SummaryRhabdoid tumours have been shown to carry somatic mutations in the INI1 (SMARCB1/hSNF5) gene. A considerable fraction of these tumours exhibit allelic losses on chromosome 22. Allelic loss on 22q also is characteristic for meningiomas, however most of these alterations are considered to be associated with mutations of the NF2 gene. We examined a series of 126 meningiomas for alterations in the INI1 gene. Four identical somatic mutations in exon 9 were detected resulting in an exchange of Arg to His in position 377 of INI1. Our observations were reproduced both by using DNA from a new round of extraction and by employing overlapping primers. This mutational hotspot therefore appears to be an important target in the formation of a fraction of meningiomas. In addition, 4 novel polymorphisms of INI1 were characterized. Our data indicate that the INI1 is a second tumour suppressor gene on chromosome 22 that may be important for the genesis of meningiomas.

We here present a sequencing strategy for the HLA-A locus which is generally applicable for all HLA class I genes. The typing strategy is based on a group-specific amplification according to the serologically defined antigens. The PCR products carry the typing-relevant polymorphic regions of the 2nd and 3rd exon including the 2nd intron. The sequencing primers were designed to match conserved sequence motifs in the 2nd intron allowing a nested sequencing approach in 3' and 5' direction. These conserved regions were identified after sequence compilation of the 2nd intron of 143 clinical samples and 48 cell lines mostly from the 9th and 10th IHWC representing all serologically defined groups of alleles. This strategy allowed the use of only one 5' and one 3' sequencing primer regardless of the amplified allele. Therefore, it was possible to use dye terminator as well as dye primer sequencing chemistry. The amplification strategy allowed the separation of the haplotypes in almost all cases. Thus, an assignment of heterozygous positions requiring high sequencing quality was not necessary, allowing the application of Sequenase as well as TaqPolymerase as sequencing enzyme. Concerning the resolution of heterozygosity it is obvious that this approach is superior to a typing system using a single pair of generic primers followed by direct sequencing, since the latter technique is not capable of defining the cis/trans linkage of polymorphic sequences and, hence, cannot exclude the presence of unknown alleles.

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