Alternative titles; symbols
HGNC Approved Gene Symbol: NDRG4
Cytogenetic location: 16q21 Genomic coordinates (GRCh38): 16:58,463,715-58,515,387 (from NCBI)
By sequencing clones obtained from a size-fractionated adult brain cDNA library, Hirosawa et al. (1999) cloned NDRG4. The deduced protein contains 273 amino acids. RT-PCR ELISA detected highest expression in adult and fetal brain and adult heart, followed by lung and testis. Lower expression was detected in other adult tissues examined, but little to no expression was detected in fetal liver. High NDRG4 expression was detected in all specific adult brain regions examined, with highest expression in amygdala, cerebellum, and thalamus.
By searching an EST database for sequences similar to NDRG1 (605262), followed by 3-prime and 5-prime RACE of human brain and heart cDNA libraries and cap-site hunting, Zhou et al. (2001) cloned 3 splice variants of NDRG4. The variants NDRG4B and NDRG4B-var, which were obtained from the brain library, encode deduced proteins of 339 and 352 amino acids with calculated molecular masses of 37.1 and 38.5 kD, respectively. Compared with NDRG4B, NDRG4B-var has a 14-amino acid insertion near the C terminus. The variant NDRG4H, which was obtained from the heart library, encodes a deduced 371-amino acid protein with a calculated molecular mass of 40.6 kD. NDRG4H differs from NDRG4B and NDRG4B-var at its N-terminal end, and it lacks the 14-amino acid insertion. Northern blot analysis detected NDRG4 transcripts of about 3.2 kb in brain and heart only. Variant-specific probes showed NDRG4B expression in brain only, whereas NDRG4H was expressed in both brain and heart, with higher expression in heart. RT-PCR confirmed expression of all 3 variants in brain and of NDRG4H in heart. RNA dot-blot analysis revealed NDRG4 expression in spinal cord, all specific brain regions examined, and all specific heart regions examined except aorta. Expression was also detected in spleen, lymph node, testis, adrenal gland, and fetal brain and heart, but not in other tissues examined. In situ hybridization of normal adult brain detected NDRG4 mRNA in cytoplasm of neurons in cerebral cortex, cerebellum, mesencephalon, pons, medulla oblongata, and spinal cord. No signal was detected in peripheral nerves or other cell types, such as glial cells. Western blot analysis of endogenous or exogenously expressed proteins showed that NDRG4B, NDRG4B-var, and NDRG4H had apparent molecular masses of 37, 39, and 41 kD, respectively.
Using expression profiling to identify genes expressed in aortic smooth muscle, followed by screening a heart cDNA library, Nishimoto et al. (2003) cloned NDRG4, which they called SMAP8. The deduced 371-amino acid protein has a calculated molecular mass of 40.7 kD. Northern blot analysis detected high expression of an approximately 3.3-kb transcript in heart and brain, with little to no expression in other tissues examined. PCR analysis showed moderate expression in aorta and vascular smooth muscle cells. Western blot analysis of heart and brain detected SMAP8 at an apparent molecular mass of about 45 kD. SMAP8 localized to the cytoplasmic fraction of transfected A10 embryonic rat aortic smooth muscle cells.
By in situ hybridization of adult mouse brain, Yamamoto et al. (2011) detected wide distribution of Ndrg4 in neurons, but not in astrocytes. Western blot analysis of adult mouse brain detected 3 Ndrg4 isoforms representing orthologs of human NDRG4B, NDRG4B-var, and NDRG4H.
Nishimoto et al. (2003) showed that homocysteine upregulated SMAP8 expression in primary human aortic smooth muscle cells and rat A10 cells, but not in human umbilical vein endothelial cells. Proliferation and migration of A10 cells significantly decreased following expression of human SMAP8. SMAP8 was phosphorylated by a serine/threonine kinase via activation of a PDGF (see 173430) signaling pathway. In addition, ERK1 (MAPK3; 601795)/ERK2 (MAPK1; 176948) and MEK1 (MAP2K1; 176872)/MEK2 (MAP2K2; 601263) were activated in SMAP8-transfected A10 cells.
Hongo et al. (2006) found that overexpression of 1 of the 6 isoforms of rat Ndrg4, Ndrg4c2, in PC12 rat pheochromocytoma cells reduced NGF (see 162030)-induced phosphorylation of Elk1 (311040), a nuclear target of Erk. Reporter gene assays revealed that Ndrg4c2 suppressed Elk1-mediated activation of a serum response element.
By RT-PCR and immunohistochemical analysis, Schilling et al. (2009) found that NDRG4 expression was increased in glioblastoma multiforme (GBM; see 137800) compared with normal human astrocytes. Knockdown of NDRG4 via short hairpin RNA reduced the viability of GBM cells via G1 cell cycle arrest and subsequent apoptosis. Knockdown of NDRG4 also reduced the viability of several GBM cell lines and primary astrocytes. Knockdown of NDRG4 in GBM tumor xenografts reduced tumor growth following intracranial injection in immunocompromised mice. Overexpression of NDRG4B or NDRG4H did not affect cell viability.
Zhou et al. (2001) determined that the NDRG4 gene contains 17 exons and spans 26 kb. Exons 1 and 2 are specific for NDRG4H, exon 3 is specific for NDRG4B and NDGR4B-var, and exon 16 is specific for NDRG4B-var. The region upstream of exon 1 contains a GGCG sequence that may represent a TATA-less promoter for NDRG4H expression. The region upstream of exon 3 contains a consensus TATA box and 2 CCAAT sequences and may represent the promoter for NDRG4B and NDRG4B-var expression.
