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(Circulation. 1995;91:1633-1640.)
© 1995 American Heart Association, Inc.

Articles

Gene for Progressive Familial Heart Block Type I Maps to Chromosome 19q13

Paul A. Brink, MD; Alet Ferreira, MS; Johanna C. Moolman, MS; Hettie W. Weymar, RCT; Pieter-Luttig van der Merwe, MD; Valerie A. Corfield, PhD

From the Department of Internal Medicine, University of Stellenbosch Medical School and Tygerberg Hospital (P.A.B.); the University of Stellenbosch and Medical Research Council Centre for Molecular and Cellular Biology, Department of Medical Physiology and Biochemistry, University of Stellenbosch Medical School (A.F., J.C.M., V.A.C.); the Section of Cardiology, Department of Medicine, Tygerberg Hospital (H.W.W); and the Section of Cardiology, Department of Pediatrics, Tygerberg Hospital, University of Stellenbosch Medical School (P.-L.van der M.), Tygerberg, South Africa.

	Abstract

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Background Progressive familial heart block type I (PF-HBI) is a dominantly inherited cardiac bundle-branch conduction disorder that has been traced through nine generations of a large South African kindred. Similar conduction disorders have been reported elsewhere; however, the cause of these diseases is unknown. The aim of the present study was to determine by linkage analysis the approximate chromosomal position of the gene causing PFHBI, thereby allowing family-based diagnosis and the development of positional cloning strategies to identify the causative gene.

Methods and Results Eighty-six members of three pedigrees, 39 members of which were affected with PFHBI, were genotyped at four linked polymorphic marker loci mapped to chromosome 19, bands q13.2-q13.3 (chromosome 19q13.2-13.3). Maximum two-point logarithm of the odds scores (which represent the logarithm of the odds ratio of detecting linkage versus nonlinkage) generated were 6.49 (=0) for the kallikrein locus, 5.72 (=0.01) for the myotonic dystrophy locus, 3.44 (=0) for the creatine kinase muscle-type locus and 4.51 (=0.10) for the apolipoprotein C2 locus. The maximum multipoint logarithm of the odds score was 11.6, with the 90% support interval positioning the PFHBI locus within a 10 cM distance centering on the kallikrein 1 locus.

Conclusions The gene for PFHBI maps to an area of approximately 10 cM on chromosome 19q13.2-13.3. There are several candidate genes in this interval; although a recombination event ruled out the myotonic dystrophy locus from direct involvement with PFHBI, the proximity of these two loci may be relevant to the observed cardiac abnormalities of myotonic dystrophy. The results provide a means of DNA-based diagnosis in the families studied and a foundation for cloning studies to identify the causative gene.

Key Words: conduction • bundle-branch block • mapping • genes

	Introduction

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Progressive familial heart block type I (PFHBI) is an autosomal dominantly inherited cardiac bundle-branch disorder that may progress to complete heart block.^{1 2 3 4} It is defined on ECG by evidence of bundle-branch disease, ie, right bundle-branch block, left anterior or posterior hemiblock, or complete heart block with broad QRS complexes.¹ Progression has been shown from a normal ECG to right bundle-branch block and from the latter to complete heart block.^{2 3} These ECG features differentiate PFHBI from progressive familial heart block type II (PFHBII), in which the onset of complete heart block is associated with narrow complexes.¹ Electrocardiographically the changes represent, respectively, bundle-branch disease (PFHBI) and atrioventricular nodal disease with an atrioventricular block and an idionodal escape rhythm (PFHBII). PFHBI is manifested symptomatically when complete heart block supervenes, either with dyspnea, syncopal episodes, or sudden death.¹ Treatment, which is best managed by regular ECG follow-up, is by the timely implantation of a pacemaker.

Several branches of a large kindred in South Africa have been identified in which PFHBI is segregating and whose family members descend from one ancestor who emigrated from Portugal in 1696.¹ It has been estimated that there may be between 1000 and 9000 gene carriers among the descendants.^{1 5 6} Although the global incidence of PFHBI is unclear, the disease is probably not confined to South Africa. At least 13 reports suggest that similar familial conduction diseases, ie, with right bundle-branch block or right bundle-branch block and complete heart block appearing in the same family, exist elsewhere, although designated differently.¹⁰

The pathophysiology of these diseases is unknown; however, linkage analysis and positional cloning^{7 8 9} offer a means of identification of disease-causing genes. Characterization of genes that predispose individuals to the development of electrophysiological disturbances may help elucidate the functioning at the molecular level of the cardiac conduction system, whether normal or abnormal.

