The molecular basis of familial hypercholesterolemia (FH) in three families of Spanish descent from La Habana was investigated by the candidate gene approach. The Arg3500Gln mutation of apolipoprotein B-100 was not found. Identification of low density lipoprotein receptor (LDLR) gene haplotypes segregating with FH guided the characterisation of three point mutations by automated sequencing. One, a Val408-->Met missense mutation, a founder mutation in Afrikaner FH patients, was recurrent, being associated with a distinct DNA haplotype. The other two, Glu256-->Lys and Val776-->Met missense mutations, were novel and modified highly conserved residues. These mutations were absent in normolipidemic subjects and were associated in heterozygous carriers with twice the cholesterol levels observed in non-carriers. Noticeably, cardiovascular complications were rarely observed in older heterozygotes, even in those with the Afrikaner FH-2 mutation. These findings confirm the molecular heterogeneity of LDLR gene mutations causing FH and the variability of their expression across different populations.

The gene for IFNgamma appears to be highly conserved as no sequence variations were detected in 265 individuals. These results suggest that mutations of the IFNgamma gene are unlikely to be a significant cause of an inherited asthma diathesis.

Background Reduced levels of interferon gamma (IFN7) mRNA and protein have been detected in the bronchoalveolar lavage fiuid of atopic asthmatics. IFN7 is secreted by TH| cells while IL-4 and !L-5 are secreted by THT cells and an imbalance in the TH1/TH2 response may be responsible for atopic asthma. The gene for IFN7 is located on chromosome 12; a region of the genome which has been shown in linkage studies to be associated with asthma. Objective To determine if there are any mutations present in the coding exons and 5' flanking region of the IFN7 gene in atopic asthmatic subjects compared with controls to explain the lower levels of this cytokine as an inherited, rather than acquired, factor in the asthmatic subjects. Methods The four exons and 5' flanking region of the IFN7 gene were amplified by polymerase chain reaction (PCR) from genomic DNA of 265 individuals from a Western Australian and a Venezuelan population. The PCR products were examined by single strand conformational polymorphism and heteroduplex analyses to see if there were any changes in the DNA migration patterns which would suggest the presence of a sequence variation. Results The four exons and the 5' flanking region of the IFN7 gene were amplified from 265 individuals from two populations. Single strand conformational polymorphism and heteroduplex analyses did not reveal any mutations in the regions examined. Conclusion The gene for IFN7 appears to be highly conserved as no sequence variations were detected in 265 individuals. These results suggest that mutations of the IFN7 gene are unlikely to be a significant cause of an inherited asthma diathesis.

Interleukin-5 (IL-5) is a potential candidate gene in the pathogenesis of asthma, as it is the main cytokine controlling eosinophil activity and eosinophils are pivotal in the development of airway inflammation. Mutation detection studies were performed on the IL-5 gene and the alpha-chain of its receptor in 30 asthmatic and 30 nonasthmatic subjects. Single-strand conformational polymorphism (SSCP) and heteroduplex analysis (HA) did not reveal any change from the reported normal sequence in all 4 exons of IL-5 as well as the promoter and 3'-untranslated regions of the gene. No SSCP variations were seen within the complete coding sequence of the IL-5 receptor alpha-chain. Mutations of the IL-5 gene coding region, its promoter and receptor are unlikely to be common causes of an inherited predisposition to asthma.

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