Eugenie L. Harris

Functional matrix metalloproteinase-9 polymorphism (C-1562T) associated with abdominal aortic aneurysm

PURPOSE Matrix metalloproteinase-9 (MMP-9) is a potent endopeptidase with activity against both collagens and elastin. Expression of MMP-9 is elevated in vascular disease, and in particular within aneurysm tissues. This study tested the hypothesis that the functionally more active T allele of the MMP9 C-1562T polymorphism may be overrepresented in patients with abdominal aortic aneurysm (AAA) compared with control subjects and patients with atherosclerotic peripheral vascular disease (PVD). METHODS Seven hundred eighty-nine unrelated persons (AAA, n = 414; control subjects, n = 203; PVD, n = 172) were genotyped for the common C-1562T functional promoter polymorphism of the MMP9 gene. RESULTS Genotypes containing the T allele of this polymorphism were significantly more common in patients with AAA compared with both control subjects and patients with PVD (adjusted odds ratio, 2.41 and 2.94, respectively). The greatest shift between groups was observed in male patients, with a difference of 20.6% in CT/TT genotypes. and 12.1% in T allele frequency between patients with AAA compared with patients with PVD. CONCLUSIONS This study provides further evidence to support the role of MMP-9 in the pathogenesis of AAA, and indicates that the MMP9 C-1562T functional polymorphism may represent a genetic component contributing to susceptibility to this vascular disease.

Spontaneous Elastic Tissue Lesions in the Rat Abdominal Aorta, a Genetically Determined Phenotype

In this study, phenotypic expression of spontaneous elastic laminae defects within the rat abdominal aorta was examined. Lesions in Brown Norway (BN) rats were compared with those of New Zealand genetically hypertensive (GH) rats. BN and GH rats were cross-bred to determine the phenotypic expression of these lesions in successive F1 and F2 generations. Lesions were assessed by distribution, number and a semiquantitative index of severity. All BN aortae contained numerous elastic tissue defects. In comparison, GH aortae contained only occasional elastic tissue lesions. F1 aortae contained lesions in numbers similar to those of the parental BN strain; however, F1 lesions were of significantly greater severity. Within the F2 generation, a wide range in both lesion numbers and severity indices was observed, with approximately a quarter of animals having lesion numbers analogous to the GH parental strain. In conclusion, this study indicates that the spontaneous elastic tissue lesions observed within BN rats are consistent with an autosomal dominant, possibly single gene, effect. Moreover, epistatic effects, derived from the GH strain, may influence the severity of these lesions. The gene(s) responsible may be important in the development of conditions such as arteriosclerosis and aneurysms in humans.

Familial abdominal aortic aneurysms in the Otago region of New Zealand

PURPOSE To investigate the familial incidence and phenotypic characteristics of patients with abdominal aortic aneurysms (AAA) in the Otago region of New Zealand. METHODOLOGY A retrospective audit based pilot study and a prospective study of patients having abdominal aortic aneurysm repair from September 1988 to September 1999 was performed. RESULTS 248 probands were enrolled, of which 19.4% had one or more first degree relative affected. The age at diagnosis of the familial (70.2) and non-familial (70.5) patients was similar. The proportion of females was increased in the familial subgroup. Hypercholesterolaemia was the only phenotypic feature to differentiate familial from non-familial patients and was associated with an earlier age of presentation. In the familial families, brothers were the most common relative affected and 77% of the families had two patients with AAA. CONCLUSION 19.4% of patients operated on in the Otago area for AAA had a familial component to their aneurysm.

Differences in mitogenic responses to angiotensin II, calf serum and phorbol ester in vascular smooth muscle cells from two strains of genetically hypertensive rat

Vascular smooth muscle cells cultured from spontaneously hypertensive (SHR), New Zealand genetically hypertensive (GH) rat strains and their control strains (Wistar-Kyoto (WKY) and normal Wistar (N) rats) were compared for mitogenic responses [( 3H]-thymidine incorporation) to angiotensin II (AII), fetal calf serum (FCS), and the phorbol ester 12-O-tetradecanoyl-phorbol-13-acetate (TPA). SHR cells showed enhanced basal [3H]-thymidine incorporation and increased responses to all three factors. In contrast, basal and FCS-stimulated [3H]-thymidine incorporation was the same or less in GH than in N cells. However, DNA synthesis was greater in GH cells in response to AII, AII + TPA or FCS + TPA. These results suggest that vascular smooth muscle cells from both hypertensive rat strains display enhanced mitogenesis, but the enhancement occurs via different intracellular signalling pathways.

Wax ester synthesis in the mouse preputial gland-tumour.

