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ted and sequenced. The longest clone, Pld1a encodes a 1075 amino acid (aa) protein that was highly similar (89% identity) to human PLD1a, especially in four conserved regions present in other PLDs. The nucleotide sequence of the second clone was identical to that of Pld1a except that the clone lacked 114 nucleotides corresponding to 38 aa in the middle. A shorter alternatively spliced form of human PLD1 (PLD1b) lacking the corresponding 38 aa was also identified. Therefore, the second clone (Pld1b) was considered to correspond to the rat counterpart of human PLD1b. The third clone, Pld2 encoding 933 aa was smaller than that of Pld1 and its aa identity to rat Pld1 was 56%. However, it contains four conserved regions and aa sequences of these regions are homologous to those of rat Pld1 and human PLD1. Its entire aa sequence was very similar (96% identity) to the recently cloned mouse PLD, Pld2. Chromosome locations of the Pld1a, Pld1b and Pld2 genes were determined in the rat and mouse by fluorescent in situ hybridization. As expected, both Pld1a and Pld1b clones were hybridized to the same chromosome regions. The Pld1 and Pld2 genes were localized to rat chromosome 2q23.3-->q24 proximal end and the proximal region of mouse Chromosome 3B, and rat chromosome 10q23.3-->q24 proximal end and mouse Chromosome 11B3, respectively. They were mapped in regions where conserved linkage homology has been identified between the two species.