Characterization, Tissue Expression, and Imprinting Analysis of the Porcine CDKN1C and NAP1L4 Genes

CDKN1C and NAP1L4 in human CDKN1C/KCNQ1OT1 imprinted domain are two key candidate genes responsible for BWS (Beckwith-Wiedemann syndrome) and cancer. In order to increase understanding of these genes in pigs, their cDNAs are characterized in this paper. By the IMpRH panel, porcine CDKN1C and NAP1L4 genes were assigned to porcine chromosome 2, closely linked with IMpRH06175 and with LOD of 15.78 and 17.94, respectively. By real-time quantitative RT-PCR and polymorphism-based method, tissue and allelic expression of both genes were determined using F1 pigs of Rongchang and Landrace reciprocal crosses. The transcription levels of porcine CDKN1C and NAP1L4 were significantly higher in placenta than in other neonatal tissues (P < 0.01) although both genes showed the highest expression levels in the lung and kidney of one-month pigs (P < 0.01). Imprinting analysis demonstrated that in pigs, CDKN1C was maternally expressed in neonatal heart, tongue, bladder, ovary, spleen, liver, skeletal muscle, stomach, small intestine, and placenta and biallelically expressed in lung and kidney, while NAP1L4 was biallelically expressed in the 12 neonatal tissues examined. It is concluded that imprinting of CDKN1C is conservative in mammals but has tissue specificity in pigs, and imprinting of NAP1L4 is controversial in mammalian species.