EXPRESSION OF A CANDIDATE ATAXIA-TELANGIECTASIA GROUP-D GENE IN CULTURED FIBROBLAST CELL-LINES AND HUMAN TISSUES

A candidate gene for ataxia-telangiectasia group D (ATDC) has been cloned (Kapp et al. 1992), sequenced and found to be a member of a recently reported gene family (Leonhardt el al. 1994). Transcriptional behaviour of ATDC has been examined in a number of cell lines and human tissues using a 3.0 kb cloned cDNA as a probe. Three normal and two ataxia-telangiectasia (A-T) group D, non-transformed fibroblast cell lines produced a 2.4 kb mRNA transcript. The size of mRNA transcripts seen and the level of expression differ in different human tissues. Many tissues have multiple transcripts of ATDC and the most prominent transcripts observed were 3.0, 2.4 and 1.6 kb. Two out of three SV-40 transformed normal and one SV-40-transformed A-T group D fibroblast cell lines demonstrated no transcription of ATDC by RNA blotting analysis. These results suggest that SV-40 transformation may affect the expression of ATDC. Reverse transcription-polymerase chain reaction analysis showed that ATDC was expressed at low levels in all of these cells. Additional Northern blot analysis demonstrated that X-irradiation with 10 Gy had no effect on ATDC expression at 1, 4 and 24 h after irradiation in either SV-40-transformed normal or in SV-40-transformed A-T group D fibroblast cell lines. Further understanding of ATDC will require cloning of additional transcripts and studies of ATDC protein behaviour.