CDKN1C and hydatidiform mole: CDKN1C shows preferential expression from the maternal allele.39 A pregnancy abnormality called a full hydatidiform mole arises from an androgenetic pregnancy in which all genetic material is of paternal origin, and thus placental cells in hydatidiform moles feature loss of CDKN1C as well as persistent trophoblastic outgrowth.40 hTSC upregulate CDKN1C at high confluence, and CDKN1C−/− hTSC lose contact inhibition and continue growing after reaching confluence.38