We have previously reported exclusion of 68 loci, representing 35% of the genome, from linkage to PFHBI.¹⁰ In this paper we report linkage of PFHBI to chromosome 19, bands q13.2-q13.3 (chromosome 19q13.2-13.3). The gene encoding myotonin protein kinase (DMK), which is implicated as a cause of myotonic dystrophy, lies within this region.^{11 12 13} Myotonic dystrophy is a disease that is itself complicated by heart block and other conduction abnormalities.

	Methods

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Subjects and Clinical Evaluation
Subjects were drawn from three pedigrees identified through previous studies.^{1 5 6} A consolidated pedigree of one large South African kindred, pedigree 2, which could be traced back nine generations, and in which PFHBI segregates, is shown in Fig 1A. These data incorporate the previously reported pedigrees 2, 3, 4, and 8¹⁰ and other family members who have since come to our attention. The previously reported pedigrees 1 and 5¹⁰ (Fig 1B) have not as yet been linked to the larger pedigree. However, because most members of all three pedigrees live in or originate from the same geographical area, the Eastern Cape in South Africa, and given the rarity of the disease, we expect a common ancestor.

View larger version (33K): [in this window] [in a new window]   Figure 1. Diagrams of pedigrees in which PFHBI segregates. A, Pedigree 2, a nine-generation kindred. B, Pedigrees 1 and 5, two smaller families that could not be linked to the main pedigree. Affected individuals had either right bundle-branch block, complicated right bundle-branch block, or complete heart block, as described in the text.

The diagnosis of PFHBI followed strict criteria, based on ECG-defined right bundle-branch block, complicated right bundle-branch block, or complete heart block with broad complexes in the absence of disease that might cause a similar defect, as previously described.¹⁰ Sinus bradycardia in isolation was regarded as normal. The Minnesota code was adhered to in making ECG diagnoses.¹⁴ Whenever available, members of the pedigrees were entered into the study irrespective of age.

DNA Analysis
Genomic DNA was extracted from lymphocytes or Epstein-Barr virus–transformed cell lines as previously described.¹⁵ To retrospectively obtain a repeat sample from a patient who died during the period of study, we extracted DNA from archival postmortem tissue sections using a method modified from Shibata et al.¹⁶ Individual sections 5 to 10 µm thick were cut from trimmed, buffered, formalin-fixed, paraffin-embedded tissue and placed in 500-µL Eppendorf tubes. The samples were deparaffinized by extraction with 1 mL of xylene followed by microcentrifugation. This extraction procedure was repeated and 1 mL of 95% ethanol was added to the residue. After microcentrifugation the ethanol wash was repeated, and the pellet was desiccated before suspension in 40 µL water. The solution was boiled for 10 minutes and microcentrifuged for 5 minutes, and 3 µL of supernatant was used to confirm polymerase chain reaction–based detection of the trinucleotide repeat at the myotonic dystrophy (DM) locus, as detailed below. Genotyping was performed at the apolipoprotein C2 (APOC2) locus,¹⁷ the creatine kinase muscle-type (CKMM) locus,¹⁸ the DM locus,^{11 12 13} and the kallikrein 1 (KLK1) locus,¹⁹ which span chromosome 19q13.2-13.3. The microsatellite dinucleotide repeat polymorphisms at the APOC2 and KLK1 loci and the CTG trinucleotide repeat at the DM locus were analyzed by polymerase chain reaction–based assays. Primers were synthesized from published sequences (DNA Synthesis Laboratory, University of Cape Town, South Africa) for the APOC2¹⁷ and DM¹¹ loci or purchased from Research Genetics for the KLK1¹⁹ locus. Each reaction was performed in a 10-µL volume that contained 300 ng of genomic DNA; 40 pmol of each primer; 67 µmol/L each of dATP, dGTP, and dTTP; 2.5 µmol/L of dCTP; 1.5 nCi of [-³²P]-dCTP; 2.5 µmol/L of MgCl₂; and 0.75 U of Taq polymerase in the buffer supplied by the manufacturer (Promega). The reaction mixes were overlaid with 25 µL of mineral oil to prevent evaporation. Cycling parameters in a polymerase chain reaction machine (ESU Electronics) were an initial incubation at 93°C for 2 minutes followed by 30 cycles at 93°C for 110 seconds, 57°C for 120 seconds, and 72°C for 140 seconds. After the addition of 6 µL of loading dye (95% formamide, 0.05% bromophenol blue, 0.05% xylene cyanole, 20 mmol/L EDTA), 6 µL of the amplification products were electrophoresed on 6% denaturing polyacrylamide gels. The gels were fixed and dried and the autoradiographs were exposed overnight at -70°C. The sizes of the different alleles were determined by reference to a sequencing ladder.