By genomic sequence analysis, Zhou et al. (2001) mapped the NDRG4 gene to chromosome 16q21-q22.3.
For discussion of a possible association between infantile myofibromatosis (see 228550) and variation in the NDRG4 gene, see 614463.0001.
Yamamoto et al. (2011) found that Ndrg4 -/- mice were born at the expected mendelian ratio, appeared normal, and were fertile. However, Ndrg4 -/- mice showed deficits in spatial learning and memory, and they exhibited increased sensitivity to ischemic stress following middle cerebral artery occlusion. Consistent with these findings, Ndrg4 -/- mice had reduced expression of the neuroprotective factor Bdnf (113505).
This variant is classified as a variant of unknown significance because its contribution to infantile myofibromatosis (see 228550) has not been confirmed.
In 2 brothers, born of distantly related parents, with infantile myofibromatosis with multicentric visceral involvement, Linhares et al. (2014) identified a homozygous c.511G-C transversion in the NDRG4 gene, resulting in a val171-to-leu (V171L) substitution at a well-conserved residue. The variant, which was found by exome sequencing and confirmed by Sanger sequencing, was not found in the dbSNP (build 137), 1000 Genomes Project, or Exome Sequencing Project (ESP6500) databases, or in several other control exome databases. The unaffected parents were heterozygous for the variant. Autozygosity mapping showed that the brothers shared a region of homozygosity at chromosome 16 that included the NDRG4 gene. Functional studies of the variant were not performed. The brothers also carried a homozygous splice site variant in the RLTPR gene (CARMIL2; 610859.0006) that was not thought to contribute to the phenotype. Linhares et al. (2014) noted that since NDRG4 may have a role in cell survival and tumor invasion and may act as a tumor suppressor gene, it is a candidate for the disorder observed in these brothers.
Schober et al. (2017) identified the same homozygous splice site mutation in the CARMIL2 gene in affected members of a family with immunodeficiency-58 (IMD58; 618131).
Hirosawa, M., Nagase, T., Ishikawa, K., Kikuno, R., Nomura, N., Ohara, O. Characterization of cDNA clones selected by the GeneMark analysis from size-fractionated cDNA libraries from human brain. DNA Res. 6: 329-336, 1999. [PubMed: 10574461] [Full Text: https://doi.org/10.1093/dnares/6.5.329]
Hongo, S., Watanabe, T., Takahashi, K., Miyazaki, A. Ndrg4 enhances NGF-induced ERK activation uncoupled with Elk-1 activation. J. Cell. Biochem. 98: 185-193, 2006. [PubMed: 16408304] [Full Text: https://doi.org/10.1002/jcb.20763]
Linhares, N. D., Freire, M. C. M., Cardenas, R. G. C. C. L., Pena, H. B., Bahia, M., Pena, S. D. J. Exome sequencing identifies a novel homozygous variant in NDRG4 in a family with infantile myofibromatosis. Europ. J. Med. Genet. 57: 643-648, 2014. [PubMed: 25241110] [Full Text: https://doi.org/10.1016/j.ejmg.2014.08.010]
Nishimoto, S., Tawara, J., Toyoda, H., Kitamura, K., Komurasaki, T. A novel homocysteine-responsive gene, smap8, modulates mitogenesis in rat vascular smooth muscle cells. Europ. J. Biochem. 270: 2521-2531, 2003. [PubMed: 12755708] [Full Text: https://doi.org/10.1046/j.1432-1033.2003.03626.x]
Schilling, S. H., Hjelmeland, A. B., Radiloff, D. R., Liu, I. M., Wakeman, T. P., Fielhauer, J. R., Foster, E. H., Lathia, J. D., Rich, J. N., Wang, X.-F., Datto, M. B. NDRG4 is required for cell cycle progression and survival in glioblastoma cells. J. Biol. Chem. 284: 25160-25169, 2009. [PubMed: 19592488] [Full Text: https://doi.org/10.1074/jbc.M109.012484]
Schober, T., Magg, T., Laschinger, M., Rohlfs, M., Linhares, N. D., Puchalka, J., Weisser, T., Fehlner, K., Mautner, J., Walz, C., Hussein, K., Jaeger, G., Kammer, B., Schmid, I., Bahia, M., Pena, S. D., Behrends, U., Belohradsky, B. H., Klein C., Hauck, F. A human immunodeficiency syndrome caused by mutations in CARMIL2. Nature Commun. 8: 14209, 2017. Note: Electronic Article. [PubMed: 28112205] [Full Text: https://doi.org/10.1038/ncomms14209]
Yamamoto, H., Kokame, K., Okuda, T., Nakajo, Y., Yanamoto, H., Miyata, T. NDRG4 protein-deficient mice exhibit spatial learning deficits and vulnerabilities to cerebral ischemia. J. Biol. Chem. 286: 26158-26165, 2011. [PubMed: 21636852] [Full Text: https://doi.org/10.1074/jbc.M111.256446]
Zhou, R.-H., Kokame, K., Tsukamoto, Y., Yutani, C., Kato, H., Miyata, T. Characterization of the human NDRG gene family: a newly identified member, NDRG4, is specifically expressed in brain and heart. Genomics 73: 86-97, 2001. [PubMed: 11352569] [Full Text: https://doi.org/10.1006/geno.2000.6496]