Is familial hemiplegic migraine a hereditary form of basilar migraine?

We studied aura symptoms in 83 patients from 6 unrelated families suffering from familial hemiplegic migraine. Fifty-five of the patients reported symptoms that allowed us to categorize them as basilar migraine (BM) patients, in accordance with the International Headache Society (IHS) criteria. In a control group of 33 patients suffering from migraine with aura and 33 patients suffering from migraine without aura, 9 patients complained of vertigo, and only one patient of diplopia during one of her attacks. None of these control patients fulfilled the IHS criteria for BM. We suggest that familial hemiplegic migraine and BM may share certain pathophysiologic mechanisms, which may consist of a (genetically determined) disturbance of basilar artery blood flow.

A four-generation Dutch family with cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), linked to chromosome 19p13

We describe a four-generation Dutch family suffering from cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL). Of twenty affected family members, ten are still alive. Age at onset of the strokes was between 29 and 52 years, with a mean of 41.8 years. This family has the typical clinical and radiological features of CADASIL (except for the occurrence of ischemic heart disease at a relatively young age in some subjects), and is linked to chromosome 19p13. This disease has so far been described in families from Finland, France, Germany, Italy, Japan, Spain and the United Kingdom, and there is a remarkable clinical and genetical homogeneity among all families reported, including this Dutch family.

Localization of a gene for non-syndromic hearing loss (DFNA5) to chromosome 7p15

Progressive hearing loss affects approximately 50% of the elderly by the age of 80, and is most likely caused by an interaction of genetic and environmental factors. Identification of the genes responsible for hereditary hearing loss is therefore important. Families with pure genetic degenerative hearing disorders may be helpful as the same genes may be also involved in age-related hearing loss in general. In this study we have performed a genome search in an extended Dutch family with autosomal dominant progressive hearing loss starting in the high frequencies. The gene causing hearing loss in this family was localized to the short arm of chromosome 7, in a 15 cM interval between markers D7S493 and D7S632.

Familial hemiplegic migraine locus on 19p13 is involved in the common forms of migraine with and without aura

Migraine is a common neurological disease of two main types: migraine with aura and migraine without aura. Familial clustering suggests that genetic factors are involved in the etiology of migraine. Recently, a gene for familial hemiplegic migraine, a rare autosomal dominant subtype of migraine with aura, was mapped to chromosome 19p13. We tested the involvement of this chromosomal region in 28 unrelated families with the common forms of migraine with and without aura, by following the transmission of the highly informative marker D19S394. Sib-pair analysis showed that affected sibs shared the same marker allele more frequently than expected by chance. Our findings thus also suggest the involvement of a gene on 19p13 in the etiology of the common forms of migraine.

Inactivation of Apoe and Apoc1 by two consecutive rounds of gene targeting: effects on mRNA expression levels of gene cluster members

The genes encoding apolipoprotein (apo) E and apoC1 are, together with the gene for apoC2, located in a conserved gene cluster on human chromosome 19q12-13.2 and mouse chromosome 7. Although the significance of apoE as a ligand for receptor-mediated uptake of lipoprotein remnant particles is undisputed, the in vivo function of apoC1 and the possible interaction between apoE and apoC1 in the modulation of plasma cholesterol and triglyceride levels is far from understood. Our strategy to unravel the metabolic relationship between apoE and apoC1 in vivo is to first generate mice deficient in both apolipoproteins, enabling future production of transgenic mice with variable ratios of normal and mutant apoE and apoC1 on a null background. Here we report the creation and characterization of mice deficient in both apoE and apoC1. As these genes are tightly genetically linked, double-deficient mice were obtained by two consecutive rounds of gene targeting in mouse embryonic stem cells. Surprisingly, double inactivation of the Apoe and Apoc1 gene loci as well as single inactivations at either one of these loci were found to affect also the RNA expression levels of the other gene members in the Apoe-c1-c2 cluster. This indicates that targeted insertions are not necessarily neutral for the expression of nearby gene members in a given gene cluster. Homozygous Apoe-c1 knockout mice are hypercholesterolemic, with serum cholesterol levels of 12.5 +/- 4.3 mM compared with 2.9 +/- 0.5 mM in control mice, resembling mice solely deficient in apoE.