At the CKMM locus the NcoI and TaqI restriction length polymorphisms¹⁸ were detected by Southern blot hybridization using methods previously described²⁰ or by a polymerase chain reaction–based method using published primer sequences.²¹ The EcoR1 polymorphism at the DM locus was examined for possible expansion of the CTG repeat to pathological levels by Southern blot hybridization.²²

Statistical Analysis
MLINK (two-point) and LINKMAP (multipoint) from the LINKAGE group of programs were used to calculate LOD (which represent the logarithm of the odds ratio of detecting linkage versus nonlinkage) scores²³ from marker, disease status, and pedigree information using the following parameters. To obtain the penetrance value, input for the LIPED²⁴ program was constructed to reflect apparent penetrance and used in an iterative fashion to find the penetrance value that maximized the likelihood,²⁵ as previously described.¹⁰ A maximal value was obtained at a penetrance of 96%. A more conservative value of 90% was used in the actual linkage calculations. Because an affectation ratio of 0.45 or more was obtained upon examination of the number of affected individuals born in each decade since 1900, we concluded that assuming 90% penetrance would not influence linkage results negatively. The same phenotypic parameters were used for possible PFHBI homozygotes as for heterozygotes. The assumptions on which estimates of the prevalence of PFHBI (0.002) were based were reported previously.¹⁰ No allowance was made for phenocopies because the prevalence of similar cardiac conduction disturbances reported in the general population is low.¹⁰

To perform the multipoint analysis for the large multigeneration families with multiallelic markers, we used the following simplifying measures. In pedigree 2, all individuals in the line of descent of the PFHBI allele were coded as affected, with the exception of individuals I.01 and I.02, who were designated as being of unknown phenotype.⁶ All individuals who married into the family were coded as unaffected. These modifications resulted in LOD score changes only after the second decimal digit when tested on a two-point analysis rerun. Alleles were then collapsed into three-allele systems for the DM and KLK1 loci and a four-allele system for the APOC2 locus. The individual alleles obviously segregating with PFHBI were maintained as separate alleles at the DM and KLK1 loci. Only the TaqI restriction length polymorphism (ie, a biallelic polymorphism) was used at the CKMM locus. Allele frequencies were adjusted to incorporate these modifications and the simplified data were analyzed on a VAX 6000-410 computer system using published gene order and genetic distances.^{19 26 27 28}

	Results

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Clinical Evaluation
Table 1 displays the clinical characteristics of subjects with PFHBI who were genotyped and in the additional affected first-degree relatives who were unavailable for genotyping. Of a total of 51 family members assessed, 22 had complete heart block, 25 had right bundle-branch block or right bundle-branch block and left posterior hemiblock or left anterior hemiblock, and 4 (individuals VIII.26 and VII.44 in pedigree 2 and I.01 and I.02 in pedigree 5) displayed no ECG abnormalities but had affected children.

View this table: [in this window] [in a new window]   Table 1. Clinical Characteristics of Subjects With Progressive Familial Heart Block Type I Genotyped in the Study and Their Affected First-Degree Relatives

Linkage of PFHBI to Chromosome 19q13
Eighty-six members of three pedigrees, 39 members of which were affected with PFHBI, were genotyped at four linked polymorphic marker loci mapped to chromosome 19q13.2-13.3. Results of pairwise linkage analysis between PFHBI and marker loci are summarized in Table 2. The highest LOD score was obtained for KLK1 (Z_max, 6.49 at =0). Marker locus APOC2 (Z_max, 4.51 at =0.10) showed several recombinants, while in separate individuals CKMM (Z_max, 3.44 at =0.05) and DM (Z_max, 5.72 at =0.01) each showed a single recombinant. These genes span a distance of about 12 cM in the following order: centromere-APOC2-CKMM-DM-KLK1-telomere.²⁶

View this table: [in this window] [in a new window]   Table 2. Two-Point Logarithm of the Odds Scores of Progressive Familial Heart Block Type I and Chromosome 19 Markers by Pedigree

The maximum LOD score for a multipoint analysis occurred at KLK1 (LOD 11.6) (Fig 2). The 1-LOD-down 90% support interval²⁹ defined an area of 10 cM centering on the KLK1 locus as being likely to contain the PFHBI gene. This distance may include the DM locus.

