Linkage analyses of five chromosome 4 markers localizes the facioscapulohumeral muscular dystrophy (FSHD) gene to distal 4q35

The genetic locus for facioscapulohumeral muscular dystrophy (FSHD) has been mapped to chromosome 4. We have examined linkage to five chromosome 4q DNA markers in 22 multigenerational FSHD families. Multipoint linkage analyses of the segregation of four markers in the FSHD families and in 40 multigenerational mapping families from the Centre d'Etude du Polymorphisme Humaine enabled these loci and FSHD to be placed in the following order: cen-D4S171-factor XI-D4S163-D4S139-FSHD-qter. One interval, D4S171-FSHD, showed significant sex-specific differences in recombination. Homogeneity tests supported linkage of FSHD to these 4q DNA markers in all of the families we studied. The position of FSHD is consistent with that generated by other groups as members of an international FSHD consortium.     

The human aldose reductase gene maps to chromosome region 7q35

Summary The human aldose reductase (AR) gene has been mapped to chromosome 7 using the polymerase chain reaction to specifically amplify the human AR sequence in hamster/human hybrid DNA and also in mouse/ human monochromosome hybrids. The assignment to chromosome 7 was confirmed by in situ hybridisation to human metaphase chromosomes using a novel, rapid hybridisation, method giving a regional localisation at 7q35.     

Mapping of facioscapulohumeral muscular dystrophy gene to chromosome 4q35-qter by multipoint linkage analysis and in situ hybridization

We have recently assigned the facioscapulohumeral muscular dystrophy (FSHD) gene to chromome 4 by linkage to the microsatellite marker Mfd 22 (locus D4S171). We now report that D4S139, a VNTR locus, is much more closely linked to FSHD. Two-point linkage analysis between FSHD and D4S139 in nine informative families showed a maximum combined lod score (Zmax) of 17.28 at a recombination fraction theta of 0.027. Multipoint linkage analysis between FSHD and the loci D4S139 and D4S171 resulted in a peak lod score of 20.21 at 2.7 cM from D4S139. Due to the small number of recombinants found with D4S139, the position of the FSHD gene relative to that of D4S139 could not be established with certainty. D4S139 was mapped to chromosome 4q35-qter by in situ hybridization, thus firmly establishing the location of the FSHD gene in the subtelomeric region of chromosome 4q. One small family yielded a negative lod score for D4S139. In the other families no significant evidence for genetic heterogeneity was obtained. Studies of additional markers and new families will improve the map of the FSHD region, reveal possible genetic heterogeneity, and allow better diagnostic reliability.     

Assignment of the human muscle adenine nucleotide translocator gene (ANT1) to 4q35 by fluorescence in situ hybridization.

The human muscle adenine nucleotide translocator gene (ANT1) was previously assigned to chromosome 4. The gene has now been further localized to the long arm of chromosome 4 at 4q35 by fluorescence in situ hybridization. This result confirms the previous assignment and precisely maps the gene to a specific chromosome band.     

The mapping of chromosome 4q markers in relation to facioscapulohumeral muscular dystrophy (FSHD).

The Basque population is one of the oldest populations of Europe. It has been suggested that the Basques arose from a population established in western Europe during the late Paleolithic Age. The Basque language (Euskera) is a supposedly pre-Indo-European language that originates from the first settlers of Europe. The variable distribution of the major cystic fibrosis (CF) mutation (delta F508 deletion) in Europe, with higher frequencies of the mutation in northern Europe and lower frequencies in southern Europe, has suggested that the delta F508 mutation was spread by early farmers migrating from the Middle East during the Neolithic period. We have studied 45 CF families from the Basque Country, where the incidence of CF is approximately 1/4,500. The birthplaces of the parents and grandparents have been traced and are distributed according to their origin as Basque or Mixed Basque. The frequency of the delta F508 mutation in the chromosomes of Basque origin is 87%, compared with 58% in those of Mixed Basque origin. The analysis of haplotypes, both with markers closely linked to the CF gene and with intragenic markers, suggests that the delta F508 mutation was not spread by the Indo-European invasions but was already present in Europe more than 10,000 years ago, during the Paleolithic period.     

