Chenming Xu

A method for noninvasive detection of fetal large deletions/ duplications by low coverage massively parallel sequencing

To report the feasibility of fetal chromosomal deletion/duplication detection using a novel bioinformatic method of low coverage whole genome sequencing of maternal plasma.

Insufficient maintenance DNA methylation is associated with abnormal embryonic development

BackgroundEarly pregnancy loss (EPL) is a frustrating clinical problem, whose mechanisms are not completely understood. DNA methylation, which includes maintenance methylation and de novo methylation directed by DNA methyltransferases (DNMTs), is important for embryo development. Abnormal function of these DNMTs may have serious consequences for embryonic development.MethodsTo evaluate the possible involvement of DNA methylation in human EPL, the expression of DNMT proteins and global methylation of DNA were assessed in villous or decidua from EPL patients. The association of maintenance methylation with embryo implantation and development was also examined.ResultsWe found that DNMT1 and DNMT3A were both expressed in normal human villous and decidua. DNMT1 expression and DNA global methylation levels were significantly down-regulated in villous of EPL. DNMT3A expression was not significantly changed in the EPL group compared to controls in either villous or decidua. We also found that disturbance of maintenance methylation with a DNMT1 inhibitor may result in a decreased global DNA methylation level and impaired embryonic development in the mouse model, and inhibit in vitro embryo attachment to endometrial cells.ConclusionsOur results demonstrate that defects in DNA maintenance methylation in the embryo, not in the mother, are associated with abnormal embryonic implantation and development. The findings of the current study provide new insights into the etiology of EPL.

Noninvasive prenatal testing of trisomies 21 and 18 by massively parallel sequencing of maternal plasma DNA in twin pregnancies.

The objective of this study is to assess the performance of noninvasive prenatal testing for trisomies 21 and 18 on the basis of massively parallel sequencing of cell‐free DNA from maternal plasma in twin pregnancies.

Effects of In Vitro Maturation on Histone Acetylation in Metaphase II Oocytes and Early Cleavage Embryos

In vitro maturation (IVM) of oocyte is an effective procedure for avoiding ovarian hyperstimulation syndrome in patients with polycystic ovaries (PCOS) during in vitro fertilization (IVF). To investigate the influences of IVM on epigenetic reprogramming and to search for the possible reasons for the lower rates of fertilization and cleavage in IVM oocytes, we examined the expression of two enzymes controlling histone acetylation, histone acetyltransferase GCN5 (GCN5) and histone deacetylase 1 (HDAC1), as well as their common target, acetyl-histone H3 (Ac-H3), in mouse metaphase II (MII) oocytes and preimplantation embryos. Results showed that IVM downregulated the protein expression of GCN5 in MII oocytes and two-cell embryos and changed the distribution of GCN5 in two-cell embryos. Expression of HDAC1 mRNA in MII oocytes and two-cell embryos decreased in the IVM group. However, none of these changes persisted after two-cell embryos. Levels of Ac-H3 in both oocytes and embryos remained unchanged after IVM. Our studies indicated that IVM could affect the protein and gene expression related to histone acetylation in oocytes and early cleavage embryos. By function of selection, parts of the changes could be recovered in late embryo development.

Meiotic segregation analysis of embryos from reciprocal translocation carriers in PGD cycles

Meiotic segregation patterns of 278 embryos from 41 preimplantation genetic diagnosis cycles of 34 reciprocal translocation carriers were analysed to investigate whether some characteristics of reciprocal translocation, including terminal breakpoints, acrocentric chromosome or carrier gender, are related to meiotic segregation patterns. The incidence of normal/balanced karyotypes in translocations with terminal breakpoints was significantly lower than those without terminal breakpoints (6.5% versus 14.4%, P = 0.005). The incidences of adjacent-1 (21.0% versus 29.6%), adjacent-2 (16.1% versus 11.1%) and 3:1 (41.9% versus 30.6%) segregation were not statistically significantly different in translocations with terminal breakpoints versus those without. Translocation with acrocentric chromosomes showed a significantly lower rate of 2:2 segregation (39.2% versus 60.2%, P = 0.001) and a higher rate of 3:1 segregation (43.1% versus 27.3%, P = 0.005) than those without acrocentric chromosomes. The incidence of 2:2 segregation was significantly higher in male than in female carriers (58.2% versus 45.0%, P = 0.019). This study suggested that reciprocal translocation involving terminal breakpoints resulted in a lower rate of normal/balanced karyotype in preimplantation embryos. Some characteristics of reciprocal translocation, such as terminal breakpoints, acrocentric chromosome and carrier gender, are related to the segregation patterns.

