Hum Genet (1993) 92 : 107-109 human .. genez, cs

�9 Springer-Verlag 1993

Original investigations

The phenylketonuria G272X haplotype 7 mutation in European populations

Jaran Apold l, Hans G. Eiken 1, Elisabeth Svensson 2, Erich Kunert 3, Libor Kozak 4, Petr Cechak 5, F l emming Giittler 6, Jacques Giltay 7, Uta Lichter-Konecki 8, Dominique Melle 9, Jadwiga Maria Jaruzelska 1~

Department of Medical Genetics, Haukeland University Hospital, N-5021 Bergen, Norway 2 Department of Clinical Chemistry I, Huddinge University Hospital, S-14186 Huddinge, Sweden 3 Abteilung for Humangenetik, Universit~its-Kinderklinik, O-7039 Leipzig, Germany 4 Department of Biochemical and Molecular Genetics, Pediatric Research Institute, CS-66262 Brno, Czechoslovakia 5 Department of Clinical Chemistry and Biochemistry, Charles University, (~S-12000 Praha, Czechoslovakia 6 Department of Inherited Metabolic Disease, John F. Kennedy Institute, DK-2600 Glostrup, Denmark 7 Klinisch Genetisch Centrum Utrecht, 3501 Utrecht, The Netherlands 8 Universit~its-Kinderklinik, D-69120 Heidelberg, Germany 9 Unite de Recherches sur les Handicaps de l'Enfant, HEpital des Enfants Malades, F-75743 Paris, France 10 Institute of Human Genetics, Polish Academy of Sciences, PL-60479 Poznan, Poland

Received: 10 July 1992 / Revised: 7 January 1993

Abstract. We have compiled data on the frequencies of the phenylketonuria G272X mutation in European popu- lations. This mutation occurs north of the Alps. It has a particularly high frequency in the Oslo Fjord region of Norway with the adjacent Bohuslan region of Sweden. An intermediate frequency was noted in a separate area, the eastern part of Germany with the adjacent western part of Czechoslovakia. The G272X mutation was associated with phenylalanine hydroxylase haplotype 7, except for one case with haplotype 3. Genealogical studies going back eight to nine generations revealed no common source for this mutation, but there was some geographical convergence to the Bohusl~in region. These findings sug- gest a single origin for this mutation, with at least one founding population in south-eastern Norway/adjacent Sweden.

Introduction

The population genetics of diseases can now be studied in a degree of detail that was previously unattainable. This is a consequence of the rapid assays of individual mutations with PCR and knowledge of their RFLP haplotype back- ground. Such studies are particularly prolific for diseases like phenylketonuria (PKU) in which the heterogeneity of the mutations leading to the disorder is very extensive (Konecki and Lichter-Konecki 1991) and in which many normal markers exist in the phenylalanine hydroxylase

Correspondence to: J. Apold

(PAH) gene in the form of highly informative RFLPs for haplotyping (Woo 1988).

The G272X mutation (Apold et al. 1990; Svensson et al. 1990) leads to classical PKU in the homozygous state because of a postulated gross truncation of the gene prod- uct. Initial data indicated that this mutation was highly re- stricted geographically, with a high frequency in Norway and an intermediate frequency in Sweden. We have now compiled data on the frequency of this mutation and its RFLP haplotype (hpt) background in European popula- tions, and attempted to trace its genealogical background in Scandinavia.

Patients and methods

The patients in the various populations were those already re- cruited for other molecular genetic analyses of the PAH locus. The G272X mutation was assayed from its abrogation of the naturally occurring BamHI site in PAH exon 7, either from Southern blots or from PCR-amplified exon 7 (Apold et al. 1990). The $273F muta- tion (Melle et al. 1991), which also abrogates this site, was ex- cluded by Sau3A cleavage (the Sau3A site is disrupted by the lat- ter mutation, but not by G272X). Genealogical studies were con- ventionally performed.

Results

The distribution of the G272X mutation in various Euro- pean populations is given in Table 1 and Fig. 1. It was as- sociated with hpt 7 (Table 1), with one exception where it was associated with hpt 3. Mutant hpt 7 was not detected in the following countries: England (L.A. Tyfield, per-

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Tab le 1. Frequency of the PKU mutation G272X and hpt 7 in Europe

Country No. of hpt 7 ch romosomes Total n'o. o f chronlosomes

Mutant Normal Mutant Normal

G272X Non-G272X

Norway 14 (16.3) 3 ~' (3.5) 7 (8.2) 86

Germany (east) 3 (3.4) I h ( 1.1 ) 6 (12.0) 88

Czechoslovakia 4 (4.4) 0 5 (5.8) 90 Sweden 4 (2.9) I (0.7) 9 (6.8) 136 Germany (west) 2 (2.0) 0 13 (13.0) 100 The Netherlands 2" (2.0) 0 ND 100 France 4 (I.5) I d (0.4) 1 I (4.4) 270 Denmark 2 (1.0) 0 18 (8.6) 210 Poland 1 ~" (0.7) I (0.7) ND 148

85

50

86

132

100

100

252

210

148

Percentages of all ch romosomes are given in parentheses. ND, " Two mutations are R243X and M II ~> The mutation is R252W ~ One of the two G272X mutations is on h p / 3 (see text) d The mutation is $273F ~" The haplotype is not determined

Not delermined

assays excluded the G272X mutation on other haplotypes in the above patient samples in England, Hungary, and Turkey.

