Expression of L1 Cell Adhesion Molecule, a Nephronal Principal Cell Marker, in Nephrogenic Adenoma.

Nephrogenic adenoma (NA) is a benign, reactive lesion seen predominantly in the urinary bladder and often associated with antecedent inflammation, instrumentation, or an operative history. Its histopathologic diversity can create diagnostic dilemmas and pathologists use morphologic evaluation along with available immunohistochemical (IHC) markers to navigate these challenges. IHC assays currently do not designate or specify NA's potential putative cell of origin. Leveraging single-cell RNA-sequencing technology, we nominated a principal (P) cell-collecting duct marker, L1 cell adhesion molecule (L1CAM), as a potential biomarker for NA. IHC characterization revealed L1CAM to be positive in all 35 (100%) patient samples of NA; negative expression was seen in the benign urothelium, benign prostatic glands, urothelial carcinoma (UCA) in situ, prostatic adenocarcinoma, majority of high-grade UCA, and metastatic UCA. In the study, we also used single-cell RNA sequencing to nominate a novel compendium of biomarkers specific for the proximal tubule, loop of Henle, and distal tubule (DT) (including P and intercalated cells), which can be used to perform nephronal mapping using RNA in situ hybridization and IHC technology. Employing this technique on NA we found enrichment of both the P-cell marker L1CAM and, the proximal tubule type-A and -B cell markers, PDZKI1P1 and PIGR, respectively. The cell-type markers for the intercalated cell of DTs (LINC01187 and FOXI1), and the loop of Henle (UMOD and IRX5), were found to be uniformly absent in NA. Overall, our findings show that based on cell type-specific implications of L1CAM expression, the shared expression pattern of L1CAM between DT P cells and NA. L1CAM expression will be of potential value in assisting surgical pathologists toward a diagnosis of NA in challenging patient samples.

MIMIC: an optimization method to identify cell type-specific marker panel for cell sorting.

Multi-omics data allow us to select a small set of informative markers for the discrimination of specific cell types and study of cellular heterogeneity. However, it is often challenging to choose an optimal marker panel from the high-dimensional molecular profiles for a large amount of cell types. Here, we propose a method called Mixed Integer programming Model to Identify Cell type-specific marker panel (MIMIC). MIMIC maintains the hierarchical topology among different cell types and simultaneously maximizes the specificity of a fixed number of selected markers. MIMIC was benchmarked on the mouse ENCODE RNA-seq dataset, with 29 diverse tissues, for 43 surface markers (SMs) and 1345 transcription factors (TFs). MIMIC could select biologically meaningful markers and is robust for different accuracy criteria. It shows advantages over the standard single gene-based approaches and widely used dimensional reduction methods, such as multidimensional scaling and t-SNE, both in accuracy and in biological interpretation. Furthermore, the combination of SMs and TFs achieves better specificity than SMs or TFs alone. Applying MIMIC to a large collection of 641 RNA-seq samples covering 231 cell types identifies a panel of TFs and SMs that reveal the modularity of cell type association networks. Finally, the scalability of MIMIC is demonstrated by selecting enhancer markers from mouse ENCODE data. MIMIC is freely available at https://github.com/MengZou1/MIMIC.

Restricted Presence of POU6F2 in Human Corneal Endothelial Cells Uncovered by Extension of the Promoter-level Expression Atlas.

Corneal endothelial cells (CECs) are essential for maintaining the clarity of the cornea. Because CECs have limited proliferative ability, interest is growing in their potentially therapeutic regeneration from pluripotent stem cells. However, the molecular mechanisms of human CEC differentiation remain largely unknown. To determine the key regulators of CEC characteristics, here we generated a comprehensive promoter-level expression profile of human CECs, using cap analysis of gene expression (CAGE) with a single molecule sequencer. Integration with the FANTOM5 promoter-level expression atlas, which includes transcriptome profiles of various human tissues and cells, enabled us to identify 45 promoters at 28 gene loci that are specifically expressed in CECs. We further discovered that the expression of transcription factor POU class 6 homeobox 2 (POU6F2) is restricted to CECs, and upregulated during human CEC differentiation, suggesting that POU6F2 is pivotal to terminal differentiation of CECs. These CEC-specific promoters would be useful for the assessment of fully differentiated CECs derived from pluripotent stem cells. These findings promote the development of corneal regenerative medicine.