The mammalian prefrontal cortex comprises a set of highly specialized brain areas containing billions of cells and serves as the centre of the highest-order cognitive functions, such as memory, cognitive ability, decision-making and social behaviour. Although neural circuits are formed in the late stages of human embryonic development and even after birth, diverse classes of functional cells are generated and migrate to the appropriate locations earlier in development. Dysfunction of the prefrontal cortex contributes to cognitive deficits and the majority of neurodevelopmental disorders; there is therefore a need for detailed knowledge of the development of the prefrontal cortex. However, it is still difficult to identify cell types in the developing human prefrontal cortex and to distinguish their developmental features. Here we analyse more than 2,300 single cells in the developing human prefrontal cortex from gestational weeks 8 to 26 using RNA sequencing. We identify 35 subtypes of cells in six main classes and trace the developmental trajectories of these cells. Detailed analysis of neural progenitor cells highlights new marker genes and unique developmental features of intermediate progenitor cells. We also map the timeline of neurogenesis of excitatory neurons in the prefrontal cortex and detect the presence of interneuron progenitors in early developing prefrontal cortex. Moreover, we reveal the intrinsic development-dependent signals that regulate neuron generation and circuit formation using single-cell transcriptomic data analysis. Our screening and characterization approach provides a blueprint for understanding the development of the human prefrontal cortex in the early and mid-gestational stages in order to systematically dissect the cellular basis and molecular regulation of prefrontal cortex function in humans.

Coal tar has been considered as a potential energy alternative because of dwindling supplies of petroleum. To determine if the coal tar could be refined and upgraded to produce clean transportation fuels, detailed investigation of its composition is necessary, particularly for identifying the acidic components that account for about one-quarter of the weight of the coal tar. A middle-temperature coal tar (MTCT) and its fractions were characterized by gas chromatography–mass spectrometry (GC–MS) and negative-ion electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) with different ion transmission modes for high- and low-mass ions. Analytical results of narrow distillation fractions from FT-ICR MS agreed reasonably well with those from GC–MS, although each technique has its own advantages and disadvantages. In this work, FT-ICR MS was demonstrated to be capable of characterizing small molecules of <100 Da using appropriate operation conditions, thus yielding mass distributions to compare to GC–MS results. A continuous distribution in double bond equivalent (DBE) and carbon number was observed with the distillates of increasing boiling point, while the composition of the distillation residue was much more complex than that of distillates. Acidic compounds containing 1–7 oxygen atoms were observed in the MTCT by FT-ICR MS, with O1 and O2 classes being dominant. Various phenolic compounds with 1–4 aromatic rings were identified on the basis of literature references, including some molecules having structures resembling known biomarkers in petroleum and coal.

Venezuela crude oil was separated into saturates, aromatics, resins, and asphaltenes (SARA) fractions. The sulfur compounds in the crude oil and its SARA fractions were reacted with iodomethane in the presence of silver tetrafluoroborate and converted to methylsulfonium salts. The methylsulfonium salts were characterized by positive-ion electrospray ionization (ESI) and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS).