Altered regulation of platelet-derived growth factor receptor-alpha gene-transcription in vitro by spina bifida-associated mutant Pax1 proteins.
Mouse models show that congenital neural tube defects (NTDs) can occur as a result of mutations in the platelet-derived growth factor receptor-alpha gene (PDGFRalpha). Mice heterozygous for the PDGFRalpha-mutation Patch, and at the same time homozygous for the undulated mutation in the Pax1 gene, exhibit a high incidence of lumbar spina bifida occulta, suggesting a functional relation between PDGFRalpha and Pax1. Using the human PDGFRalpha promoter linked to a luciferase reporter, we show in the present paper that Pax1 acts as a transcriptional activator of the PDGFRalpha gene in differentiated Tera-2 human embryonal carcinoma cells. Two mutant Pax1 proteins carrying either the undulated-mutation or the Gln --> His mutation previously identified by us in the PAX1 gene of a patient with spina bifida, were not or less effective, respectively. Surprisingly, Pax1 mutant proteins appear to have opposing transcriptional activities in undifferentiated Tera-2 cells as well as in the U-2 OS osteosarcoma cell line. In these cells, the mutant Pax1 proteins enhance PDGFRalpha-promoter activity whereas the wild-type protein does not. The apparent up-regulation of PDGFRalpha expression in these cells clearly demonstrates a gain-of-function phenomenon associated with mutations in Pax genes. The altered transcriptional activation properties correlate with altered protein-DNA interaction in band-shift assays. Our data provide additional evidence that mutations in Pax1 can act as a risk factor for NTDs and suggest that the PDGFRalpha gene is a direct target of Pax1. In addition, the results support the hypothesis that deregulated PDGFRalpha expression may be causally related to NTDs.
Joosten
P H
PH
Department of Cell Biology, University of Nijmegen, Toernooiveld 1, 6525 ED Nijmegen, The Netherlands. P.Joosten@sci.kun.nl
Hol
F A
FA
van Beersum
S E
SE
Peters
H
H
Hamel
B C
BC
Afink
G B
GB
van Zoelen
E J
EJ
Mariman
E C
EC
D019943:Amino Acid Substitution; D000818:Animals; D001483:Base Sequence; D018236:Carcinoma, Embryonal; D017931:DNA Primers; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D005786:Gene Expression Regulation; D005973:Glutamine; D006639:Histidine; D006801:Humans; D051379:Mice; D008817:Mice, Mutant Strains; D008969:Molecular Sequence Data; D051761:Paired Box Transcription Factors; D017354:Point Mutation; D011401:Promoter Regions, Genetic; D014176:Protein Biosynthesis; D020796:Receptor, Platelet-Derived Growth Factor alpha; D017479:Receptors, Platelet-Derived Growth Factor / Q000096:biosynthesis / Q000235:genetics*; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D016135:Spinal Dysraphism / Q000235:genetics*; D015534:Trans-Activators / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism; D014158:Transcription, Genetic; D014162:Transfection; D014407:Tumor Cells, Cultured
D017931:DNA Primers; D004268:DNA-Binding Proteins; D051761:Paired Box Transcription Factors; D011993:Recombinant Fusion Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D005973:Glutamine; C070835:PAX1 transcription factor; D006639:Histidine; D020796:Receptor, Platelet-Derived Growth Factor alpha; D017479:Receptors, Platelet-Derived Growth Factor