Delineation of 7q11.2 deletions associated with Williams-Beuren syndrome and mapping of a repetitive sequence to within and to either side of the common deletion.

The majority of Williams-Beuren syndrome (WBS) patients have been shown to have a microdeletion within 7q11.2 including the elastin gene locus. The extent of these deletions has, however, not been well characterized. Thirty-five deletion patients were tested for all polymorphic markers in the 7q11.2 region bounding ELN to define the extent of deletions associated with WBS. With only one exception, ELN, D7S1870, and one copy of the D7S489 locus (D7S489U) were always included in the deletions. One patient showed lack of maternal inheritance at D7S1870 and not at ELN or D7S489U. A product corresponding to D7S489U was amplified from YAC 743G6 and from the P1 clone RMC07P008, thereby localizing both to within the common deletion. The boundary of the deleted region on the proximal (centromeric) side is D7S653 and on the distal side is D7S675, neither of which were ever included in the deletion. One locus, D7S489L, was variably deleted in patients, indicating a minimum of two common breakpoints on the proximal side. At least one additional repeat amplified by D7S489 (D7S489M) was localized to a YAC contig mapping distal to the common deletion. The D7S489 sequence is highly homologous to several cDNA clones in the GenBank database and contains an Alu sequence. It is possible that this andsolidusor other repetitive sequences in this region could play a role in the mechanism of deletion.

Robinson WP ，Waslynka J ，Bernasconi F ，Wang M ，Clark S ，Kotzot D ，Schinzel A ... -  《GENOMICS》

Fine-scale comparative mapping of the human 7q11.23 region and the orthologous region on mouse chromosome 5G: the low-copy repeats that flank the Williams-Beuren syndrome deletion arose at breakpoint sites of an evolutionary inversion(s).

Williams-Beuren syndrome (WBS) is a developmental disorder caused by haploinsufficiency for genes deleted in chromosome band 7q11.23. A common deletion including at least 16-17 genes has been defined in the great majority of patients. We have completed a physical and transcription map of the WBS region based on analysis of high-throughput genome sequence data and assembly of a BAC/PAC/YAC contig, including the characterization of large blocks of gene-containing low-copy-number repeat elements that flank the commonly deleted interval. The WBS deletions arise as a consequence of unequal crossing over between these highly homologous sequences, which confer susceptibility to local chromosome rearrangements. We have also completed a clone contig, genetic, and long-range restriction map of the mouse homologous region, including the orthologues of all identified genes in the human map. The order of the intradeletion genes appears to be conserved in mouse, and no low-copy-number repeats are found in the region. However, the deletion region is inverted relative to the human map, exactly at the flanking regions. Thus, we have identified an evolutionary inversion with chromosomal breakpoints at the sites where the human 7q11.23 low-copy-number repeats are located. Additional comparative mapping suggests a model for human chromosome 7 evolution due to serial inversions leading to genomic duplications. This high-resolution mouse map provides the framework required for the generation of mouse models for WBS mimicking the human molecular defect.

Valero MC ，de Luis O ，Cruces J ，Pérez Jurado LA ... -  《GENOMICS》

A duplicated gene in the breakpoint regions of the 7q11.23 Williams-Beuren syndrome deletion encodes the initiator binding protein TFII-I and BAP-135, a phosphorylation target of BTK.

Williams-Beuren syndrome (WBS) is a neurodevelopmental disorder with multisystemic manifestations caused by heterozygosity for a partial deletion of chromosome band 7q11.23. The breakpoints cluster within regions located approximately 1 cM either side of the elastin (ELN) locus. We have characterized a duplicated region near the common deletion breakpoints, which includes a transcribed gene. The centromeric (C) and telomeric (T) copies are almost identical in the duplicated 3[prime] portions but diverge at their 5[prime]-ends. C-specific 4.3 kb mRNA and T-specific 5.4 kb mRNA are widely expressed in embryonic and adult tissues. The telomeric gene gives rise to several alternatively spliced forms and is deleted in all WBS individuals who have documented ELN deletions. Database searches revealed that this gene encodes BAP-135, a protein phosphorylated by Bruton's tyrosine kinase in B cells, as well as the multifunctional transcription factor TFII-I, hence the gene name GTF2I. The centromeric gene is not deleted in WBS and appears to be a partially truncated expressed pseudogene with no protein product (gene name GTF2IP1). Both loci map to different genomic clone contigs that also contain other deleted and non-deleted loci. A probe from the shared region recognizes a >3 Mb Not I junction fragment that is unique to individuals with the WBS deletion. Therefore, the duplicated region containing GTF2I and GTF2IP1 respectively is located close to the deletion breakpoints and may predispose to unequal meiotic recombination between chromosome 7 homologs and/or to intrachromosomal rearrangements. Hemizygosity for GTF2I may also contribute to the WBS phenotype.

Pérez Jurado LA ，Wang YK ，Peoples R ，Coloma A ，Cruces J ，Francke U ... -  《HUMAN MOLECULAR GENETICS》

Interstitial deletion of chromosome 7q in a patient with Williams syndrome and infantile spasms.

Interstitial deletion of 7q11.23-q21.11 was identified by cytogenetic methods in a 4-year-old boy with Williams syndrome (WS) and infantile spasms. Deletion of the elastin (ELN) gene and the DNA polymorphic markers, D7S1870, D7S2490, D7S2518, and D7S2421, were identified in the patient, but the loci for D7S653 and D7S675 were not involved. Zackowski et al. (1990) reported that 6 of 16 patients with the interstitial deletion of 7q11.2-q22 had abnormal electro encephalograms, or seizures, or both, and that infantile spasms were present in 2 of the 6 patients. WS is a well defined developmental disorder characterized by distinct facial features, gregarious personality, and congenital heart defects. Seizures are not generally associated with this syndrome. WS commonly is characterized by deletion of the loci for ELN and D7S1870, but not those for D7S2490, D7S2518, or D7S2421. This suggests that a gene responsible for infantile spasms is located in the 2.7-cM interval between loci D7S1870 and D7S675.

Mizugishi K ，Yamanaka K ，Kuwajima K ，Kondo I ... -  《JOURNAL OF HUMAN GENETICS》

[Genetic diagnosis of Williams syndrome].

Williams syndrome is a complex developmental disorder. The major cardiovascular component of Williams syndrome is supravalvular aortic stenosis, a progressive disease that may need surgical repair. Williams syndrome is associated with heterozygous microdeletion in the chromosomal region 7q11.23 encompassing the elastin gene. We have identified a new, highly informative tetranucleotide repeat polymorphism within the human elastin gene. This marker together with other, previously described elastin gene markers was used to show deletion of the elastin gene in nine sporadic Williams syndrome patients from Hungary. Application of polymorphisms within and flanking the elastin gene on chromosome 7 provides a fast, polymerase chain reaction based method for mutational analysis of Williams syndrome patients.

Urbán Z ，Kiss E ，Kádár K ，Szabolcs J ，Csiszár K ，Boyd DC ，Fekete G ... -  《ORVOSI HETILAP》