Am. J. Hum. Genet. 46:92-94, 1990

Linkage of Hereditary Motor and Sensory Neuropathy Type I to the Pericentromeric Region of Chromosome 17 H. R. Middleton-Price,* A. E. Harding,T C. Monteiro,*J.

Bercianoj and S. Malcolm*

*Mothercare Department of Paediatric Genetics, Institute of Child Health; and tUniversity Department of Clinical Neurology, Institute of Neurology, London; and tHospital Nacional "Marques de Valdecilla," Santander, Spain

Summary Vance et al. have reported linkage of hereditary motor and sensory neuropathy type I (HMSN I) to the pericentromeric region of chromosome 17. We have studied eight families with HMSN I (also called the hypertrophic form of Charcot-Marie-Tooth disease) for linkage of the disease locus to polymorphic loci in the centromeric region of chromosome 17. Linkage has been confirmed for D17S58 (EW301) with a maximum lod score of 5.89 at 0 = 0.08 and for D17S71 (pA10-41) with a maximum lod score of 3.22 at 0 = 0.08. EW301 is on 17p, 5.5 centimorgans from the centromere. Two families, previously reported as being linked to the Duffy blood group locus on chromosome 1, were included in this study, and one now provides positive lod scores for chromosome 17 markers. There was no evidence of heterogeneity.

Introduction

The hereditary motor and sensory neuropathies (HMSN) are a heterogeneous group of disorders which can be classified on the basis of their clinical, genetic, neurophysiological, and pathological features (Harding and Thomas 1980). HMSN I, the commonest type of inherited neuropathy, with a prevalence of about 1 in 5,000 in the United Kingdom, is characterized by slowly progressive distal weakness and wasting, predominantly affecting the anterior tibial and peroneal muscles. Foot deformity, areflexia, and distal sensory loss are frequent, and upper-limb ataxia or tremor and peripheral nerve hypertrophy occur in about one-third of cases. Early reports suggested that the disease locus might be on chromosome 1, near the Duffy blood group locus (Bird et al. 1982; Guiloffet al. 1982). This conclusion was supported by the study of a single large family by Stebbins and Conneally (1982), but it rapidly became obvious that this did not apply to all families (Bird et al. 1983; Dyck et al. 1983). More recent work from many groups, including ours, failed to confirm the chroReceived June 14, 1989; revision received August 23, 1989. Address for correspondence and reprints: Dr. Sue Malcolm, Mothercare Department of Paediatrics Genetics, Institute of Child Health, 30 Guilford Street, London WC1N 1EH, England. i 1990 by The American Society of Human Genetics. All rights reserved. 0002-9297/90/4601-OO11$02.00

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mosome 1 map position in a large number of families (over 50 worldwide) (Griffiths et al. 1988; MiddletonPrice et al. 1989). It thus appeared that the earlier significant lod score obtained for HMSN I resulted by chance or that HMSN I is genetically heterogeneous. In either case, the gene locus (or loci) must map elsewhere in the genome in the majority of families. Following a recent report from Vance and colleagues (Vance et al. 1989), in which linkage was found between HMSN I and markers from the centromeric region of chromosome 17 in six families, we have confirmed this in eight families, including two previously suggested to be linked to the Duffy blood group (Guiloffet al. 1982). Two polymorphic probes, EW301 and pA10-41, were used. These probes have been studied extensively because of their linkage to the neurofibromatosis I locus (Goldgar et al. 1989), and it has been shown that the order on the short arm of chromosome 17 is cen-5.5cM-EW301-3 .3cm-pAlO-41-tel. Material and Methods The origins and clinical details of the families have been described elsewhere (Middleton-Price et al. 1989). Hybridization probes D17S58 (EW301) and D17S71 (pA10-41) were provided by Dr. D. Barker. EW301 identifies RFLPs with TaqI (4.5 kb and 3.1 kb) and Bg1II