Six Norwegian and two Swedish families contributed to the construction of extensive family trees tot the transmit- ting parent. In five families the genealogies could be traced over eight to nine generations (to the seventeenth or eighteenth century). No common ancestor could be identified. Geographically, however, three of the transmit- ting parents in the Swedish families originated in the Bo- huslfin region of Sweden (Fig. 1 ). One also had a branch to the Osffold county in Norway, which is adjacent to Bo- huslfin. Furthermore, three of the six Norwegian families providing extensive information on their backgrounds had branches back to the Bohuslfin area. Also, one of the Dan- ish families came from Ostfold County.

"--,v)

Fig. 1. Frequency of the G272X mutation in Europe. In countries where the G272X mutation occurs, its percentage of all PKU chro- mosomes is given (the number of mutant alleles analyzed is shown in Table 1 ). In countries without this mutalion the total number of mutant alleles analyzed is also given

sonal communication), Scotland (E Cockburn, personal communication), Switzerland (Sullivan et al. 1989), Hun- gary (Daiger et al. 1989; G. Fekete, personal communica- tion), Bulgaria (Kalaydjieva et al. 1990), Italy (Dianzani et al. 1990), and Turkey (Lichter-Konecki et al. 1989; I. Ozalp, personal communication). In addition, direct

Discussion

The G272X mutation is particularly frequent in one geo- graphical area: south-eastern Norway (the Oslo Fjord re- gion) with adjacent Sweden (Bohusl~in). For Norway as a whole, G272X accounts tot one-sixth of all PKU alleles. All Norwegian PKU patients with this mutation come from the Oslo Fjord region (Apold et al. 1990). Therefore, the frequency of G272X is considerably higher in this re- gion, about 32% of mutant alleles. It is also relatively common in eastern Germany (east of the river Elbe) with adjacent western Czechoslovakia (Bohemia/Moravia). It is noted less frequently in some of the other continental European countries north of the Alps: Denmark, The Netherlands, Germany (west of the river Elbe), France, and Poland. The pattern seen for the distribution of G272X has clear similarities to that of the IVS-12 muta- tion (Eisensmith et al. 1992).

This distribution could be explained by a single, rela- tively recent origin of the G272X mutation in the Oslo

Fjord region, followed by some dissemination to neigh- boring countries. A single origin o f the mutation is also suggested by the almost exclusive linkage o f G272X to hpt 7. The single case where G272X occurred on a non- hpt 7 background (i.e., hpt 3) can be explained by one crossover event. Hpt 7 is probably old (Hertzberg et al. 1989) and, therefore, it is not surprising that there is more than one mutation on this haplotype background. This al- most complete lack of G272X spreading to other haplo- types also suggests that its origin is relatively recent com- pared with that o f mutations, like R408W, that occur on several haplotypes (Konecki and Lichter-Konecki 1991).

Alternatively, in spite o f the linkage disequilibrium ob- served, G272X might be an old mutation, already present among the proto-Europeans, with founder effect and ran- dom drift leading to the different frequencies presently found. The inability to trace a c o m m o n ancestor by genea- logical methods would be in accordance with an early ori- gin o f this mutation, but could as well reflect limitations in the methods.

The geographical distribution of G272X has parallels to known demic migrations. In Norway, it occurs in the area occupied by the NCstvet paleolithic population, with which it may have spread, given that it is an ancient mu- tation. In the neolithic period there was a large immigra- tion to south-eastern Norway f rom continental Europe through southern Sweden. In this context, it might be o f interest that the two eastern German families with the G272X and some available genealogical information, had transmitting grandparents f rom the coast of the Baltic Sea.

Events in historic time have contributed too. These may also be relevant even if the G272X is a relatively recent mutation. There is archaeological evidence from the Ro- man period o f extensive connection specifically between Bohemia and Scandinavia. Before the tenth century the rivers Trave, Elbe, and Saale separated Germans and Slavs, and this may be reflected in the present difference in the frequency of G272X on both sides o f these borders, a difference also noted for the R408W mutation (Kalayd- j ieva et al. 1991). The Black Death (1346-54) certainly had important effects on small populations. Both before and after the Black Death there were extensive trading routes between Scandinavia and continental Europe, al- lowing for dispersion of the G272X mutation.

Acknowledgement. The work of JMJ was in part performed in Dr. Arnold Munnich's laboratory.

109

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Note added in proof. The number of PKU alleles studied in Nor- way has been increased to a total of 196. Of these, 29 are G272X (14.8%), a fraction not differing much from that given in Table 1 for 86 alleles.