View larger version (12K): [in this window] [in a new window]   Figure 2. LINKMAP plot of chromosome 19, band q13, showing the relative likelihoods for the various locations of the PFHBI gene with reference to a fixed order of linked DNA markers. On the basis of the 1-LOD-down support interval, the most likely location for the locus for PFHBI is distal to the CKMM locus, encompassing a 10 cM length centering on the KLK1 locus.

Recombination Event at the DM Locus
At the DM locus, one recombination event was seen between individual VIII.46 and IX.25 in pedigree 2 (Fig 3). The latter, who was affected with PFHBI, inherited from his affected father the same length CTG repeat (allele 14) and EcoRI polymorphism (allele 2) at the DM locus as his unaffected sibling IX.24, who showed no evidence of recombination events. Because the DMK gene was a candidate for the cause of PFHBI, it was important to confirm the recombination event in IX.25. Unfortunately, this child had died at the age of 2 years, so a new blood sample was unobtainable. However, genomic DNA was extracted from formalin-fixed, paraffin-embedded postmortem material. The CTG repeat at the DM locus was polymerase chain reaction–amplified from this source and a genotype of 13:14 was confirmed. The mother (VIII.45) was not affected with PFHBI, as assessed by ECG testing, and to date no ancestral links between her and the PFHBI families have been found. Eighteen of the 37 PFHBI-affected individuals were heterozygous for alleles within the normal range of the myotonic dystrophy–causing trinucleotide repeat. All possessed a 5-repeat–length allele and one other allele of up to 21 repeats. One subject, IX.25, in whom the recombination event was seen, was heterozygous with alleles of 13- and 14-repeat lengths. The remaining affected individuals were apparently homozygous for the 5-repeat–length allele, a result compatible with their parents' genotype. Furthermore, in none of the affected individuals with the single 5-repeat–length band was there evidence of triplet repeat expansion, which might have been undetectable by polymerase chain reaction–based amplification, upon Southern blot analysis of the DM locus (results not shown).

View larger version (32K): [in this window] [in a new window]   Figure 3. Genotypes of apolipoprotein C2 locus, creatine kinase muscle-type locus, myotonic dystrophy locus, and kallikrein 1 locus in pedigrees with PFHBI. Abridged kindred structures are shown for pedigree 2; the symbols correspond to the key in Fig 1. The haplotypes were constructed from the results of the combination of alleles inherited at each locus in the order of the genotypes listed above (APOCII, CKMM, DM, and KLK1, respectively). Genotypes indicated by a slash indicate two indistinguishable alternatives, and haplotypes in brackets could not be assigned with certainty because of pedigree position. - indicates not tested.

To refine the chromosomal position of the recombination event and facilitate molecular diagnosis, haplotypes for the four marker loci genotyped were deduced (Fig 3). The haplotype of affected individuals at the CKMM, DM, and KLK1 combined locus was 4:5:7, with the exception of a subset of pedigree 2, VII.36 and children (2:5:7), and individual IX.25, who displayed a 4:14:7 haplotype inherited from his phase-known affected father. As discussed above, a recombination event appeared to have occurred between DM and KLK1 in IX.25, suggesting that the PFHBI locus lies telomeric to the DM locus.

	Discussion

Top Abstract Introduction Methods Results Discussion References

 
In this study, PFHBI, a familial cardiac bundle-branch conduction disorder, was genetically mapped to a group of four linked loci on chromosome 19q13.2-13.3. Multipoint mapping has positioned the gene to within a 10 cM distance, centering on the KLK1 locus. In the families investigated, markers may now be used to support ECG-based diagnosis. This is important to the identification of persons in whom routine clinical follow-up would be advisable because of the progressive nature of the disease.^{1 2 3 4} Furthermore, fine mapping and attempts to identify the causative gene by positional cloning can be initiated. In pedigree 2, unaffected siblings VIII.59 and VIII.60 and their affected sister VIII.58 all carry the 4:5:7 (CKMM:DM:KLK1) haplotype inherited from their affected father, who is homozygous at these loci. Additionally, detection of frequent recombination events between APOC2 and rarer events between CKMM and DM and the disease currently precludes unequivocal identification of the disease-causing chromosomal region in all branches of the pedigree. Fine mapping with other markers across this region should allow identification of an invariant disease haplotype, resolving molecular diagnosis and confirming the presence of a founder effect.