Different sperm sources and parameters can influence intracytoplasmic sperm injection outcomes before embryo implantation

To evaluate the effects of sperm with different parameters and sources on the outcomes of intracytoplasmic sperm injection (ICSI), 1972 ICSI cycles were analyzed retrospectively. Groups 1 to 5 were composed of cycles using ejaculated sperm and were grouped according to sperm quantity, quality, and morphology into normal (288 cycles), or mild (329 cycles), moderate (522 cycles), severe (332 cycles), and extremely severe (171 cycles) oligozoospermia and/or asthenozoospermia and/or teratozoospermia (OAT) groups. Group 6 was composed of 250 cycles using testicular or epididymal sperm, and Group 7 consisted of 80 cycles using frozen-thawed sperm. We found that fertilization rates were gradually reduced from Groups 1 to 6, and reached statistical difference in Groups 5 and 6 (P<0.05). The high-quality embryo rate was higher in Group 1 than in Groups 2, 3, 5, 6, and 7 (P<0.05). No statistical differences were observed in the rates of embryo cleavage, clinical pregnancy, miscarriage, live-birth, premature birth, low birth weight, weeks of premature birth, average birth weight, or sex ratio for all seven groups (P>0.05). A total of nine cases of malformation were observed, with a malformation rate of 1.25% (9/719). In conclusion, different sperm sources and parameters can affect ICSI outcomes before embryo implantation. A full assessment of offspring malformation will require further study using a larger sample size.

Triplet pregnancy and successful twin delivery in a patient with congenital cervical atresia who underwent transmyometrial embryo transfer and multifetal pregnancy reduction

OBJECTIVE To report an unusual case of congenital cervical atresia and tubal factor infertility, achieving triplet pregnancy through transmyometrial embryo transfer (ET) resulting in the delivery of healthy twins after multifetal pregnancy reduction (MFPR). DESIGN Case report and literature review. SETTING University hospital. INTERVENTION(S) Controlled ovarian hyperstimulation, oocyte retrieval, in vitro fertilization, transmyometrial ET, MFPR procedure for triplet pregnancy. PATIENT(S) A 33-year-old patient with endometriosis-associated and tubal factor infertility who underwent uterovaginal canalization surgery for congenital cervical atresia 9 years ago. MAIN OUTCOME MEASURE(S) Successful delivery after transmyometrial ET followed by MFPR. RESULT(S) A total of three IVF cycles and four procedures of transmyometrial ET were performed. In the third cycle a triplet pregnancy was achieved. MFPR was performed 35 days after embryos transfer, two healthy babies delivered at 31 weeks gestation. CONCLUSION(S) With aggressive therapy, successful pregnancy is possible in similar patients.

A novel mutation of IDS gene in a Chinese patient with mucopolysaccharidosis II by next-generation sequencing.

