Anim. Blood Grps biochem. Genet. 4 (1973): 79-82

Phosphohexose isomerase polymorphism in horse erythrocytes

Kaj Sandberg

Department of Animal Breeding, Agricultural College, 750 07 Uppsala, Sweden

Received: 2 March 1973

Summary

Four individual patterns of phosphohexose isomerase (PHI) from horse red cells were found by starch gel electrophoresis. Population and family data of two Swe- dish horse breeds were consistent with the theory that the PHI types were con- trolled by three codominant, autosomal alleles designated PKIF, PHI' and PHIS ( F , Z and S).

Introduction

The enzyme phosphohexose isomerase (PHI) plays an important role in the carbo- hydrate metabolism, by catalysing the reversible conversion of glucose-6-phosphate to fructose-6-phosphate. In literature three desipations for the enzyme are used syncnymously, namely GPI (glucosephosphate isomerase), PGI (phosphoglucose isomerase) and PHI. Genetically controlled variants of PHI are described in man (Detter et al., 1968; Fitch et al., 1968), in mice (Carter & Parr, 1967; DeLorenzo & Ruddle, 1969), in pigs (Saison, 1970; Tariverdian, 1970) and in fish (Yndgaard, 1972). In mice the PHI locus has proved to be linked to the albino (c) and the hemoglobin ,&chain (Hbb) loci in linkage group I (Hutton & Roderick, 1970) and in pigs a close linkage between the loci for PHI, 6-PGD (6-phosphogluconate de- hydrogenase) and the H blood group system was demonstrated by Andresen (1971). PHI variants with reduced catalytic activity have been found in man. In some cases such PHI deficiency is associated with hemolytic anemia (Baughan et al., 1968; Tariverdian et al., 1970).

The present communication will describe a genetically controlled polymorphism in PHI from horse red cells.

Materials and methods

Starch gel electrophoresis of lysates from horse erythrocytes was performed in a continuous phosphate buffer system at pH 7.2. With this system the PGM (phos-

79

K. SANDBERG

Fig. 1. Photograph showing a starch gel with four different PHI types.

phoglucomutase), AP (acid phosphatase), 6-PGD and PHI phenotypes were deter- mined in the same electrophoretic run. The details of the technique are given else- where (Bengtsson & Sandberg, 1973). The blood samples used in this study were drawn in Alsever’s solution and sent to our laboratory for routine blood typing. The horse material belonged to the Swedish Trotter breed and the North-Swedish Horse breed.

Results and discussion

Fig. 1 is a photograph showing the four different PHI patterns observed. The most common type designated I and the rare type designated F, both consisted of a single heavy band. The F and I types were supposed to represent homozygotes. The three band pattern designated FI was composed of a fast fraction, a slow fraction and a fraction with an intermediate migration rate. This is a typical heterozygous pattern of a protein with a dimeric structure. The fourth PHI type designated IS appeared to consist of two bands, migrating quite close to each other. Due to the fact that the IS pattern was somewhat obscured by a hemoglobin fraction it was not possible to decide whether there was also a third faint band present. Occasion- ally such a band could be imagined.

Table 1. Inheritance of PHI types in 1382 matings.

Mating type Number and type of offspring

F FI I IS

F X I 6 FI X FI 3 6 5 FI X IS 2 FI X I 124 115 I x IS 6 5 I X I 1110

80 Anim. Blood Grps biochem. Genet. 4 (1973)

PHI POLYMORPHISM IN HORSE ERYTHROCYTES

Table 2. Frequencies of PHI alleles in two horse breeds.

