Alternative titles; symbolsV-SIS PLATELET-DERIVED GROWTH FACTOR, BETA POLYPEPTIDEPLATELET-DERIVED GROWTH FACTOR, B CHAINPDGF, B CHAINPDGF2ONCOGENE SISSIMIAN SARC...
Alternative titles; symbols
Other entities represented in this entry:
HGNC Approved Gene Symbol: PDGFB
Cytogenetic location: 22q13.1 Genomic coordinates (GRCh38): 22:39,223,358-39,244,981 (from NCBI)
▼ Cloning and Expression
Retroviruses have been identified as the etiologic agents of naturally occurring tumors in several animal species, including certain human T-cell leukemias and lymphomas. Some of the viruses rapidly induce tumors when inoculated into animals and can transform cells in vitro. The genomes of these viruses contain sequences, called viral onc genes, which are directly responsible for transformation both in vitro and in vivo. Evidence indicates that these onc genes originated from normal cellular genes by recombination between a parent nontransforming virus and host cellular DNA. Molecular hybridization indicates considerable evolutionary conservation of the cellular genes that give rise to viral transforming genes, suggesting that cellular onc genes may code for important functions in cell growth or tissue differentiation. Dalla-Favera et al. (1981) reported the detection, molecular cloning and genomic organization of the human onc gene (c-sis) related to the transforming gene (v-sis) of simian sarcoma virus (SSV) derived from the woolly monkey. The gene was cloned from the human DNA library of Maniatis. The protein product of the c-sis gene has not been identified. Many of the known transforming proteins are kinases that have the unusual property of phosphorylating tyrosine residues. Some are structurally and functionally similar to cellular protein kinases involved in the regulation of the Na-K-ATPase pump. In an addendum to another paper (Wong-Staal et al., 1981), the same workers reported finding more than 1 allelic form of the c-sis locus.
Doolittle et al. (1983) concluded that the SIS oncogene is the same as, or very closely related to, the gene for platelet-derived growth factor. The conclusion was based on the demonstration of extensive sequence similarity. Waterfield et al. (1983) likewise pointed out the close structural similarity. PDGF is the major polypeptide mitogen in serum for cells of mesenchymal origin.
Josephs et al. (1984) concluded that the SIS gene encodes 1 chain of human PDGF. PDGF has 2 dissimilar subunits, A and B. It is the B chain that has homology to SIS (Collins et al., 1985).
▼ Gene Function
Kelly et al. (1985) showed that the PDGF B chain alone is sufficient for mitogenesis.
Hermansson et al. (1988) presented evidence implicating an autocrine growth stimulation by PDGFB in the pathologic proliferation of endothelial cells characteristically found in glioblastomas.
Most proliferating cells are programmed to undergo apoptosis unless specific survival signals are provided. Platelet-derived growth factor promotes cellular proliferation and inhibits apoptosis. Romashkova and Makarov (1999) showed that PDGF activates the RAS/PIK3/AKT1/IKK/NFKB1 pathway. In this pathway, NFKB1 (164011) does not induce c-myc and apoptosis, but instead induces putative antiapoptotic genes. In response to PDGF, AKT1 (164730) transiently associates with IKK (see 600664) and induces IKK activation. The authors suggested that under certain conditions PIK3 (see 171834) may activate NFKB1 without the involvement of NFKBIA (164008) or NFKBIB (604495) degradation.
Choi et al. (2005) demonstrated that PRDX2 (600538) is a negative regulator of PDGF signaling. Peroxiredoxin type II (Prx II) deficiency results in increased production of peroxide, enhanced activation of PDGF receptor (PDGFR; see 173490) and phospholipase C-gamma-1 (172420), and subsequently increased cell proliferation and migration in response to PDGF. These responses are suppressed by expression of wildtype Prx II, but not an inactive mutant. Notably, Prx II is recruited to PDGFR upon PDGF stimulation, and suppresses protein tyrosine phosphatase inactivation. Prx II also leads to the suppression of PDGFR activation in primary culture and in a murine restenosis model, including PDGF-dependent neointimal thickening of vascular smooth muscle cells. Choi et al. (2005) concluded that their results demonstrate a localized role for endogenous peroxide in PDGF signaling, and indicate a biologic function for Prx II in cardiovascular disease.