A survey of known genes in the defined area focused attention on the intriguing proximity of the PFHBI locus to the one encoding myotonin protein kinase, which is implicated in causing myotonic dystrophy.^{11 12 13} PFHBI and myotonic dystrophy have similar cardiac complications, namely bundle-branch blocks or intraventricular conduction disturbances.^{30 31 32 33} Myotonic dystrophy is caused by instability of a CTG triplet repeat in the 3' untranslated region of the DMK gene,^{11 12 13 34 35} with affected individuals having copy numbers ranging from 50 to more than 2000 repeats. The recombination event between PFHBI and the DM locus and the absence of a pathologically expanded CTG repeat in PFHBI-affected individuals effectively excluded direct involvement of the DMK gene in PFHBI. However, it has been proposed that it is through its effects on chromosome structure that triplet repeat expansion within the DMK gene interferes with the expression of multiple neighboring genes, resulting in the highly variable clinical presentation that is a hallmark of myotonic dystrophy.^{34 36 37} It can be speculated that one of these adjacent genes is involved in the specific cardiac conduction disturbances characteristic of myotonic dystrophy, and that when this gene harbors a particular mutation it causes the clinical features of PFHBI. Consequently, identifying the exact relationship of the PFHBI locus to the DMK locus may help elucidate the mechanisms of both diseases. Additional family members not previously available will be genotyped for possible other recombination events in the targeted region.

The exclusion of the DMK gene as a direct cause of PFHBI allows consideration of other candidate genes in the defined area. The highest LOD score obtained in the study, and one with no recombination events, was at the KLK1 locus, which forms part of a linked group of kallikreins.¹⁹ The kallikreins, generally considered important intravascularly, have been shown to be present in cardiac tissue in the rat.³⁸ Some of the cardiac effects of the tissue renin-angiotensin system may be mediated through a kallikrein³⁸ and could be involved in the pathophysiology of PFHBI. Included in the kallikrein gene cluster is the R-ras gene,³⁹ a member of the ras gene superfamily.⁴⁰ The description of a possible association of the H-ras proto-oncogene with the long QT syndrome,⁴¹ which is characterized by cardiac arrhythmias, justifies consideration of R-ras as a candidate for involvement in PFHBI. A plausible mechanism may be through a role in abnormal growth or differentiation of the conduction system, a possibility proposed by Brink and Torrington in their initial description of PFHBI.¹

In general, the chromosome 19q13.2-13.3 region seems particularly rich in genes with known cardiac functions or associations with cardiac pathology. The histidine-rich calcium-binding protein⁴² is a luminal sarcoplasmic reticulum protein. It is thought that sarcoplasmic reticulum proteins may play a role in binding calcium; mutations in this gene could therefore affect intracellular calcium homeostasis. The apolipoproteins, by virtue of their connection with atherosclerosis, are often associated with cardiac dysfunction.⁴³ However, multiple recombination events at the APOC2 locus effectively excluded not only this gene as a candidate but apolipoprotein genes C1 and E as well, because all three genes are clustered within a 50-kilobase region of chromosome 19q13.2-13.3.⁴⁴ Similarly, the candidature of creatine kinase muscle-type, the enzyme product that plays a key role in cellular energy metabolism,⁴⁵ was excluded by the presence of one recombination event. The gene for troponin T also resides in the candidate region.⁴⁶ The troponin complex plays an important role in linking excitation to contraction of the sarcomere.⁴⁷ Its role in conduction tissue is uncertain, but it is known that conduction tissue is modified muscle and that it possesses rudimentary sarcomeric structures. Several other genes of unknown function^{37 48} and HTF (HpaII tiny fragments) islands,⁴⁹ generally associated with the 5' end of expressed genes,⁵⁰ have been identified in this extensively studied and gene-rich area of chromosome 19.

These results not only allow selective follow-up of individuals at risk for PFHBI, on the basis of genotypic analysis in the families studied, but define the chromosomal location of a gene causing cardiac pacing abnormalities. Additionally, establishment of the position of the loci for PFHBI and myotonic dystrophy relative to each other may shed light on the pathophysiology of both diseases. Eventually, finding and characterizing the gene that causes PFHBI may help unravel the underlying molecular mechanisms of the cardiac conduction system.

	Footnotes

 
Reprint requests to Valerie A. Corfield, US/MRC Centre for Molecular and Cellular Biology, PO Box 19063, Tygerberg 7505, Republic of South Africa.

Received May 17, 1994; revision received October 5, 1994; accepted October 24, 1994.