Breed F I S n

North-Swedish Horse 0.037 0.955 0.008 121 Swedish Trotter 0.065 0.934 0.001 1104

The inheritance of the PHI types in 1382 matings is shown in Table 1. The distribution of the different types of offspring correspond to the interpretation that the PHI types are controlled by three codominant, autosomal alleles, PHIF, PHI] and PHIS (F, Z and S ) . Three exceptions to this rule were observed. They could all be explained by erroneous registration on the basis of genetic incompatibility involving other blood protein systems and blood group factors. The gene fre- quencies of the two investigated breeds were estimated by gene counting with a representative material of parental animals including all the champion stallions in Sweden (Table 2). The distribution of the PHI types agreed very well with that expected assuming genetic equilibrium (Table 3). As one allele has a very high frequency the PHI system was not efficient in detecting erroneous paternities within the breeds studied. The probability of detecting a falsely assigned stallion was calculated to about 6% in the Swedish Trotter and about 4% in the North-Swedish Horse, using the formula advanced by Gahne (1961).

The enzyme PHI seemed to be quite stable since samples kept frozen for 3-4 years did not visibly differ from fresh samples in electrophoretic pattern or staining intensity. Any quantitative assay of PHI activity in individual horse samples has no,t been carried out so far. Judging from the staining intensity of different samples on the gel there was not any pronounced difference in enzyme activity between individual horses.

Acknowledgment

I thank Mr Sven Bengtsson for skilful assistance.

Table 3. Observed and expected distribution of PHI types in two horse breeds.

Breed PHI types

F FI I IS

North-Swedish Obs. - 9 110 2 Horse Exp . 0.1 8.6 110.4 1.9 Swedish Obs. 4 135 963 2 Trotter Exp. 4.7 134.1 963.1 2.1

Anim. Blood Grps biochem. Genet. 4 (1973) 81

K. SANDBERG

References

Andresen, E., 1971. Linear sequence of the autosomal loci PHI, H and 6-PGD in pigs. Anim. Blood Grps biockem. Genet. 2: 119-120.

Baughan, M. A., N. N. Valentine, D. E. Paglia, P. 0. Ways, E. R. Simons & Q. B. De Marsh, 1968. Hereditary hemolytic anemia associated with GPI deficiency - a new enzyme defect of human erythrocytes. Blood 32: 237-249.

Bengtsson, S. & K. Sandberg, 1973. A method for simultaneous electrophoresis of four horse red cell enzyme systems. Anim. Blood Grps biochem. Genet. 4: 000-000.

Carter, J. C. & C. W. Parr, 1967. Isoenzymes of phosphoglucose isomerase in mice. Nature, Lond. 216: 511.

DeLorenzo, R. J. & F. H. Ruddle, 1969. Genetic control of two electrophoretic variants of glucosephosphate isomerase in the mouse (Mus rncrscu[us). Biochem. Genet. 3: 151-162.

Detter, J. C., P. 0. Ways, E. R. Giblett, M. A. Baughan,. D. A. Hopkinson, S. Povey & H. Hams, 1968. Inherited variations in human phosphohexose isomerase. Ann. hum. Genet.,

Fitch, L. I., C. W. P a n & S. G. Welch, 1968. Phosphoglucose isomerase variation in man.

Gahne, B., 1961. Studies of transferrins in serum and milk of Swedish cattle. Anim. Prod. 3:

Hutton, J. J. & T. H. Roderick, 1970. Linkage analyses using biochemical variants in mice. III. Linkage relationships of eleven biochemical markers. Biochem. Genet. 4: 339-350.

Saison, R., 1970. Serum and red cell enzyme systems in pigs. Proc. 11th Eur. Conf. Anim. Blood Grps biochem. Polymorphism (Warsaw, 1968): 321-328.

Tariverdian, G., 1970. Zur Populationsgenetik der Phosphohexoseisomeraen beim Schwein. Humangenetik 9: 110-112.

Tariverdian, G., H. Arnold, K. G. Blume, U. Lenkeit & G. W. Lohr, 1970. Zur Formalgenetik der Phosphoglucoseisomerase. Untersuchung einer Sippe mit PGI Defizienz. Hurnangenerik

Yndgaard, C . F., 1972. Genetically determined electrophoretic variants of phosphoglucose isomerase and 6-phosphogluconate dehydrogenase in Zoarces viviparus L. Hereditas 71:

Lond. 31: 329-338.

Biochem. J . 110: 56 P.

135-145.

10: 218-223.

151-154.

82 Anim. Blood Grps biockem. Genet. 4 (1973)