Mitochondrial DNA Variation In Patients With Early Embryonic Development Defects

Background Oocyte maturation,fertilization,and early embryonic development are complex and largely dependent on mitochondria to provide abundant energy.Mitochondria have a separate set of genetic material from the nuclear genes-mitochondrial DNA(mtDNA).Any quantitative or qualitative defects in the mtDNA may determine the alteration of the mitochondrial function,resulting in impairment of cellular oxidative phosphorylation and affecting intracellular ATP supply,leading to impaired oocyte maturation,abnormal fertilization,and low embryonic developmental potential,ultimately leading to female infertility.There is a relative lack of studies on mtDNA variants in patients with early embryonic developmental defects due to oogenic factors.Based on this,we set up this case-control study.Peripheral blood was collected from primary infertile women who suffered recurrent IVF and/or ICSI failures due to defects of early embryonic development and healthy controls.Mitochondrial genomic variation analysis was performed to reveal the relationship between mtDNA variants and early embryonic developmental defects.Objective To explore whether mtDNA variations affect early embryonic development.Materials and Methods In this study,we recruited 582 infertile women.All cases should meet the following criteria:1)20 years≤age≤40 years;2)with normal chromosome constitution;3)primary infertility;4)suffered≥2 failures of IVF and/or ICSI cycles with no available embryos for transfer;5)cases whose male partners have severe oligospermia,asthenozoospermia and teratozoospermia were excluded.A total of 1082 in-house controls of healthy women who had no history of infertility and a normal fetus delivered by natural pregnancy were collected.Peripheral blood was extracted from all subjects and next-generation sequencing was performed.Haplogroup classification was performed by MiTool;haplogroup frequencies,the frequency of mtDNA variants and the mean number of mtDNA variants were compared;the correlation between mtDNA variants and defects of early embryonic development was analyzed by logistic regression.Subsequently,Mitomap database was used to obtain the conservation index of the mtDNA variants and bioinformatics software was used to predict the effect of mtDNA variants and to assess potentially deleterious mtDNA variants in cases.Results 1)This study found that infertile women with early embryonic development defects carried more mtDNA variants,especially in the D-loop region(11.98±2.67 vs.11.68±2.69,p=0.030),ATP6 gene(1.34±0.91 vs.1.22±0.88,p=0.014),and CYTB gene(2.46±0.72 vs.2.34±0.67,p=0.001).2)By univariate logistic regression analysis,16 mtDNA variants were associated with the increased risk of early embryonic development defects,including D-loop region(T146C,A508G,A16066G,C16245T,T16249C,C16256T,T16311C,and T16519C),ATP8 gene A8459G,CYTB gene(T15071C,A15218G,G15314A,and A15851G),tRNAProT15968C,and RNR2 gene(C3172ins and A3221G).3)In addition,we further identified 16 mtDNA variants predicted by the software to be"potentially deleterious",including protein-coding variants(G3391A,A3721G,G6852A,T8516C,A9029G,T9167C,G11778A,and C11981T),tRNA region variants(A3243G,T3253C,A7551G,A12156G,A12177G,and A12286G)and rRNA region variants(C792T and T1452C),which were not present in the control group.Conclusion MtDNA variants are associated with early embryonic development defects in primary infertile women and increase the risk of abnormal embryonic development.