Trends of fetal chromosome analysis by amniocentesis before and after beginning of noninvasive prenatal testing: A single-center experience in Japan.

AIM: This study is to investigate the role of amniocentesis for prenatal diagnosis before and after the beginning of noninvasive prenatal testing (NIPT) in Japan. METHODS: We performed a retrospective analysis of genetic amniocentesis at mid-trimester (15-20 gestational weeks) for fetal karyotype analysis at Nagoya City University between April 2006 and March 2020. The indications, test results, and the detection rate of fetal abnormal karyotype were compared before (phase 1, P1) and after (phase 2, P2) beginning of NIPT at April 2013. RESULTS: A total of 2458 (P1: 1132, P2: 1326) amniocentesis were enrolled in this study. The most frequent indication was advanced maternal age in both phases (P1: 78.2% %, P2: 81.1%). In P2, 110 patients (8.3%) received amniocentesis after positive or nonreportable NIPT results. Other indications were fetal abnormal findings by ultrasounds (P1: 15.4%, P2: 17.7%), abnormal maternal serum screening results (P1: 8.0%, P2: 10%), previous child with fetal chromosome aberration (P1: 6.5%, P2: 3.5%), and translocation of either partner (P1:1.5%, P2: 2.1%). The detection rate for fetal chromosomal aberrations including all indications was significantly increased in P2 (15.9%, 95% CI 14.0-18.0) as compared to P1 (9.0%, 7.4-10.8). However, if the indication was only advanced maternal age, the positive detection rate kept low in both phases (P1: 5.2%, 3.7-7.1, P2: 4.2%, 2.9-5.9). CONCLUSION: Since the initiation of NIPT, the detection rate of fetal chromosomal abnormalities was higher in this study, suggesting that amniocentesis cannot be strongly recommended for advanced maternal age alone.

Performance and outcomes of noninvasive prenatal testing for twin pregnancies in Japan.

AIM: The purpose of this study was to describe the characteristics of women with twin pregnancies who undergo noninvasive prenatal testing (NIPT) as well as the post-partum and neonatal outcomes of such cases in Japan. METHODS: The study population consisted of women who were pregnant with twins and who underwent NIPT using massively parallel sequencing (MPS) at Nagoya City University Hospital between April 2013 and June 2016. Questionnaires were completed pre-NIPT and post-partum. RESULTS: Among 4009 women who underwent NIPT during the study period, 75 women (1.9%) were pregnant with twins. Fifteen women (20%) experienced vanishing twin/intrauterine fetal deaths at <22 weeks, and 60 women (80%) had normal twin pregnancies at the time of genetic counseling for NIPT. The use of NIPT was correlated with increased proportions of women using assisted reproductive technology (ART). The test had a high performance, with a false-positive rate of 1.7% and no false negatives. CONCLUSION: In this study, NIPT had a high performance, with a false positive rate of 1.7% and no false negatives. When treating women with twin pregnancies, the efficacy of NIPT should be explained during genetic counseling. Further larger studies are required to assess the reliability and validity of NIPT in twin pregnancies.

Recognition of cyclic-di-GMP by a riboswitch conducts translational repression through masking the ribosome-binding site distant from the aptamer domain.

The riboswitch is a class of RNA-based gene regulatory machinery that is dependent on recognition of its target ligand by RNA tertiary structures. Ligand recognition is achieved by the aptamer domain, and ligand-dependent structural changes of the expression platform then usually mediate termination of transcription or translational initiation. Ligand-dependent structural changes of the aptamer domain and expression platform have been reported for several riboswitches with short (<40 nucleotides) expression platforms. In this study, we characterized structural changes of the Vc2 c-di-GMP riboswitch that represses translation of downstream open reading frames in a ligand-dependent manner. The Vc2 riboswitch has a long (97 nucleotides) expression platform, but its structure and function are largely unknown. Through mutational analysis and chemical probing, we identified its secondary structures that are possibly responsible for switch-OFF and switch-ON states of translational initiation.

Mutational analysis of structural elements in a class-I cyclic di-GMP riboswitch to elucidate its regulatory mechanism.

The Vc2 riboswitch possesses an aptamer domain belonging to the class-I c-di-GMP riboswitch family. This domain has been analysed and the molecular mechanism by which it recognizes the c-di-GMP ligand has been elucidated. On the other hand, the regulatory mechanism of the full-length Vc2 riboswitch to control its downstream open reading frame (ORF) remains largely unknown. In this study, we performed in vivo reporter assays and in vitro biochemical analyses of the full-length riboswitch and its aptamer domain. We evaluated the results of in vivo and in vitro analyses to elucidate the regulatory mechanism of the Vc2 riboswitch. The present results suggest that recognition of c-di-GMP ligand by the Vc2 riboswitch aptamer domain downregulates expression of its downstream ORF primarily at the translational level.

Optimization of RNA-based c-di-GMP fluorescent sensors through tuning their structural modules.

Cyclic diguanylate (c-di-GMP) is a second messenger of bacteria and its detection is an important issue in basic and applied microbiology. As c-di-GMP riboswitch ligand-binding domains (aptamer domains) capture c-di-GMP with high affinity and selectivity, they are promising platforms for the development of RNA-based c-di-GMP sensors. We analyzed two previously reported c-di-GMP sensor RNAs derived from the Vc2 riboswitch. We also designed and tested their variants, some of which showed improved properties as RNA-based c-di-GMP sensors.