al. (2014) identified a de novo heterozygous c.344G-C transversion in the NR2F1 gene, resulting in an arg115-to-pro (R115P) substitution at a highly conserved residue in the DNA-binding domain. The mutation was found by whole-exome sequencing. In vitro functional expression assays with a luciferase reporter in HEK293 cells showed that the mutant protein had significantly decreased transcriptional activity compared to wildtype.
In a 2-year-old girl with Bosch-Boonstra-Schaaf optic atrophy syndrome (BBSOAS; 615722), Bosch et al. (2014) identified a de novo heterozygous c.339C-A transversion in the NR2F1 gene, resulting in a ser113-to-arg (S113R) substitution at a highly conserved residue in the DNA-binding domain. The mutation was found by whole-exome sequencing. In vitro functional expression assays with a luciferase reporter in HEK293 cells showed that the mutant protein had significantly decreased transcriptional activity compared to wildtype.
In an 18-year-old girl with Bosch-Boonstra-Schaaf optic atrophy syndrome (BBSOAS; 615722), Bosch et al. (2014) identified a de novo heterozygous c.755T-C transition in the NR2F1 gene, resulting in a leu252-to-pro (L252P) substitution at a highly conserved residue in the ligand-binding domain. In vitro functional expression assays with a luciferase reporter in HEK293 cells showed that the mutant protein had significantly decreased transcriptional activity compared to wildtype.
In a 35-year-old woman with Bosch-Boonstra-Schaaf optic atrophy syndrome (BBSOAS; 615722), Bosch et al. (2014) identified a de novo heterozygous c.335G-A transition in the NR2F1 gene, resulting in an arg112-to-lys (R112K) substitution at a highly conserved residue in the DNA-binding domain. The mutation was found by whole-exome sequencing. In vitro functional expression assays with a luciferase reporter in HEK293 cells showed that the mutant protein had significantly decreased transcriptional activity compared to wildtype.
In 2 unrelated patients (individuals 13 and 14), aged 3 and 12 years, respectively, with Bosch-Boonstra-Schaaf optic atrophy syndrome (BBSOAS; 615722), Chen et al. (2016) identified a de novo heterozygous c.2T-C transition in the NR2F1 gene affecting the start codon (M1?). The mutation was identified by whole-exome sequencing and confirmed by Sanger sequencing. The mutation was not found in any of the parents. Fibroblasts from both patients showed reduced NR2F1 mRNA and protein expression, indicating that the mutation affects both gene transcription and translation.
In a 17-year-old Spanish girl with Bosch-Boonstra-Schaaf optic atrophy syndrome (BBSOAS; 615722), Martin-Hernandez et al. (2018) identified a de novo heterozygous c.286A-G transition (c.286A-G, NM_005654) in the NR2F1 gene, resulting in a lys96-to-glu (K96E) substitution in a conserved region of the DNA-binding domain. The mutation was found by whole-exome sequencing and confirmed by Sanger sequencing. Neither parent had the mutation. The mutation was not found in the 1000 Genomes Project, EVS, ExAC, or gnomAD databases. A dual-luciferase assay in HEK293T cells transfected with a plasmid containing the K96E mutation showed that the mutation resulted in reduced transcriptional activity.
In a 7-year-old Korean boy with Bosch-Boonstra-Schaaf optic atrophy syndrome (BBSOAS; 615722), Park et al. (2019) identified a heterozygous c.513C-G transversion (c.513C-G, NM_005654.4) in the NR2F1 gene, resulting in a tyr171-to-ter (Y171X) substitution in the DBD domain. Parental testing was not performed. The mutation was identified using a next-generation sequencing panel of 429 genes associated with hereditary optic neuropathy. The mutation was not identified in the 1000 Genomes Project, EVS, ExAC, or gnomAD databases. Functional studies were not performed.
By whole-exome sequencing in a 31-year-old woman diagnosed with BBSOAS, Starosta et al. (2020) identified heterozygosity for a de novo Y171X mutation in the NR2F1 gene. The patient had previously been reported with a diagnosis of congenital disorder of glycosylation type Ic (CDG1C; 603147) and a homozygous Y131H mutation in the ALG6 gene (604566.0007); this variant has been reclassified as a variant of unknown significance based on its frequency in the gnomAD database. Starosta et al. (2020) noted phenotypic overlap between the 2 disorders.
In a 30-year-old man with Bosch-Boonstra-Schaaf optic atrophy syndrome (BBSOAS; 615722), Bojanek et al. (2020) identified a de novo heterozygous c.82C-T transition (c.82C-T, NM_005654.5) in the NR2F1 gene, resulting in a gln28-to-ter (Q28X) substitution. The mutation was identified by trio whole-exome sequencing and confirmed by Sanger sequencing. Functional studies were not performed.
In a boy with Bosch-Boonstra-Schaaf optic atrophy syndrome (BBSOAS; 615722), Walsh et al. (2020) identified a de novo heterozygous 1-bp deletion (c.1080del, NM_005654.5) in the ligand-binding domain of the NR2F1 gene, resulting in a frameshift and premature termination (Asn362fsTer33). The mutation was identified by trio whole-exome sequencing of the coding exons of 4,813 genes associated with known clinical phenotypes. The mutation was confirmed in the patient by Sanger sequencing and was shown to be absent in his parents. Because the mutation occurred in the last exon of N2RF1, Walsh et al. (2020) speculated that the resultant mRNA might not be subject to nonsense-mediated decay.
Alfano, C., Viola, L., Heng, J. I.-T., Pirozzi, M., Clarkson, M., Flore, G., De Maio, A., Schedl, A., Guillemot, F., Studer, M. COUP-TFI promotes radial migration and proper morphology of callosal projection neurons by repressing Rnd2 expression. Development 138: 4685-4697, 2011. [PubMed: 21965613] [Full Text: https://doi.org/10.1242/dev.068031]
Armentano, M., Filosa, A., Andolfi, G., Studer, M. COUP-TFI is required for the formation of commissural projections in the forebrain by regulating axonal growth. Development 133: 4151-4162, 2006. [PubMed: 17021036] [Full Text: https://doi.org/10.1242/dev.02600]
Bojanek, E. K., Mosconi, M. W., Guter, S., Betancur, C., Macmillan, C., Cook, E. H. Clinical and neurocognitive issues associated with Bosch-Boonstra-Schaaf optic atrophy syndrome: a case study. Am. J. Med. Genet. 182A: 213-218, 2020. [PubMed: 31729143] [Full Text: https://doi.org/10.1002/ajmg.a.61409]
Bosch, D. G. M., Boonstra, F. N., Gonzaga-Jauregui, C., Xu, M., de Ligt, J., Jhangiani, S., Wiszniewski, W., Muzny, D. M., Yntema, H. G., Pfundt, R., Vissers, L. E. L. M., Spruijt, L., and 12 others. NR2F1 mutations cause optic atrophy with intellectual disability. Am. J. Hum. Genet. 94: 303-309, 2014. [PubMed: 24462372] [Full Text: https://doi.org/10.1016/j.ajhg.2014.01.002]
Bovetti, S., Bonzano, S., Garzotto, D., Giannelli, S. G., Iannielli, A., Armentano, M., Studer, M., De Marchis, S. COUP-TFI controls activity-dependent tyrosine hydroxylase expression in adult dopaminergic olfactory bulb interneurons. Development 140: 4850-4859, 2013. [PubMed: 24227652] [Full Text: https://doi.org/10.1242/dev.089961]
Chen, C.-A., Bosch, D. G. M., Cho, M. T., Rosenfeld, J. A., Shinawi, M., Lewis, R. A., Mann, J., Jayakar, P., Payne, K., Walsh, L., Moss, T., Schreibr, A., and 23 others. The expanding clinical phenotype of Bosch-Boonstra-Schaaf optic atrophy syndrome: 20 new cases and possible genotype-phenotype correlations. Genet. Med. 18: 1143-1150, 2016. Note: Erratum: Genet. Med. 19: 962 only, 2017. [PubMed: 26986877] [Full Text: https://doi.org/10.1038/gim.2016.18]
Faedo, A., Tomassy, G. S., Ruan, Y., Teichmann, H., Krauss, S., Pleasure, S. J., Tsai, S. Y., Tsai, M.-J., Studer, M., Rubenstein, J. L. R. COUP-TFI coordinates cortical patterning, neurogenesis, and laminar fate and modulates MAPK/ERK, AKT, and beta-catenin signaling. Cerebral Cortex 18: 2117-2131, 2008. [PubMed: 18165280] [Full Text: https://doi.org/10.1093/cercor/bhm238]