HMSN I Linkage to Chromosome 17

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(10 kb and 8 kb). pA10-41 identifies both an RFLP with bands of 2.4 kb and 1.9 kb with MspI and an RFLP with bands of 2.8 kb and 2.6 kb with PvuII. Standard techniques for DNA extraction, restriction, blotting, and hybridization were used (Middleton-Price et al. 1989). In the case of pA10-41 the insert was purified following EcoRI digestion by separation on a 0.8% agarose gel and was isolated using Geneclean (Bio 101, La Jolla). EW301 was used as the entire plasmid, but hybridization of repetitive sequences was removed by preannealing with total human DNA. The required volume of radiolabeled probe was mixed with 1.2 vol 3 M NaCl, 0.3 M Na3 citrate, 1.2 vol sonicated placental DNA at a concentration of 10 mg/ml, 1.4 vol 10 mM Tris 8.0, 1 mM EDTA. The mix was boiled for 10 min and then left at 650C for 30 min before adding to the hybridization solution. Two-point lod scores were calculated using the LIPED computer program. For each probe, the results for the two enzymes were combined into a haplotype, and the data were entered as a four-allele system. Haplotype frequencies were calculated using data from unrelated individuals and were entered as follows: for EW301TaqI +; BglII +, .45; TaqI +, BglII -, .01; TaqI -, Bg1II +, .30; TaqI -, BgIII -, .24; for pA10-41-MspI +, PvuII +, .43; MspI +, PvuII -, .10; MspI -, PvuII +, .45; MspI -, PvuII -, .02. As there were rather few data on which to base these frequencies, we also analyzed the data by using equal haplotype frequencies. No significant differences were observed. Three-point data were calculated using the LINKMAP section of the LINKAGE program. The Haldane mapping function was used to calculate genetic distances.

Results Two-Point Lod Scores Two-point lod scores between HMSN I and the D17S58 and D17S71 loci for each family are presented in table 1. The maximum lod scores obtained were 5.89 at recombination fraction (0 = .08 (95% confidence limits .04-.20) for D17S58 and 3.22 at 0 = .08 (95% confidence limits .03-.25) for D17S71. As the two loci are 3 centimorgans (cM) apart, the agreement between the two distances is as expected. One crossover was observed in a male meiosis, and three were observed in female meioses. Female:male recombination in this region is 2:1 (Goldgar et al. 1989). Three-Point Lod Scores

Figure 1 shows LINKMAP analysis for HMSN I and the two 17p loci. Some meioses showed crossovers with both probes, making it less likely that the disease gene locus falls between the probe loci than outside them. This is confirmed by the formal LINKMAP analysis. However, without further probes it is impossible to tell whether the disease locus is centromeric or telomeric. When the data from both loci in the multipoint analysis are combined, the maximum lod score rises to 8.2 at 5 cM from either probe. Discussion

The results presented here confirm the finding of Vance et al. (1989) that the HMSN I locus maps to the pericentromeric region of chromosome 17 and further suggest that there is little or no heterogeneity. We present data from eight families. The four cross-

Table I Two-Point Lod Scores between HMSN I and Chromosome 17 Markers

e pA 10-41

EW301 FAMILY

.001

.05

.10 .15 .20 .30 .40

FG ........ 2.71 2.49 2.25 2.00 1.74 1.18 GV ........ 1.33 1.19 1.04 .89 .74 .45 HED ...... .64 .56 .49 .41 .33 .17 .14 HEN ...... .13 .12 .10 .08 .04 MO ....... - 2.75 .41 .75 .84 .81 .59 PE ........ - 1.61 - 0.03 .15 .21 .21 .14 SM ........ - 1.20 0.37 .54 .58 .55 .43 WH ....... .60 .56 .51 .46 .41 .29 .14 5.68 5.85 5.49 4.87 3.29 Total ....

.57 .20 .05 .01 .24 .05 .24 .16 1.52

.001 1.20 .46 .0 .18 -2.41 .88 -1.80 1.80 .31

.05

.10

.15

.20

.30

.40

1.16 1.02 .92 .82 .59 .32 .39 .32 .25 .19 .08 .02 .0 .0 .0 .0 .0 .0 .18 .18 .17 .16 .13 .08 -.76 -.51 -.37 -.28 -.17 -.08 .77 .66 .57 .48 .32 .16 -.19 .02 .10 .12 .10 .03 1.65 1.49 1.31 1.13 .73 .31 3.20 3.18 2.95 2.62 1.78 .84

Middleton-Price et al.

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tunity to apply the use of closely linked markers to clinical practice is now imminent.

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Acknowledgments We are grateful both to Dr. Jeffrey Vance and colleagues for communicating their data to us before publication and to Dr. David Barker for providing the probes. We thank Drs. S. Huson, D. Kumar, and M. Patton and Professor P. K. Thomas for providing family samples. Financial support from the Medical Research Council (H.R.M.-P.), Child Health Research Appeal Trust (S.M.), and NATO (C.M.) is gratefully acknowledged.