Homozygotes for CDKN2 (p16) germline mutation in Dutch familial melanoma kindreds

The p16 gene (CDKN2) which is localized on chromosome 9p21, is deleted in a significant number of sporadic cancers. Moreover, germline mutations identified in some melanoma-prone kindreds last year suggested that CDKN2 is identical to the 9p21-linked melanoma susceptibility gene (MLM); however, failure to identify p16 mutations in all melanoma kindreds putatively linked to 9p21 left some doubts. We have analysed CDKN2 coding sequences in 15 Dutch familial atypical multiple mole-melanoma (FAMMM) syndrome pedigrees, and identified a 19 basepair (bp) germline deletion in 13 of them. All 13 families originate from an endogamous population. The deletion causes a reading frame shift, predicted to result in a severely truncated p16 protein. Interestingly, two family members are homozygous for the deletion, one of whom shows no obvious signs of disease. This surprising finding demonstrates that homozygotes for this CDKN2 mutation are viable, and suggests the presence of a genetic mechanism that can compensate for the functional loss of p16. Our results also greatly strengthen the notion that p16 is indeed MLM.

Molecular genetic reevaluation of the Dutch hyperekplexia family

OBJECTIVES

To confirm linkage of the locus of the major form of hyperekplexia to markers on chromosome 5q, to screen for a point mutation in the gene encoding the alpha 1 subunit of the glycine receptor, and to investigate whether the putative "minor" form of hyperkeplexia consisting of an excessive startle response without stiffness, is based on the same genetic defect as the major form.

DESIGN

A survey of various symptoms of hyperekplexia was performed in the Dutch pedigree. Linkage studies were performed for these symptoms.

SETTING

Subjects were visited at home, and the genetic study was performed at University Hospital Leiden, (the Netherlands).

PATIENTS

A history was taken from 76 subjects in the pedigree, and neurologic examinations were performed on 61 subjects from four generations of the pedigree.

MAIN OUTCOME MEASURES

The main outcome measures were lod scores for markers on chromosome 5q for the major and minor forms of hyperekplexia and periodic leg movements during sleep. Mutations in the alpha 1 subunit of the glycine receptor were detected by screening the exons with denaturing gradient gel electrophoresis.

RESULTS

Exaggerated startle responses were reported in 44 patients. The major form consisted of stiffness in addition to the excessive startle reaction and occurred in 28 subjects. Sixteen of 44 subjects had startle responses without stiffness, indicating the minor form. Linkage was found between markers CSF1-R, D5S209, and D5S119 and the disease locus for the major form, but not for the minor form. The alpha 1 subunit of the glycine receptor showed a G to A transition mutation in codon 271 for the major form, but not for the minor form.

CONCLUSIONS

Linkage and an abnormal glycine receptor were found only in the major form of hyperekplexia. Recognition of a major form is based on additional stiffness. This is therefore the most important diagnostic symptom. The minor form is not a different expression of the same genetic defect and may represent a normal but pronounced startle response.

CDKN2 explains part of the clinical phenotype in Dutch familial atypical multiple-mole melanoma (FAMMM) syndrome families

Combined multi-point linkage analysis in seven Dutch families with FAMMM syndrome confirmed the location of a melanoma susceptibility (MLM) gene in the 9p21 area. The occurrence of a shared high-risk haplotype in six of the families strongly suggests a founder effect in the Leiden region. No indication for locus heterogeneity was observed. Recently, the CDKN2 (p16) gene, an important regulator of the cell cycle, was isolated from the 9p21 region. A 19-bp germline deletion in the CDKN2 gene was detected in the high-risk haplotype, suggesting CDKN2 to be identical to MLM. Loss of heterozygosity studies in melanoma and pancreatic carcinoma from gene carriers strongly support the view that CDKN2 is a general tumour suppressor gene predisposing not only to melanoma but also to other malignancies. Interestingly, the occurrence of apparent clinical FAMMM cases with melanoma but without the high-risk deletion haplotype suggests the necessity of additional (naevus) genes to explain the complete FAMMM phenotype.