	References

Top Abstract Introduction Methods Results Discussion References

 

1. Brink AJ, Torrington M. Progressive familial heart block—two types. S Afr Med J. 1977;52:53-59. [Medline] [Order article via Infotrieve]
   
2. Van der Merwe P-L, Weymar HW, Torrington M, Brink AJ. Progressive familial heart block, part II: clinical and ECG confirmation of progression—report on 4 cases. S Afr Med J. 1986;70:356-357. [Medline] [Order article via Infotrieve]
   
3. Van der Merwe P-L, Weymar HW, Torrington M, Brink AJ. Progressive familial heart block (type I): a follow-up study after 10 years. S Afr Med J. 1988;73:275-276. [Medline] [Order article via Infotrieve]
   
4. Van der Merwe P-L. Die identifikasie van hoë-risiko pasiënte met latente siekte in families met tipe I progressiewe familiële hartblok. Tygerberg, Republic of South Africa: University of Stellenbosch; 1988. Thesis.
   
5. Torrington M, Weymar HW, Van der Merwe P-L, Brink AJ. Progressive familial heart block, part I: extent of the disease. S Afr Med J. 1986;70:353-355. [Medline] [Order article via Infotrieve]
   
6. Van der Merwe P-L, Weymar HW, Kalis NN. The extent of familial heart block type I: a new perspective. Cardiovasc J S Afr. 1994;5:125-126.
   
7. Hejtmancik JF, Brink PA, Towbin J, Hill R, Brink L, Tapscott T, Trakhtenbroit A, Roberts R. Localization of gene for familial hypertrophic cardiomyopathy to chromosome 14q1 in a diverse US population. Circulation. 1991;83:1592-1597. [Abstract/Free Full Text]
   
8. Collins FS. Positional cloning: let's not call it reverse anymore. Nature Genet. 1992;1:3-6. [Medline] [Order article via Infotrieve]
   
9. Keating M. Linkage analysis and long QT syndrome: using genetics to study cardiovascular disease. Circulation. 1992;85:1973-1986. [Abstract/Free Full Text]
   
10. Brink PA, Moolman JC, Ferreira A, De Jager T, Weymar HW, Martell RW, Torrington M, Van der Merwe P-L, Corfield VA. Genetic linkage studies of progressive familial heart block, a cardiac conduction disorder. S Afr J Sci. 1994;90:236-240.
    
11. Brook JD, McCurrach ME, Harley HG, Buckler AJ, Church D, Aburatani H, Hunter K, Stanton VP, Thirion JP, Hudson T, Sohn R, Zemelman B, Snell RG, Rundle SA, Crow S, Davies J, Shelbourne P, Buxton J, Jones C, Juvonen V, Johnson K, Harper PS, Shaw DJ, Housman DE. Molecular basis of myotonic dystrophy: expansion of a trinucleotide repeat (CTG) at the 3' end of a transcript encoding a protein kinase gene. Cell. 1992;68:799-808. [Medline] [Order article via Infotrieve]
    
12. Mahadevan M, Tsilfidis C, Sabourin L, Shutler G, Amemiya C, Jansen G, Neville C, Narang M, Barceló J, O'Hoy K, Leblond S, Earle-MacDonald J, De Jong PJ, Wieringa B, Korneluk RG. Myotonic dystrophy mutation: an unstable CTG repeat in the 3' untranslated region of the gene. Science. 1992;255:1253-1255. [Abstract/Free Full Text]
    
13. Fu Y-H, Pizzuti A, Fenwick RG Jr, King J, Rajnarayan S, Dunne PW, Dubel J, Nasser GA, Ashizawa T, De Jong P, Wieringa B, Korneluk R, Perryman MB, Epstein HF, Caskey CT. An unstable triplet repeat in a gene related to myotonic muscular dystrophy. Science. 1992;255:1256-1258. [Abstract/Free Full Text]
    
14. Higgins ITT, Kannel WB, Dawber TR. The electrocardiogram in epidemiological studies: reproducibility, validity, and international comparison. Br J Prev Soc Med. 1965;19:53-68. [Medline] [Order article via Infotrieve]
    
15. Corfield VA, Moolman JC, Martell R, Brink PA. Polymerase chain reaction-based detection of MN blood-group specific sequences in the human genome. Transfusion. 1993;33:119-124. [Medline] [Order article via Infotrieve]
    
16. Shibata DK, Arnheim N, Markin WJ. Detection of human papilloma virus in paraffin-embedded tissue using the polymerase chain reaction. J Exp Med. 1988;167:225-230. [Abstract/Free Full Text]
    
17. Smeets HJM, Brunner HG, Ropers H-H, Wieringa B. Use of variable simple sequence motifs as genetic markers: application to study of myotonic dystrophy. Hum Genet. 1989;83:245-251.[Medline] [Order article via Infotrieve]
    
