Mouse Pon3 (paraoxonase 3) is mainly expressed in the adult liver and lung
tissues. There is no evidence of imprinting in neonatal liver or lung. Maternally biased
expression was observed in placental and yolk sac tissues (day 10 and 13 respectively) although
strain specific effects were also detected. 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.
In addition biased maternal expression was observed in the visceral yolk sac (Hudson QJ et al, 2011).
However, Okae H et al, (2012) provided
strong evidence of negligible expression of Pon3 by qPCR and whole transcriptome sequencing in E
13.5 placentas. They suggest that this gene is not imprinted. This is concordant with the caution
from Proudhon and Bourc'his (2010) who suggest that maternal contamination of placental tissues may
cause apparent imprinted maternal expression.
In a Pon3 knockout mouse, which showed lethality in homozygotes, body weight and placental weight
were similar among the heterozygotes irrespective of the parent of origin of the mutant allele,
which is not supportive of imprinting (Kempster SL et al, 2012).