AN INSERTIONAL MUTATION IN THE BTF3 TRANSCRIPTION FACTOR GENE LEADS TO AN EARLY POSTIMPLANTATION LETHALITY IN MICE

The gene that encodes the general transcription factor known as BTF3 w as disrupted in mouse embryonic stem cells in a random mutagenesis scr een for developmental genes with the ROSA beta-geo (Friedrich and Sori ano, 1991) retroviral gene trap vector. The BTF3 mutation was transmit ted through the germline of chimaeric mice. While the endogenous BTF3 gene is ubiquitously expressed, the expression pattern of the beta-gal actosidase reporter gene present in the gene trap vector in BTF3 heter ozygotes was restricted. Mice homozygous for the mutant allele died so on after implantation, around embryonic day 6.5. Thus, BTF3 is essenti al for postimplantation development. The isolation of the BTF3 sequenc es in this ROSA beta-geo insertion was facilitated by a relatively sim ple single lacZ primer reverse transcription PCR strategy.