Mutations in the low density lipoprotein receptor gene of familial hypercholesterolemic patients detected by denaturing gradient gel electrophoresis and direct sequencing

Familial hypercholesterolemia (FH) results from mutations in the low density lipoprotein receptor (LDLR) gene. We applied denaturing gradient gel electrophoresis (DGGE) to screen for sequence variations in the coding and splice site consensus sequences of the LDLR gene. For amplification of each exon by the polymerase chain reaction (PCR), optimal pairs of primers were designed by the MELT 87 computer algorithm. To increase the sensitivity, an artificial GC-clamp was included in either the 5'- or the 3'-end of each fragment. DGGE screening of 32 apparently unrelated heterozygous FH patients revealed 16 unique different aberrant DGGE patterns in 27 patients, while in a group of 32 normal subjects none of these DGGE patterns could be observed, suggesting that the aberrant patterns represent disease-causing mutations. Interestingly, 16 out of 27 patients showed an aberrant DGGE pattern in the part of the gene encoding the ligand binding domain (exons 2-6). Direct solid-phase sequencing of the corresponding exon-specific PCR products revealed the nature of the mutations: three nonsense, four splicing, two frameshift, one silent, and six missense mutations. Six of the mutations have been previously reported, while ten are novel mutations. These results indicate that DGGE provides a reliable method for the detection of the presence of point mutations in the LDLR gene of FH patients, thereby facilitating the introduction of rapid DNA diagnosis for this common and genetically heterogeneous disorder.

Increased response to cholesterol feeding in apolipoprotein C1-deficient mice

The function of apolipoprotein (apo) C1 in vivo is not well understood. From in vitro studies it has been reported that an excess of apoC1 relative to apoE inhibits receptor-mediated uptake of remnant lipoproteins [Sehayek and Eisenberg (1991) J. Biol. Chem. 266, 22453-22459]. In order to gain a better understanding of the role of apoC1 in lipoprotein metabolism in vivo, we have generated apoC1-deficient mice by gene targeting in embryonic stem cells. Homozygous mutant mice are viable and do not show overt abnormalities. Serum triacylglycerol levels are increased by 60% on both a standard mouse diet and a mild hypercholesterolaemic diet compared with controls. Total serum cholesterol levels are similar to controls on the two diets. However, the level of high-density lipoprotein cholesterol in the apoC1-deficient mice fed on the mild hypercholesterolaemic diet is slightly decreased, which is accompanied by a 3-fold increase in very-low-density plus low-density lipoprotein (VLDL+LDL) cholesterol. On a severe atherogenic diet, the homozygous apoC1-deficient mice become hypercholesterolaemic, with a serum cholesterol level of 10.7 +/- 3.3 mM compared with 6.7 +/- 1.8 mM and 5.1 +/- 1.6 mM in heterozygous and control mice respectively. The increase in cholesterol is mainly confined to the VLDL+LDL-sized fractions. Binding experiments revealed that lipoproteins lacking apoC1 with d < 1.006 g/ml are poor competitors for 125I-labelled LDL binding to the LDL receptor on HepG2 cells. This suggests that total apoC1 deficiency leads to impaired receptor-mediated clearance of remnant lipoproteins rather than enhanced uptake, as was expected from data reported in the literature.

Facioscapulohumeral muscular dystrophy in the Dutch population

Extrapolating the figures from a previous study on FSHD in a province of The Netherlands to the entire Dutch population suggests that at present a nearly complete overview is obtained of all symptomatic kindred. In 139 families, dominant inheritance was observed in 97, a pattern compatible with germline mosaicism in 6, while sporadic cases were found in 36 families. A mutation frequency of 9.6% was calculated. Mental retardation and severe retinal vasculopathy were reported in low frequencies (1%). Early onset was seen more frequently in sporadic cases. Chromosome 4 linkage appeared excluded in 3 of 22 autosomal-dominant families. The clinical pictures in the linked and nonlinked families were identical.

The FSHD-linked locus D4F104S1 (p13E-11) on 4q35 has a homologue on 10qter

Facioscapulohumeral muscular dystrophy (FSHD) has recently been shown to be associated with deletions that are detectable using probe p13E-11 (D4F104S1). Although these deletions reside within large, highly polymorphic restriction fragments (20-300 kb), the "mutant" fragment is usually shorter than 28 kb and can routinely be detected using conventional agarose gel electrophoresis. Yet, the complete visualization of the alleles requires pulsed-field gel electrophoresis (PFGE). Family studies showed that p13E-11 detects two nonallelic loci in this size range, only one of which originates from chromosome 4q35. We have assigned the other p13E-11 locus to chromosome 10qter by linkage analysis in CEPH pedigrees. Knowing the location of both loci improves the diagnostic reliability, as the exact origin of "small" EcoRI fragments can be determined by haplotyping. Since FSHD shows genetic heterogeneity, this 10qter locus became an interesting candidate to be the second FSHD locus. However, analysis of a large chromosome 4-unlinked FSHD family did not provide evidence for linkage on chromosome 10qter.

