Hum. Genet. 49, 159--166 (1979)

© by Springer-Vedag 1979

Linkage Studies on the Human Pi, Gm, GLO, and HLA Genes

K. Bender*, C. R. Mt~ller, Anita Schmidt, Ulrike Strohmaier, and T. F. Wienker

Institut ffir Humangenetik und Anthropologie der Universit~.t Freiburg, Albertstrasse 11, D-7800 Freiburg, Federal Republic of Germany

Summary. Linkage data of the four gene markers Pi, Gm, GLO, and H L A exclude Gm and Pi gene assignment to the short arm of chromosome 6. The findings, however, do not disprove the following gene order: H L A - - G L O - - cen t romere- -Gm--Pi .

Introduction

The autosomal gene loci Pi (al-antitrypsin) and Gm have been shown to be linked, with recombination frequencies of about 19% in males and 26% in females (Gedde-Dahl et al., 1972, 1975; Noades and Cook, 1976). The precise position of this linkage group in the human gene map is not yet known. It can almost certainly be excluded from chromosomes 1, 13, 16, 17, 18,21,and 22, however, and from most regions of chromosomes 5, 9, 10, 11, 14, 15, 19, and 20 (Noades and Cook, 1976; Noades et al., 1978). Therefore the Pi and Gm genes are most probably situated on one of the remaining chromosomes, i.e., 2, 3,4, 6, 7, 8, or 12. Borgaonkar et al. (1973) postulated from their findings in a family with a C6/ G21 translocation [t(6p;21q)] that the Gm genes might be situated on chromo- some 6. Recently, Smith and Hirschhorn (1978) presented evidence for the location of the genes for the human immunoglobulin heavy chains (i.e., the Gm genes) on chromosome 6. These observations implicate synteny between the established chromosome 6 markers HLA, GLO, and PGM3 (Bodmer, 1976) and the P i : G m linkage group.

We report here on H L A / G L O / G m / P i linkage data and their contribution to the problem of the chromosomal assignment of the Gm and Pi genes.

Materials and Methods

We have analyzed 36 complete two- and three-generation families with a total of 190 children of undoubted paternity. These families were all informative for linkage studies in double back- cross matings between at least two of the four markers Pi, Gm, GLO and HLA-A, B. The lod

* To whom offprint requests should be sent

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Linkage Studies on the Human Pi, Gm, GLO, and HLA Genes 163

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Fig. l a--e. Lod scores a For HLA : GLO (peak lod in males is 10.67 at 0 = 0.05; in females 6.35 at 0 = 0.09; combined 16.80 at 0=0.07); b For Gm:Pi (peak lod in males is 1.08 at 0= 0.23; combined 1.28 at 0= 0.25); e For Gin: GLO, Pi:GLO, Gm:HLA, Pi:HLA

scores (Zl in two-generation and nr : r in phase-known three-generation families) were computed according to the formulas given by Maynard-Smith et al. (1961). Gm and GLO phenotyping was performed according to standard methods, that of Pi by isoelectric focusing of serum samples on polyacrylamide Ampholine PAG plates (LKB; pH range 3.5--5.0) with the Multiphore apparatus 2117 (LKB) as described by Genz et al. (1977), and that of HLA antigens in peripheral lymphocytes by the lymphocytotoxic microtechnique of Kissmeyer-Nielsen and Kjerbye (1967).

Results and Discussion

The famil ies con t r ibu t ing to the l inkage studies are l isted in Table 1. The lod scores are p lo t t ed in F igure 1. There is a clear indica t ion for Pi: Gm l inkage on the one hand ( G e d d e - D a h l et al., 1972, 1975) and GLO:HLA l inkage on the o ther ( M a y r et a1.,1976) at r ecombina t ion fract ions of 0 = 0 . 2 5 and 0.07, respect ively (bo th sexes combined) . L inkage can be excluded, however , be tween the Pi and bo th the HLA and GLO loci. Slightly posi t ive lod scores were ca lcula ted for the Gm/GLO and the Gm/HLA combina t ions (Fig. 1).

Our da ta are in agreement with previous studies in which no measurab le l inkage re la t ionships could be found between the c h romosome 6 shor t a rm marke r s (i.e., HLA, GLO, PGM3) and the Gm (Mayr and Mayr , 1974; L a m m et

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Fig. 2. Ideogram of the genetic map of human chromosome 6 (adopted from Francke and Pellegrino, 1977, including the available deletion mapping data. The distances are given in centimorgans [cM]). The HLA genes are most probably situated at 6p21 (i.e., 25--30 cM from the telomere). Since the HLA : Gm and the GLO : Gm segregations are nearly independent, the Gm genes cannot be located on 6p. The slightly positive lod scores for HLA:Gm and GLO : Gm linkage, however, are compatible with a location of Gm on the proximal part of 6q. This is in agreement with the finding of Smith and Hirschhorn (1978) that somatic cell hybrids with a deletion of human 6ql6-*qter retained the genes for human immunoglobulin heavy chains. Upper brace, Gm localization exclusion due to a boy monosomic for 6p23~pter but still heterozygous for Gm (see Noades et al., 1976). Lower brace, Gm localization exclusion due to the findings of somatic cell hybrids with deletion of a large distal portion of the long arm of chromosome 6 (6ql6~qter) but still secreting human Ig heavy chains (Smith and Hirsch- horn, 1978)

al., 1975; Wei tkamp et al., 1975) and the Pi loci (Wei tkamp et al., 1975), respec- tively.

