A locus for congenital preauricular fistula maps to chromosome 8q11.1-q13.3

The incidence of congenital preauricular fistula (CPF) is >1.1% in both Chinese and Caucasians, but it is even higher in Blacks. We mapped the locus for CPF to chromosome 8q11.1-q13.3 by linkage analysis of a family composed of 7 affected and 11 nonaffected members. The two-point LOD score was 2.40, shown by markers D8S285 and D8S1113 at a recombination fraction (theta) of 0.00. Results from three other markers (D8S1110, D8S260, and D8S1136) in the same region further support the linkage. Haplotype analysis for this family confined the locus to within an interval of approximately 26.7 cM, flanked by markers D8S532 and D8S279. A LOD score of <3 is likely due to the limitation of family size.     

A third locus for hereditary haemorrhagic telangiectasia maps to chromosome 12q

Hereditary haemorrhagic telangiectasia (HHT) or Rendu-Osler-Weberdisease is an autosomal dominant vascular disorder which associatesepistaxis, mucocutaneous and visceral telangiectases, and recurrenthaemorrhage with chronic anaemia and visceral shuntings. Recently,the tumour growth factor (TGF)ß binding protein endoglinlocalized to 9q33–34 was identified as responsible forHHT in several large kindreds with pulmonary arteriovenous malformations(PAVMs). Additional linkage studies demonstrated that HHT isa genetically heterogeneous disorder with families unlinkedto this region of 9q. In the families in which HHT was not linkedto chromosome 9, less PAVMs were present. Furthermore, in oneof these families, HHT was found linked to 3p22, where the TGFßII receptor is located. In this linkage study, we have analysed DNA from two families,In which HHT was unlinked to chromosome 9q and 3p, and PAVMswere absent, with a series of genetic markers on the centromericregion of chromosome 12. Using two-point linkage analysis, asignificant lod score of 2^zmx = 7.86 at     

A new locus for autosomal recessive non-syndromic mental retardation maps to 1p21.1-p13.3

Autosomal recessive inheritance of non-syndromic mental retardation (ARNSMR) may account for approximately 25% of all patients with non-specific mental retardation (NSMR). Although many X-linked genes have been identified as a cause of NSMR, only three autosomal genes are known to cause ARNSMR. We present here a large consanguineous Turkish family with four mentally retarded individuals from different branches of the family. Clinical tests showed cognitive impairment but no neurological, skeletal, and biochemical involvements. Genome-wide mapping using Human Mapping 10K Array showed a single positive locus with a parametric LOD score of 4.92 in a region on chromosome 1p21.1-p13.3. Further analyses using polymorphic microsatellite markers defined a 6.6-Mb critical region containing approximately 130 known genes. This locus is the fourth one linked to ARNSMR.     

An autosomal dominant posterior polar cataract locus maps to human chromosome 20p12-q12

We assigned the locus for a previously reported new type of autosomal dominant posterior polar cataract (CPP3) to 20p12-q12 by a genome-wide two-point linkage analysis with microsatellite markers. CPP3 is characterized by progressive, disc-shaped, posterior subcapsular opacity. The disease was seen in 10 members of a Japanese family and transmitted in an autosomal dominant fashion through four generations. We obtained a maximum lod score (Zmax) of 3.61 with a recombination fraction (theta) of 0.00 for markers D20S917, D20S885 and D20S874. Haplotype analysis gave the disease gene localization at a 15.7-cM interval between D20S851 and D20S96 loci on chromosome 20p12-q12. Since the BFSP1 that encodes the lens-specific beaded filament structural protein 1 (filensin) has been mapped around the CPP3 region, we performed sequence analysis on its entire coding region. However, no base substitution or deletion was detected in the CPP3 patients. The mapping of the CPP3 locus to 20p12-q12 not only expands our understanding of the genetic heterogeneity in autosomal dominant posterior polar cataracts but also is a clue for the positional cloning of the disease gene.     