Kratchmarova et al. (2005) found that the differentiation of human mesenchymal stem cells into bone-forming cells is stimulated by epidermal growth factor (EGF; 131530) but not PDGF. They used mass spectrometry-based proteomics to comprehensively compare proteins that were tyrosine-phosphorylated in response to EGF and PDGF and their associated partners. More than 90% of these signaling proteins were used by both ligands, whereas the phosphatidylinositol 3-kinase pathway was exclusively activated by PDGF, implicating it as a possible control point. Indeed, chemical inhibition of phosphatidylinositol 3-kinase (see 603157) in PDGF-stimulated cells removed the differential effect of the 2 growth factors, bestowing full differentiation effect onto PDGF. Kratchmarova et al. (2005) concluded that their study shows that quantitative proteomics can directly compare entire signaling networks and discover critical differences capable of changing cell fate.
During the development of atherosclerotic plaques, vascular smooth muscle cells change from the physiologic contractile phenotype to the pathophysiologic synthetic phenotype. They then migrate into the intima where they proliferate and produce extracellular matrix. Chen et al. (2006) found that PDGFB and IL1B (147720) cooperate in inducing contractile-to-synthetic phenotype modulation of human aortic smooth muscle cells in culture. Phenotypic modulation by PDGFB and IL1B involved crosstalk between their corresponding receptors PDGFRB (173410) and IL1R1 (147810) and was mediated through the PI3K (see 171834)/AKT (see 164730)/P70S6K (608938) signaling pathway.
Chojnacki et al. (2008) found that PDGF stimulated fetal human PDGF-responsive neural precursor cells (PRPs) to generate neurospheres that differentiated primarily into oligodendrocytes, which acquired myelin basic protein (159430) expression, as well as neurons and a small number of astrocytes. Together with PDGF, FGF2 (134920) promoted fetal human PRP expansion and self-renewal. In contrast, adult human PRPs isolated from the corpus callosum required twice the culture period to generate neurospheres, which contained oligodendrocytes, as well as astrocytes, but not neurons. FGF2 did not promote adult human PRP self-renewal. Chojnacki et al. (2008) concluded that differences in the intrinsic proliferation, phenotype, and self-renewal properties of fetal and adult human PRPs indicate that they are distinct populations, which may result in distinct myelin-production capabilities.
In a cultured bovine retinal pericyte model, Geraldes et al. (2009) demonstrated that hyperglycemia persistently activates PRKCD (176977) and MAPK14, thus increasing expression of SHP1 (PTPN6; 176883), and that this occurs independently of NFKB activation. This signaling cascade leads to PDGFRB dephosphorylation and a reduction in downstream signaling from this receptor, resulting in pericyte apoptosis, the most specific vascular histopathology associated with diabetic complications (see 603933). The authors observed increased PRKCD activity and an increase in the number of acellular capillaries in diabetic mouse retinas, which were not reversible with insulin treatment that achieved normoglycemia. Unlike diabetic age-matched wildtype mice, diabetic Prkcd -/- mice did not show activation of MAPK14 or SHP1, inhibition of PDGFB signaling in vascular cells, or the presence of acellular capillaries. The authors also observed PRKCD, MAPK14, and SHP1 activation in brain pericytes and in the renal cortex of diabetic mice. Geraldes et al. (2009) concluded that this represents a new signaling pathway by which hyperglycemia can induce PDGFB resistance and increased vascular cell apoptosis to cause diabetic vascular complications.
By Western blot, immunofluorescence, and confocal microscopy analyses, Charbonneau et al. (2016) demonstrated that the receptor tyrosine kinase PDGFR was specifically upregulated in rheumatoid arthritis (RA; 180300) synoviocytes and synovial tissues. PDGFR activation involved TGFB-induced upregulation of PDGFB mediated by the TGFBR1 (190181)/SMAD (see 601366) and PI3K/AKT pathways. Charbonneau et al. (2016) proposed that an overreactive TGFB/PDGFB/PDGFR pathway is involved in synoviocyte-driven extracellular matrix degradation in RA.
▼ Gene Structure
Dalla-Favera et al. (1981) determined that the SIS gene extends over a region of about 12 kb, which includes 1.2 kb of v-sis-related sequences interrupted by 4 intervening sequences.
Studies of hybrids between thymidine kinase-deficient mouse cells and human fibroblasts carrying a 22/17 translocation showed that the sis gene is in the region 22q11-qter (Dalla-Favera et al., 1982). Swan et al. (1982) also mapped c-sis to chromosome 22 by somatic cell hybridization. They pointed out that the simian sarcoma virus was the only known transforming retrovirus of primate origin.
On germline chromosomes by in situ hybridization, Jhanwar et al. (1984) assigned SIS to 22q13.1, a site distal to the breakpoint involved in formation of the Philadelphia chromosome, 22q11. Julier et al. (1985) concluded from multilocus linkage tests that the oncogene SIS locus is most likely distal to MB and that both are distal to IGL. The following tentative map was derived: cen--IGL--0.10--D22S1--0.20--MB--0.07--(SIS, P1).