Facioscapulohumeral muscular dystrophy in the Dutch population

Extrapolating the figures from a previous study on FSHD in a province of The Netherlands to the entire Dutch population suggests that at present a nearly complete overview is obtained of all symptomatic kindred. In 139 families, dominant inheritance was observed in 97, a pattern compatible with germline mosaicism in 6, while sporadic cases were found in 36 families. A mutation frequency of 9.6% was calculated. Mental retardation and severe retinal vasculopathy were reported in low frequencies (1%). Early onset was seen more frequently in sporadic cases. Chromosome 4 linkage appeared excluded in 3 of 22 autosomal-dominant families. The clinical pictures in the linked and nonlinked families were identical.

Fish mapping of 250 cosmid and 26 YAC clones to chromosome 4 with special emphasis on the FSHD region at 4q35

Facioscapulohumeral muscular dystrophy (FSHD) is located on chromosome 4q35, close to the telomere. FSHD patients carry deletions within a cluster of tandemly repeated DNA. Although expression of a functional FSHD gene will be altered in patients, the sequence itself may be unaffected by this deletion. Hence, the FSHD gene could lie outside of the deleted region. This study employs fluorescent in situ hybridization using chromosome 4-specific cosmid and YAC clones to rapidly saturate chromosome 4 with new markers. Some 250 cosmids and 26 YACs were regionally mapped, of which 5 YACs and 55 cosmids mapped to the distal portion of 4q. Only one of these clones (D4S1454) mapped telomerically to a translocation breakpoint specified by D4S187. Using two-color interphase mapping, the following marker order was obtained: Cen-D4S187-D4S1454-HSPCAL2-D4S163-D4S139-D4F35S1. Absence of additional markers mapping distal to D4F35S1 indicates that the linkage group containing the FSHD gene lies extremely close to the 4q telomere.

Early onset facioscapulohumeral muscular dystrophy

We report 10 patients (5 familial, 5 sporadic) with facioscapulohumeral muscular dystrophy (FSHD) with onset of facial and shoulder girdle weakness in early infancy. They showed the same broad range of clinical signs and symptoms as can be seen normally in FSHD. In 7 patients Southern blotting with p13E-11 was performed which showed an abnormal EcoRI fragment (13-22 kb) in 6 of them. We conclude that early onset FSHD does not differ from regular FSHD clinically or genetically. However, the precise mechanisms involved in the extensive clinical variability of the disease are still unknown.

On the significance of retinal vascular disease and hearing loss in facioscapulohumeral muscular dystrophy

We have performed retinal fluorescein angiography and audiometry in 32 familial and 7 sporadic cases of facioscapulohumeral muscular dystrophy. A mild to moderate retinal vasculopathy, consisting of retinal teleangiectasis and microaneursyms, was present in 18 of 37 evaluable angiograms (49%); 5 patients had minimal changes and 14 angiograms (38%) were normal. High frequency hearing loss was found in 25 (64%) out of 39 patients. Retinal changes were absent in 5 of 18 families (6 cases examined), and after correction for age and sex, hearing function was normal in 5 of 19 families (7 cases examined). Age and severity of the myopathy did not have a clear relationship with the retinal vasculopathy or the hearing loss. There were no differences between families in which the myopathy was linked to chromosome 4q35 and families in which linkage could not be proven. Minimal retinal vascular changes and high tone hearing loss can be observed occasionally in the normal population. Therefore, although retinal vasculopathy and hearing loss are part of the clinical picture of FSHD, these signs cannot be accepted as decisive criteria for FSHD in clinically equivocal cases.

Search for the FSHD gene using cDNA selection in a region spanning 100 kb on chromosome 4q35

Facioscapulohumeral muscular dystrophy (FSHD) is caused by deletions of 3.3-kb tandemly repeated units contained within a large polymorphic EcoRI fragment close to the telomere of chromosome 4q. Since the rearrangements were assumed to interfere with the structure or function of the putative FSHD gene, the gene search was focused on cosmids containing these repeat units and, in addition, cosmids spanning 75 kb of upstream sequences. cDNA selection hybridization was applied to four overlapping cosmid clones, yielding a total of 150 putative cDNA clones. These clones showed a random distribution across the cosmid contig, except for three regions which contained a much larger number of clones. Nine cDNA clones hybridized to a 2.2-kb EcoRI fragment, located 22 kb centromeric to the 3.3-kb repeated units. This 2.2-kb fragment showed evolutionary conservation, and analysis of the sequence by "GRAIL" predicted the presence of several exons. Transcripts homologous to this fragment could be identified but none of them originated from the 4q35 locus. Strikingly, most clones revealed 4-10 homologous loci, and no single copy clones could be isolated. These findings are in line with earlier observations by fluorescent in situ hybridization (FISH) showing hybridization of individual cosmid clones to multiple chromosomes. The presence of homologous regions on other chromosomes seriously complicates the cloning of the FSHD gene.

