目的 探讨7个假肥大型肌营养不良(DMD)性腺嵌合体家系的遗传学病因。 方法 选择2014年9月至2022年3月就诊于中信湘雅生殖与遗传专科医院的7个DMD性腺嵌合体家系为研究对象。收集家系的临床资料，应用胚胎植入前单基因遗传学检测(PGT-M)对家系6先证者的母亲进行助孕，采集7个家系的先证者、先证者母亲及其他患者的外周静脉血样、家系1 ~ 4胎儿的羊水、家系6体外培养胚胎的细胞，提取基因组DNA，用多重连接探针扩增(MLPA)对DMD基因进行检测，对家系1 ~ 3、5 ~ 6先证者、其他患者、胎儿、体外培养胚胎进行基于短串联重复序列(STR)/单核苷酸多态性(SNP)的单体型分析。 结果 MLPA检测结果显示，家系1 ~ 4、5、7的先证者与胎儿/先证者弟弟存在相同的DMD基因变异，其母亲DMD基因均未见异常；家系6的先证者仅与1枚体外培养胚胎(共9枚)存在相同的DMD基因变异，其母亲与通过PGT-M成功助孕胎儿的DMD基因均未见异常。STR单体型分析结果显示家系1 ~ 3、5的先证者与胎儿/先证者弟弟均遗传了相同的母源X染色体；SNP单体型分析结果显示，家系6先证者仅与1枚体外培养的胚胎(共9枚)继承了相同的母源X染色体。家系1胎儿与家系6中PGT-M助孕成功胎儿出生后随访均健康，家系2 ~ 3先证者的母亲选择了引产。 结论 基于STR/SNP的单体型分析是判断性腺嵌合体的有效方法，对生育过DMD基因变异患儿而外周血基因型正常的女性应考虑性腺嵌合体风险，再次妊娠时建议进行产前诊断与生殖干预，避免缺陷患儿的出生。 Objective To explore the genetic basis for 7 families with gonadal mosaicism for Duchenne muscular dystrophy (DMD). Methods For the 7 families presented at the CITIC Xiangya Reproductive and Genetic Hospital from September 2014 to March 2022, clinical data were collected. Preimplantation genetic testing for monogenic disorders (PGT-M) was carried out for the mother of the proband from family 6. Peripheral venous blood samples of the probands, their mothers and other patients from the families, amniotic fluid samples from families 1 ~ 4 and biopsied cells of embryos cultured in vitro from family 6 were collected for the extraction of genomic DNA. Multiplex ligation-dependent probe amplification (MLPA) was carried out for the DMD gene, and short tandem repeat (STR)/single nucleotide polymorphism (SNP)-based haplotypes were constructed for the probands, other patients, fetuses and embryos. Results The results of MLPA showed that the probands and the fetuses/probands′ brothers in families 1 ~ 4, 5, 7 had carried the same DMD gene variants, whilst the probands′ mothers were all normal. The proband in family 6 carried the same DMD gene variant with only 1 embryo (9 in total) cultured in vitro, and the DMD gene of the proband′s mother and the fetus obtained through the PGT-M were normal. STR-based haplotype analysis showed that the probands and the fetuses/probands′ brothers in families 1 ~ 3 and 5 have inherited the same maternal X chromosome. SNP-based haplotype analysis showed that the proband from family 6 has inherited the same maternal X chromosome with only 1 embryo (9 in total) cultured in vitro. The fetuses in families 1 and 6 (via PGT-M) were both confirmed to be healthy by follow up, whilst the mothers from families 2 and 3 had chosen induced labor. Conclusion Haplotype analysis based on STR/SNP is an effective method for judging gonad mosaicism. Gonad mosaicisms should be suspected for women who have given births to children with DMD gene variants but with a normal peripheral blood genotype. Prenatal diagnosis and reproductive intervention may be adapted to reduce the births of further affected children in such families.
Abstract
Objective To explore the genetic basis for 7 families with gonadal mosaicism for Duchenne muscular dystrophy (DMD). Methods For the 7 families presented at the CITIC Xiangya Reproductive and Genetic Hospital from September 2014 to March 2022, clinical data were collected. Preimplantation genetic testing for monogenic disorders (PGT-M) was carried out for the mother of the proband from family 6. Peripheral venous blood samples of the probands, their mothers and other patients from the families, amniotic fluid samples from families 1 ~ 4 and biopsied cells of embryos cultured in vitro from family 6 were collected for the extraction of genomic DNA. Multiplex ligation-dependent probe amplification (MLPA) was carried out for the DMD gene, and short tandem repeat (STR)/single nucleotide polymorphism (SNP)-based haplotypes were constructed for the probands, other patients, fetuses and embryos. Results The results of MLPA showed that the probands and the fetuses/probands′ brothers in families 1 ~ 4, 5, 7 had carried the same DMD gene variants, whilst the probands′ mothers were all normal. The proband in family 6 carried the same DMD gene variant with only 1 embryo (9 in total) cultured in vitro, and the DMD gene of the proband′s mother and the fetus obtained through the PGT-M were normal. STR-based haplotype analysis showed that the probands and the fetuses/probands′ brothers in families 1 ~ 3 and 5 have inherited the same maternal X chromosome. SNP-based haplotype analysis showed that the proband from family 6 has inherited the same maternal X chromosome with only 1 embryo (9 in total) cultured in vitro. The fetuses in families 1 and 6 (via PGT-M) were both confirmed to be healthy by follow up, whilst the mothers from families 2 and 3 had chosen induced labor. Conclusion Haplotype analysis based on STR/SNP is an effective method for judging gonad mosaicism. Gonad mosaicisms should be suspected for women who have given births to children with DMD gene variants but with a normal peripheral blood genotype. Prenatal diagnosis and reproductive intervention may be adapted to reduce the births of further affected children in such families.
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