In the mouse SIS maps to chromosome 15 (Kozak et al., 1983), which shows other evidence of homology of synteny to human chromosome 22--diaphorase-1 (613213) and arylsulfatase A (607574) are on MM15 and HSA22.
Chromosomal translocations involving 22q12 have been found in most cases of Ewing sarcoma (612219) (Aurias et al., 1983; Turc-Carel et al., 1983). Bechet et al. (1984) showed that the SIS oncogene is not activated in Ewing sarcoma. By in situ hybridization, Bartram et al. (1984) concluded that SIS is located in the region 22q12.3-22q13.1, far from the breakpoint 22q11 of CML (608232), and that SIS segregates with the translocated part of chromosome 22 to various chromosomes in Ph1-positive cases of CML but remains on chromosome 22 in Ph1-negative cases. Thus, SIS is probably not involved in the malignant process.
PDGFB/COL1A1 Fusion Gene
Dermatofibrosarcoma protuberans (DFSP; 607907), an infiltrative skin tumor of intermediate malignancy, presents specific cytogenetic features such as reciprocal translocations t(17;22)(q22;q13) and supernumerary ring chromosomes derived from t(17;22). Simon et al. (1997) characterized the breakpoints from translocations and rings in dermatofibrosarcoma protuberans and its juvenile form, giant cell fibroblastoma, on the genomic and RNA levels. They found that these rearrangements fuse the PDGFB gene and the COL1A1 gene (120150). Simon et al. (1997) commented that PDGFB has transforming activity and is a potent mitogen for a number of cell types, but its role in oncogenic processes was not fully understood. They noted that neither COL1A1 nor PDGFB had hitherto been implicated in tumor translocations. The gene fusions deleted exon 1 of PDGFB and released this growth factor from its normal regulation; see 190040.0002.
▼ Molecular Genetics
Nakanishi et al. (2007) used RT-PCR to examine the COL1A1/PDGFB transcript using frozen biopsy specimens from 3 unrelated patients with DFSP and identified fusion of COL1A1 exon 25, exon 31, and exon 46, respectively, to exon 2 of the PDGFB gene. Clinical features and histopathology did not demonstrate any specific characteristics associated with the different transcripts.
In a family in which 4 persons developed meningiomas (607174) at a median age about 10 years younger than that found for meningioma patients in the general population, as reported by Bolger et al. (1985), Smidt et al. (1990) identified a deletion in the fifth intron of the PDGFB (SIS) gene (190040.0001).
Idiopathic Basal Ganglia Calcification 5
Keller et al. (2013) identified 6 different heterozygous putative loss-of-function mutations in the PDGFB gene (see, e.g., 190040.0003-190040.0007) in 6 (18.8%) of 13 families with idiopathic basal ganglia calcification-5 (IBGC5; 615483). The phenotype was characterized by progressive neurologic symptoms and associated with brain calcification mainly affecting the basal ganglia, although some patients had more extensive calcification affecting the thalamus, cerebellum, or white matter. Symptoms included motor disturbances, such as dyskinesias or parkinsonism, headache, cognitive impairment, and psychiatric manifestations, including apathy and depression. Some patients were asymptomatic.
▼ Animal Model
Disruption of the Pdgfb gene or the gene for its receptor in mice leads to the development of lethal hemorrhage and edema in late embryogenesis and absence of kidney glomerular mesangial cells. Lindahl et al. (1997) found that mouse embryos deficient in Pdgfb lack microvascular pericytes, which normally form part of the capillary wall, and develop numerous capillary microaneurysms that rupture at late gestation. Endothelial cells of the sprouting capillaries in mutant mice appeared to be unable to attract PDGF-receptor-beta-positive pericyte progenitor cells. Pericytes may contribute to the mechanical stability of the capillary wall. Comparisons made between PDGF-null mouse phenotypes suggested a general role for PDGFs in the development of myofibroblasts.
By targeting Pdgfb ablation to the endothelium, Enge et al. (2002) created viable mice with extensive inter- and intra-individual variation in the density of pericytes throughout the central nervous system. They found a strong inverse correlation between pericyte density and the formation of a range of retinal microvascular abnormalities reminiscent of those seen in diabetic humans. Proliferative retinopathy invariably developed when pericyte density was less than 50% of normal. Since a reduction of pericyte density was sufficient to cause retinopathy in mice, Enge et al. (2002) hypothesized that pericyte loss may also lead to human diabetic retinopathy (see 603933).
