Osteoporosis is a common aging-related disease diagnosed primarily using bone mineral density (BMD). We assessed genetic determinants of BMD as estimated by heel quantitative ultrasound (eBMD) in 426,824 individuals, identifying 518 genome-wide significant loci (301 novel), explaining 20% of its variance. We identified 13 bone fracture loci, all associated with eBMD, in ~1.2M individuals. We then identified target genes enriched for genes known to influence bone density and strength (maximum odds-ratio=58, p=10 −75 ) from cell-specific features, including chromatin conformation and accessible chromatin sites. We next performed rapid-throughput skeletal phenotyping of 126 knockout mice lacking target genes and found an increased abnormal skeletal phenotype frequency compared to 526 unselected lines (p<0.0001). In-depth analysis of one gene, DAAM2 , showed a disproportionate decrease in bone strength relative to mineralization. This genetic atlas provides evidence testing how to link associated-SNPs to causal genes, offers new insights into osteoporosis pathophysiology and highlights opportunities for drug development.

The complex relationship between metabolic disease risk and body fat distribution in humans involves cellular characteristics which are specific to body fat compartments. Here we show depotspecific differences in the stromal vascual fraction of visceral and subcutaneous adipose tissue by performing single-cell RNA sequencing of tissue specimen from obese individuals. We characterize multiple immune cells, endothelial cells, fibroblasts, adipose and hematopoietic stem cell progenitors. Subpopulations of adipose-resident immune cells are metabolically active and associated with metabolic disease status and those include a population of potential dysfunctional CD8+ T cells expressing metallothioneins. We identify multiple types of adipocyte progenitors that are common across depots, including a subtype enriched in individuals with type 2 diabetes. Depot-specific analysis reveals a class of adipocyte progenitors unique to visceral adipose tissue, *

Mutations were identified in the Cu/Zn superoxide dismutase gene (SOD1) in ϳ15% of patients with familial amyotrophic lateral sclerosis. Transgenic animals expressing mutant SOD1 in all tissues develop an ALS-like phenotype. To determine whether neuron-specific expression of mutant SOD1 is sufficient to produce such a phenotype, we generated transgenic animals carrying the G37R mutation that is associated with the familial form of ALS (FALS), which is driven by the neurofilament light chain promoter. The transgenic animals express high levels of the human SOD1 protein in neuronal tissues, especially in the large motor neurons of the spinal cord, but they show no apparent motor deficit at up to 1.5 years of age. Our animal model suggests that neuron-specific expression of ALSassociated mutant human SOD1 may not be sufficient for the development of the disease in mice.

The Reelin signaling cascade plays a crucial role in the correct positioning of neurons during embryonic brain development. Reelin binding to apolipoprotein E receptor 2 (ApoER2) and very-low-density-lipoprotein receptor (VLDLR) leads to phosphorylation of disabled 1 (Dab1), an adaptor protein which associates with the intracellular domains of both receptors. Coreceptors for Reelin have been postulated to be necessary for Dab1 phosphorylation. We show that bivalent agents specifically binding to ApoER2 or VLDLR are sufficient to mimic the Reelin signal. These agents induce Dab1 phosphorylation, activate members of the Src family of nonreceptor tyrosine kinases, modulate protein kinase B/Akt phosphorylation, and increase long-term potentiation in hippocampal slices. Induced dimerization of Dab1 in HEK293 cells leads to its phosphorylation even in the absence of Reelin receptors. The mechanism for and the sites of these phosphorylations are identical to those effected by Reelin in primary neurons. These results suggest that binding of Reelin, which exists as a homodimer in vivo, to ApoER2 and VLDLR induces clustering of ApoER2 and VLDLR. As a consequence, Dab1 becomes dimerized or oligomerized on the cytosolic side of the plasma membrane, constituting the active substrate for the kinase; this process seems to be sufficient to transmit the signal and does not appear to require any coreceptor.Correct positioning of neurons of the cortical plate depends on Reelin, an extracellular matrix protein produced by CajalRetzius cells (10), on the Reelin receptors apolipoprotein E receptor 2 (ApoER2) and very-low-density-lipoprotein receptor (VLDLR) (35), and on the intracellular adaptor protein disabled 1 (Dab1) (30). Mutations in the corresponding genes, i.e., the Reelin gene (as in the reeler mouse) (12) and the Dab1 gene (as in the scrambler and yotari mice) (16,32,37), and deletions of the genes for both ApoER2 and VLDLR (35) result in identical cortical layering defects, suggesting that the gene products are part of the same signaling pathway. The current working model proposes that Reelin binds to ApoER2 and VLDLR (11,14). Subsequent phosphorylation of Dab1 is a key event leading to the ultimate cell responses required for correct positioning of newly generated neurons (17, 18). Dab1 was originally identified as an interaction partner of Src (15) and contains a phosphotyrosine binding domain which interacts with the unphosphorylated NPXY motif present in the cytoplasmic domains of ApoER2 and VLDLR (19,34). Phosphorylation of Dab1 induced by Reelin is dependent on the presence of ApoER2 and VLDLR (5) and occurs on Tyr198 and Tyr220 (20). Recent studies demonstrated that members of the Src family of nonreceptor tyrosine kinases (SFKs) are involved in Dab1 phosphorylation in neurons (2, 6). Coreceptors, such as members of the family of cadherin-related neuronal receptors (CNRs), have been proposed to be involved in this pathway (31). Neuronal migration is also regulated by cyclin-dependent kinase 5 (27, 28), but whether t...