The microsomal fraction from the mouse preputial gland tumour contains an acyltransferase which catalyzes the synthesis of wax esters. The enzyme is inhibited by moderate concentrations of free fatty acids (40 muM or more) but the inhibition is relieved by the addition of bovine serum albumin. The specific activity of the enzyme increases markedly between the 20th and 30th days of tumor growth. A number of other lipid synthesizing enzymes show similar trends for specific activity as related to tumour age.

COSEGREGATION OF THE Tnfα LOCUS WITH CARDIOVASCULAR PHENOTYPES IN THE F2 GENERATION OF A NEW ZEALAND GENETICALLY HYPERTENSIVE AND BROWN NORWAY CROSS

1. The association of the Tnfα locus with several cardiovascular phenotypes and body mass has been studied in the F2 generation of a reciprocal cross between rats of the New Zealand genetically hypertensive (GH) and the normotensive Brown Norway (BN) strains. In the total F2 population the GH allele of Tnfα cosegregated with increased intra‐arterial blood pressure (BP) in a recessive manner. A similar but weaker effect was observed for tail BP.

Strain-specific deletions in exon 10 of rat K-kininogen and T1-kininogen genes allow mapping of both genes to rat chromosome 11.

Species:Mouse Locus name: methionine synthase or 5-methyltetrahydrofolatehomocysteine methyltransferase Locus symbol:Mtr Map position: proximal–D13Mit1–1.06 cM ± 1.06 SE– Mtr, D13Bir4, D13Bir6–1.06 ± 1.06–D13Abb1e–2.13 ± 1.49–D13Bir7–distal Method of mapping:Mtr was localized by RFLP analysis of 96 animals from an interspecific backcross panel ((C57BL/6JEi × SPRET/Ei)F1 × SPRET/Ei) provided by The Jackson Laboratory, Bar Harbor, Me. (BSS panel) [1]. Database deposit information: The data are available from the Mouse Genome Database, accession number MGD-JNUM-39061. Molecular reagents:A 1095-bp mouse cDNA was obtained by reverse transcription/PCR of mouse liver RNA, with degenerate oligonucleotides based on regions of homology within the methionine synthase sequences of lower organisms. The two primers (D1730 and D1733), as described by Leclerc et al. [2], were successful in amplifying both human and mouse cDNAs. The PCR products from both species were subcloned and sequenced; they showed 89% identity. The mouse cDNA was labeled by random priming and hybridized to Southern blots of EcoRI-digested mouse genomic DNA. Allele detection:Allele detection was performed by RFLP analysis of an EcoRI polymorphism. The C57BL/6J strain has alleles of approximately 13 kb, while theMus spretusstrain has alleles of approximately 9 kb and 4 kb. A constant band of approximately 0.5 kb was seen in both strains. Previously identified homologs: Human MTR has been mapped to chromosomal band 1q43 by fluorescence in situ hybridization [2–4]. Discussion: Methionine synthase (EC 2.1.1.13, 5-methyltetrahydrofolate-homocysteine methyltransferase) catalyzes homocysteine remethylation to methionine, with 5-methyltetrahydrofolate as the methyl donor and methylcobalamin as a cofactor. Nutritional deficiencies and genetic defects in homocysteine metabolism result in varying degrees of hyperhomocysteinemia. Dramatic elevations in plasma and urinary homocysteine levels are associated with the inborn error of metabolism, homocystinuria. Consequent to the recent isolation of the human cDNA for methionine synthase [2–4], two groups of investigators have identified mutations in methionine synthase in homocystinuric patients [2, 5]. Mild elevations in plasma homocysteine are thought to be a risk factor for both vascular disease and neural tube defects [6–8]. A genetic variant in methylenetetrahydrofolate reductase (MTHFR), the enzyme that synthesizes 5-methyltetrahydrofolate for the methioninesynthase reaction, is the most common genetic determinant of hyperhomocysteinemia identified thus far [9]. Mild defects in the methionine synthase reaction are also potential candidates for hyperhomocysteinemia and the associated multifactorial diseases. A common variant has been reported for the human methionine synthase gene, but its physiologic consequences have not yet been determined [2, 4]. The mapping of the human MTR gene to 1q43 and of the mouse gene to proximal Chromosome (Chr) 13 is consistent with previous findings of human/mouse homologies between these 2 chromosomal regions; the human and mouse nidogen genes have been mapped to 1q43 and proximal Chr 13, respectively [10]. Several genes have already been implicated in neural tube defects in mice [11]. Studies involving the mouse methionine synthase gene will be useful in assessing the role of this important enzyme in the development of birth defects and/or vascular disease.