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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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Can deminished c-fos transactivation be one cause of adipose tissue malformation? Postulated model how the identyfied c-fos promoter mutation affects signalling by cFos and AP-1 and interferes with adipocte differentiation. The BSCL genes (italic; seipin, AGPAT2, lamininA/C, caveolin, cavin) are included at the levels of functional interaction in c-fos signalling.
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Figure 6: Can deminished c-fos transactivation be one cause of adipose tissue malformation? Postulated model how the identyfied c-fos promoter mutation affects signalling by cFos and AP-1 and interferes with adipocte differentiation. The BSCL genes (italic; seipin, AGPAT2, lamininA/C, caveolin, cavin) are included at the levels of functional interaction in c-fos signalling.

Mentions: In conclusion we describe the identification of a de novo point mutation in the promoter of the immediately early transcription factor c-fos gene which might be associated with a CGL outcome. We show alteration of the transcription pattern in cells due to reduced c-fos expression in our patient. Furthermore we suggest a hypothetical model how reduced c-fos expression potentially interferes with target genes also necessary for differentiation or maturation of preadipocytes (Figure 6). Our findings provide evidence for the addition of c-Fos to the list of genes which might cause congenital lipodystrophy.


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)

Can deminished c-fos transactivation be one cause of adipose tissue malformation? Postulated model how the identyfied c-fos promoter mutation affects signalling by cFos and AP-1 and interferes with adipocte differentiation. The BSCL genes (italic; seipin, AGPAT2, lamininA/C, caveolin, cavin) are included at the levels of functional interaction in c-fos signalling.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 6: Can deminished c-fos transactivation be one cause of adipose tissue malformation? Postulated model how the identyfied c-fos promoter mutation affects signalling by cFos and AP-1 and interferes with adipocte differentiation. The BSCL genes (italic; seipin, AGPAT2, lamininA/C, caveolin, cavin) are included at the levels of functional interaction in c-fos signalling.
Mentions: In conclusion we describe the identification of a de novo point mutation in the promoter of the immediately early transcription factor c-fos gene which might be associated with a CGL outcome. We show alteration of the transcription pattern in cells due to reduced c-fos expression in our patient. Furthermore we suggest a hypothetical model how reduced c-fos expression potentially interferes with target genes also necessary for differentiation or maturation of preadipocytes (Figure 6). Our findings provide evidence for the addition of c-Fos to the list of genes which might cause congenital lipodystrophy.

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