Genetic linkage map of facioscapulohumeral muscular dystrophy and five polymorphic loci on chromosome 4q35-qter

A genetic map of five polymorphic markers in the area of the facioscapulohumeral muscular dystrophy (FSHD) gene on chromosome 4q35-qter has been constructed. With these five markers, a number of recombinants have been identified that allow ordering of the marker and the disease loci. The most likely locus order and the relative position of the FSHD gene supported by the recombinants is centromere-D4S171-F11-D4S187-D4S163-D4S139-FS HD-telomere. However, at least one recombination event appears to be inconsistent with this order and suggests a location of FSHD proximal to D4S139.     

Mapping of facioscapulohumeral muscular dystrophy gene to chromosome 4q35-qter by multipoint linkage analysis and in situ hybridization

We have recently assigned the facioscapulohumeral muscular dystrophy (FSHD) gene to chromosome 4 by linkage to the microsatellite marker Mfd 22 (locus D4S171). We now report that D4S139, a VNTR locus, is much more closely linked to FSHD. Two-point linkage analysis between FSHD and D4S139 in nine informative families showed a maximum combined lod score (Z_max) of 17.28 at a recombination fraction θ of 0.027. Multipoint linkage analysis between FSHD and the loci D4S139 and D4S171 resulted in a peak lod score of 20.21 at 2.7 cM from D4S139. Due to the small number of recombinants found with D4S139, the position of the FSHD gene relative to that of D4S139 could not be established with certainty. D4S139 was mapped to chromosome 4q35-qter by in situ hybridization, thus firmly establishing the location of the FSHD gene in the subtelomeric region of chromosome 4q. One small family yielded a negative lod score for D4S139. In the other families no significant evidence for genetic heterogeneity was obtained. Studies of additional markers and new families will improve the map of the FSHD region, reveal possible genetic heterogeneity, and allow better diagnostic reliability.     

Linkage localization of facioscapulohumeral muscular dystrophy (FSHD) in 4q35.

Fasioscapulohumeral muscular dystrophy (FSHD) has recently been localized to 4q35. We have studied four families with FSHD. Linkage to the 4q35 probes D4S163, D4S139, and D4S171 was confirmed. We found no recombinants helpful in detailed localization of the FSHD gene. Two of our families include males with a rapidly progressive muscle disease that had been diagnosed, on the basis of clinical features, as Duchenne muscular dystrophy. One of these males is available for linkage study and shares the haplotype of his FSHD-affected aunt and cousin.     

A gene for autosomal recessive limb-girdle muscular dystrophy in Manitoba Hutterites maps to chromosome region 9q31-q33: evidence for another limb-girdle muscular dystrophy locus.

Characterized by proximal muscle weakness and wasting, limb-girdle muscular dystrophies (LGMDs) are a heterogeneous group of clinical disorders. Previous reports have documented either autosomal dominant or autosomal recessive modes of inheritance, with genetic linkage studies providing evidence for the existence of at least 12 distinct loci. Gene products have been identified for five genes responsible for autosomal recessive forms of the disorder. We performed a genome scan using pooled DNA from a large Hutterite kindred in which the affected members display a mild form of autosomal recessive LGMD. A total of 200 markers were used to screen pools of DNA from patients and their siblings. Linkage between the LGMD locus and D9S302 (maximum LOD score 5.99 at recombination fraction .03) was established. Since this marker resides within the chromosomal region known to harbor the gene causing Fukuyama congenital muscular dystrophy (FCMD), we expanded our investigations, to include additional markers in chromosome region 9q31-q34.1. Haplotype analysis revealed five recombinations that place the LGMD locus distal to the FCMD locus. The LGMD locus maps close to D9S934 (maximum multipoint LOD score 7.61) in a region that is estimated to be approximately 4.4 Mb (Genetic Location Database composite map). On the basis of an inferred ancestral recombination, the gene may lie in a 300-kb region between D9S302 and D9S934. Our results provide compelling evidence that yet another gene is involved in LGMD; we suggest that it be named "LGMD2H."     

