Recently we have presented an electrophoretic comparison of genetically determined human serum albumin variants from diverse populations, distinguishing 20 different types of 'monomeric' variants as well as three 'dimeric' variants (Weitkamp et al. 1973; Weitkamp & Neel, 1972). A t this time we compare the 20 previously described types of monomeric variants with 30 more variants, generally rare, and extend our data and conclusions on the population distribution of albumin variants. MATERIALS AND METHODS Each albumin variant, its source, and ethnic origin are listed in the Appendix. Many of the new variants were found in several individuals in a single family. In other cases the variants were found in one or more individuals in a single village. The electrophoretic comparisons were made in the three starch-gel systems, acetate-EDTA a t pH 5.0, tris-lithium-succinate-citrate a t pH 6.0 and tris-EDTA-borate a t pH 6.9, used previously (Weitkamp et al. 1973). RESULTS The results of the comparison of 30 new or recently described serum albumin variants with 20 variants previously distinguished using three starch-gel electrophoretic systems are presented in Table 1. Although the amount of separation reported here for the 20 variants previously described differs slightly from the earlier results, due to minor variations in electrophoretic conditions, the conclusions regarding their mobility relative to normal albumin and to each other remain the same. Three new variants, RS I, Xavante, and Yanomama-2, all slowly migrating, have been identified. Electropherograms showing these variants adjacent to variants with similar mobility are presented in Fig. 1. Albumin RS I, found in an indigene from Somali, has been mentioned in two previous reports. Porta et al. (1972) found it (identified as R.s.) indistinguishable from SO/BS on cellulose acetate electrophoresis a t pH 9-25. The sample available a t the time of our prior comparison (Weitkamp et al. 1973) was sufficiently degraded, as determined by the smeared patterns in the pH 6.0 and 6.9 systems and the altered mobility of normal albumin in the pH 5.0 system, to preclude determination of its mobility. In the present sample, both the normal and variant albumin bands stain less intensely with Amido Black 1OB than the albumin bands
No abstract
* I n a related screening effort (undertaken by Dr P. Kale, private communication) a total of 2412 of our South American Indian haemolysates were reexamined for possible electrophoretic haemoglobin variants using a cellulose acetate methodology ; no haemoglobin variants were observed.
SUMMARY This paper presents the results of an electrophoretic survey of approximately 4000 individuals from the cities of Hiroshima and Nagasaki, Japan, for four serum proteins: albumin, ceruloplasmin, haptoglobin and transferrin. The haptoglobin gene frequencies obtained for the HP1‐HP2 polymorphism are in agreement with earlier reports. Rare electrophoretic variants of albumin, ceruloplasmin and haptoglobin occur with frequencies of 2.48, 0.50 and 0.58 per 1000 determinations, respectively. The noteworthy finding of 8 distinct transferrin variants in these populations, with a combined frequency of 20.90 per 1000 determinations, is also presented. Four of these variants (DCh1, B1, B3 and Dhir2 which corresponds electrophoretically to D4) have been reported in other populations in Japan, but the other five have not previously been differentiated.
Summary The frequencies in Hiroshima and Nagasaki of rare variants (represented in less than 2 % of the individuals surveyed) is summarized for a series of 22 proteins (25 polypeptides). The average number of persons examined for each protein was 3312. There are three pairs of homologous proteins in the series: PGM, and PGM, CA I and CA 11, and HGB A and A,. Only for the first pair is there a significant difference between the two in the total frequency and number of different kinds of variants; it is suggested this may reflect differences in the mutation rates of the corresponding structural genes. For 23 of these polypeptides, comparable data are available for British Caucasians. The average frequency of variants for loci in common in the two series is 2.0/1000 person determinations for Japanese and 1.6/1000 for Caucasoids. At two loci (PGMl and PHI) there were significantly more variants in Japanese than in British; these two loci account for the greater average frequency of variants in Japanese. However, a conservative comparison of number of diflerent variants (electromorphs) encountered, using the 0 statistic of Ewens (1972), yields no significant difference for any of the 22 possible contrasts. The potential usefulness of data of this type in reaching conclusions regarding comparability of mutation rates in two populations is discussed. For the present, the fact that one electromorph may shelter multiple different amino acid substitutions in a protein limits the inferences to be drawn from such contrasts. It is 8 pleasure to acknowledge our indebtedness to Dr Peter Smouse and Dr Warren Ewens for statistical consultations, but responsibility for the tentative interpretations is entirely our own.
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