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References

Figure I Multipoint analysis of HMSN I vs. D17S58 and D17S71: odds ratio vs. male genetic distance in centimorgans.

over events were observed in three pedigrees. Three crossovers were observed in one large family (MO), but a maximum lod score of 0.84 at 0 = .15 was still seen in this family with probe EW301, which was the most informative of the two probes used. The study by Vance et al. presented data from six families, two of which contributed heavily to the positive lod score, thus throwing little light on the question of heterogeneity. Our study includes the two families (WH and HEN) originally reported by Guiloff et al. (1982) as showing linkage to the Duffy blood group locus. In our previous study (Middleton-Price et al. 1989), although the data from these two families were not significant on their own, application of the HOMOG computer program suggested that they could fall within a group containing about 20% of all families which map to chromosome 1. Unfortunately, family HEN is virtually uninformative so far for probes from 17p, but the results presented here suggest that it is unlikely for family WH, which, together with the majority of HMSN I families, maps to chromosome 17. This makes the prospects for clinical application of these probes much more prom-

ising. Vance et al. (1989) reported a maximum lod score of 10.49 at 5 cM for DS17S58. The combined data from the two studies gives a maximum lod score of 16.2 at 5 cM. Although this 0 value is currently too high for clinical application, many probes have been isolated and mapped from this region of chromosome 17 because the neurofibromatosis I gene locus maps to 17q11.2 (Ledbetter et al. 1989). Rapid progress toward isolating the HMSN I locus should now be possible, and the oppor-

Bird TD, Ott J, Giblett ER (1982) Evidence for linkage of Charcot-Marie-Tooth neuropathy to the Duffy locus on chromosome 1. Am J Hum Genet 34:388-394 Bird TD, Ott J, Giblett ER, Chance PF, Sumi SM, Kraft GH 1983) Genetic linkage evidence for heterogeneity in CharcotMarie-Tooth neuropathy (HMSN type I). Ann Neurol 14: 675-684 Dyck PJ, Ott J, Moore SB, Swanson CJ, Lambert EH (1983) Linkage evidence for genetic heterogeneity among kinships with hereditary motor and sensory neuropathy type I. Mayo Clin Proc 58:430-435 Goldgar DE, P Green, Parry DM, Mulvhill JJ (1989) Multipoint linkage analysis in neurofibromatosis type I: an international collaboration. Am J Hum Genet 44:6-12 Griffiths LR, Nicholson GA, Ross DA, Zwi M, McLeod JG, Mohandas T, Morris BJ (1988) Regional chromosomal assignment of human renin gene to lq21-qter and use in linkage studies in Charcot-Marie-Tooth disease. Cytogenet Cell Genet 45:231-233 Guiloff RJ, Thomas PK, Contreras M, Armitage S, Schwartz G, Sedgwick EM (1982) Linkage of autosomal dominant type I hereditary motor and sensory neuropathy to the Duffy locus on chromosome 1. J Neurol Neurosurg Psychiatry 45:669-674

Harding AE, Thomas PK (1980) Clinical features of hereditary motor and sensory neuropathy types I and II. Brain 103:259-280 Ledbetter DH, Rich DC, O'Connell P, Leppert M, Carey JC (1989) Localization of NF1 to 17q11.2 by balanced translocation. Am J Hum Genet 44:20-24 Middleton-Price HR, Harding AE, Berciano J, Pastor JM, Huson SM, Malcolm S (1989) Absence of linkage of hereditary motor and sensory neuropathy type I to chromosome 1 markers. Genomics 4:192-197 Stebbins NB, Conneally PM (1982) Linkage of dominantly inherited Charcot-Marie-Tooth neuropathy to the Duffy locus on chromosome 1. Am J Hum Genet 34:195A. Vance JM, Nicholson GA, Yamaoka LH, Stajich J, Stewart CS, Speer MC, Hung W-Y, et al (1989) Linkage of CharcotMarie-Tooth neuropathy type la to chromosome 17. Exp Neurol 104:186-189

Linkage of hereditary motor and sensory neuropathy type I to the pericentromeric region of chromosome 17.

Vance et al. have reported linkage of hereditary motor and sensory neuropathy type I (HMSN I) to the pericentromeric region of chromosome 17. We have ...
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