THE BABOON EXPRESSES THE CALBINDIN-D9K GENE IN INTESTINE BUT NOT IN UTERUS AND PLACENTA - IMPLICATION FOR CONSERVATION OF THE GENE IN PRIMATES

Expression of the Calbindin-D-9k (CaBP-9k) gene was studied in the bab oon. Northern blot analysis using a human CaBP-9k cDNA probe detected expression in duodenum but not in uterus and placenta. Reverse transcr iption/polymerase chain reaction (RT/PCR) confirmed this expression pa ttern and indicated a high degree of identity between the baboon and h uman CaBP-9k mRNAs. PCR was employed to amplify the intron A region of the baboon CaBP-9k gene using human-derived primers and baboon genomi c DNA. The baboon intron was closely related to the human CaBP-9k intr on A, including the presence a complete Alu-repetitive element. Most s ignificantly, a 13 nucleotide long element at the 5' end of the baboon intron matched exactly the human sequence. This element represents a nonfunctional variation of an estrogen response element found at the s ame location in the rat CaBP-9k gene. The rat element functions as an enhancer and mediates uterine and possibly placental CaBP-9k expressio n in the rat and probably most other mammals. The finding of a modifie d ERE in baboon as in human suggests that during primate evolution the expression of this mammalian-specific gene has been eliminated in ute rus and placenta. This scenario raises the question of the role of CaB P-9k in these reproductive tissues. (C) 1995 Wiley-Liss.