This should be interpreted as strong evidence against a locat ion of the Gm and Pi genes on the short a rm of chromosome 6, since (1) the HLA genes are situated at the middle posi t ion (6p21 ~ p22) of 6p, which has a total length of abou t 50 cM (Breuning et al., 1977; Francke and Pellegrino, 1977; Grzeschik et al., 1978), and (2) the Gm genes have to be excluded from 6p23 ~ pter due to the observat ion of a boy monosomic for this por t ion and yet heterozygous for Gm (Edwards et al., cited i n Noades et al., 1976; cf. Fig. 2). Therefore, if the Gm and Pi loci are si tuated on chromosome 6, they must be assigned to the long arm.

Linkage Studies on the Human Pi, Gin, GLO, and HLA Genes 165

The following observat ion of Smith and Hirschhorn (1978) implicates a further localization restriction, at least for the Gm genes: somatic cell hybrids with a large terminal delet ion of the long arm of chromosome 6 (6q16--* qter) still retained the genes for the h u m a n immunog lobu l in heavy chains, thus excluding the Gm genes from the distal por t ion of 6q. Indeed, as can be seen from Figure 2, there is ample space on 6q even at recombinat ion frequencies of over 36% for GLO-Gm and over 44% for HLA-Gm. This would suggest the possible gene order HLA-GLO-cen t romere - -Gm-Pi .

Acknowledgements. We thank the families for their cooperation and we highly appreciate the kind help of Dr. med. Reinhard Bender (Kinder- und Sportfacharzt in Eutin) in taking the blood samples in families F44, F44A, F45, F46, F53, F74, and F75.

Thus work was supported by the Deutsche Forschungsgemeinschaft (Be 352/II).

References

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Borgaonkar, D. S., Bias, W. B., Chase, G. A., Sadasivan, G., Herr, H. M., Golomb, H. M., Bahr, G. F., Kunkel, L. M.: Identification of a C6/G21 translocation chromosome by the Q-M and Giemsa banding techniques in a patient with Down's syndrome, with possible assignment of Gm locus. Clin. Genet. 4, 53--57 (1973)

Breuning, M. H., Van Den Berg-Loonen, E. M., Bernini, L. F., Bijlsma, J. B., Van Loghem, E., Meera-Khan, P., Nijenhuis, L. E.: Localization of HLA on the short arm of chromosome 6. Hum. Genet. 37, 131--139 (1977)

Francke, U., Pellegrino, M. A.: Assignment of the major histocompatibility complex to a region of the short arm of human chromosome 6. Proc. Natl. Acad. S ci. USA 74, 1147--1151 (1977)

Gedde-Dahl, T. Jr., Fagerhol, M. K., Cook, P. J. L., Noades, J. E.: Autosomal linkage between the Gm and Pi loci in man. Ann. Hum. Genet. 35, 393--399 (1972)

Gedde-Dahl, T. Jr., Cook, P. J. L., Fagerhol, M. K., Pierce, J. A.: Improved estimate of the Gm-Pi linkage. Ann. Hum. Genet. 39, 43--50 (1975)

Genz, T., Martin, J.-P., Cleve, H.: Classification of al-antitrypsin (Pi) phenotypes by iso- electrofocusing. Distinction of six subtypes of the Pi M phenotype. Hum. Genet. 38,325--332 (1977)

Grzeschik, K. H., Mayerovfi, A., Bender, K., Johannsmann, R.: Regional submapping of human chromosome 6 by the use of human-mouse somatic cell hybrids. Human Gene Mapping 4 (in press, 1979)

Kissmeyer-Nielsen, F., Kjerbye, K. E.: Lymphocytotoxic microtechnique. Purification of lymphocytes by flotation. In: Histocompatibility testing 1967, pp. 381--383. Kopenhagen: Munksgaard 1967

Lamm, L. U., Thorsen, I.-L., Petersen, G. B., Jorgensen, J., Henningsen, K., Bech, B., Kiss- meyer-Nielsen, F.: Data on the HL-A linkage group. Ann. Hum. Genet. 38,383--390 (1975)

Maynard-Smith, S., Penrose, L. S., Smith, C. A. B.: Mathematical tables for research workers in human genetics. London: Churchill 1961

Mayr, W. R., Mayr, D.: Analyse der Kopplung zwischen dem HLA-System und anderen Loci. Humangenetik 24, 129--133 (1974)

Mayr, W. R., Mayr, D., K6mpf, J., Bissbort, S., Ritter, H.: Possible linkage of HLA and GLO. Hum. Genet. 31,241--242 (1976)

Noades, J. E., Cook, P. J. L.: Family studies with the Gm : Pi linkage group. Baltimore Con- ference (1975). Third International Workshop on Human Gene Mapping. Birth Defects: Original Article Series XII: 7, 341--344. New York: The National Foundation, 1976

166 K. Bender et al.

Noades, J. E., Ball, M. J., McCloghry, F. J.: An investigation of a proposed linkage between Rhesus and Gm systems. Blur 37, 27--29 (1978)

Smith, M., Hirschhorn, K.: Location of the genes for human heavy chain immunoglobulin to chromosome 6. Proc. Natl. Acad. Sci. USA 75, 3367--3371 (1978)

Weitkamp, L. R., May, A. G., Johnston, E.: The linkage relationships of HL-A with other genetic marker systems. Hum. Hered. 25, 337--345 (1975)

Received January 30, 1979