【作者】 冯晨；

【导师】 秦莹莹；

【作者基本信息】 山东大学 ， 妇产科学（专业学位）， 2023， 硕士

【摘要】 背景:环状染色体(ring chromosomes,RCs)是一种罕见的染色体结构异常,伴随或不伴随遗传物质的丢失,在临床妊娠中发生率仅为1/25000。RCs结构不稳定,在细胞分裂过程中可能产生动态嵌合体、丢失部分细胞成分,并由此产生高度异质的临床表现。其中最常表现为以严重生长迟缓和不同程度智力障碍为特征的环状染色体综合征(ring syndrome),其他表现还包括染色体特异性缺失和重复综合征、基因相关的器官和组织缺陷、肿瘤易感性以及生育障碍等。既往文献中曾以病例报告的形式提出RCs携带者面临的生育困境,如不孕、不育、自然流产及不良妊娠风险增加等,推测可能与RCs不稳定的染色体结构影响生殖细胞形成和减数分裂过程有关。随着辅助生殖技术尤其是胚胎植入前遗传学检测(preimplantation genetic testing,PGT)的发展,RCs携带者可以通过对胚胎进行遗传学分析,筛选整倍体胚胎,从而降低因胚胎非整倍体因素引起的不良妊娠结局发生风险。但是,由于RCs发生率极低,RCs携带者行PGT后助孕结局及胚胎核型分析的相关研究非常有限,缺乏RCs携带者诊疗的临床共识,RCs携带者的生殖遗传咨询仍面临诸多争议。目的:分析RCs携带者临床特征、助孕妊娠结局,行PGT-A助孕携带者分析胚胎整倍体率,为RCs携带者个体化生育指导提供理论参考和临床依据。方法:收集我院2014年3月-2022年4月行辅助生殖助孕的7例RCs携带者,根据携带者基本情况、妊娠结局及胚胎整倍体情况综合分析RCs携带者的助孕结局。结果:(1)共纳入7例RCs携带者,分别记为P1-P7。其中女性RCs携带者2例,P1为常染色体RC携带者,出现卵巢储备下降;P2为RC X嵌合体携带者,确诊早发性卵巢功能不全。5例男性携带者(P3-P7)中4例为常染色体RCs携带者、1例为RC Y嵌合体携带者,均表现为严重少精子症或无精子症。(2)4例携带者(1例女性、3例男性)行PGT-A:共检测胚胎33枚,其中整倍体胚胎8枚(24.24%)、非整倍体胚胎21枚(63.64%)、嵌合体胚胎4枚(12.12%),发生于亲缘RCs的非整倍体/嵌合体胚胎占32.00%(8/25)。女性携带者共检测胚胎11枚,其中整倍体胚胎1枚(9.09%)、非整倍体胚胎7枚(63.64%)、嵌合体胚胎3枚(27.27%),80.00%(8/10)为发生于亲缘RCs的非整倍体/嵌合体胚胎。男性携带者共检测胚胎22枚,其中整倍体胚胎7枚(31.82%)、非整倍体胚胎14枚(63.64%)、嵌合体胚胎1枚(4.55%),没有发生于亲缘RCs的非整倍体/嵌合体胚胎。男女RCs携带者胚胎整倍体率没有统计学差异,但女性RCs携带者亲缘RCs非整倍体/嵌合体胚胎发生风险显著高于男性RCs携带者(P<0.001)。(3)P1移植整倍体胚胎后未妊娠;3例男性RCs携带者的配偶移植整倍体胚胎后2例足月分娩、1例未妊娠。(4)4例携带者行供卵或供精助孕:P2接受供鲜卵助孕,未获得可移植胚胎;P6行供精人工授精(artificial insemination with donor sperm,AID)未妊娠,供精体外助孕移植后异位妊娠手术治疗;P4拟行PGT未获囊胚,配偶行AID及供精体外助孕均未妊娠;P7之配偶移植PGT检测可用囊胚未孕后,行AID妊娠,早产剖宫产1子1女。结论:RCs携带者胚胎整倍体率低,其中女性RCs携带者尤甚;RCs携带者行PGT筛选整倍体胚胎,能够降低胚胎因素导致的不良妊娠风险。男性发生21号染色体环化均表现为严重少弱精子症甚至无精子症,提示21号染色体空间结构改变或破坏可能影响了参与精子发生的关键基因的功能,具体机制有待于进一步研究。更多还原

【Abstract】 Background:Ring chromosomes,which is defined as the result of breakage and fusion at the distal regions of both chromosome arms,belong to a rare type of intra-chromosome structural abnormality with an estimated pregnancy incidence of 1 in 25,000,following the loss of genetic materials or not.Ring chromosome carriers are at a significantly increased risk of fertility difficulties such as infertility,spontaneous abortion,and neonatal growth retardation,which has been repeatedly presented in the case reports in the previous literatures.Due to the effects of multiple factors such as the low incidence of ring chromosomes and the limited level of genetic testing technology,the specific mechanism of adverse pregnancies in carriers remains unclear.With the advancement of assisted reproduction,especially the development of preimplantation genetic testing(PGT),ring chromosome carriers can receive euploid embryos through genetic analysis,thus significantly reduced the incidence of adverse pregnancies caused by chromosomal abnormalities.However,owing to the low incidence of ring chromosomes,the high mortality rate of severe phenotypic carriers and the potential low marriage rate,the reproduction situation of ring chromosome carriers are reported sporadically in the previous literature,and no clinical consensus on the pre-pregnancy and prenatal diagnosis of them are formed,which increase the limitations of reproductive genetic counseling for carriers.Objective:To investigate the meiosis behavior and genetic pattern of ring chromosome,the proportion of abnormal embryos and pregnancy outcomes of ring chromosome carriers,so as to provide more information for genetic counseling and assisted reproduction of carriers.Methods:Collecting and analyzing the blastocyst testing results and assisted reproductive outcomes of ring chromosome carriers during March 2014 to April 2022.The chromosomal composition of trophectoderm cells was defined by next generation sequencing and arraybased comparative genomic hybridization.The genetic pattern of ring chromosomes and the significance of PGT were synthetically analyzed according to the basic information of carriers,embryo karyotypes and pregnancy outcomes.Results:A total of 7 carriers were included and 2 female carriers showed decreased ovarian reserve in varying degrees and 5 male carriers showed oligospermia or azoospermia.Three carriers received oocyte/sperm donation.The carrier P2 received oocyte donation but did not obtain cleavage or blastocyst embryos.The carrier P4 intended to receive PGT but did not obtain blastocyst and received donor sperm later but failed to be pregnant.The carrier P6 underwent sperm donation but developed to ectopic pregnancy,which was treated with transabdominal surgery.Four carriers received PGT-A.For female carrier P1,only 1 euploid embryo was obtained in the second cycle,while transplantation was failed.For carrier P3,one euploid embryo was obtained in the first cycle but transplantation was failed,and in the second cycle,3 euploid embryos were obtained and a balanced embryo was implanted successfully,which had resulted a healthy boy.For carrier P5,2 euploid embryos were obtained and a balanced embryo was implanted successfully,which resulted in a healthy girl.For carrier P7,one euploid embryo was obtained but transplantation failed.A total of 33 embryos were detected,including 8 euploid embryos(24.24%)and 8 aneuploid/mosaic embryos with ring chromosome related abnormality(32.00%).Conclusions:Ring chromosome carrier,especially female carriers,have a low rate of embryo euploidy.Screening of euploid embryos by PGT can reduce the risk of adverse pregnancy caused by embryonic factors.更多还原