Table 1.

Imprinted genes highly expressed in the placenta. Origin, parental origin of the expressed allele; M, maternally expressed; P, paternally expressed; ncRNA, non-coding RNA; FGR, fetal growth restriction; Dup, duplication; UPD, uniparental disomy; ICR, imprinting control region; LBW, low birthweight; BW, birthweight; HC, head circumference; CVS, chorionic villus sampling tissues; CRL, crown–rump length; PIP, phosphatidylinositol phosphate lipid; mat del, maternally inherited deletion; pat del, paternally inherited deletion; T1D, type 1 diabetes; TNDM, transient neonatal diabetes mellitus; BWS, Beckwith–Wiedemann syndrome; SRS, Silver–Russell syndrome; CNV, copy number variation; asterisk, findings from this study.

locus	gene	origin	description	mouse KO phenotypes	human growth phenotypes
6q24	PLAGL1	P	zinc finger protein	FGR, bone malformation, high neonatal lethality [15]	TNDM (pUPD6, pDup6q24, ICR hypomethylation) [16]
6q25	IGF2R	M/biallelic	clearance of IGF2	fetal and placental overgrowth, organ and skeletal abnormalities [11]	CVS expression positively correlated to BW [17] and CRL*
7p12	GRB10	M/P	GF receptor-bound protein	fetal and placental overgrowth [10]	implicated in SRS (mDup7p11.2–13) [18]; term placenta expression negatively associates with HC*
7q21.3	PEG10	P	retrotransposon derived	embryonic lethal due to placental malformation [19]	hypermethylation at ICR and reduced expression in LBW cord blood [20]; upregulated in FGR placenta [21]
7q32.2	MEST	P/biallelic	α/β hydrolase fold family	fetal and placental growth restriction, high postnatal lethality, abnormal maternal behaviour [12]	implicated in SRS (mUPD 7q31-qter) [22]
11p15	H19	M	long ncRNA	fetal and placental overgrowth [13,23]	ICR1 hypomethylation [24] and CNV [25] in SRS
	IGF2	P	growth factor	fetal and placental growth restriction	CVS expression positively correlated to BW [17] and CRL*; implicated in BWS and Wilm's tumour [26]
	CDKN1C	M	tumour suppressor	gestational fetal and placental overgrowth [27]	mutated in IMAGe [28], BWS [29] and SRS [30] patients
	SLC22A18	M	organic cation transporter	not reported	term placenta expression associated with HC [31]
	PHLDA2	M	PH domain, PIP binding	placental overgrowth [32]	highly expressed in lower BW and FGR placenta [21,33–35]; promoter variant associated with BW [36]
14q32	DLK1	P	transmembrane glycoprotein	pre- and postnatal growth restriction, high perinatal lethality, obese postnatally [37]	associated with T1D [38], UPD14 syndromes [26], T1D SNP correlated to BW*
	MEG3	M	ncRNA	postnatal lethal (mat del), pre- and postnatal growth restriction, high perinatal lethality (pat del) [39]	associated with T1D [38], reduced expression in FGR placenta [35]
19q13.4	PEG3	P	zinc finger protein	placental and fetal growth restriction, abnormal maternal behaviour [14]	tumour suppressor [40]