Summary Cerebral organoids (COs) are rapidly accelerating the rate of translational neuroscience based on their potential to model complex features of the developing human brain. Several studies have examined the electrophysiological and neural network features of COs; however, no study has comprehensively investigated the developmental trajectory of electrophysiological properties in whole-brain COs and correlated these properties with developmentally linked morphological and cellular features. Here, we profiled the neuroelectrical activities of COs over the span of 5 months with a multi-electrode array platform and observed the emergence and maturation of several electrophysiologic properties, including rapid firing rates and network bursting events. To complement these analyses, we characterized the complex molecular and cellular development that gives rise to these mature neuroelectrical properties with immunohistochemical and single-cell transcriptomic analyses. This integrated approach highlights the value of COs as an emerging model system of human brain development and neurological disease.

Summary IL-7 and IL-7Rα bind the γc receptor forming a complex crucial to several signaling cascades leading to the development and homeostasis of T and B cells. We report the IL-7Rα ectodomain uses glycosylation to modulate its binding constants to IL-7, unlike the other receptors in the γc family. IL-7 binds glycosylated IL-7Rα 300-fold more tightly than unglycosylated IL-7Rα, and the enhanced affinity is attributed primarily to an accelerated on-rate. Structural comparison of IL-7 in complex to both forms of the IL-7Rα reveals that glycosylation does not participate directly in the binding interface. The SCID mutations of the IL-7Rα locate outside the binding interface with IL-7 suggesting that the expressed mutations cause protein folding defects in IL-7Rα. The IL-7/IL-7Rα structures provide the first view into the molecular recognition events of the IL-7 signaling cascade and provide sites to target for designing new therapeutics to treat IL-7 related diseases.

Solution NMR spectroscopy represents a powerful tool for examining the structure and function of biological macromolecules. The advent of multidimensional (2D-4D) NMR, together with the widespread use of uniform isotopic labeling of proteins and RNA with the NMR-active isotopes, 15 N and 13 C, opened the door to detailed analyses of macromolecular structure, dynamics and interactions of smaller macromolecules (< ~25 kDa). Over the past 10 years, advances in NMR and isotope labeling methods have expanded the range of NMR-tractable targets by at least an order of magnitude. Here we briefly describe the methodological advances that allow NMR spectroscopy of large macromolecules and their complexes, and provide a perspective on the wide range of applications of NMR to biochemical problems.Solution NMR spectroscopy represents a powerful tool for examining the structure and function of biological macromolecules. The advent of multidimensional (2D-4D) NMR, together with the widespread use of uniform isotopic labeling of proteins and RNA with the NMR-active isotopes, 15 N and 13 C, opened the door to detailed analyses of macromolecular structure, dynamics and interactions of smaller macromolecules (< ~25 kDa). Work on these proteins and nucleic acids has been very fruitful and allowed us to learn much about structurefunction relationships, but is inherently limitied, as the majority of macromolecular complexes of biochemical interest are significantly larger than 25 kDa. Indeed, although much can be learned by examining macromolecules in isolation, mechanistic insights are often only gained upon studying functional higher-order assemblies with partner molecules.NMR studies of large molecules and complexes are complicated by the increased linewidths associated with slower tumbling, and the spectral overlap from the large number of unique signals. Over the past 10 years, advances in NMR and isotope labeling methods have expanded the range of NMR-tractable targets by at least an order of magnitude (for recent reviews, see (1,2)). Here we briefly describe the methodological advances that allow NMR spectroscopy of large macromolecules and their complexes, and provide a perspective on the wide range of applications of NMR to biochemical problems. Overcoming Size Limitations: Narrow Lines and Simple SpectraThe slow tumbling of larger macromolecules in solution leads to faster relaxation of transverse magnetization (short T 2 ) due to enhanced spin-spin interactions. One simple, albeit limited, solution to this problem is to increase the overall molecular tumbling rate by recording NMR spectra at elevated temperatures. This can be highly effective for thermostable macromolecules, with the caveat that behavior at physiological temperatures should be † Authors supported by grants from the National Science Foundation (MCB-0092962) and National Institutes of Health (GM067807) *Contact information: foster.281@osu.edu, 614-292-1377, FAX: 614-292-6773. NIH Public Access [3][4][5][6]. Another ingenious approach to reduce tu...

No abstract

We report here an unliganded receptor structure in the common gamma-chain (γ c ) family of receptors and cytokines. The crystal structure of the unliganded form of the interleukin-7 alpha receptor (IL-7Rα) extracellular domain (ECD) at 2.15 Å resolution reveals a homodimer forming an "X" geometry looking down onto the cell surface with the C termini of the two chains separated by 110 Å and the dimer interface comprising residues critical for IL-7 binding. Further biophysical studies indicate a weak association of the IL-7Rα ECDs but a stronger association between the γ c /IL-7Rα ECDs, similar to previous studies of the full-length receptors on CD4 + T cells. Based on these and previous results, we propose a molecular mechanism detailing the progression from the inactive IL-7Rα homodimer and IL-7Rα-γ c heterodimer to the active IL-7-IL-7Rα-γ c ternary complex whereby the two receptors undergo at least a 90°rotation away from the cell surface, moving the C termini of IL-7Rα and γ c from a distance of 110 Å to less than 30 Å at the cell surface. This molecular mechanism can be used to explain recently discovered IL-7-and γ c -independent gain-of-function mutations in IL-7Rα from B-and Tcell acute lymphoblastic leukemia patients. The mechanism may also be applicable to other γ c receptors that form inactive homodimers and heterodimers independent of their cytokines.X-ray crystallography | biophysics | homodimerization | cancer mutations