Mammalian pre-implantation development is a complex process involving dramatic changes in the transcriptional architecture1–4. We report here a comprehensive analysis of transcriptome dynamics from oocyte to morula in both human and mouse embryos, using single-cell RNA sequencing. Based on single-nucleotide variants in human blastomere messenger RNAs and paternal-specific single-nucleotide polymorphisms, we identify novel stage-specific monoallelic expression patterns for a significant portion of polymorphic gene transcripts (25 to 53%). By weighted gene co-expression network analysis5,6, we find that each developmental stage can be delineated concisely by a small number of functional modules of co-expressed genes. This result indicates a sequential order of transcriptional changes in pathways of cell cycle, gene regulation, translation and metabolism, acting in a step-wise fashion from cleavage to morula. Cross-species comparisons with mouse pre-implantation embryos reveal that the majority of human stage-specific modules (7out of 9) are notably preserved, but developmental specificity and timing differ between human and mouse. Furthermore, we identify conserved key members (or hub genes) of the human and mouse networks. These genes represent novel candidates that are likely to be key in driving mammalian pre-implantation development. Together, the results provide a valuable resource to dissect gene regulatory mechanisms underlying progressive development of early mammalian embryos.

Neurofibrillary tangles (NFTs), composed of truncated and hyperphosphorylated tau, are a common feature of numerous aging-related neurodegenerative diseases including Alzheimer’s disease (AD). However, the molecular mechanisms mediating tau truncation and aggregation during aging remain elusive. Here we show that asparagine endopeptidase (AEP), a lysosomal cysteine proteinase, is activated during aging and proteolytically degrades tau, abolishes its microtubule assembly function, induces tau aggregation, and triggers neurodegeneration. AEP is upregulated and active during aging, and is activated in tau P301S transgenic mice and human AD brain, leading to tau truncation in NFTs. Deletion of AEP from tau P301S transgenic mice substantially reduces tau hyperphosphorylation, alleviates the synapse loss and rescues impaired hippocampal synaptic function and the cognitive deficits. Infection of uncleavable tau N255AN368A mutant rescues tau P301S-induced pathological and behavioral defects. Together, these observations indicate that AEP acts as a crucial mediator of tau-related clinical and neuropathological changes in neurodegenerative diseases. Inhibition of AEP may be therapeutically useful for treating tau-mediated neurodegenerative diseases.

Research question Whether SARS-CoV-2 infection has effects on ovarian reserve, sex hormone and menstruation of women of child-bearing age. Design This is a retrospective, cross-sectional study. Clinical and laboratory data from 237 women of child-bearing age diagnosed with COVID-19 were retrospectively reviewed. Menstrual data from 177 patients were analyzed. Blood samples from the early follicular phase were tested for sex hormones and Anti-mullerian hormone (AMH). Results Among 237 patients confirmed with COVID-19, severely ill patients had more comorbidities than mildly ill patients (34% vs 8%), especially for patients with diabetes, hepatic disease and malignant tumors. Among 177 patients with menstrual records, 45 (25%) patients presented with menstrual volume changes, and 50 (28%) patients had menstrual cycle changes, mainly a decreased volume (21%) and a prolonged cycle (19%). The average sex hormone and AMH levels of women of child-bearing age with COVID-19 were not different from those of age-matched controls. Conclusions Average sex hormone levels and ovarian reserve did not change significantly in COVID-19 women of child-bearing age. Nearly one-fifth of patients exhibited a menstrual volume decrease or cycle prolongation. The menstruation changes of these patients might be the consequence of transient sex hormone change cause by suppression of ovarian function that soon resumed after recovery.