BACKGROUND Mucopolysaccharidosis (MPS) is induced by the absence or malfunctioning of lysosomal enzymes. MPS I and MPS II are similar in phenotypes but they are different in genotypes, which are caused by the deficiencies of alpha-L-iduronidase gene (IDUA) and iduronate 2-sulfatase gene (IDS) respectively. In this work, a 5-year-old Chinese young male with manifestations of MPS in a family with unaffected parents was described. METHODS 12 kb of all the targeted exon sequences plus flanking sequences chromosomal DNA of IDS and IDUA genes from the proband and 20 other case-unrelated controls were captured and sequenced by using next-generation sequencing technology. RESULTS One single-nucleotide deletion variant (c.1270delG) resulting in frameshift and premature truncation of I2S enzyme was detected, out of 20 controls, only in the proband, and which was further verified by Sanger sequencing. The probands mother was also proved carrying c.1270delG by Sanger method but not for his father. CONCLUSIONS The novel variant (c.1270delG) is a candidate disease-causing mutation predicted to affect the normal structure and function of the enzyme. Target sequence capture and next-generation sequencing technology can be effective for the gene testing of MPS II disorder.

Effective Noninvasive Zygosity Determination by Maternal Plasma Target Region Sequencing

Background Currently very few noninvasive molecular genetic approaches are available to determine zygosity for twin pregnancies in clinical laboratories. This study aimed to develop a novel method to determine zygosity by using maternal plasma target region sequencing. Methods We constructed a statistic model to calculate the possibility of each zygosity type using likelihood ratios (Li) and empirical dynamic thresholds targeting at 4,524 single nucleotide polymorphisms (SNPs) loci on 22 autosomes. Then two dizygotic (DZ) twin pregnancies,two monozygotic (MZ) twin pregnancies and two singletons were recruited to evaluate the performance of our novel method. Finally we estimated the sensitivity and specificity of the model in silico under different cell-free fetal DNA (cff-DNA) concentration and sequence depth. Results/Conclusions We obtained 8.90 Gbp sequencing data on average for six clinical samples. Two samples were classified as DZ with L values of 1.891 and 1.554, higher than the dynamic DZ cut-off values of 1.162 and 1.172, respectively. Another two samples were judged as MZ with 0.763 and 0.784 of L values, lower than the MZ cut-off values of 0.903 and 0.918. And the rest two singleton samples were regarded as MZ twins, with L values of 0.639 and 0.757, lower than the MZ cut-off values of 0.921 and 0.799. In silico, the estimated sensitivity of our noninvasive zygosity determination was 99.90% under 10% total cff-DNA concentration with 2 Gbp sequence data. As the cff-DNA concentration increased to 15%, the specificity was as high as 97% with 3.50 Gbp sequence data, much higher than 80% with 10% cff-DNA concentration. Significance This study presents the feasibility to noninvasively determine zygosity of twin pregnancy using target region sequencing, and illustrates the sensitivity and specificity under various detecting condition. Our method can act as an alternative approach for zygosity determination of twin pregnancies in clinical practice.

Evaluation of human sperm function after being cryopreserved within the zona pellucida

OBJECTIVE To investigate the fertilization ability, chromatin structure, and DNA integrity of spermatozoa after being cryopreserved within an empty zona pellucida (ZP). DESIGN Prospective study. SETTING Reproductive research center in a university-affiliated hospital. PATIENT(S) Normozoospermic patients. INTERVENTION(S) Spermatozoa were cryopreserved within the ZP or with traditional methods. MAIN OUTCOME MEASURE(S) The sperm recovery rate, sperm motility, fertilization ability, chromatin structure, and DNA integrity were assessed before and after cryopreservation. RESULT(S) Significantly higher sperm recovery rate was identified for the spermatozoa cryopreserved within the ZP than those cryopreserved with traditional methods, but the motility recovery was similar. Frozen-thawed samples showed increased damage to the sperm chromatin and DNA, which were assessed by acridine orange test (AO) and terminal deoxynucleotidyl transferase-mediated dUDP nick-end labeling assay; however, no difference of chromatin and DNA integrity was observed for spermatozoa cryopreserved within the ZP or with traditional methods. In addition, the fertilization ability, as assessed by injecting spermatozoa into hamster oocytes, was similar for spermatozoa cryopreserved with different cryopreservation methods. CONCLUSION(S) Cryopreservation of spermatozoa within an empty ZP results in higher sperm recovery rate, and the post-thaw sperm functions of spermatozoa cryopreserved within the ZP are comparable with spermatozoa cryopreserved with traditional methods.