Hum Genet (1992) 89 : 122

9 Springer-Verlag i992

DNA variants A rare MspI RFLP of the DMD probe p20 (DXS269) S. Uhlhaas 1, E. Bakker 2, C.van Broeckhoven 3, A. Barlh-Schulz 4, and W. Friedl 1 tInstitut for Humangenetik der Universitfit, Wilhelmstrasse 31, W-5300 Bonn 1, Federal Republic of Germany 2Department of Human Genetics, Leiden University, Sylvius Laboratory, Wassenaarseweg 72, NL-2333 AL Leiden, The Netherlands 3Department of Biochemistry, University of Antwerp, Universiteitsplein 1, B-2610 Wilrijk, Belgium 4Institut ftir Humangenetik der Universit~it, Theodor-Stern-Kai 7, W-6000 Frankfurt/M. 70, Federal Republic of Germany Received September 15, 1991

Summary. A rare polymorphism of the probe p20 in the Duchenne muscular dystrophy gene is reported.

Probe p20 (DXS269) is a 2.65-kb intronic junction fragment from the Duchenne muscular dystrophy ( D M D ) gene, and has been cloned in the PstI site of p K U N 1 ( W a p e n a a r et al. 1988); p20 is located in the intron between exons 44 and 45 of the D M D gene, which has been assigned to Xp21.2 (Murray et al. 1982). A 2-allele polymorphism identified by MspI has previously been described (Wapenaar et al. 1988), with bands at 6 . 0 k b (A1) and 3.5 kb (A2). H e r e , we describe an additional rare restriction fragment length polymorphism (RFLP) detected by MspI, with bands at 1.5 kb + 0.3 kb (B1) and 1.8 kb (B2). The allele frequencies (studied in 455 X-chromosomes from an unrelated sample of Dutch, Belgian and German Caucasians) are: A1 (0.76); A2 (0.24); B1 (0.94); B2 (0.06). Codominant segregation of the allele system B described here was observed in numerous 2-generation families, including healthy males. An example is shown in Fig. 1. It is worthwhile paying attention to the possibility of the appearance of this second rare MspI R F L P observed with probe p20. Since this probe maps to a region of the D M D gene prone to deletions, the appearance of the 1.8-kb allele (instead of the "constant band" at 1.5 kb)

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Fig. I. Pedigree showing the segregation of the rare MspI RFLP of probe p20 could lead to misinterpretation of results, especially when the D M D patient is not available for analysis.

References Murray JM, Davies KE, Harper PS, Meredith L, Mueller CR, Williamson R (1982) Linkage relationship of a cloned DNA sequence on the short arm of the X chromosome to Duchenne muscular dystrophy. Nature (London) 300 : 69-71 Wapenaar MC, Kievits T, Hart KA, Abbs S, Blonden LAJ, Dunnen JT den, Grootscholten PM, Bakker E, Verellen-Dumoulin C, Bobrow M, Ommen GJB van, Pearson PL (1988) A deletion hot spot in the Duchenne muscular dystrophy gene. Genomics 2:101-108

A rare MspI RFLP of the DMD probe p20 (DXS269).

Hum Genet (1992) 89 : 122 9 Springer-Verlag i992 DNA variants A rare MspI RFLP of the DMD probe p20 (DXS269) S. Uhlhaas 1, E. Bakker 2, C.van Broeck...
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