PROJECT
1. Fibulin-2 exhibits high degree of variability, but no structural changes concordant with abdominal aortic aneurysms Kuivaniemi H, Marshall A, Ganguly A, Chu ML, Abbott WM, Tromp G EUROPEAN JOURNAL OF HUMAN GENETICS 6: (6) 642-646 NOV-DEC 1998 Abstract: We used conformation sensitive gel electrophoresis and direct sequencing of PCR products to screen for mutations in the cDNA for fibulin-2, an extracellular matrix protein, from 11 patients with abdominal aortic aneurysms and two controls, When compared with the published reference sequence, a total of 14 single-base sequence variations were detected, Seven of the changes were neutral in that they did not result in an amino acid substitution, There were five missense changes at sites not conserved between human and mouse, and two missense changes at sites conserved between human and mouse, All but two of the sequence variants studied were also present in an additional set of 102 control alleles analyzed, One of these two changes was a missense mutation, but it did not segregate with abdominal aortic aneurysms in the family, whilst the other change was neutral, In conclusion, fibulin-2 has a large number of sequence variations in comparison with our previous analyses of type III collagen, and these variations will be useful in association studies, There was an excellent overall agreement between direct sequencing of PCR-products and conformation sensitive gel electrophoresis. Comment by mdt: POOF ! There goes another interesting candidate gene. 2. Analysis of coding sequences for tissue inhibitor of metalloproteinases 1 (TIMP1) and 2 (TIMP2) in patients with aneurysms Wang XJ, Tromp G, Cole CW, Verloes A, Sakalihasan N, Yoon S, Kuivaniemi H MATRIX BIOLOGY 18: (2) 121-124 APR 1999 Abstract: Aneurysms are characterized by dilation, i.e. expansion and thinning of all the arterial wall layers, which is accompanied by remodeling of the connective tissue. Genes involved in the regulation of tissue remodeling are therefore candidate genes. We analyzed TIMP1 and TIMP2 coding sequences in 12 individuals with abdominal aortic aneurysms (AAA), one individual with AAA and intracranial aneurysms (IA), four individuals with IA and two clinically unaffected individuals. We identified two nucleotide variants in both the TIMP1 and the TIMP2 coding sequences. All differences occurred in the third base positions of codons and were neutral polymorphisms. A significant difference was observed in the frequency of TIMP2 nt 573 polymorphism between 168 alleles from AAA patients and 102 control alleles. (C) 1999 Elsevier Science B.V./International Society of Matrix Biology. All rights reserved. Comment by mdt: Yes, we found one of the transitions in TIMP 1 several years ago (Tilson MD, Reilly JM, Brophy CM, Webster EL, Barnett TR. Expression and sequence of the gene for tissue inhibitor of metalloproteinases in patients with abdominal aortic aneurysms. J Vasc Surg 18: 266-70, 1993.), but now the picture is more complete. 3. Genetic analysis of MMP3, MMP9, and PAI-1 in Finnish patients with abdominal aortic or intracranial aneurysms Yoon S, Tromp G, Vongpunsawad S, Ronkainen A, Juvonen T, Kuivaniemi H BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS 265: (2) 563-568 NOV 19 1999 Abstract: MMP3, MMP9, and PAI-1 are present at increased levels in abdominal aortic aneurysms (AAAs), The promoters of these genes contain polymorphisms, with alleles that exhibit different transcriptional activities in vitro. Association studies were performed using these polymorphisms and DNA isolated from 47 AAA patients, 57 intracranial aneurysm (IA) patients, and 174 controls, all from Finland, PAI-1 and MMP9 genotypes did not associate with aneurysms, The frequency of the 5A MMP3 allele was somewhat higher in the AAA than that in the control group (P = 0.0609 after Bonferroni correction), whereas the MMP3 allele frequencies in the IA group did not differ from those of the controls (P = 0.9667), These findings suggest that the transcriptionally more active 5A MMP3 allele might be a genetic risk factor for AAA among Finns. They are in agreement with previous studies demonstrating higher level of MMP3 expression in AAA than in controltissues. (C) 1999 Academic Press. Comment by mdt: I've seen data with a much lower p than .06 fizzle, so I wouldn't look for too much here. 4. Immunoglobulin A antibodies against Chlamydia pneumoniae are associated with expansion of abdominal aortic aneurysm Lindholt JS, Juul S, Vammen S, Lind I, Fasting H, Henneberg EW BRITISH JOURNAL OF SURGERY 86: (5) 634-638 MAY 1999 Abstract: Background: The aim of this study was to examine the possible association between the progression of small abdominal aortic aneurysm (AAA) and chronic infection with Chlamydia pneumoniae. Methods: Patients from a hospital-based mass screening programme for AAA with annual follow-up (mean 2.7 years) were included. After initial interview, 139 men aged 65-73 years with a small AAA underwent examination and blood sampling. Immunoglobulin (Ig) G and IgA titres against C. pneumoniae were measured by a microimmunofluorescence test. Results: Some 83 (95 per cent confidence interval 74-93) per cent of the men had an IgA titre of 20 or more, or an IgG titre of 32 or more. Men with an IgA titre of 20 or more had a 48 per cent higher AAA expansion rate than those with a titre of less than 20 (3.1 versus 2.1 mm/year; P < 0.05). Multiple linear and logistic regression analyses showed that an IgA titre of 20 or more was a significant independent predictor of increased AAA expansion, adjusted for known risk factors of expansion. Initial AAA size and serum total cholesterol level were also predictors of expansion. Conclusion: A high proportion of men with a small AAA had signs of chronic infection with C. pneumoniae. Aneurysm progression correlated with evidence of chronic C. pneumoniae infection. Comment by mdt: I wonder why... One possibility is that chlamydia is a molecular mimic of a structural aortic microfibrillar protein, as we have suggested may be the case with cytomegalovirus, some herpes viruses, and T. Pallidum. I have not noticed similarities to chlamydia in sequences that we have published, but it looks like there is going to be a whole family of tissue specific (and non- specific) microfibrillar proteins. Another possibility is that as an aneurysm enlarges, there is a greater area of flow surface exposed to reduced shear conditions; and that would have the predictable consequence of increasing the burden of atherosclerotic plaque. Since chlamydia seems to like keeping house in plaque, the increased burden of plaque might make infection with the organism more likely. And, as I once heard Judah Folkman say, if you can think of two good explanations for a scientific fact, there are likely to be six others you haven't thought of yet.