Isolation, characterization and chromosomal localization of the porcine ciliary neurotrophic factor (CNTF) gene

In the mouse, ciliary neurotrophic factor (CNTF) maintains embryonic stem cells in an undifferentiated state; yet, the heterologous protein has no similar effects on porcine embryonic stem (ES) cells. Consequently, we cloned and sequenced the porcine CNTF gene and assigned it to chromosome 2. The CNTF gene was found to contain two exons, which encoded a deduced polypeptide of 200 amino acids in length with 83%, 82%, 82% and 81% amino acid similarity when compared to known sequences in the rabbit, rat, human and mouse, respectively. Eight non-conservative amino acid changes were identified in the porcine protein when compared with other species. Comparison of the 5' region of the porcine CNTF and other mammalian cytokines indicated the presence of several conserved transcription-factor binding motifs, suggesting their importance for controlling the specific expression of these proteins. In addition, CNTF was localized to porcine chromosomes by fluorescence in situ hybridization (FISH). Chromosome arm length ratios were calculated for 40 early metaphase chromosomes and 32 (80%) indicated that the pig CNTF gene is located on chromosome 2p1.6. This was confirmed by aligning R-banded FISH-labelled chromosomes to the standard porcine ideogram.