Inoue, M., Iida, A., Satoh, S., Kodama, T., Watanabe, S. COUP-TFI and -TFII nuclear receptors are expressed in amacrine cells and play roles in regulating the differentiation of retinal progenitor cells. Exp. Eye Res. 90: 49-56, 2010. [PubMed: 19766631] [Full Text: https://doi.org/10.1016/j.exer.2009.09.009]
Martin-Hernandez, E., Rodriguez-Garcia, M. E., Chen, C.-A., Cotrina-Vinagre, F. J., Carnicero-Rodriguez, P., Bellusci, M., Schaaf, C. P., Martinez-Azorin, F. Mitochondrial involvement in a Bosch-Boonstra-Schaaf optic atrophy syndrome patient with a novel de novo NRF2F1 gene mutation. J. Hum. Genet. 63: 525-528, 2018. [PubMed: 29410510] [Full Text: https://doi.org/10.1038/s10038-017-0398-3]
Miyajima, N., Kadowaki, Y., Fukushige, S., Shimizu, S., Semba, K., Yamanashi, Y., Matsubara, K., Toyoshima, K., Yamamoto, T. Identification of two novel members of erbA superfamily by molecular cloning: the gene products of the two are highly related to each other. Nucleic Acids Res. 16: 11057-11073, 1988. [PubMed: 2905047] [Full Text: https://doi.org/10.1093/nar/16.23.11057]
Park, S. E., Lee, J. S., Lee, S.-T., Kim, H. Y., Han, S.-H., Han, J. Targeted panel sequencing identifies a novel NR2F1 mutations in a patient with Bosch-Boonstra-Schaaf optic atrophy syndrome. Ophthalmic Genet. 40: 359-361, 2019. [PubMed: 31393201] [Full Text: https://doi.org/10.1080/13816810.2019.1650074]
Qiu, Y., Krishnan, V., Zeng, Z., Gilbert, D. J., Copeland, N. G., Gibson, L., Yang-Feng, T., Jenkins, N. A., Tsai, M.-J., Tsai, S. Y. Isolation, characterization, and chromosomal localization of mouse and human COUP-TF I and II genes. Genomics 29: 240-246, 1995. [PubMed: 8530078] [Full Text: https://doi.org/10.1006/geno.1995.1237]
Rech, M. E., McCarthy, J. M., Chen, C.-A., Edmond, J. C., Shah, V. S., Bosch, D. G. M., Berry, G. T., Williams, L., Madan-Khetarpal, S., Niyazov, D., Shaw-Smith, C., Kovar, E. M., Lupo, P. J., Schaaf, C. P. Phenotypic expansion of Bosch-Boonstra-Schaaf optic atrophy syndrome and further evidence for genotype-phenotype correlations. Am. J. Med. Genet. 182A: 1426-1437, 2020. [PubMed: 32275123] [Full Text: https://doi.org/10.1002/ajmg.a.61580]
Starosta, R. T., Tarnowski, J., Vairo, F. P. E., Raymond, K., Preston, G., Morava, E. Bosch-Boonstra-Schaaf optic atrophy syndrome (BBSOAS) initially diagnosed as ALG6-CDG: functional evidence for benignity of the ALG6 c.391T-C (p.Tyr131His) variant and further expanding the BBSOAS phenotype. Europ. J. Med. Genet. 63: 103941, 2020. [PubMed: 32407885] [Full Text: https://doi.org/10.1016/j.ejmg.2020.103941]
Tang, K., Xie, X., Park, J.-I., Jamrich, M., Tsai, S., Tsai, M.-J. COUP-TFs regulate eye development by controlling factors essential for optic vesicle morphogenesis. Development 137: 725-734, 2010. [PubMed: 20147377] [Full Text: https://doi.org/10.1242/dev.040568]
Walsh, S., Gosswein, S. S., Rump, A., von der Hagen, M., Hackmann, K., Schrock, E., Di Donato, N., Kahlert, A.-K. Novel dominant-negative NR2F1 frameshift mutation and a phenotypic expansion of the Bosch-Boonstra-Schaaf optic atrophy syndrome. Europ. J. Med. Genet. 63: 104019, 2020. Note: Electronic Article. [PubMed: 32712214] [Full Text: https://doi.org/10.1016/j.ejmg.2020.104019]
Zhou, C., Tsai, S. Y., Tsai, M.-J. COUP-TFI: an intrinsic factor for early regionalization of the neocortex. Genes Dev. 15: 2054-2059, 2001. [PubMed: 11511537] [Full Text: https://doi.org/10.1101/gad.913601]