Samples from Southern Italy were used for this study. The centenarians' sample comprised 2191 unrelated subjects (1078 males and 1113 females) older than 100 years. Controls comprised 25 unrelated subjects (13 males and 12 females) younger than 80 years. All subjects were free of clinically overt pathologies, particularly the centenarians who were in fairly good health status and did not suffer from major pathologies or disabilities. Buffy coats were extracted for DNA analyses from blood samples of all subjects who had given their informed consent.Standard procedures were followed for the analysis of INS-FokI and IGF2-AvalI-RFLP. These genes are located downstream of the INS gene and in exon 3 of the IGF2 gene, respectively. The genomic DNA was amplified using PCR, followed by restriction analysis. The genotypic and allelic counts and frequencies were computed for each marker, and Hardy-Weinberg equilibrium was verified using exact tests. Chi-square statistics were used to test for homogeneity between sample groups, and maximum likelihood estimation was used to estimate haplotypic frequencies. The results showed no significant difference between sex-matched centenarians and younger individuals or between age-matched males and females. Linkage disequilibrium studies showed significant disequilibrium between each of the markers and the HUMTHO1 short or long alleles. Pairwise linkage disequilibrium between markers was not significant for INS and IGF2 markers, but it was highly significant for each of these markers with HUMTHO1. Exact tests were applied to verify the null hypothesis of homogeneity between haplotypic frequency distributions. The distribution of TH-INS haplotypes was not rare. The genotypic and allelic data relevant to INS-FokI-RFLP and IGF2-AvalI-RFLP are shown in Tables 6 and 7, respectively.Sorry, the text provided seems to be a mix of numbers, symbols and words without any clear structure or meaning. It is not possible to proofread or improve it without more information about the context and purpose of the text. Please provide a valid text for me to assist you.Unfortunately, the text appears to be a combination of meaningless characters and symbols. It is impossible to proofread or improve the text without any context or understanding of what it is trying to convey. Please provide a valid text for me to work on.Centenarians for both the INS and IGF2 systems may be the consequence of sex-specific survival factors spanning the entire 11p15.5 chromosomal region considered. In any case, the results are in line with a number of findings observed in the model system Drosophila melanogaster, where sex-specific quantitative trait loci affecting longevity have been shown. It is worth noting that linkage disequilibrium exists between the HUMTHO1 microsatellite and minisatellite 6(4,7), which controls gene expression. An intriguing speculation suggested by the above considerations and in line with our findings is that more than one gene enclosed in the 11p15 region may exert concerted action on the longevity trait by means of a shared regulator, for example, the HUMTHO1 microsatellite. In this case, the functional interaction between stress-response genes and metabolic-pathway control genes may have evolved into a physically tight relationship, putting master-genes such as TH and IGF2 in a small piece of genome where they control vital functions for development and survival, and possibly play a role in determining longevity in humans. The knowledge offered by the Human Genome Project will enable us to check many more markers in the region of interest, possibly in full linkage disequilibrium with functional variants. In any case, the results of this pivotal study encourage further investigation in this intriguing region of the human genome.