The mouse Pon genes show similarity with the three human PON genes that are closely related paralogs
(65% amino acid similarity). In the mouse Pon2 is ubiquitously expressed and biallelic expression
was observed in neonatal brain, skeletal muscle, spleen, kidney, liver and lung tissues. Significant
preferential maternal expression was observed in placental and yolk sac tissues (day 10 and 13
respectively). The Pon genes are part of a larger cluster of imprinted genes on mouse chromosome 6,
which include the paternally expressed genes Peg10 and Sgce (Ono
R, et al. 2003).
D et al, (2008) confirmed extra-embryonic specific preferential maternal expression.
However, Okae H et al, (2012) provided
strong evidence of negligible expression of Pon2 by qPCR and whole transcriptome sequencing in E
13.5 placentas. They suggest that this gene is not imprinted. This is concordant with Proudhon and Bourc'his, (2010) caution that maternal contamination of placental tissues may
cause apparent imprinted maternal expression.