Probable assignment of the Duffy blood group locus to chromosome 1 in man.

In this paper (an abstract of which appeared earlier') we report what we believe is the first assignment of a specific gene locus to a specific autosome in man. Estimates are given of recombination values between the common blood group/ serum protein loci and an element (Un) that controls the expression of an anomalous uncoiled region of chromosome 1 in a newly studied family (V1lDE) as well as in two small pedigrees (V11CR and V11PP) reported in the literature.2 3 We present evidence that the Duffy blood group locus Fy, already believed to be linked to a congenital cataract locus4 Cae, is close to this uncoiler element Un, and that all three are probably on chromosome no. 1. A report of another family,5 slightly favoring linkage between Fy and one of the break points of a no. 1 inversion, is also considered. Methods. -Cytogenetic study: For chromosome analysis of family VllDE, venous blood was drawn with a heparinized syringe and cultured for 72 hr in a mixture of medium 199, fetal bovine serum, and phytohemagglutinin, according to a modification of the technique of Lejeune.6 In this system, the lymphocytes underwent mitosis and were arrested at metaphase by 0.02 jg colchicine/ml culture fluid added for the final 2 hr of culture. At culture termination, the lymphocytes were treated with 0.9% (hypotonic) sodium citrate, fixed in 3: 1 ethanol-acetic acid and then placed on a slide, dried by flaming, and stained in a 4%/0 (v/v) giemsa solution. Polymorphic marker loci: Loci with two or more alleles were investigated in family VIlDE as follows. Blood group typing was done for antigens, A, B, D, C, c, E, e, M, N, S, s, P,, K, k, Kpa, Kpb, Jka, Fya, Fyb, Lua, Lub, Lea, and Leb. The saline tube test and antiglobulin test were used where appropriate. The immunoglobulins Gm 1, 2, 3, 5, 6, 13, 14, and Inv 1 were typed by the agglutination inhibition method.7 Vertical polyacrylamide gel electrophoresis8 was used to type the serum proteins haptoglobin (Hp), transferrin (Tf), and group-specific component (Gc). The known alleles at the Duffy blood group locus are the common9 Fya and Fyb, a relatively rare'0 Fyx, and a "silent allele"9 Fy, that is largely confined to Negroes. Anti-Fya (lot 13) and anti-Fyb (lot Brent) from Spectra Biologicals were used exclusively. Extensive use of these reagents has indicated that they are monospecific. One drop of the appropriate antiserum and two drops of a washed 2% cell suspension in saline were incubated at 370C for 30-60 min. The cells were then washed three times in saline and the Coombs test performed. All reactions were either 4+ or negative. Since weak reactions were not observed, it is assumed that the Fy(b+) individuals were not Fyx. If any of the Fy(a+b-) individuals in family V1lDE are, in fact, Fy(a+x+), it is not apparent from the pedigree. Results. -The marker chromosome with an anomalous region: The marker chromosome occurring in family V1lDE is shown in Figures 1 and 2. This chromosome differs from the usual no. 1 by having a greater over-all length and a greater length of the long arm. A region extends from the centromere along part of each long arm in which the chromatids may be thinner with, occasionally, an alternating pattern of light and dark staining, suggestive of coils. Rather than