Regional mapping of facioscapulohumeral muscular dystrophy gene on 4q35: Combined analysis of an international consortium

Members of an international consortium for linkage analysis of the facioscapulohumeral muscular dystrophy (FSHD) gene have pooled data for joint analyses, in an attempt to determine the precise location of the FSHD gene and the order of four DNA markers on 4q35 region. Six laboratories determined a total of 3,078 genotypes in 65 families, consisting of a total of 504 affected subjects and 559 unaffected subjects. For each marker, a mean of 648 meioses were informative. D4S139 and D4S163 were identified as the closest linked markers to the FSHD locus, with 99% upper confidence intervals of recombination fractions of .08 and .10, respectively. We have used the CRI-MAP program to construct the most likely order of cen-D4S171-F11-D4S163-D4S139-FSHD-tel, with favorable odds of 10(8)-10(114) over all other orders except that in which F11 and D4S171 are reversed, for which the odds ratio was 191:1. With this order, the genetic map of this region extends 25.5 cM in males and 13.8 cM in females (averaging 19.5 cM for sexes combined); the sex difference was statistically significant (P = .0013). Comparison between families for the two-point and multipoint lod scores involving FSHD showed no evidence for heterogeneity of this disorder. However, after the completion of this analysis, one large family which might show heterogeneity was identified. In view of this and the fact that all of the linked markers reside on the same side of the FSHD locus, the clinical application of these markers is not recommended at this time.     

FRG1, a gene in the FSH muscular dystrophy region on human chromosome 4q35, is highly conserved in vertebrates and invertebrates

The human FRG1 gene maps to human chromosome 4q35 and was identified as a candidate for facioscapulohumeral muscular dystrophy. However, FRG1 is apparently not causally associated with the disease and as yet, its function remains unclear. We have cloned homologues of FRG1 from two additional vertebrates, the mouse and the Japanese puffer fish Fugu rubripes, and investigated the genomic organization of the genes in the two species. The intron/exon structure of the genes is identical throughout the protein coding region, although the Fugu gene is five times smaller than the mouse gene. We have also identified FRG1 homologues in two nematodes; Caenorhabditis elegans and Brugia malayi. The FRG1 protein is highly conserved and contains a lipocalin sequence motif, suggesting it may function as a transport protein.     

Assignment of the tibial muscular dystrophy locus to chromosome 2q31.

Tibial muscular dystrophy (TMD) is a rare autosomal dominant distal myopathy with late adult onset. The phenotype is relatively mild: muscle weakness manifests in the patient's early 40s and remains confined to the tibial anterior muscles. Histopathological changes in muscle are compatible with muscular dystrophy, with the exception that rimmed vacuoles are a rather common finding. We performed a genomewide scan, with 279 highly polymorphic Cooperative Human Linkage Center microsatellite markers, on 11 affected individuals of one Finnish TMD family. The only evidence for linkage emerged from markers in a 43-cM region on chromosome 2q. In further linkage analyses, which included three other Finnish TMD families and which used a denser set of markers, a maximum two-point LOD score of 10.14 (recombination fraction of .05) was obtained with marker D2S364. Multipoint likelihood calculations, combined with the haplotype and recombination analyses, restricted the TMD locus to an approximately 1-cM critical chromosomal region without any evidence of heterogeneity. Since all the affecteds share one core haplotype, the dominance of one ancestor mutation is obvious in the Finnish TMD families. The disease locus that was found represents a novel muscular dystrophy locus, providing evidence for the involvement of one additional gene in the distal myopathy group of muscle disorders.     