Cao et al. (2003) reported that a combination of 2 angiogenic factors, PDGF-BB and FGF2 (134920), synergistically induces vascular networks, which remain stable for more than a year even after depletion of angiogenic factors. In both rat and rabbit ischemic hindlimb models, PDGF-BB and FGF2 together markedly stimulated collateral arteriogenesis after ligation of the femoral artery, with a significant increase in vascularization and improvement in paw blood flow. A possible mechanism of angiogenic synergism between PDGF-BB and FGF2 involves upregulation of the expression of PDGF receptor-alpha (PDGFRA; 173490) and PDGF receptor-beta (PDGFRB; 173410) by FGF2 in newly formed blood vessels. Cao et al. (2003) showed that single angiogenic factors, including FGF2, VEGF (192240), and PDGF-BB, were unable to establish stable vascular networks. In contrast, a combination of PDGF-BB and FGF2, but not PDGF-BB and VEGF or VEGF and FGF2, synergistically induced angiogenesis and long-lasting functional vessels. While each of the angiogenic factors FGF2, VEGF and PDGF-BB is able to stimulate angiogenesis in the short term, none of these factors alone is able to maintain these newly formed vessels.
Keller et al. (2013) found that 4-month-old mice homozygous for a hypomorphic Pdgfb allele developed clusters of calcified nodules in the midbrain and thalamus. At age 1 year, mutant mice had more extensive calcification involving the basal forebrain, midbrain, and pons. The lesions were punctate and composed of calcium phosphate. Transgenic reexpression of 2 copies of wildtype endothelial Pdgfb in Pdgfb-null mice prevented the development of brain calcification, whereas reexpression of 1 copy of the rescue allele did not prevent calcification. The findings suggested that it is endothelial Pdgfb, rather than neuronal Pdgfb, that drives the pathology. Keller et al. (2013) postulated that the brain calcification may result from defects in pericytes and the blood-brain barrier.
▼ ALLELIC VARIANTS ( 7 Selected Examples):
PDGFB, 135-BP DEL, IVS5
In a family in which 4 persons developed meningiomas (607174) at a median age about 10 years younger than that found for meningioma patients in the general population, as reported by Bolger et al. (1985), Smidt et al. (1990) identified a deletion in the fifth intron of the SIS gene. Normally the SIS gene has an Alu sequence in this region which includes 2 perfect 130-nucleotide repeated sequences, separated by 5 bp. The deleted allele was missing 1 copy of the 130-bp repeat and the intervening 5 bp. An identical deletion was also found in DNA from 1 of 13 sporadic meningiomas. Whether the deletion inactivates the SIS allele, in analogy to the loss of function of suppressor genes in the development of retinoblastoma and Wilms tumor, or activates the expression of the SIS gene is not clear. A point mutation in the fourth intron of the HRAS gene (190020) is associated with overexpression (Cohen and Levinson, 1988).
.0002 DERMATOFIBROSARCOMA PROTUBERANS, SOMATIC
PDGFB, PDGFB/COL1A1 FUSION
Simon et al. (1997) demonstrated a fusion between intron 43 of the type I collagen (COL1A1; 120150) gene and intron 1 of the platelet-derived growth factor-beta gene that resulted in dermatofibrosarcoma protuberans (DFSP; 607907). The fusion process deleted exon 1 of PDGFB and released its growth factor from normal regulation. Normally, PDGFB is believed to reach the cell surface in order to generate an autocrine growth signal. In the case of a putative chimeric COL1A1/PDGFB protein, COL1A1 would provide the signal peptide, which is a prerequisite for export of the protein. Simon et al. (1997) showed breaks in 4 different regions of the COL1A1 gene in the 5 tumors studied, indicating that the COL1A1 contribution to the putative chimeric protein may be accessory and less likely to be crucial for potential growth factor activity. Normally PDGFB is processed by N- and C-terminal peptidases into a mature growth factor. The domains that are recognized by these enzymes are present in the putative chimeric COL1A1/PDGFB protein, as they are encoded by PDGFB exon 3 and exon 6, respectively. This suggested that the proteolytic processing of the putative chimeric COL1A1/PDGFB protein may occur as for the normal PDGFB. Shimizu et al. (1999) concluded that the COL1A1/PDGFB fusion gene associated with DFSP contributes to tumor formation through ectopic production of PDGF-BB, the homodimer formed by disulfide-linking, and the formation of an autocrine loop. Their findings thus suggested that PDGF receptors could be a target for pharmacologic treatment of DFSP and giant cell fibroblastoma, through the use of PDGF receptor kinase inhibitors.