18. Coerwinkel-Driessen M, Schepens J, van Zandvoort P, van Oost B, Mariman E, Wieringa B. NcoI RFLP at the creatine kinase-muscle type gene locus (CKMM chromosome 19). Nucleic Acids Res. 1988;16:8743. [Free Full Text]
    
19. Richards RI, Holman K, Shen Y, Kozman H, Harley H, Brook D, Shaw D. Human glandular kallikrein genes: genetic and physical mapping of the KLK1 locus using a highly polymorphic microsatellite PCR marker. Genomics. 1991;11:77-82. [Medline] [Order article via Infotrieve]
    
20. Brink PA, Steyn LT, Coetzee GA, Van der Westhuyzen DR. Familial hypercholesterolemia in South African Afrikaners: PvuII and StuI polymorphisms in the LDL-receptor gene consistent with a predominating founder gene effect. Hum Genet. 1987;77:32-35. [Medline] [Order article via Infotrieve]
    
21. Lavedan C, Duros C, Savoy D, Leblond S, Bailly J, Korneluk R, Junien C. Direct haplotyping by double digestion of PCR-amplified creatine kinase (CKMM): application to myotonic dystrophy diagnosis. Genomics. 1990;8:739-740. [Medline] [Order article via Infotrieve]
    
22. Buxton J, Shelbourne P, Davies J, Jones C, Van Togeren T, Aslanidis C, De Jong P, Jansen G, Anvret M, Riley B, Williamson R, Johnson K. Detection of an unstable fragment of DNA specific to individuals with myotonic dystrophy. Nature. 1992;355:547-548. [Medline] [Order article via Infotrieve]
    
23. Lathrop GM, Lalouel JM. Easy calculations of lod scores and genetic risks on small computers. Am J Hum Genet. 1984;36:460-465. [Medline] [Order article via Infotrieve]
    
24. Ott J. Estimation of the recombination fraction in human pedigrees: efficient computation of the likelihood for human linkage studies. Am J Hum Genet. 1974;26:588-597. [Medline] [Order article via Infotrieve]
    
25. Ott J. Analysis of Human Genetic Linkage. Baltimore, Md: Johns Hopkins University Press; 1985:134.
    
26. Harley H, Walsh KV, Rundle S, Brook JD, Sarfarazi M, Koch MC, Floyd JL, Harper PS, Shaw DJ. Localization of the myotonic dystrophy locus to 19q13.2-19q13.3 and its relationship to twelve polymorphic loci on 19q. Hum Genet. 1991;87:73-80. [Medline] [Order article via Infotrieve]
    
27. Brunner HG, Smeets H, Lambermon HMM, Coerwinkel-Driessen M, Van Oost BA, Wieringa B, Ropers HH. A multipoint linkage map around the locus for myotonic dystrophy on chromosome 19. Genomics. 1989;5:589-595. [Medline] [Order article via Infotrieve]
    
28. Johnson K, Shelbourne P, Davies J, Buxton J, Nimmo E, Siciliano MJ, Bachinski LL, Anvret M, Harley H, Rundle S, Miki T, Brunner H, Williamson R. A new polymorphic probe which defines the region of chromosome 19 containing the myotonic dystrophy locus. Am J Hum Genet. 1990;46:1073-1081. [Medline] [Order article via Infotrieve]
    
29. Conneally PM, Edwards JH, Kidd KK, Lalouel J-M, Morton NE, OH J, White R. Report of the committee on methods of linkage analysis and reporting. Cytogenet Cell Genet. 1985;40:356-359. [Medline] [Order article via Infotrieve]
    
30. Hawley RJ, Gottdiener JS, Gay JA, Engel WK. Families with myotonic dystrophy with and without cardiac involvement. Arch Intern Med. 1983;143:2134-2136. [Abstract]
    
31. Perloff JK, Stevenson WG, Roberts NK, Cabeen W, Weiss J. Cardiac involvement in myotonic muscular dystrophy (Steinert's disease): a prospective study of 25 patients. Am J Cardiol. 1984;54:1074-1081. [Medline] [Order article via Infotrieve]
    
32. Wintzen AR, Schipperheyn JJ. Cardiac abnormalities in myotonic dystrophy. J Neurol Sci. 1987;80:259-268. [Medline] [Order article via Infotrieve]
    
33. Prystowsky EN, Pritchett ELC, Roses AD, Gallagher J. The natural history of conduction system disease in myotonic muscular dystrophy as determined by serial electrophysiological studies. Circulation. 1979;60:1360-1364. [Abstract/Free Full Text]
    
34. Mahadevan MS, Ameniya C, Jansen G, Sabourin L, Baud S, Neville CE, Wormskamp N, Segers B, Batzer M, Lamerdin J, De Jong P, Wieringa B, Korneluk RG. Structure and genomic sequence of the myotonic dystrophy (DM kinase) gene. Hum Mol Genet. 1993;2: 299-304.
    