Plasma lipoproteins in familial dysbetalipoproteinemia associated with apolipoproteins E2(Arg158-->Cys), E3-Leiden, and E2(Lys146-->Gln), and effects of treatment with simvastatin

Using a density-gradient ultracentrifugation technique, we analyzed in detail the plasma lipoprotein profiles of 18 patients with familial dysbetalipoproteinemia (FD) who had apolipoprotein (apo) E2(Arg158-->Cys) homozygosity (the E2-158 variant, n = 6), apoE3-Leiden heterozygosity (the E3-Leiden variant, n = 6), or apoE2(Lys146-->Gln) heterozygosity (the E2-146 variant, n = 6), with average plasma cholesterol concentrations of 8.99 +/- 1.34 mmol/L, 9.29 +/- 1.55 mmol/L, and 8.46 +/- 1.10 mmol/L, respectively. No significant differences in sex, age, body mass index, dietary habits, and standard laboratory tests between the three groups were observed. The lipoprotein profiles of all FD patients were characterized by higher concentrations of very-low-density lipoprotein (VLDL) 1, VLDL2, and intermediate-density lipoprotein (IDL) and a higher cholesteryl ester content of VLDL1 and VLDL2 than in 6 normolipidemic control subjects with an average plasma cholesterol concentration of 5.90 +/- 0.53 mmol/L. Major differences between the plasma lipoprotein profiles of patients with the E2-158 variant, the E3-Leiden variant, and the E2-146 variant and the normolipidemic control subjects were in IDL cholesterol concentration (1.70 +/- 0.26, 1.50 +/- 0.26, 1.05 +/- 0.36, and 0.47 +/- 0.14 mmol/L, respectively), LDL cholesterol concentration (1.83 +/- 0.50, 3.09 +/- 0.32, 3.79 +/- 0.76, and 3.77 +/- 0.56 mmol/L, respectively), and the molar ratio of IDL cholesterol to LDL cholesterol (0.98 +/- 0.28, 0.48 +/- 0.04, 0.28 +/- 0.09, and 0.12 +/- 0.03, respectively). After 10 weeks of simvastatin treatment the concentrations of plasma cholesterol, VLDL2 cholesterol, IDL cholesterol, and LDL cholesterol in 3 patients with the E2-158 variant fell significantly, by 46%, 56%, 53%, and 48%, respectively; they also fell in 3 patients with the E3-Leiden variant, by 48%, 54%, 57%, and 52%, respectively, and in 3 patients with the E2-146 variant, by 38%, 55%, 46%, and 35%, respectively. Simvastatin therapy lowered plasma activity of cholesteryl ester transfer protein but had no significant effect on plasma activity of lecithin:cholesterol acyltransferase. It is concluded that patients with FD due to various apoE variants have different lipoprotein profiles, mainly with regard to IDL and LDL levels, although they have a number of similar features of dysbetalipoproteinemia. Simvastatin therapy effectively reduced the plasma concentrations of total cholesterol, VLDL2 cholesterol, IDL cholesterol, and LDL cholesterol in the three groups of patients studied. It is proposed that apoE-dependent defects of the conversion of IDL to LDL may be an important mechanism in the pathophysiology of FD.

Diet-induced hypercholesterolemia and atherosclerosis in heterozygous apolipoprotein E-deficient mice

Apolipoprotein (apo) E is a ligand for the receptor-mediated uptake of lipoprotein remnant particles. Complete absence of apo E in humans leads to a severe form of type III hyperlipoproteinemia. We have used targeted inactivation in murine embryonic stem cells, as also described by others, to specifically study the effects of heterozygous Apoe gene loss on the development of hyperlipidemia. After 6 weeks on a severe semi-synthetic atherogenic diet, heterozygous null mutants, with only one functional Apoe alle, developed hypercholesterolemia as compared with controls (10.1 mM vs. 4.7 mM serum cholesterol). Interestingly, serum cholesterol levels in female heterozygotes were doubled as compared with male heterozygotes (15.0 mM vs. 7.5 mM). On this diet, heterozygous apo E deficient mice also showed an increased susceptibility to atherosclerosis, depending on gender (mean lesion area per section of 9524 microns 2 vs. 61,388 microns 2 for males and females, respectively), whereas wild-type mice displayed far fewer lesions (354 microns 2 and 9196 microns 2 for males and females, respectively). This study indicates that a subnormal expression-level of the Apoe gene leads to hypercholesterolemia and, consequently, to an increased susceptibility to the development of atherosclerosis.

