Identification of a novel spliced variant of the SYT gene expressed in normal tissues and in synovial sarcoma

Abstract

Summary Synovial sarcoma (SS) is cytogenetically characterized by the translocation t(X;18)(p11.2-q11.2) generating a fusion between the SYT gene on chromosome 18 and one member of the SSX family gene (SSX1; SSX2; SSX4) on chromosome X. Here, we report for the first time that 2 forms of SYT mRNA are present in both normal tissues and SSs. By amplifying the full-length SYT cDNA of two SSs, we detected 2 bands, here designated N-SYT and I-SYT. The latter, previously undescribed, contains an in-frame insertion of 93 bp. Its sequencing revealed a 100% homology with the mouse SYT gene. These two SYT forms were present, although in different amounts, in all human normal tissues examined, including kidney, stomach, lung, colon, liver and synovia. Coexistence of N-SYT and I-SYT (both fused with SSX) was detected in a series of 59 SSs (35 monophasic and 24 biphasic) and in a SS cell line. A preliminary analysis of the differential expression levels of N-SYT and I-SYT in SSs revealed that the latter was consistently overexpressed, suggesting a role in SS pathogenesis. 1087-1094 © 2001 Cancer Research Campaign doi: 10.1054/ bjoc.2001.1710, available online at http://www.idealibrary.com on http://www.bjcancer.com MATERIALS AND METHODS Tumours and patients59 SSs were analysed by RT-PCR on frozen material. 31 showed the non-random translocation SYT-SSX1, 16 the SYT-SSX2 and one the SYT-SSX4; in the remaining 11 tumours no specific fusion transcript has been yet detected and these are the subject of further studies. Among the SYT-SSX1 tumours, 16/31 (51.6%) were monophasic and 15/31 (48.4%) biphasic; in the SYT-SSX2 group 12/16 (75%) were monophasic and 4/16 (25%) biphasic. The single SYT-SSX4 tumour was monophasic. There were 21 primary tumours, 15 local relapses and 23 metastases; in 2 cases (patients n. 27 and 42) we analysed both the primary tumour and the metastasis, and in 4 cases (patients n. 25, 28, 41 and 55) we analysed relapses and/or metastases ( Table 2).The human synovial sarcoma CME cell line was kindly provided by Dr B Kazmierczak (Renwick et al, 1995); these cells had the typical (X;18) translocation and showed the SYT-SSX2 fusion transcript.6 normal tissue samples (kidney, stomach, liver, lung, colon and synovia) derived from different patients surgically treated in our Institute were also analysed. RNA extraction and reverse-transcription reaction (RT-PCR)Total RNA was extracted using the RNAzol method (GIBCO BRL, Life Technology) from snap-frozen tissue samples stored at -80˚C. One µg of RNA was reverse-transcribed to cDNA with oligo(dT) and random examers primers, using Superscript II reverse transcriptase (GIBCO BRL, Paisley, UK), according to the manufacturer's conditions. One µl of cDNA was used as template for each PCR reaction, which was performed using AmpliTaq (Perkin Elmer), according to the manufacturer's conditions. All the amplification products were stained with ethidium bromide and analysed on 1.8% agarose gel. SYT-SSX PCRThe detection of the putative SYT-SSX1 or SYT-SSX2 fusion transcript ...

Detection of SS18-SSX fusion transcripts in formalin-fixed paraffin-embedded neoplasms: analysis of conventional RT-PCR, qRT-PCR and dual color FISH as diagnostic tools for synovial sarcoma

“…21 However, having performed a meta-analysis of published data we find that SS18-SSX2 occurs significantly more frequently in monophasic than in biphasic synovial sarcoma (Po0.001): this meta-analysis included a total of 1033 cases, of which 314 were biphasic synovial sarcoma and only 42 of these harbored the SS18-SSX2 transcript. 5,20,22,27,30,37,39,46,47,[49][50][51][54][55][56][57][58][59][60][61][62][63][64][65] The low frequency of both the SS18-SSX2 fusion type and the biphasic subtype of synovial sarcoma best explain the discrepant results observed in various studies. In our study, we also failed to find a significant association between poorly differentiated areas of synovial sarcoma and SS18 gene rearrangement, thereby supporting the work by Guillou et al…”

Loss of SS18-SSX1 Inhibits Viability and Induces Apoptosis in Synovial Sarcoma

“…Most importantly, we have identified a consistent deletion in the expected coding sequence of the SS18 domain of the SS18-SSX1 oncoprotein, which corresponds to the loss of exon 8 in the SS18 domain of the fusion protein. Although this deletion has been described by Tamborini et al [36], the nature of its contribution to the oncogenic potential of synovial sarcoma has not been elucidated. In addition, we demonstrate that this deleted sequence is present in the genomic DNA of the cell lines, indicating that this deletion is a posttranscriptional event.…”

The (Epi)genetics of human synovial sarcoma

“…The latter alternative splicing event (Fig. 2) may have a direct effect on the SS18 transcription activation potential and, more importantly, on synovial sarcoma pathogenesis (Tamborini et al, 2001). Modifications of the QPGY domain, mostly created in vitro by deletion mutagenesis, were found to abrogate both the SS18 transcription activation and multimerization capacities (Brett et al, 1997;Thaete et al, 1999;Perani et al, 2003).…”