Germline mosaicism in 4q35 facioscapulohumeral muscular dystrophy (FSHD1A) occurring predominantly in oogenesis

Facioscapulohumeral muscular dystrophy (FSHD) is an autosomal dominantly inherited neuromuscular disorder affecting facial and shoulder girdle muscles with subsequent progression to the pelvic girdle and lower extremities. The major gene involved has been localized to chromosome 4q35 (FSHD1A). The 4q35 DNA marker p13E-11 (D4F104S1) detects a de novo EcoRI DNA rearrangement of < 30 kb in isolated and familial cases. The intrafamilial size of the fragment is constant, inversely correlated with the severity, and directly correlated with the age of onset of the condition. There has been evidence of parental mosaicism in FSHD1A for the D4F104S1 locus. Four female and three male clinically unaffected parents have been described to be carriers of EcoRI fragments of the same size as their affected offspring, but with a markedly less intensive hybridization signal (semi-quantitative evidence). In our total sample of 42 FSHD1A families, we found semi-quantitative evidence of parental D4F104S1 mosaicism in 11 families (EcoRI fragment size range: 12–27 kb). On analysis with adjacent 4q35 probes (D4S163, D4S139), additional qualitative evidence of germline mosaicism could be obtained in two families. In our mosaic families and in the families reported in the literature, a female predominance of mosaicism carriers (13 females versus 5 males) could be noted. In our sample, mosaicism was observed in multigeneration families, in families with isolated cases, and in families with two and three affected children from seemingly unaffected parents. A short EcoRI fragment once having emerged in a mosaicism carrier was found to be transmitted autosomal dominantly to subsequent generations. Of all reported sporadic patients, 19% have a mosaic parent. Finding evidence of parental mosaicism in all our families with more than one affected child of seemingly unaffected parents suggests that there is no autosomal recessively inherited form of FSHD1A. Received: 5 March 1996 / Revised: 14 May 1996     

Cytogenetic and immuno-FISH analysis of the 4q subtelomeric region,which is associated with facioscapulohumeral muscular dystrophy

Facioscapulohumeral muscular dystrophy (FSHD) is caused by the shortening of a copy-number polymorphic array of 3.3 kb repeats (D4Z4) at one allelic 4q35.2 region. How this contraction of a subtelomeric tandem array causes FSHD is unknown but indirect evidence suggests that a short array has a cis effect on a distant gene or genes. It was hypothesized that the length of the D4Z4 array determines whether or not the array and a large proximal region are heterochromatic and thereby controls gene expression in cis. To test this, we used fluorescence in situ hybridization probes with FSHD and control myoblasts to characterize the distal portion of 4q35.2 with respect to the following: intense staining with the chromatin dye 4,6-diamidino-2-phenylindole; association with constitutively heterochromatic foci; extent of binding of heterochromatin protein 1; histone H3 methylation at lysine 9 and lysine 4; histone H4 lysine 8 acetylation; and replication timing within S-phase. Our results indicate that 4q35.2 does not resemble constitutive heterochromatin in FSHD or control myoblasts. Furthermore, in these analyses, the allelic 4q35.2 regions of FSHD myoblasts did not behave differently than those of control myoblasts. Other models for how D4Z4 array contraction causes long-distance regulation of gene expression in cis need to be tested.Communicated by S. Gerbi     

The porcine TTR locus maps to chromosome 6q

The sequence of a cDNA clone encoding porcine transthyretin (prealbumin) was used to develop polymorphic markers for the TTR locus. The single-strand conformation polymorphism (SSCP) detected is caused by a silent AIT mutation in the penultimate coding codon and can also be revealed as a SacI restriction fragment length polymorphism (RFLP). The TTR locus was mapped to chromosome 6q by segregation and linkage analysis with these polymorphisms. This assignment confirms the predictions of homology between human chromosome 18 and pig chromosome 6q2.5-2.6.     

A gene for limb-girdle muscular dystrophy maps to chromosome 15 by linkage

Limb-girdle muscular dystrophy (LGMD) is inherited as a monogenic, autosomal recessive trait. A genetically homogeneous group of families from the Isle of La Réunion, comprising individuals at high risk for this disorder, was systematically analysed using a panel of 85 polymorphic markers spanning approximately 30% of the human genome. Linkage was detected between the LGMD gene and the marker D15S25, uncovered with the probe pTHH114 and restriction enzyme RsaI (lod score = 5.52 at a 0 = 0.0), localising this gene onto chromosome 15. Such a lod score corresponds to odds of 3.3 x 105 in favor of linkage versus absence of linkage. Additional families from other populations will need to be examined before the role of this newly identified locus can be understood.