A gene for ataxic cerebral palsy maps to chromosome 9p12-q12

Cerebral palsy (CP) has an incidence of approximately 1 in 750 births, although this varies between ethnic groups. Genetic forms of the disease account for about 2% of cases in most countries, but contribute a larger proportion in certain sub-types of the condition and in populations with a large proportion of consanguineous marriages. Ataxic cerebral palsy accounts for 5-10% of all forms of CP and it is estimated that approximately 50% of ataxic cerebral palsy is inherited as an autosomal recessive trait. We have identified a complex consanguineous Asian pedigree with four children in two sibships affected with ataxic cerebral palsy and have used homozygosity mapping to map the disorder in this family. A genome-wide search was performed using 343 fluorescently labelled polymorphic markers and linkage to chromosome 9p12-q12 was demonstrated. A maximum Lod score of 3.4 was observed between the markers D9S50 and D9S167 using multipoint analysis, a region of approximately 23cM. We have identified a family that segregates both ataxic CP and ataxic diplegia and have mapped the genetic locus responsible in this family to chromosome 9p12-q12. The identification of gene(s) involved in the aetiology of CP will offer the possibility of prenatal/premarital testing to some families with children affected with the disorder and will greatly increase our understanding of the development of the control of motor function.     

A novel locus for autosomal dominant congenital cerulean cataract maps to chromosome 12q

Cataracts are the commonest cause of blindness worldwide. Inherited cataract is a clinically and genetically heterogeneous disease that most often shows autosomal dominant inheritance. In this study, we report the identification of a novel locus for cerulean cataract type 5 (CCA5), also known as blue-dot cataract on chromosome 12q24. To date, four loci for autosomal dominant congenital cerulean cataract have been mapped on chromosomes, 17q24, 22q11.2–12.2, 2q33–35 and 16q23.1. To map this locus we performed genetic linkage analysis using microsatellite markers in a five-generation English family. After the exclusion of all known loci and several candidate genes we obtained significantly positive LOD score (Z) for marker D12S1611 (Z_max=3.60; at θ=0). Haplotype data indicated that CCA5 locus lies within a region of 14.3 Mb interval between the markers D12S1718 and D12S1723. Our data are strongly suggestive of a new locus for CCA5 on chromosome 12.     

Autosomal recessive mesoaxial synostotic syndactyly with phalangeal reduction maps to chromosome 17p13.3

Previously we have described a novel and distinct form of non-syndromic osseous syndactyly segregating in an autosomal recessive pattern in a consanguineous Pakistani family. The limb findings include mesoaxial reduction of the fingers, synostoses of the third and fourth metacarpals with associated single phalanges, fifth finger clinodactyly, and preaxial webbing of toes. We identified another published report of this phenotype in a large, inbred Turkish family. In the present study we mapped the phenotype in the Pakistani and Turkish families to chromosome 17p13.3 (multipoint LOD score 5.1). The identification of a single locus for this complex limb malformation in two families with distinct ethnic backgrounds supports the hypothesis that this is a distinct form of syndactyly. Since this form of syndactyly is phenotypically distinct from the previously described eight types, we propose to name this phenotype mesoaxial synostotic syndactyly with phalangeal reduction (MSSD, type IX syndactyly, Malik-Percin type).     

Confirmation of assigment of a locus for rubinstein-taybi syndrome gene to 16p13.3

A two month-old girl was diagnosed as a case of Rubinstein-Taybi syndrome (RTS) on typical facial dysmorphism, broad and duplicated distal phalanges of thumbs and halluces, growth retardation and psychomotor development delay. Chromosome analysis demonstrated a de novo pericentric inversion of one chromosome 16: 46,XX,inv(16)(p13.3;q13). This association confirms assignment of a locus for RTS gene to 16p13.3, as two others translocations involving the same breakpoint have already been reported. © 1992 Wiley-Liss, Inc.     

Submicroscopic deletion of chromosome region 16p13.3 in a Japanese patient with Rubinstein-Taybi syndrome

In a series of 25 Japanese patients with Rubinstein-Taybi syndrome, we screened, by high-resolution GTG banding and fluorescence in situ hybridization of a cosmid probe (RT1, D16S237), for microdeletions associated with this syndrome. In one patient, a microdeletion was demonstrated by in situ hybridization, but none were detected by high-resolution banding. © 1994 Wiley-Liss, Inc.     

A locus for spondylocarpotarsal synostosis syndrome at chromosome 3p14

Spondylocarpotarsal synostosis syndrome is a rare autosomal recessive disorder characterised by vertebral fusions, frequently manifesting as an unsegmented vertebral bar, as well as fusions of the carpal and tarsal bones.

