Cancer-associated fi broblasts (CAF) are major players in the progression and drug resistance of pancreatic ductal adenocarcinoma (PDAC). CAFs constitute a diverse cell population consisting of several recently described subtypes, although the extent of CAF heterogeneity has remained undefi ned. Here we use single-cell RNA sequencing to thoroughly characterize the neoplastic and tumor microenvironment content of human and mouse PDAC tumors. We corroborate the presence of myofi broblastic CAFs and infl ammatory CAFs and defi ne their unique gene signatures in vivo. Moreover, we describe a new population of CAFs that express MHC class II and CD74, but do not express classic costimulatory molecules. We term this cell population "antigenpresenting CAFs" and fi nd that they activate CD4 + T cells in an antigen-specifi c fashion in a model system, confi rming their putative immune-modulatory capacity. Our cross-species analysis paves the way for investigating distinct functions of CAF subtypes in PDAC immunity and progression. SIGNIFICANCE : Appreciating the full spectrum of fi broblast heterogeneity in pancreatic ductal adenocarcinoma is crucial to developing therapies that specifi cally target tumor-promoting CAFs. This work identifi es MHC class II-expressing CAFs with a capacity to present antigens to CD4 + T cells, and potentially to modulate the immune response in pancreatic tumors.

Blood glucose levels are tightly controlled by the coordinated action of at least four cell types constituting pancreatic islets. Changes in the proportion and/or function of these cells are associated with genetic and molecular pathophysiology of monogenic, type 1, and type 2 (T2D) diabetes. Cellular heterogeneity impedes precise understanding of the molecular components of each islet cell type that govern islet (dys)function, particularly the less abundant delta and gamma/pancreatic polypeptide (PP) cells. Here, we report single-cell transcriptomes for 638 cells from nondiabetic (ND) and T2D human islet samples. Analyses of ND single-cell transcriptomes identified distinct alpha, beta, delta, and PP/gamma cell-type signatures. Genes linked to rare and common forms of islet dysfunction and diabetes were expressed in the delta and PP/gamma cell types. Moreover, this study revealed that delta cells specifically express receptors that receive and coordinate systemic cues from the leptin, ghrelin, and dopamine signaling pathways implicating them as integrators of central and peripheral metabolic signals into the pancreatic islet. Finally, single-cell transcriptome profiling revealed genes differentially regulated between T2D and ND alpha, beta, and delta cells that were undetectable in paired whole islet analyses. This study thus identifies fundamental cell-type-specific features of pancreatic islet (dys)function and provides a critical resource for comprehensive understanding of islet biology and diabetes pathogenesis.[Supplemental material is available for this article.]Pancreatic islets of Langerhans are clusters of at least four different hormone-secreting endocrine cell types that elicit coordinatedbut distinct-responses to maintain glucose homeostasis. As such, they are central to diabetes pathophysiology. On average, human islets consist mostly of beta (54%), alpha (35%), and delta (11%) cells; up to a few percent gamma/pancreatic polypeptide (PP) cells; and very few epsilon cells (Brissova et al. 2005;Cabrera et al. 2006;Blodgett et al. 2015). Human islet composition is neither uniform nor static but varies between individuals and across regions of the pancreas (Brissova et al. 2005;Cabrera et al. 2006;Blodgett et al. 2015). Cellular heterogeneity complicates molecular studies of whole human islets and may mask important role(s) for less common cells in the population (Dorrell et al. 2011b;Bramswig et al. 2013;Nica et al. 2013;Blodgett et al. 2015;Liu and Trapnell 2016). Moreover, it complicates attempts to identify epigenetic and transcriptional signatures distinguishing diabetic from nondiabetic (ND) islets, leading to inconsistent reports of genes and pathways affected (Gunton et al. 2005;Marselli et al. 2010;Taneera et al. 2012;Dayeh et al. 2014). Conventional sorting and enrichment techniques are unable to specifically purify each human islet cell type (Dorrell et al. 2008;Nica et al. 2013;Bramswig et al. 2013;Hrvatin et al. 2014;Blodgett et al. 2015), thus a precise understanding of the transcriptiona...

Characterization of the cardiac cellulome, the network of cells that form the heart, is essential for understanding cardiac development and normal organ function and for formulating precise therapeutic strategies to combat heart disease. Recent studies have reshaped our understanding of cardiac cellular composition and highlighted important functional roles for non-myocyte cell types. In this study, we characterized single-cell transcriptional profiles of the murine non-myocyte cardiac cellular landscape using single-cell RNA sequencing (scRNA-seq). Detailed molecular analyses revealed the diversity of the cardiac cellulome and facilitated the development of techniques to isolate understudied cardiac cell populations, such as mural cells and glia. Our analyses also revealed extensive networks of intercellular communication and suggested prevalent sexual dimorphism in gene expression in the heart. This study offers insights into the structure and function of the mammalian cardiac cellulome and provides an important resource that will stimulate studies in cardiac cell biology.

Retinal ganglion cells (RGCs) convey the major output of information collected from the eye to the brain. Thirty subtypes of RGCs have been identified to date. Here, we analyze 6225 RGCs (average of 5000 genes per cell) from right and left eyes by single-cell RNA-seq and classify them into 40 subtypes using clustering algorithms. We identify additional subtypes and markers, as well as transcription factors predicted to cooperate in specifying RGC subtypes. Zic1, a marker of the right eye-enriched subtype, is validated by immunostaining in situ. Runx1 and Fst, the markers of other subtypes, are validated in purified RGCs by fluorescent in situ hybridization (FISH) and immunostaining. We show the extent of gene expression variability needed for subtype segregation, and we show a hierarchy in diversification from a cell-type population to subtypes. Finally, we present a website for comparing the gene expression of RGC subtypes.

The lateral hypothalamic area (LHA) coordinates an array of fundamental behaviors, including sleeping, waking, feeding, stress and motivated behavior. The wide spectrum of functions ascribed to the LHA may be explained by a heterogeneous population of neurons, the full diversity of Reprints and permissions information is available at www.nature.com/reprints.