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A mutation in the c-fos gene associated with congenital generalized lipodystrophy.

Knebel B, Kotzka J, Lehr S, Hartwig S, Avci H, Jacob S, Nitzgen U, Schiller M, März W, Hoffmann MM, Seemanova E, Haas J, Muller-Wieland D - Orphanet J Rare Dis (2013)

Bottom Line: Several genes (BSCL1-4) were found to be associated to the syndrome but not all CGL patients carry mutations in these genes.Cellular investigations demonstrate that the wild type c-fos promoter can reconstitute the signaling defect in the patient, excluding further upstream signaling alterations, and vice versa the investigations with the c-fos promoter containing the identified mutation generally reduce basal and inducible c-fos transcription activity.As a consequence of the identified point mutation gene expression including c-Fos targeted genes is significantly altered, shown exemplified in cells of the patient.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Clinical Biochemistry and Pathobiochemistry, German Diabetes Center at the Heinrich-Heine-University Duesseldorf, Leibniz Center for Diabetes Research, Duesseldorf, Germany.

ABSTRACT

Background: Congenital generalized lipodystrophy (CGL) or Berardinelli-Seip congenital lipodystrophy (BSCL) is a rare genetic syndrome characterized by the absence of adipose tissue. As CGL is thought to be related to malfunctions in adipocyte development, genes involved in the mechanisms of adipocyte biology and maintenance or differentiation of adipocytes, especially transcription factors are candidates. Several genes (BSCL1-4) were found to be associated to the syndrome but not all CGL patients carry mutations in these genes.

Methods and results: In a patient with CGL and insulin resistance we investigated the known candidate genes but the patient did not carry a relevant mutation. Analyses of the insulin activated signal transduction pathways in isolated fibroblasts of the patient revealed a postreceptor defect altering expression of the immediate early gene c-fos. Sequence analyses revealed a novel homozygous point mutation (c.-439, T→A) in the patients' c-fos promoter. The point mutation was located upstream of the well characterized promoter elements in a region with no homology to any known cis-elements. The identified mutation was not detected in a total of n=319 non lipodystrophic probands. In vitro analyses revealed that the mutation facilitates the formation of a novel and specific protein/DNA complex. Using mass spectrometry we identified the proteins of this novel complex. Cellular investigations demonstrate that the wild type c-fos promoter can reconstitute the signaling defect in the patient, excluding further upstream signaling alterations, and vice versa the investigations with the c-fos promoter containing the identified mutation generally reduce basal and inducible c-fos transcription activity. As a consequence of the identified point mutation gene expression including c-Fos targeted genes is significantly altered, shown exemplified in cells of the patient.

Conclusion: The immediate-early gene c-fos is one essential transcription factor to initiate adipocyte differentiation. According to the role of c-fos in adipocyte differentiation our findings of a mutation that initiates a repression mechanism at c-fos promoter features the hypothesis that diminished c-fos expression might play a role in CGL by interfering with adipocyte development.

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Gene expression alterations due to diminished c-fos expression. A) Gene expression date were analyzed for statistically significant different gene expression (1.5-fold difference; p<0.05). Resulting transcript IDs were subjected to automated annotation for conserved AP-1 transcription factor binding sites. B) The pathways showing altered transcriptional regulation were deduced from differential gene expression identified. Colored genes (red and green) were identified differentially regulated by microarray analysis. Genes directly regulated by c-fos are indicated (blue line). Predicted transcription factors (white) involved in observed gene regulation were deduced using Ingenuity Pathway Analysis ((IPA System (http://www.ingenuity.com).
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Figure 5: Gene expression alterations due to diminished c-fos expression. A) Gene expression date were analyzed for statistically significant different gene expression (1.5-fold difference; p<0.05). Resulting transcript IDs were subjected to automated annotation for conserved AP-1 transcription factor binding sites. B) The pathways showing altered transcriptional regulation were deduced from differential gene expression identified. Colored genes (red and green) were identified differentially regulated by microarray analysis. Genes directly regulated by c-fos are indicated (blue line). Predicted transcription factors (white) involved in observed gene regulation were deduced using Ingenuity Pathway Analysis ((IPA System (http://www.ingenuity.com).

Mentions: To test if the mutation and novel protein/DNA complex observed has an impact in cellular context, we performed a gene expression survey in the patient (Additional file 1: Table S1). Functional analyses of these results revealed that multiple metabolic or transcriptional processes and a large fraction of genes involved in cell cycle control and differentiation were affected (Additional file 2: Table S2). Data base analyses suggest that most of differentially regulated transcripts bear the c-fos responsive AP-1 promoter consensus sequence (Figure 5A). Further in silico analyses indicate that next to c-fos and further AP-1 complex factors, differentially expressed transcripts in the patient are also regulated by transcription factors necessary in adipocyte differentiation and maturation i.e. ATF4, PPARα, SREBP-1or-2 and CEBP family members (Figure 5B).


