Transgene constructs.

(A) Genomic organization of the human CSF-1 gene, in which the mouse CSF-1 intron–exon boundaries are conserved, showing exons (1-10), reported alternative splicing events (I-V), oligonucleotide primers forCsf1^op mutation genotyping (P1, P2), and the exon 10 RPA probe used to detect exon 10–containing mRNA expression. (B) TgN(FLCsf1)Ers, or TgC, encoding full-length mouse CSF-1 and comprising exons 2 to 9, derived from alternative splicings I and IV and the hGH poly(A) addition site (hatched), under the control of the CSF-1 promoter and first intron, showing relevant restriction enzyme sites, the oligonucleotide primers used for genotyping (P3, P4), the transmembrane domain (TM), and the RPA probe used to detect the transgene and exon 9–containing mRNAs. (C) TgN(Csf1-Z)Ers, or TgZ, encoding lacZ under the control of the CSF-1 promoter and first intron. Positions of the mutated ATG (*ATG), translation start codon (ATG), SV40 nuclear localization sequence (NLS) (checkered),lacZ coding sequence, SV40 polyadenylation signal (heavy crosshatch), and oligonucleotide primers (P5, P6) used to detect the transgene by PCR are indicated.