Alternative splicing of CREB and CREM mRNAs in an immortalized germ cell line.

Alternative splicing of CREB (cAMP response element binding protein) and CREM (cAMP response element modulator) mRNAs in separated pachytene spermatocyte, round spermatid, and elongated spermatid fractions and the germ cell-derived immortalized cell line GC-2spd(ts) was studied by reverse transcription polymerase chain reaction (RT-PCR). Both primary germ cells and the GC-2spd(ts) cell line expressed the testis-specific CREB splice variant containing exon W. In the CREB C-E exon region, both primary germ cells and GC-2spd(ts) cells produced RT-PCR products that included exon Y. RT-PCR using CREM primers produced multiple bands in primary germ cells. The truncated CREAM deltaC-G form was found in all the germ cell fractions. The smaller splice forms of CREM were more prominent in the GC-2spd(ts) cells. GC-2spd(ts) cells resembled F9 teratocarcinoma cells more closely than primary germ cells with respect to the relative expression of both CREB and CREM alternative splice products. In Sertoli cells, RT-PCR products of CREB exon lacking W and the product corresponding to CREM delta C-G were most prominent. These data show that the GC-2spd(ts) cell line retains some qualitative characteristics of primary germ cells with respect to alternative splicing of CREB and CREM mRNA.