TGFß superfamily signaling regulates the state of human stem cell pluripotency and capacity to create well-structured telencephalic organoids.

Telencephalic organoids generated from human pluripotent stem cells (hPSCs) are a promising system for studying the distinct features of the developing human brain and the underlying causes of many neurological disorders. While organoid technology is steadily advancing, many challenges remain, including potential batch-to-batch and cell-line-to-cell-line variability, and structural inconsistency. Here, we demonstrate that a major contributor to cortical organoid quality is the way hPSCs are maintained prior to differentiation. Optimal results were achieved using particular fibroblast-feeder-supported hPSCs rather than feeder-independent cells, differences that were reflected in their transcriptomic states at the outset. Feeder-supported hPSCs displayed activation of diverse transforming growth factor ß (TGFß) superfamily signaling pathways and increased expression of genes connected to naive pluripotency. We further identified combinations of TGFß-related growth factors that are necessary and together sufficient to impart broad telencephalic organoid competency to feeder-free hPSCs and enhance the formation of well-structured brain tissues suitable for disease modeling.

Utilization Efficiency of Human Milk Oligosaccharides by Human-Associated Akkermansia Is Strain Dependent.

Akkermansia muciniphila is a mucin-degrading bacterium found in the human gut and is often associated with positive human health. However, despite being detected by as early as 1 month of age, little is known about the role of Akkermansia in the infant gut. Human milk oligosaccharides (HMOs) are abundant components of human milk and are structurally similar to the oligosaccharides that comprise mucin, the preferred growth substrate of human-associated Akkermansia. A limited subset of intestinal bacteria has been shown to grow well on HMOs and mucin. We therefore examined the ability of genomically diverse strains of Akkermansia to grow on HMOs. First, we screened 85 genomes representing the four known Akkermansia phylogroups to examine their metabolic potential to degrade HMOs. Furthermore, we examined the ability of representative isolates to grow on individual HMOs in a mucin background and analyzed the resulting metabolites. All Akkermansia genomes were equipped with an array of glycoside hydrolases associated with HMO deconstruction. Representative strains were all able to grow on HMOs with various efficiencies and growth yields. Strain CSUN-19, belonging to the AmIV phylogroup, grew to the highest level in the presence of fucosylated and sialylated HMOs. This activity may be partially related to the increased copy numbers and/or the enzyme activities of the α-fucosidases, α-sialidases, and ß-galactosidases. This study examines the utilization of individual purified HMOs by Akkermansia strains representing all known phylogroups. Further studies are required to examine how HMO ingestion influences gut microbial ecology in infants harboring different Akkermansia phylogroups. IMPORTANCE Human milk oligosaccharides (HMOs) are the third most abundant component of breast milk and provide several benefits to developing infants, including the recruitment of beneficial bacteria to the human gut. Akkermansia strains are largely considered beneficial bacteria and have been detected in colostrum, breast milk, and young infants. A. muciniphila MucT, belonging to the AmI phylogroup, contributes to the HMO deconstruction capacity of the infant. Here, using phylogenomics, we examined the genomic capacities of four Akkermansia phylogroups to deconstruct HMOs. Indeed, each phylogroup contained differences in their genomic capacities to deconstruct HMOs, and representative strains of each phylogroup were able to grow using HMOs. These Akkermansia-HMO interactions potentially influence gut microbial ecology in early life, a critical time for the development of the gut microbiome and infant health.

Identification of neural oscillations and epileptiform changes in human brain organoids.

Brain organoids represent a powerful tool for studying human neurological diseases, particularly those that affect brain growth and structure. However, many diseases manifest with clear evidence of physiological and network abnormality in the absence of anatomical changes, raising the question of whether organoids possess sufficient neural network complexity to model these conditions. Here, we explore the network-level functions of brain organoids using calcium sensor imaging and extracellular recording approaches that together reveal the existence of complex network dynamics reminiscent of intact brain preparations. We demonstrate highly abnormal and epileptiform-like activity in organoids derived from induced pluripotent stem cells from individuals with Rett syndrome, accompanied by transcriptomic differences revealed by single-cell analyses. We also rescue key physiological activities with an unconventional neuroregulatory drug, pifithrin-α. Together, these findings provide an essential foundation for the utilization of brain organoids to study intact and disordered human brain network formation and illustrate their utility in therapeutic discovery.