Genetics of seven Dutch familial atypical multiple mole-melanoma syndrome families: a review of linkage results including chromosomes 1 and 9

Familial atypical multiple mole-melanoma syndrome is characterized by the familial occurrence of malignant melanoma of the skin in combination with multiple atypical precursor nevi; its pattern shows a dominant inheritance in pedigrees. During the last 5 years we have performed linkage analysis in seven Dutch familial atypical multiple mole-melanoma families to define the locus of the underlying gene defect. In 1989 it was reported that in familial melanoma families in the USA a disease-gene was located on chromosome 1p. However, in the Dutch families we could exclude this chromosome from harboring the Dutch familial atypical multiple mole-melanoma gene. Very recently a new candidate locus was found on chromosome 9p, which could be confirmed in our family material. A melanoma-associated gene was linked to several markers on chromosome 9p21. In a linkage analysis in which only melanoma patients were considered as affected, marker D9S171 showed a maximum lod score of 3.11 (theta 0.0). After introducing family members with 10 or more, or five or more, atypical nevi as affected in addition to the melanoma patients, the maximum lod score rose to 4.88 (theta 0.05) and 3.79 (theta 0.07), respectively. Interestingly, the sharing of a unique chromosome 9p21 haplotype among most melanoma patients in the families from two different villages suggests that an old common mutation is present in the Leiden region.

Chromosome 4q35 haplotypes and DNA rearrangements segregating in affected subjects of 19 Italian families with facioscapulohumeral muscular dystrophy (FSHD)

Four DNA markers on the distal long arm of chromosome 4 have been analyzed for their linkage to facioscapulohumeral muscular dystrophy locus (FSHD) in a series of 16 Italian families. We found that, in two families, the disease is not linked to the 4q35 markers, indicating the presence of genetic heterogeneity among Italian FSHD families. Linkage analysis in the remaining families supports the order cen-D4S171-D4S163-D4S139-D4S810-FSHD-qter, in agreement with the physical map from the literature. EcoRI digestion and hybridization with the distal marker p13E-11 (D4S810)1 detected DNA rearrangements in the affected members of both sporadic and familial cases of FSHD, with family-specific fragments ranging in size between 15 kb and 28 kb. In three sporadic FSHD cases, the appearance of a new "small" fragment not present in either parent was clearly associated with the development of FSHD disease. However, in the familial cases analyzed, we observed two recombinations between all four 4q35 markers and the disease locus in apparently normal subjects, leaving open the possibility of nonpenetrance of the FSHD mutation.

The incidence of mini- and micro-satellite repetitive DNA in the canine genome

We have estimated the incidence of microand mini-satellites in the dog genome. A genomic phage library from canine liver, with an average insert size of 16 kb, was screened to detect potentially polymorphic microand mini-satellite sequences, which may be useful for the development of markers of inherited diseases, for fingerprinting, or for population genetics. Synthetic oligonucleotide probes were used to search for microsatellite sequences, and minisatellites were investigated with eight heterologous VNTR probes. (CA)n.(GT)n sequences were by far the most frequent, with a calculated average distance between consecutive loci of 42 kb. The average distance between loci of tri- or tetra-nucleotide repeats was about 330 kb. Mean inter-locus distances were 320 kb for (GGC)n, 205 kb for (GTG)n, 563 kb for (AGG)n, 320 kb for (TCG)n, 233 kb for (TTA)n, 384 kb for (CCTA)n, 368 kb for (CTGT)n, 122 kb for (TTCC)n, 565 kb for (TCTA)n, and 229 kb for (TAGG)n. Cross-hybridization with eight human minisatellite probes was found at average distances of 1400 kb; only one did not hybridize at all. We conclude that the di-, tri and tetra-nucleotide short tandem repeats, as well as some minisatellite sequences, are potentially useful as genetic markers, for mapping of the canine genome, and also for paternity testing and the analysis of population characteristics.