Downregulation of transforming growth factor, beta receptor 2 and Notch signaling pathway in human abdominal aortic aneurysm.
OBJECTIVE
Mutations in FBN1 and TGFBR2 genes are the main causative mutations identified in Marfan syndrome (MFS). The major vascular complication of MFS is aneurysm formation. Abdominal aortic aneurysm (AAA) is an acquired disease of later life of unknown etiology. The aim of this study was to examine if genetic aberrations in MFS-related genes FBN1 and TGFBR2 are present in patients with AAA.


METHODS
We assessed the presence of copy number variation (CNV) in FBN1 and TGFBR2 genes in AAA biopsies from twelve patients. We also analyzed the expression of these genes in AAA biopsies compared to control biopsies from six organ donors. In addition we assessed the expression of two members of the Notch signaling pathway NOTCH3 and HEY2 as well as aortic smooth muscle cell (AoSMC) differentiation marker TAGLN in AAA and control biopsies.


RESULTS
Loss of one copy (deletion) of the FBN1 exon 66 sequence and TGFBR2 exon 8 was identified in 7 (58%) and 11 (92%) of the 12 AAA biopsies. No copy number amplifications (duplications) were detected. Patients carrying TGFBR2 exon 8 deletion showed marked downregulation of this gene in AAA biopsies compared to control biopsies (0.699 vs. 1.765, p = 0.038). Notch signaling components NOTCH3 and HEY2 were markedly downregulated in AAA, while expression of the AoSMC differentiation marker TAGLN did not differ between AAA and control biopsies (0.468 vs. 0.486, p = 0.546).


CONCLUSIONS
This study suggests an acquired impairment in TGF-β signaling that along with downregulation of the Notch signaling pathway may contribute to the pathogenesis of AAA.
Vascular Biology Unit, School of Medicine, James Cook University, Townsville, Queensland 4811, Australia.
Erik
E
Biros
Philip J
PJ
Walker
Maria
M
Nataatmadja
Malcolm
M
West
Jonathan
J
Golledge
D017544:Aortic Aneurysm, Abdominal / Q000235:genetics* / Q000473:pathology; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics*; D001706:Biopsy; D016022:Case-Control Studies; D056915:DNA Copy Number Variations; D015536:Down-Regulation; D005091:Exons; D000071838:Fibrillin-1; D000071837:Fibrillins; D005784:Gene Amplification; D017353:Gene Deletion; D020022:Genetic Predisposition to Disease; D057895:Haploinsufficiency; D006801:Humans; D008382:Marfan Syndrome / Q000235:genetics; D008840:Microfilament Proteins / Q000235:genetics; D009124:Muscle Proteins / Q000235:genetics; D009154:Mutation; D017346:Protein Serine-Threonine Kinases / Q000235:genetics*; D011793:Queensland; D060888:Real-Time Polymerase Chain Reaction; D000071656:Receptor, Notch3; D000077294:Receptor, Transforming Growth Factor-beta Type II; D051880:Receptors, Notch / Q000235:genetics*; D018125:Receptors, Transforming Growth Factor beta / Q000235:genetics*; D012097:Repressor Proteins / Q000235:genetics*; D015398:Signal Transduction / Q000235:genetics*; D054392:Adipokines
D051792:Basic Helix-Loop-Helix Proteins; D000071838:Fibrillin-1; D000071837:Fibrillins; D008840:Microfilament Proteins; D009124:Muscle Proteins; D017346:Protein Serine-Threonine Kinases; D000071656:Receptor, Notch3; D000077294:Receptor, Transforming Growth Factor-beta Type II; D051880:Receptors, Notch; D018125:Receptors, Transforming Growth Factor beta; D012097:Repressor Proteins; C000605722:FBN1 protein, human; D054392:Adipokines; C405693:HEY2 protein, human; C499374:NOTCH3 protein, human; C051615:transgelin