A new polyacrylamide gel isoelectric focusing (PAGIEF) technique has been developed that allows rapid and reliable identification of Apolipoprotein E (APOE) phenotypes directly from plasma or serum without any prior treatment. This method was used to determine the APOE phenotypes in samples from Central and Southern Italy, Sicily, and Sardinia. The frequencies observed for the APOE*2, APOE*3, and APOE*4 alleles in Central and Southern Italy (Sicily included) were similar (0.066, 0.851, 0.083 and 0.056, 0.858, 0.085 respectively) though lower APOE*4 frequencies were found in the more southern regions. The Sardinian population showed APOE gene frequencies (APOE*2 = 0.050, APOE*3 = 0.898, APOE*4 = 0.052) to be significantly different from those of the rest of Italy owing to the low APOE*4 frequency, the lowest among Caucasian populations. The frequencies were compared with those found in other European populations. A clear cut North-South decreasing cline was found for APOE*4 allele frequencies and an opposite trend was found for APOE*3 frequencies. The overall dispersion of European populations as determined by the three APOE allele frequencies was graphically represented using coordinate analysis. The tendency of the APOE*4 frequency to decline with latitude both at the Italian and at the European level was discussed with reference to similar trends observed for dietary habits (saturated fat intake).

The distribution of the two alleles of FXIIIA and the three alleles of FXIIIB were studied in populations from mainland Italy and from Sardinia. The frequencies of the FXIIIA*2 allele were 0.266 and 0.265. The frequencies of FXIIIB*1 were 0.787 and 0.765; of B*2, 0.070 and 0.094; of B*3, 0.143 and 0.141. A new cathodal FXIIIA allele (A*7) was described in the Rome sample. No significant difference in the distribution of allele frequencies for either system was found between the two populations studied. For typing both markers, good results were also obtained by using whole blood instead of plasma.

The genetic variation of the human plasma proteins ORM1, C6, C7 and APO C-II was investigated by isoelectric focusing followed by immunoblotting in populations from mainland Italy and Sardinia. The frequencies of ORM1*1 were 0.621 and 0.564, while those of C6*A were 0.657 and 0.706 on mainland Italy and in Sardinia, respectively. In the Roman sample, 8 het-erozygotes with C6 variant alleles were encountered, while none were observed in Sardinians. For C7 and APO C-II a number of heterozygotes with the rare alleles C7*2 and APO C-II*2 were found, but their frequency did not reach polymorphic levels in either population. The two populations showed a significant difference in the gene frequencies distribution for ORM1.