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Debate remains around the anatomical origins of specific brain cell subtypes and lineage relationships within the human forebrain1–7. Thus, direct observation in the mature human brain is critical for a complete understanding of its structural organization and cellular origins. Here we utilize brain mosaic variation within specific cell types as distinct indicators for clonal dynamics, denoted as cell-type-specific mosaic variant barcode analysis. From four hemispheres and two different human neurotypical donors, we identified 287 and 780 mosaic variants, respectively, that were used to deconvolve clonal dynamics. Clonal spread and allele fractions within the brain reveal that local hippocampal excitatory neurons are more lineage-restricted than resident neocortical excitatory neurons or resident basal ganglia GABAergic inhibitory neurons. Furthermore, simultaneous genome transcriptome analysis at both a cell-type-specific and a single-cell level suggests a dorsal neocortical origin for a subgroup of DLX1+inhibitory neurons that disperse radially from an origin shared with excitatory neurons. Finally, the distribution of mosaic variants across 17 locations within one parietal lobe reveals that restriction of clonal spread in the anterior–posterior axis precedes restriction in the dorsal–ventral axis for both excitatory and inhibitory neurons. Thus, cell-type-resolved somatic mosaicism can uncover lineage relationships governing the development of the human forebrain.

Several genetic risk factors for Alzheimer’s disease implicate genes involved in lipid metabolism and many of these lipid genes are highly expressed in glial cells1. However, the relationship between lipid metabolism in glia and Alzheimer’s disease pathology remains poorly understood. Through single-nucleus RNA sequencing of brain tissue in Alzheimer’s disease, we have identified a microglial state defined by the expression of the lipid droplet-associated enzyme ACSL1 with ACSL1-positive microglia being most abundant in patients with Alzheimer’s disease having the APOE4/4genotype. In human induced pluripotent stem cell-derived microglia, fibrillar Aβ induces ACSL1expression, triglyceride synthesis and lipid droplet accumulation in an APOE-dependent manner. Additionally, conditioned media from lipid droplet-containing microglia lead to Tau phosphorylation and neurotoxicity in an APOE-dependent manner. Our findings suggest a link between genetic risk factors for Alzheimer’s disease with microglial lipid droplet accumulation and neurotoxic microglia-derived factors, potentially providing therapeutic strategies for Alzheimer’s disease.

The structure of the human neocortex underlies species-specific traits and reflects intricate developmental programs. Here we sought to reconstruct processes that occur during early development by sampling adult human tissues. We analysed neocortical clones in a post-mortem human brain through a comprehensive assessment of brain somatic mosaicism, acting as neutral lineage recorders1,2. We combined the sampling of 25 distinct anatomic locations with deep whole-genome sequencing in a neurotypical deceased individual and confirmed results with 5 samples collected from each of three additional donors. We identified 259 bona fide mosaic variants from the index case, then deconvolved distinct geographical, cell-type and clade organizations across the brain and other organs. We found that clones derived after the accumulation of 90–200 progenitors in the cerebral cortex tended to respect the midline axis, well before the anterior–posterior or ventral–dorsal axes, representing a secondary hierarchy following the overall patterning of forebrain and hindbrain domains. Clones across neocortically derived cells were consistent with a dual origin from both dorsal and ventral cellular populations, similar to rodents, whereas the microglia lineage appeared distinct from other resident brain cells. Our data provide a comprehensive analysis of brain somatic mosaicism across the neocortex and demonstrate cellular origins and progenitor distribution patterns within the human brain.

Two hematopoietic cytokines are currently gaining increasing attention within neurological research. Erythropoietin (EPO) and granulocyte-colony stimulating factor (G-CSF) have long been known for their ability to induce the proliferation of certain populations of hematopoietic lineage cells. However, it has recently been found that EPO, G-CSF, and their respective receptors are also expressed in the human central nervous system (CNS) and may be an important part of the brain's endogenous system of protection. Both hematopoietic cytokines have been shown to have neuroprotective potential in a variety of animal disease models both in vitro and in vivo, through the inhibition of apoptosis, induction of angiogenesis, exertion of anti-inflammatory and neurotrophic effects, as well as by the enhancement of neurogenesis. EPO and G-CSF have been extensively studied in the context of hematological disorders and have recently been successfully applied in the first clinical trials in stroke patients. Intravenous high-dose EPO therapy was associated with an improvement in the clinical outcome and preclinical studies with intravenous high-dose G-CSF therapy have clearly shown that it has considerable neuroprotective potential in the acute, as well as in the chronic phase of stroke. In this review, the current knowledge of the neuroprotective mechanisms of EPO and G-CSF is summarized with regard to in vitro and in vivo data. Focus is placed on the role of EPO in neurological disease models with an emphasis on its influence on functional outcome. New experimental results are assessed in detail and correlated with the findings of recent clinical studies.