The POU1F1 transcription factor is expressed in the pituitary gland, where it regulates pituitary de- velopment and the expression of the growth hor- mone, prolactin and thyrotropin b-subunit genes (Cohen et al. 1996). The POU1F1 protein contains 2 domains, termed POU-specific and POU-homeo, which are both necessary for high-affinity DNA binding to genes encoding growth hormone and prolactin (Sturm et al. 1988). Mutations within the POU1F1 gene are associated with growth hor- mone, thyroid-stimulating hormone beta subunit, and prolactin deficiency and hypopituitarism in humans (Hendriks-Stegeman et al. 2001). It is proved that dwarfism in mice and humans can be associated with a low or absent POU1F1 gene ac- tivity. The porcine POU1F1 gene is located on chro- mosome 13, and it has 6 exons and 5 introns. Its cDNA sequence and partial genomic sequence have been characterized in several labs (Chung et al. 1998; Yu et al. 2001). Previous research has revealed its polymorphisms by using the POU1F1 POU domain probe, RFLP and PCR-RFLP tech- niques. The MspI polymorphisms were signifi- cantly correlated with pig birth weight in the Iowa State University pig resource families (Yu et al. 1995). The associations of POU1F1 haplotypes and the markers around POU1F1 (10–20 cM apart) with early weights and growth rate were confirmed by Yu et al. (1999). We demonstrated a significant genotype effect of POU1F1 on 45, 70, and 180-day body weight and average daily weight gain (ADG) in the finishing period in a crossbred pig population as well (Song et al. 2005). However, most of them were within the last 3 exons, and no polymorphism near the 5’ flanking region was reported. Actually, such polymorphisms are generally associated with the sequence elements and may completely abolish the inducibility of the promoter or decrease its activity significantly. J Appl Genet 48(4), 2007, pp. 371–374 Short communication Polymorphisms in intron 1 of the porcine POU1F1 gene Cheng-Yi Song 1 , Bo Gao 1 , Shang-Hui Teng 1 , Xiao-Yang Wang 1 , Fei Xie 1 , Guo-hong Chen 1 , Zhi-Yue Wang 1 , Rong-bin Jing 1 , Jiu-De Mao 2 1 College of Animal Science & Technology, Yangzhou University, Jiangsu, China 2 Division of Biological Sciences, University of Missouri-Columbia, Columbia, MO, USA Abstract. This study was conducted to detect polymorphisms in intron 1 of porcine POU1F1 (POU domain, class 1, transcription factor 1, Pit1, renamed as POU1F1) by comparative sequencing. Within the intron, 23 sites of variation were identified, including 16 single-nucleotide substitutions, 4 single-nucleotide indels, 2 short (3-bp and 17-bp), and one long (313-bp) indels. Several important regulatory motifs were found within the 313-bp indel by in silico analysis. The 313-bp indel was next genotyped in 11 Chinese native pig breeds and 4 western meat-type pig breeds. The appearance of genotypes varied between breeds: among Chinese native breeds, no AA and AB genotypes were found in Tibetan, Lingao, Min, Rongchang, and Songliao Black pigs, no AA genotype was found in Fenjing and Leping Spotted pigs, whereas in Pietrain and Landrace there were no BB genotypes, and all 19 Duroc pigs were AA homozygotes. The western meat-type pigs had high A allele frequencies and the Chi- nese pigs had more B alleles, except Jianquhai pigs. A positive association of the AA genotype with birth weight was observed in a commercial pig line. This paper demonstrated that the genetic variation in intron 1 of the pig POU1F1 gene was high and these polymorphisms may provide useful makers for QTL analysis. Keywords: early growth traits, genotyping, intron 1, pig, polymorphism, Pit1, POU1F1. Received: May 25, 2007. Revised: July 8, 2007. Accepted: August 18, 2007. Correspondence: C.Y. Song, College of Animal Science & Technology, Yangzhou University, 12 Wenhui East Road, Yangzhou, Jiangsu Province, 225009, P.R, China; e-mail: chengyilab@hotmail.com