Evidence that SE is distal to LU on chromosome 19q

T. ZELINSKI, G. COGHLAN, c. R. GREENBERG, P. J. MCALPINE, AND M. LEWIS

Analysis of a family informative for chromosome 19 loci establishes that the Lutheran blood group locus (LU) lies between the third component of human complement (C3) and the secretor loci (SE). Previously published lod scores for C3:LU are increased from 2.94 to 3.80. The linkage relationships (2 and 8 ) between C3, LU, and SE are examined, and the proposed order and approximate genetic distances are determined to be: pter - - C3 - 10.6cM - cen - 7.4cM - LU - 9cM - SE -- qter. TRANSFUSION 1989;29:304-305,

THE FIRST AUTOSOMAL LINKAGE GROUP described in humans1*2 (LU and SE) eluded chromosomal as- signment for three decades. Its expansion to include the C3 locus was pivotal to its eventual assignment to chromosome 19.3 However, the positioning of LU and SE relative to C3 has remained controversial. On the basis of two-point lod score linkage analysis, Eiberg et aL3 concluded that SE lies between C3 and LU, an order reiterated by Gedde-Dahl et al.4 in their study incorporating the apolipoprotein E (APOE) lo- cus. On the other hand, Lewis et a1.,5T6 using the same type of analysis, presented data favoring the order C3 - LU - SE and arguing for a long-arm position of SE distal to LU.

None of the above studies included an individual family that might substantiate either order. This report presents a family in which recombination between LU and SE occurred in a paternal gamete while the align- ment of C3 - LU alleles was maintained. The family was discovered during a study of hypophosphatasia;’ the chromosome 19 information gained was thus for- tuitous.

Materials and Methods Venous blood samples were drawn into ACD for determi-

nation of phenotypes in the 15 established autosomal blood group systems and into EDTA for DNA studies relative to hypophosphatasia. Recombination between LU and SE was the basis for further investigation with DNA probes that de- tect restriction-fragment-length polymorphisms (RFLPs) for the chromosome 19 loci C3, apolipoprotein C-2 (APOC2), and low-density lipoprotein receptor (LDLR).

The methods and reagents used in the determination of Lutheran, Lewis, and Landsteiner-Weiner (LW) phenotypes have been described p r e v i o ~ s l y . ~ . ~ Secretor phenotypes were based on Lewis red cell (RBC) types, and the genotypes were based on deduction. The details of the recombinant DNA

From the Rh Laboratory, Department of Pediatrics and Child Health, and the Department of Human Genetics, Faculty of Medicine, University of Manitoba, Winnipeg, Manitoba, Canada.

SupportedbyMRC(Canada)GrantsMT3391 (ML)and MT6112 (PJM), the Manitoba Health Research Council (CRG), and the Children’s Hospital of Winnipeg Research Foundation, Inc.

Received for publication August 2, 1988; revision received October 3, 1988, and accepted October 5, 1988.

technology involved was described elsewhere,I0.’ I as was the identification of the chromosome 19 probes.6

Linkage analysis was made by a computer program that calculates lod scores for 0 values 0.05,0.10,0.20,0.30, and 0.40. Peak lod scores (i) and O values and 95 percent likelihood limits were obtained from a computer-determined curve based on the above calculated lod scores. The locus order (Fig. 1) was established by inspection.

Results .

The inheritance of the paternal alleles in generation 111 members of the informative family is depicted in Fig. 1. The father in generation I1 was heterozygous for C3, LU, and SE and homozygous for LDLR, Landsteiner-Weiner blood group LW, and APOC2 loci. His C3, LU allelic alignment was known, whereas that for SE was assumed on the basis of the LU, SE alignments in children 111-2 to -7, which are compatible with the known LUSE recombination fraction. The counts afforded by the members of generation 111 are thus: C3:LU, 1R:6NR LUSE, z 6: l ; C3:SE, z 5:2. The addi- tion of the lod scores for these counts to those compiled by Lewis et aL6 resulted in slight refinements in linkage data for the three locus pair combinations as shown in Table 1; in particular, 2 for C3:LU is increased from 2.94 at O = 0.19 to 3.80 at O= 0.18.

