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.

WBSCR14, a putative transcription factor gene deleted in Williams-Beuren syndrome: complete characterisation of the human gene and the mouse ortholog.

Williams-Beuren syndrome (WBS) is a neurodevelopmental disorder affecting several systems caused by a heterozygous deletion in the chromosomal region 7q11.23. A common interval that includes up to 17 genes reported so far is deleted in the great majority of patients. Elastin haploinsufficiency is responsible for the cardiovascular features, but the specific contribution of other deleted genes to the WBS phenotype remains unknown. We have fully characterised a gene commonly deleted in WBS, WBSCR14, previously reported in a truncated form as WS-bHLH. The WBSCR14 cDNA encodes an 852amino acid protein with a basic helix-loop-helix-leucine-zipper motif (bHLHZip) and a bipartite nuclear localisation signal (BNLS), suggesting a function as a transcription factor. WBSCR14 is expressed as a 4.2kb transcript predominantly in adult liver and at late stages of foetal development. The WBSCR14 locus encompasses 33 kb of genomic DNA with 17 exons. Two intragenic polymorphic dinucleotide repeats have been identified and used to verify hemizygosity in WBS patients. We have also cloned the mouse ortholog and mapped its locus to mouse chromosome 5, in a region of conserved synteny with human 7q11.23. Given that other bHLHZip proteins are dosage sensitive and based on the putative function of WBSCR14 as a transcription factor, hemizygosity at this locus could be involved in some features of WBS.

Tex27, a gene containing a zinc-finger domain, is up-regulated during the haploid stages of spermatogenesis.

Tex27 is a gene encoding a protein containing a zinc-finger domain in the carboxy terminal region and a transactivation domain in the amino terminal region. The Tex27 cDNA was isolated from a subtractive library that was enriched for genes preferentially expressed during the development of the seminiferous epithelium. Northern and in situ hybridization analyses demonstrated that Tex27 is differentially expressed in the testis, showing an increased expression in the germ cells corresponding to postmeiotic stages of spermatogenesis. This expression pattern in testis has been described for other C2H2-type zinc-finger proteins in mouse and human, like CTfin51, Zpf29, Sp1, and Zpf37. RFLP-Southern assays revealed that Tex27 is conserved in mammals. The polypeptide analysis and expression pattern suggest that Tex27 is a potential transcription factor preferentially expressed in postmeiotic cells during mouse spermatogenesis.

Gene expression of mouse M1 and M2 pyruvate kinase isoenzymes correlates with differential poly[A] tract extension of their mRNAs during the development of spermatogenesis.

In eukaryotes, different isoenzymes for pyruvate kinase have been characterized. M2-type Pk cDNA from a mouse fetal ovary library was isolated and differential expression for M1 and M2-types during testis development was observed. While the presence of M2 mRNAs decreases throughout the development of spermatogenesis, we deduced that M1 type expression increases in adult testis coinciding with the presence of elongating spermatids in the seminiferous epithelium. Polyadenylation tests showed a concurrent increase in the length of the polyadenylation tail of transcribed M1-type pyruvate kinase mRNAs in prepuberal to adult seminiferous tubules. A similar relationship between poly[A] tail extension and differential increase of gene expression was detected for M1-type mRNA in adult brain and muscle. Length of poly[A] tail of M2-type transcripts is shown to decrease during the development of mouse testis. These results suggest that changes in the length of the poly[A] tail of transcripts are associated with differential expression of both regulated isoenzymes during testicular development.