Relevance of sperm imprinted gene methylation on assisted reproductive technique outcomes and pregnancy loss: a systematic review

Figures & data

Table 1. Summary of the studies included in this review

Author(s)	Year	Country	Population	Outcome	Results
Sperm DNA fragmentation
Darbandi et al.	Darbandi et al. 2019	Iran	151 normozoospermic men	Methylation of H19, IGF2	ROS positively correlates with the IGF2 gene methylation status (r = 0.19, p < 0.05), SDF (r = 0.40, p < 0.05), and negatively with H19 methylation (r = −0.20, p < 0.05)
Ni et al.	Ni et al. 2019	China	66 semen samples	Methylation of H19, IGF2, KCNQ1, GTL2, MEST, PEG3, SNRPN	The mean methylation level of IGF2 in the group with DFI ≥25% was lower compared to the group with DFI <25% (13.7 ± 3% vs. 31.5 ± 5.3%, p < 0.05) IGF2 methylation negatively correlates with DFI (r = −0.448, p < 0.05) KCNQ1 methylation positively correlates with SDF (r = 0.354, p < 0.05)
Pregnancy loss
Ankolkar et al.	2012	India	26 patients with idiopathic recurrent pregnancy loss 26 controls	Methylation of H19	Methylation of H19 was significantly reduced in patients compared to controls
Ankolkar et al.	2013	India	23 patients with idiopathic recurrent pregnancy loss 23 controls	Methylation of GTL2, MEST, PLAGL1	No difference in methylation rate of the investigated genes between patients and controls
ART outcome
El Hajj et al.	El Hajj et al. 2011	Germany	141 sperm samples from couples undergoing to ART: 106 undergoing to ART for male-factor infertility 28 undergoing to ART for female-factor infertility (controls)	Methylation of H19, GTL2, LIT1, MEST, NESPAS, PEG3, SNRPN	Patients showed significantly lower H19 methylation compared to controls (92.3 ± 3.5% vs. 93.1 ± 2.2%, p < 0.05) Patients showed significantly lower SNRPN methylation compared to controls (3.8 ± 2.1% vs. 4.9 ± 3.0%, p < 0.05) Fertilization rate and ART outcome did not differ between sperm samples with normal versus abnormal methylation imprints
Kuhtz et al.	2014	Germany	54 couples undergoing to ART: 27 men with normal sperm parameters 27 patients with OAT	Methylation of GTL2, LIT1, PEG3, SNRPN	The percentage of abnormally demethylated GTL2 alleles was significantly higher in sperm samples with negative ART outcome, than in those leading to a child after ICSI Percentage of abnormally methylated PEG3 alleles was different among groups
Montjean et al.	2013	France	294 men with normal karyotype: 119 with normozoospermia 116 with mild oligozoospermia 59 with severe oligozoospermia	Methylation of MEST, H19	20% of patients with oligozoospermia shows methylation errors in the H19 gene Hypermethylation of PEG1/MEST was found in 3.3% and in 3% of mild oligozoospermic or severe oligozoospermic patients, respectively No difference in ART outcome between oligozoospermic patients with altered methylation profile compared to oligozoospermic patients with normal methylation profile
Tang et al.	2017	China	97 infertile patients and 31 proven fertile men. Infertile patients were grouped in 69 cases with normal imprinting and 24 cases with abnormal imprinting	Methylation of H19, SNRPN, LIT1	H19 methylation was significantly lower in infertile patients compared to controls (91.6 ± 3.0% vs. 93.1 ± 2.1%). No significant difference was found for SNRPN (2.2 ± 5.0% vs. 1.3 ± 1.7%) and LIT1 (0.9 ± 1.7% vs. 0.6 ± 0.9%) No difference in fertilization, good embryo, clinical pregnancy, and delivery rates, as well as birth parameters (birth weight and delivery week) was found between patients with normal and abnormal imprinting in sperm
Cryopreservation
Khosravizadeh et al.	2020	Iran	10 healthy men	Methylation of SNRPN, UBE3A	No change in the methylation pattern after cryopreservation
Klaver et al.	2012	Germany	10 normozoospermic men	Methylation of LIT1, SNRPN, MEST, GTL2, H19	No change in the methylation pattern after cryopreservation

Table 2. Summary of imprinted genes evaluated in the present study

Gene	OMIM	Chromosome	Imprinting	Gene function
DLK1	176290	14q32.2	Paternal	Encodes for an epidermal growth factor (DLK1)
GTL2 (or MEG3)	605636	14q32.2	Maternal	Encodes for a ncRNA involved in regulation of gene expression
H19	103280	11p15.5	Maternal	Encodes for a ncRNA involved in regulation of gene expression
IGF2	147470	11p15.5	Paternal	Encodes for a growth factor (IGF2)
KCNQ1	607542	11p15.5-p15.4	Maternal	Encodes for a polypeptide with structural features of a voltage-gated potassium channel
LIT1 (or KCNQ1OT1)	604115	11p15.5	Paternal	Encodes for the Long QT intronic transcript 1 (LIT1) RNA. The loss of imprinting is involved in the pathogenesis of the Beckwith-Wiedemann syndrome
MEST (or PEG1)	601029	7q32.2	Paternal	Loss of imprinting is involved in severe intrauterine growth retardation
NESPAS (or GNAS-AS1)	610540	20q13.32	Paternal	Encodes for an antisense transcript of the GNAS complex locus. Involved in the pathogenesis of pseudohypoparathyroidism type Ib
PEG3	601483	19q13.43	Paternal	Encodes for a zing finger protein expressed in ovary and placenta
PLAGL1 (or ZAC)	603044	6q24.2	Paternal	The knockdown in mice resulted in intrauterine growth restriction
SNRPN	182279	15q11.2	Paternal	Encodes for a small nuclear ribonucleoprotein polypeptide. It is involved in the pathogenesis of the Prader Willi syndrome

Abbreviations: DLK1, delta-like non canonical ligand 1; GNAS-AS1, GNAS complex locus, antisense transcript; GTL2, Gene trap locus 2; H19, imprinted maternally expressed non-coding transcript; IGF2, Insulin-like growth factor 2; KCNQ1, Potassium Channel, voltage-gated, KQT-like subfamily, member 1; KCNQ1OT1, KCNQ1-overlapping transcript 1; LIT1, Long QT intronic transcript 1; MEG3, maternally expressed gene 3; MEST, Mesoderm specific transcript; NESPAS, NESP antisense; PEG1, paternally expressed gene 1; PEG3, paternally expressed gene 3; PLAGL1, pleomorphic adenoma gene-like 1; SNRPN, small nuclear ribonucleoprotein polypeptide N; ZAC, ZAC tumor suppression gene.

Figure 1. PRISMA flow diagram

Darbandi M, Darbandi S, Agarwal A, Baskaran S, Dutta S, Sengupta P, Khorram Khorshid HR, Esteves S, Gilany K, Hedayati M, et al. 2019. Reactive oxygen species-induced alterations in H19-Igf2 methylation patterns, seminal plasma metabolites, and semen quality. J Assist Reprod Genet. 36(2):241–253. doi:10.1007/s10815-018-1350-y

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Ni W, Pan C, Pan Q, Fei Q, Huang X, Zhang C. 2019. Methylation levels of IGF2 and KCNQ1 in spermatozoa from infertile men are associated with sperm DNA damage. Andrologia. 51(5):e13239. doi:10.1111/and.13239.

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