To characterize the functional and structural properties of the COL1A1/PDGFB fusion protein, Shimizu et al. (1999) generated a stable NIH 3T3 cell line that contained a tumor-derived chimeric gene resulting from a COL1A1 intron-7/PDGFB intron-1 fusion. Expression of the fusion protein led to morphologic transformation and increased growth rate of these cells. A PDGF receptor kinase inhibitor reversed the transformed phenotype and reduced the growth rate of the cells expressing the fusion protein but had no effect on control cells. The presence of dimeric fusion protein precursors was demonstrated through PDGFB immunoprecipitation of metabolically labeled cells and also by PDGFB immunoprecipitation followed by immunoblotting with COL1A1 antibodies. Pulse-chase studies demonstrated that the COL1A1/PDGFB precursor was processed to an end product that was indistinguishable from wildtype PDGF-BB, the homodimer formed by disulfide linking. Finally, COL1A1/PDGFB-expressing cells generated tumors after subcutaneous injection into nude mice, and tumor growth was reduced by treatment with the PDGF receptor kinase inhibitor. Shimizu et al. (1999) concluded that the COL1A1/PDGFB fusion gene associated with DFSP contributes to tumor formation through ectopic production of PDGF-BB and the formation of an autocrine loop. Their findings thus suggested that PDGF receptors could be a target for pharmacologic treatment of DFSP and giant cell fibroblastoma, through the use of PDGF receptor kinase inhibitors.
Simon et al. (2001) demonstrated that stably transfected clones that expressed the COL1A1-PDGFB chimeric protein became growth-factor independent and tumorigenic in nude mice. In addition, supernatants of the transfected cells significantly stimulated fibroblastic cell growth through the activation of the PDGFB receptor pathway. These results strongly suggested that the chimeric gene expression associated with DFSP induces tumor formation through production of mature PDGFB in an autocrine or paracrine way.
.0003 BASAL GANGLIA CALCIFICATION, IDIOPATHIC, 5
In affected members of a Serbian family (family S) with idiopathic basal ganglia calcification-5 (IBGC5; 615483), originally reported by Kostic et al. (2011), Keller et al. (2013) identified a heterozygous c.433C-T transition in exon 4 of the PDGFB gene, resulting in a gln145-to-ter (Q145X) substitution. The mutation, which was found by genome sequencing and confirmed by Sanger sequencing, segregated with the disorder in the family. The mutation was not present in the Exome Variant Server database, in 173 in-house controls, or in 578 ancestry-matched controls. The mutation was predicted to lead to a loss of protein function.
.0004 BASAL GANGLIA CALCIFICATION, IDIOPATHIC, 5
In 3 members of a Brazilian family (family B) with IBGC5 (615483), Keller et al. (2013) identified a heterozygous c.356T-C transition in exon 4 of the PDGFB gene, resulting in a leu119-to-pro (L119P) substitution in a predicted receptor-binding loop. The mutation was not present in the Exome Variant Server or dbSNP databases, in 173 in-house controls, or in 378 ancestry-matched controls. No functional studies were performed on the variant, but the mutation was predicted to lead to a loss of protein function. (In the article, the nucleotide change was cited as c.356T-C and c.356C-T; Keller (2013) confirmed that the correct change is c.356T-C.)
.0005 BASAL GANGLIA CALCIFICATION, IDIOPATHIC, 5
In 9 affected members of a large 3-generation French family (family F) with IBGC5 (615483), Keller et al. (2013) identified a heterozygous c.726G-C transversion after exon 6 of the PDGFB gene, resulting in an extension of the protein beyond the termination codon (Ter242TyrExtTer89). The mutation was not present in the Exome Variant Server database or in 173 in-house controls. No functional studies were performed on the variant, but the mutation was predicted to lead to a loss of protein function.
.0006 BASAL GANGLIA CALCIFICATION, IDIOPATHIC, 5
In 5 affected members of a German family (family F8) with IBGC5 (615483), Keller et al. (2013) identified a heterozygous c.445C-T transition in exon 4 of the PDGFB gene, resulting in an arg149-to-ter (R149X) substitution. The mutation was not present in the Exome Variant Server database or in 173 in-house controls or 278 German controls. The mutation was predicted to lead to a loss of protein function.
.0007 BASAL GANGLIA CALCIFICATION, IDIOPATHIC, 5
In affected members of a family (family 10) with IBGC5 (615483), Keller et al. (2013) identified a heterozygous c.3G-A transition in exon 1 of the PDGFB gene, resulting in disruption of the translation initiation codon. The mutation was not present in the Exome Variant Server database or in 173 in-house controls. No functional studies were performed on the variant, but the mutation was predicted to lead to a loss of protein function.