H3.3K122A results in a neomorphic phenotype in mouse embryonic stem cells.

The histone variant H3.3 acts in coordination with histone posttranslational modifications and other chromatin features to facilitate appropriate transcription. Canonical histone H3 and histone variant H3.3 are post-translationally modified with the genomic distribution of these marks denoting different features and with more recent evidence suggesting that these modifications may influence transcription. While the majority of posttranslational modifications occur on histone tails, there are defined modifications within the globular domain, such as acetylation of H3K122/H3.3K122. To understand the function of the residue H3.3K122 in transcriptional regulation, we attempted to generate H3.3K122A mouse embryonic stem (mES) cells but were unsuccessful. Through multi-omic profiling of mutant cell lines harboring two or three of four H3.3 targeted alleles, we have uncovered that H3.3K122A is neomorphic and results in lethality. This is surprising as prior studies demonstrate H3.3-null mES cells are viable and pluripotent, albeit with reduced differentiation capacity. Together, these studies have uncovered a novel dependence of a globular domain residue of H3.3 for viability and broadened our understanding of how histone variants contribute to transcription regulation and pluripotency in mES cells.

Quantifying cell-state densities in single-cell phenotypic landscapes using Mellon.

Cell-state density characterizes the distribution of cells along phenotypic landscapes and is crucial for unraveling the mechanisms that drive diverse biological processes. Here, we present Mellon, an algorithm for estimation of cell-state densities from high-dimensional representations of single-cell data. We demonstrate Mellon's efficacy by dissecting the density landscape of differentiating systems, revealing a consistent pattern of high-density regions corresponding to major cell types intertwined with low-density, rare transitory states. We present evidence implicating enhancer priming and the activation of master regulators in emergence of these transitory states. Mellon offers the flexibility to perform temporal interpolation of time-series data, providing a detailed view of cell-state dynamics during developmental processes. Mellon facilitates density estimation across various single-cell data modalities, scaling linearly with the number of cells. Our work underscores the importance of cell-state density in understanding the differentiation processes, and the potential of Mellon to provide insights into mechanisms guiding biological trajectories.

Quantifying Cell-State Densities in Single-Cell Phenotypic Landscapes using Mellon.

Cell-state density characterizes the distribution of cells along phenotypic landscapes and is crucial for unraveling the mechanisms that drive cellular differentiation, regeneration, and disease. Here, we present Mellon, a novel computational algorithm for high-resolution estimation of cell-state densities from single-cell data. We demonstrate Mellon's efficacy by dissecting the density landscape of various differentiating systems, revealing a consistent pattern of high-density regions corresponding to major cell types intertwined with low-density, rare transitory states. Utilizing hematopoietic stem cell fate specification to B-cells as a case study, we present evidence implicating enhancer priming and the activation of master regulators in the emergence of these transitory states. Mellon offers the flexibility to perform temporal interpolation of time-series data, providing a detailed view of cell-state dynamics during the inherently continuous developmental processes. Scalable and adaptable, Mellon facilitates density estimation across various single-cell data modalities, scaling linearly with the number of cells. Our work underscores the importance of cell-state density in understanding the differentiation processes, and the potential of Mellon to provide new insights into the regulatory mechanisms guiding cellular fate decisions.

A Review of First Line Infertility Treatments and Supporting Evidence in Women with Polycystic Ovary Syndrome.

Polycystic ovary syndrome (PCOS) is the most common cause of anovulatory infertility in women of reproductive age. Lifestyle change is considered the first line treatment for the management of infertile anovulatory women with PCOS, and weight loss for those who are overweight or obese. First line medical ovulation induction therapy to improve fertility outcomes is letrozole, whilst other less efficacious ovulation induction agents, such as clomiphene citrate, metformin, and metformin combined with clomiphene citrate, may also be considered. Metformin combined with clomiphene citrate is more effective than clomiphene citrate alone. In obese women with PCOS, clomiphene citrate could be used in preference to metformin alone whilst clomiphene citrate could be added to metformin alone in order to improve reproductive outcome in all women with PCOS. Gonadotrophins, which are more effective than clomiphene citrate in therapy naïve women with PCOS, can be considered a first line therapy in the presence of ultrasound monitoring, following counselling on the cost and the potential risk of multiple pregnancy.

A brief update on the evidence supporting the treatment of infertility in polycystic ovary syndrome.

BACKGROUND: Polycystic ovary syndrome (PCOS) is complex with reproductive, metabolic and psychological features. Infertility is a prevalent presenting feature of PCOS with approximately 75% of these women suffering infertility due to anovulation, making PCOS by far the most common cause of anovulatory infertility. Previous guidelines either lacked rigorous evidence-based processes, did not engage consumer and international multidisciplinary perspectives, or were outdated. AIMS: This review paper aims to provide a brief update on the best available and most current research evidence supporting the treatment of PCOS which informed the recommendations in the assessment and treatment of infertility section of the international evidence-based guideline on PCOS 2018. MATERIALS AND METHODS: International evidence-based guideline development engaged professional societies and consumer organisations with multidisciplinary experts and women with PCOS directly involved at all stages. RESULTS: Lifestyle change alone is considered the first-line treatment for the management of infertile anovulatory PCOS women who are overweight or obese. Letrozole should now be considered first-line pharmacological treatment for ovulation induction to improve fertility outcomes. Clomiphene citrate alone and metformin alone could also be used as first-line pharmacological therapy, although both are less effective than letrozole and metformin is less effective than clomiphene citrate in obese women. Gonadotrophins or laparoscopic ovarian surgery are usually second-line ovulation induction therapies. In the absence of an absolute indication for in vitro fertilisation (IVF) / intracytoplasmic sperm injection, women with PCOS and anovulatory infertility could be offered IVF as third-line therapy where first- or second-line ovulation induction therapies have failed. CONCLUSION: This review provides the best available evidence informing recommendations (along with clinical expertise and consumer preference) which provide clinicians with clear advice on best practice for the management of infertile women with PCOS.

A Review of Second- and Third-line Infertility Treatments and Supporting Evidence in Women with Polycystic Ovary Syndrome.

In clomiphene-citrate-resistant anovulatory women with polycystic ovary syndrome (PCOS) and no other infertility factors, either metformin combined with clomiphene citrate or gonadotrophins could be used as a second-line pharmacological therapy, although gonadotrophins are more effective. Gonadotrophins could also be used as a second-line pharmacological therapy in anovulatory women with PCOS and clomiphene-citrate-failure. Laparoscopic ovarian surgery can also be used as a second-line therapy for ovulation induction in anovulatory women with clomiphene-citrate-resistant PCOS and no other infertility factors. The usefulness of letrozole as a second-line pharmacological treatment for ovulation induction in clomiphene-citrate-resistant women with PCOS requires further research. In terms of improving fertility, both pharmacological anti-obesity agents and bariatric surgery should be considered an experimental therapy in anovulatory women with PCOS and no other infertility factors. Where first- or second-line ovulation induction therapies have failed, in vitro fertilization (IVF)/ intracytoplasmic sperm injection (ICSI) could be offered as a third-line therapy in women with PCOS in the absence of an absolute indication for IVF/ICSI. For women with PCOS undergoing IVF/ICSI treatment, the gonadotropin-releasing hormone (GnRH) antagonist protocol is preferred and an elective frozen embryo transfer strategy could be considered. In assisted conception units with sufficient expertise, in-vitro maturation (IVM) of oocytes could be offered to women with PCOS.