35. Tsilfidis C, MacKenzie AE, Mettler G, Barceló J, Korneluk RG. Correlation between CTG trinucleotide repeat length and frequency of severe congenital myotonic dystrophy. Nat Genet. 1992;1:192-195. [Medline] [Order article via Infotrieve]
    
36. Perryman MB, Friedman DL, Fu Y-H, Caskey CT. Molecular genetics of myotonic dystrophy. Trends Cardiovasc Med. 1993;3:82-84.
    
37. Jansen G, Mahadevan M, Ameniya C, Wormskamp N, Segars B, Hendriks W, O'Hoy K, Baird S, Sabourin L, Lennon G, Jap PL, Iles D, Coerwinkel M, Hofker M, Carrano AV, De Jong PJ, Korneluk RG, Wieringa B. Characterization of the myotonic dystrophy region predicts multiple protein isoform-encoding mRNAs. Nat Genet. 1992;1:261-266. [Medline] [Order article via Infotrieve]
    
38. Nolly HL, Saed G, Scili G, Carretero OA, Scili AG. The kallikrein-kinin system in cardiac tissue: recent progress on kinins. Agents Actions. 1992;38:62-72.
    
39. Smeets HJM, Hermens R, Brunner HG, Ropers H-H, Wieringa B. Identification of variable simple sequence motifs in 19q13.2-qter: markers for the myotonic dystrophy locus. Genomics. 1991;9:257-263. [Medline] [Order article via Infotrieve]
    
40. Lowe DG, Capon DJ, Delwart E, Sakaguchi AY, Naylor SL, Goedell DV. Structure of the human and murine R-ras genes, novel genes closely related to ras proto-oncogenes. Cell. 1987;48:137-146. [Medline] [Order article via Infotrieve]
    
41. Keating M, Atkinson D, Dunn C, Timothy K, Vincent GM, Leppert M. Linkage of a cardiac arrhythmia, the long QT syndrome, and the Harvey ras-1 gene. Science. 1991;252:704-706.[Abstract/Free Full Text]
    
42. Hofmann SL, Topham M, Hsieh C-L, Francke U. cDNA and genomic cloning of HRC, a human sarcoplasmic reticulum protein, and localization of the gene to human chromosome 19 and mouse chromosome 7. Genomics. 1991;9:656-669. [Medline] [Order article via Infotrieve]
    
43. Breslow JL. Apolipoprotein genes and atherosclerosis. Clin Investig. 1992;70:377-384.
    
44. Myklebost O, Rogne S. A physical map of the apolipoprotein gene cluster on human chromosome 19. Hum Genet. 1988;78:244-247. [Medline] [Order article via Infotrieve]
    
45. Wallimann T. Dissecting the role of creatine kinase. Curr Biol. 1994;1:42-46.
    
46. Samson F, Lee JE, Hung WY, Potter TG, Herbstreith M, Roses AD, Gilbert JR. Isolation and localization of a slow troponin (TnT) gene on chromosome 19 by subtraction hybridization of a cDNA muscle library using myotonic dystrophy muscle cDNA. J Neurosci Res. 1990;27:441-451. [Medline] [Order article via Infotrieve]
    
47. Gahlmann R, Troutt AB, Wade RP, Gunning P, Kedes L. Alternative splicing generates variants in important functional domains of human slow skeletal troponin T. J Biol Chem. 1987;262:16122-16126. [Abstract/Free Full Text]
    
48. Riegman PHJ, Vlietsra RJ, Suurmeijer VL, Cleutjens CBJM, Trapman J. Characterization of the human kallikrein locus. Genomics. 1992;14:6-11. [Medline] [Order article via Infotrieve]
    
49. Smeets H, Bachinski L, Coerwinkel M, Schepens J, Hoeijmakers J, Van Duin M, Grzeschik K-H, Weber CA, De Jong P, Siciliano MJ, Wieringa B. A long range restriction map of the human chromosome 19q13 region: close physical linkage between CKMM and the ERCC1 and ERCC2 genes. Am J Hum Genet. 1990;46:492-501. [Medline] [Order article via Infotrieve]
    
50. Bird AP. CpG-rich islands and the function of DNA methylation. Nature. 1986;321:209-213.[Medline] [Order article via Infotrieve]
    

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