During mouse preimplantation development, the exclusive expression of the Xist gene from the paternally inherited allele is thought to play a role in the inactivation of the paternally inherited X chromosome in the extra-embryonic cell lineages of the developing female embryo. Recently, inactivation of the paternally inherited X chromosome has also been shown to occur in the extraembryonic cell lineages of the human female conceptus. In this paper, we determine whether the pattern of XIST expression in human preimplantation embryos is similarly correlated with paternal X inactivation. We developed procedures sensitive to the single cell, for the simultaneous analysis of XIST and HPRT expression and of sexing, initially using human fibroblast cells. Application of these procedures to human cleavage-stage embryos derived by in vitro fertilization revealed a pattern of XIST expression different from that in the mouse. Transcripts of the XIST gene were detected as early as the 1-cell zygote and, with increasing efficiency, through to the 8-cell stage of preimplantation development. In addition, transcripts of XIST were detected in both male (hence from the maternally inherited allele) and female preimplantation embryos. This pattern of expression is not consistent with a role for the early expression of the XIST gene in the choice of paternal X inactivation in the extraembryonic cell lineages of the developing human embryo.

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Background: In 2020, health systems across the world responded to the COVID-19 pandemic by making rapid changes to reduce the risk of exposure in patients and healthcare professionals. The use of point-of-care tests (POCT) has been a central strategy in dealing with the COVID-19 pandemic. The aims of this study were to evaluate the impact of POCT strategy (1) on maintaining elective surgeries by removing the risk of delayed pre-appointment testing and turn-around times and (2) on time dedicated for end-to-end appointment and management, and (3) to assess the feasibility of using the ID NOW® among healthcare professionals and patients in a primary care setting, requiring pre-surgical appointment and minor ENT surgery in the Townsend House Medical Centre (THMC), Devon, United Kingdom. Methods: A logistic regression was performed to identify factors associated with the risk of canceled or delayed surgeries and medical appointments. Second, a multivariate linear regression analysis was conducted to calculate changes in the time dedicated to administrative tasks. A questionnaire was developed to assess the acceptance of POCT in patients and staff. Results: 274 patients were included in this study; 174 (63.5%) in Group 1 (Usual Care) and 100 (36.5%) in Group 2 (Point of Care). Multivariate logistic regression showed that the percentage of postponed or canceled appointments was similar between the two groups (adjusted OR = 0.65, [95%CI: 0.22–1.88]; p = 0.42). Similar results were observed for the percentage of postponed or canceled scheduled surgeries (adjusted OR = 0.47, [95%CI: 0.15–1.47]; p = 0.19). The time dedicated to administrative tasks was significantly lowered by 24.7 min in G2 compared to G1 (p < 0.001). 79 patients in G2 (79.0%) completed the survey, and the majority agreed or strongly agreed that it improved care management (79.7%), decreased administrative time (65.8%), reduced the risk of canceled appointments (74.7%) and the traveling time to do COVID-19 test (91.1%). Having point-of-care testing in the clinic in the future seemed more than welcome by 96.6% of patients; 93.6% declared to be less stressed by having the test at the clinic than waiting for the results of the test realized elsewhere. The five healthcare professionals of the primary care center completed the survey, and all agreed that the POCT positively influences the workflow and can be successfully implemented into routine primary care. Conclusions: Our study shows that NAAT-based point-of-care SARS-CoV-2 testing significantly improved flow management in a primary care setting. POC testing was a feasible and well-accepted strategy by patients and providers.

We have detected a novel splice variant of the hypoxanthine-guanine phosphoribosyl transferase (HPRT) gene in two human oocytes and four preimplantation embryos from the 4-cell to the 8-cell stage of development. The novel HPRT transcript lacks exons 4, 5 and 6 of the normal HPRT gene. The same parental origin for the two oocytes and two of the preimplantation embryos, in which the alternatively spliced transcript was detected, might suggest that the alternative splicing is influenced by genetic background. Mutations in the HPRT gene which cause alternative mRNA splicing are implicated in Lesch-Nyhan syndrome. However, the relatively high frequency of detection of this novel HPRT transcript described here (6/109 oocytes and preimplantation embryos) suggests that it is not involved in Lesch-Nyhan syndrome. It is probable that the alternative HPRT transcript is derived from the aberrant splicing of a small percentage of the total mRNA produced from normal HPRT alleles. The presence of this alternative transcript in human preimplantation embryos may complicate an reverse transcription-polymerase chain reaction-based preimplantation diagnosis of Lesch-Nyhan syndrome.

PCR-based cDNA libraries from single human preimplantation embryos provide a new and important resource for the identification and study of novel genes or gene families. As such, they will increase our basic understanding of the molecular control of human development. In the clinical context, the libraries identify the time of onset of specific genes, and hence the diseases resulting from mutation of these genes, and provide information about new methods of preimplantation diagnosis. The molecular analysis of early gene transcription in human embryogenesis may be expected to lead to advances in contraception, assisted reproduction, and preimplantation genetic diagnosis.