Aqp1 (aquaporin 1) showed exclusive maternal expression in the placentas of reciprocal crosses of
C57BL/6J and DBA/2 mice (12 placentas were examined and all showed maternal expression - personal
communication). In heterozygous knockout mice, loss of the maternal, but not the paternal allele
resulted in placental and embryonic overgrowth, an increased number and branching of blood vessels,
and an increase in the labyrinth area in placentae of E12.5–E18.5 mice (Guo J et al, 2016). A differentially
methylated region could not be detected.