REASSESSMENT OF GERMLINE HEAVY-CHAIN TRANSCRIPTS FROM 2 MURINE V-H FAMILIES

While expression of functional heavy chain immunoglobulin mRNA require s rearrangement of variable (V-H), diversity (D) and (J(H)) gene segme nts, these individual gene segments can be transcribed prior to their rearrangement. It has been proposed that the resulting germline, or st erile, transcripts play an important role in the rearrangement process because strong correlations between rearrangement frequency and steri le transcript levels have been observed in some studies. Murine V-H ge nes have been grouped into families on the basis of coding sequence ho mology. V-H families rearrange in a developmentally regulated manner, so that rearrangements of genes from several V-H families are detected earlier than rearrangements of J558 family genes. Paradoxically, the only V-H family for which sterile transcripts have been documented is the J558 family. We used RT-PCR analyses to ask whether sterile transc ripts from other V-H families could be detected in fetal liver samples prior to their rearrangement. While J558 family germline transcripts were easily detected, no sterile transcripts were observed from the S1 07 family. Our studies also revealed the ability of small quantities o f degraded genomic DNA to nonspecifically prime cDNA synthesis, emphas izing the need for caution in interpreting RT-PCR data in which family -specific oligos are used for cDNA production. These results cast doub t on the idea that sterile transcripts are required for V(H)DJ(H) rear rangement. (C) 1997 Published by Elsevier Science Ltd. All rights rese rved.