A mutation in the c-fos gene associated with congenital generalized lipodystrophy.

Knebel B, Kotzka J, Lehr S, Hartwig S, Avci H, Jacob S, Nitzgen U, Schiller M, März W, Hoffmann MM, Seemanova E, Haas J, Muller-Wieland D - Orphanet J Rare Dis (2013)

Gene expression alterations due to diminished c-fos expression. A) Gene expression date were analyzed for statistically significant different gene expression (1.5-fold difference; p<0.05). Resulting transcript IDs were subjected to automated annotation for conserved AP-1 transcription factor binding sites. B) The pathways showing altered transcriptional regulation were deduced from differential gene expression identified. Colored genes (red and green) were identified differentially regulated by microarray analysis. Genes directly regulated by c-fos are indicated (blue line). Predicted transcription factors (white) involved in observed gene regulation were deduced using Ingenuity Pathway Analysis ((IPA System (http://www.ingenuity.com).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3750569&req=5

Figure 5: Gene expression alterations due to diminished c-fos expression. A) Gene expression date were analyzed for statistically significant different gene expression (1.5-fold difference; p<0.05). Resulting transcript IDs were subjected to automated annotation for conserved AP-1 transcription factor binding sites. B) The pathways showing altered transcriptional regulation were deduced from differential gene expression identified. Colored genes (red and green) were identified differentially regulated by microarray analysis. Genes directly regulated by c-fos are indicated (blue line). Predicted transcription factors (white) involved in observed gene regulation were deduced using Ingenuity Pathway Analysis ((IPA System (http://www.ingenuity.com).
Mentions: To test if the mutation and novel protein/DNA complex observed has an impact in cellular context, we performed a gene expression survey in the patient (Additional file 1: Table S1). Functional analyses of these results revealed that multiple metabolic or transcriptional processes and a large fraction of genes involved in cell cycle control and differentiation were affected (Additional file 2: Table S2). Data base analyses suggest that most of differentially regulated transcripts bear the c-fos responsive AP-1 promoter consensus sequence (Figure 5A). Further in silico analyses indicate that next to c-fos and further AP-1 complex factors, differentially expressed transcripts in the patient are also regulated by transcription factors necessary in adipocyte differentiation and maturation i.e. ATF4, PPARα, SREBP-1or-2 and CEBP family members (Figure 5B).

Bottom Line: Several genes (BSCL1-4) were found to be associated to the syndrome but not all CGL patients carry mutations in these genes.Cellular investigations demonstrate that the wild type c-fos promoter can reconstitute the signaling defect in the patient, excluding further upstream signaling alterations, and vice versa the investigations with the c-fos promoter containing the identified mutation generally reduce basal and inducible c-fos transcription activity.As a consequence of the identified point mutation gene expression including c-Fos targeted genes is significantly altered, shown exemplified in cells of the patient.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Clinical Biochemistry and Pathobiochemistry, German Diabetes Center at the Heinrich-Heine-University Duesseldorf, Leibniz Center for Diabetes Research, Duesseldorf, Germany.

ABSTRACT

Background: Congenital generalized lipodystrophy (CGL) or Berardinelli-Seip congenital lipodystrophy (BSCL) is a rare genetic syndrome characterized by the absence of adipose tissue. As CGL is thought to be related to malfunctions in adipocyte development, genes involved in the mechanisms of adipocyte biology and maintenance or differentiation of adipocytes, especially transcription factors are candidates. Several genes (BSCL1-4) were found to be associated to the syndrome but not all CGL patients carry mutations in these genes.

Methods and results: In a patient with CGL and insulin resistance we investigated the known candidate genes but the patient did not carry a relevant mutation. Analyses of the insulin activated signal transduction pathways in isolated fibroblasts of the patient revealed a postreceptor defect altering expression of the immediate early gene c-fos. Sequence analyses revealed a novel homozygous point mutation (c.-439, T→A) in the patients' c-fos promoter. The point mutation was located upstream of the well characterized promoter elements in a region with no homology to any known cis-elements. The identified mutation was not detected in a total of n=319 non lipodystrophic probands. In vitro analyses revealed that the mutation facilitates the formation of a novel and specific protein/DNA complex. Using mass spectrometry we identified the proteins of this novel complex. Cellular investigations demonstrate that the wild type c-fos promoter can reconstitute the signaling defect in the patient, excluding further upstream signaling alterations, and vice versa the investigations with the c-fos promoter containing the identified mutation generally reduce basal and inducible c-fos transcription activity. As a consequence of the identified point mutation gene expression including c-Fos targeted genes is significantly altered, shown exemplified in cells of the patient.

Conclusion: The immediate-early gene c-fos is one essential transcription factor to initiate adipocyte differentiation. According to the role of c-fos in adipocyte differentiation our findings of a mutation that initiates a repression mechanism at c-fos promoter features the hypothesis that diminished c-fos expression might play a role in CGL by interfering with adipocyte development.

Show MeSH
Related in: MedlinePlus