In a study of three consanguineous families and one non-consanguineous family, linkage analysis was used to establish the chromosomal location of the disease gene. Linkage analysis localised the disease gene to chromosome 3p14. A maximum lod score of 6.49 (q = 0) was obtained for the marker at locus D3S3532 on chromosome 3p. Recombination mapping narrowed the linked region to the 5.7 cM genetic interval between the markers at loci D3S3724 and D3S1300. A common region of homozygosity was found between the markers at loci D3S3724 and D3S1300, defining a physical interval of approximately 4 million base pairs likely to contain the disease gene.

Identification of the gene responsible for this disorder will provide insight into the genes that play a role in the formation of the vertebral column and joints.

     

Confirmation of assignment of a locus for Rubinstein-Taybi syndrome gene to 16p13.3.

A two month-old girl was diagnosed as a case of Rubinstein-Taybi syndrome (RTS) on typical facial dysmorphism, broad and duplicated distal phalanges of thumbs and halluces, growth retardation and psychomotor development delay. Chromosome analysis demonstrated a de novo pericentric inversion of one chromosome 16: 46,XX,inv(16)(p13.3;q13). This association confirms assignment of a locus for RTS gene to 16p13.3, as two others translocations involving the same breakpoint have already been reported.     

A patient with an interstitial duplication of chromosome 5p11-p13.3 further confirming a critical region for 5p duplication syndrome

Partial or complete trisomy 5p has been associated with characteristic facial features, developmental delay, seizures, congenital heart defects, and respiratory compromise. We present a child with developmental delay, seizures, and congenital cardiac anomalies found to have a previously unreported de novo interstitial duplication of chromosome 5p, 46,XX,dup(5) (p11p13.3). The breakpoints of the duplication were further confirmed by fluorescence in situ hybridization analysis using bacterial artificial chromosome probes specific for the affected region. Comparison with previously reported cases of patients with duplications of 5p suggests loci of interest for both congenital heart anomalies and seizures.     

A locus for primary ciliary dyskinesia maps to chromosome 19q

Primary ciliary dyskinesia is an autosomal recessive condition characterised by chronic sinusitis, bronchiectasis, and subfertility. Situs inversus occurs in 50% of cases (Kartagener syndrome). It has an estimated incidence of 1 in 20 000 live births. The clinical phenotype is caused by defective ciliary function associated with a range of ultrastructural abnormalities including absent dynein arms, absent radial spokes, and disturbed ciliary orientation. The molecular genetic basis is unknown. A genome scan was performed in five Arabic families. Using GENEHUNTER, a maximal multipoint lod score (HLOD) of 4.4 was obtained on chromosome 19q13.3-qter at alpha (proportion of linked families) = 0.7. A 15 cM critical region is defined by recombinations at D19S572 and D19S218. These data provide significant evidence for a PCD locus on chromosome 19q and confirm locus heterogeneity.     

A fourth locus for hereditary hemorrhagic telangiectasia maps to chromosome 7

Hereditary hemorrhagic telangiectasia (HHT) is a genetically and clinically heterogeneous multisystem vascular dysplasia. Mutations of the endoglin and ACVRL1 genes are known to cause HHT. However, existence of HHT families in which linkage to these genes has been excluded has suggested that other gene(s) can cause HHT in some families. Recently, a family was reported to be linked to chromosome 5q, the HHT3 locus. Here we report on linkage results on a family with classic features of HHT, albeit a less severe phenotype with regards to epistaxis and telangiectases, in which linkage to HHT1, HHT2, and HHT3 is ruled out. Whole genome linkage analysis and fine mapping results suggested a 7 Mb region on the short arm of chromosome 7 (7p14) between STR markers D7S2252 and D7S510. We obtained a maximum two point LOD score of 3.60 with the STR marker D7S817. This region was further confirmed by haplotype analysis. These findings suggest the presence of another gene causing HHT (HHT4). The features in this family that strongly suggest the presence of a hereditary, multisystem vascular dysplasia would be easily missed during the typical evaluation and management of a patient with an AVM. This family helps emphasize the need to obtain a very detailed, targeted medical and family history for even mild, infrequent but recurring nosebleed, subtle telangiectases. Further studies of the candidate region and the identification of the gene responsible for the vascular anomalies in this family will add to our understanding of vascular morphogenesis and related disorders.