Discussion The information contained in this report reinforces

the argument of Lewis et a1.6 that LU lies between C3 and SE. The known alignment of C3 and LU alleles and the postulated alignment of SE alleles, as depicted in Fig. 1, are maintained in five of seven offspring in generation 111. A single crossover between C3ILU and SE and between C3 and LUISE is the simplest explanation for the alignments in children 111-1 and m-5, respectively. The alternate order, C3 - SE - LU, would require a double crossover to account for the alignment in In-1, an unlikely event in view of chiasmata studies on chromosome 19.12

The recombination fraction of 0.09 for LUSE and the identical recombination fractions for C3:LU and C3:SE (0.18, Table 1) appear to be unreconcilable as a measure of genetic distance. This anomaly could be explained by interference, i.e., that crossing-over occurs either between C3 and LU or between C3 and

304

TKANSFUSION IYXO-VoI 24. N o 4 305 SE IS DISTAL TO LU ON 19Q

I C3 LU 81-81 -I' SE Se/se

11: 81-82 81-81

FIG. 1 . Allelic alignment in a family informative for C3, LU, and SE. Only paternal gametes were indicated for generation 111 members; maternal alleles were obligatory.

SE. However, there is no benefit to speculation so long as the likelihood limits are so broad.

Consequently, we conclude that the family data presented here provide the most reliable evidence for order and that the best estimate of approximate dis- tances is:

pter - - C3 - 10.6cM - cen - 7.4cM - LU - 9cM - SE --qter.

Table 1. Pairwise linkage relationship between C3, LU. and SE derived from paternal meioses

Locus pair 2 8 Likelihood limits

c3: L u 3.80 0.18 0.08-0.30 0.04-0.1 5 LU:SE 11.59 0.09

C3:SE 4.83 0.18 0.09-0.28

the Lutheran (Lu) blood group locus on chromosome 19. Hum Genet 198467:178-82.

5. Lewis M, Kaita H, Coghlan G, et al. The chromosome 19 linkage group LDLRC3:LW:LU:SE (abstract). Cytogenet Cell Genet 1987;46:650.

6. Lewis M, Kaita H, Coghlan G, et al. The chromosome 19 linkage group LDLR, C3, LW, APOCZ, LU, SE in man. A n n Hum Genet 1988;52: 137-44.

7. Chodirker BN, Evans JA, Lewis M, et al. Infantile hypophosphatasia-linkage with the RH locus. Genomics

8. Lewis M, Kaita H, Chown B, Giblett ER, Anderson J. C8tt GB. The Lutheran and secretor loci: genetic linkage analysis. Am J Hum Genet I977;29: 10 1-6.

9. Lewis M, Kaita H, Philipps S , et al. The LWC3 recombination fraction in female meioses. A n n Hum Genet 1987;5 1:201-3.

10. Zelinski T, Verville G, White L, Haemerton JL, McAlpine PJ, Lewis M. Confirmation of the assignment of MYCL to chromosome I in humans and its position relative to RH, UMPK, and PGMI. Genomics 1988:2:154-6.

11 . Zelinski T, Kaita H, Lewis M, et al. The Colton blood group locus: a linkage analysis. Transfusion 1988;28:435-8.

12. Laurie DA, Hulten MA. Further studies on chiasma distribu- tion and interference in the human male. Ann Hum Genet 1985;49:203- 14.

1987;1:280-2.

Acknowledgments The authors thank the members of the family who cooperated

in this study. They also thank Dr. G. Fey for providing the C3. I I probe and Grace McDonald for typing the manuscript.

Teresa Zelinski, PhD, Assistant Professor, Department of Pedi- atrics and Child Health, Faculty of Medicine, University of Man- itoba. Rh Laboratory. 735 Notre Dame Avenue, Winnipeg, Manitoba. Canada R3E OL8. [Reprint requests].

References I . Mohr J. Estimation of linkage between Lutheran and Lewis

blood groups. Acta Path Microbiol Scand 195 1;29:339-44. 2. Mohr J. A study of linkage in Man. Copenhagen: Munksgaard,

1954:l 19. 3. Eiberg H, Mohr J, Neilsen LS, Simonsen N. Genetics and

linkage relationships of the C3 polymorphism: discovery of C3-Se linkage and assignment of LES-C3-DM-Se-PEfD-Lu synteny to chromosome 19. Clin Genet 1983;24:159-70.

4. Gedde-Dahl T, Olaisen B, Teisberg P, Wilhelmy MC, Mevag B, Helland R. The locus for apolipoprotein E (apoE) is close to

Gail Coghlan, BSc, Research Technician, Department of Pedi- atrics and Child Health, University of Manitoba, and Rh Labora- tory, Health Sciences Centre.

Cheryl R. Greenberg, MD, Associate Professor, Department of Pediatrics and Child Health and Department of Human Genetics, University of Manitoba.

Phyllis J. McAlpine, PhD, Professor, Department of Human Ce- netics, University of Manitoba.

Marion Lewis, BA, DSc, Professor, Department of Pediatrics and Child Health, University of Manitoba, and Rh Laboratory, Health Sciences Centre.