Biology subjects

Tward, A. D.

Publications and source records attributed to Tward, A. D..

5 recordsLinked to original sources

bioRxiv2022

Single-Cell Multi-Omic Roadmap of Human Fetal Pancreatic Development

The critical cellular transitions that govern human pancreas development are largely unknown. We performed large-scale single-cell RNA-sequencing (scRNA-Seq) to interrogate human fetal pancreas development from 8-20 weeks post conception. We identified 103 distinct cell types, including four novel endocrine progenitor subtypes displaying unique transcriptional features and differentiation potency. Integration with single-nucleus Assay for Transposase Accessible Chromatin Sequencing (snATAC-Seq) identified candidate regulators of human endocrine cell fate and revealed development-specific regulatory annotation at diabetes risk loci. Comparison of in vitro stem cell-derived and endogenous endocrine cells predicted aberrant genetic programs leading to the generation of off-target cells. Finally, knock-out studies revealed that the gene FEV regulates human endocrine differentiation. This work establishes a roadmap of human pancreatic development, highlights previously unappreciated cellular diversity and lineage dynamics, and provides a blueprint for understanding pancreatic disease and physiology, as well as generating human stem cell-derived islet cells in vitro for regenerative medicine purposes.

developmental biology↗

bioRxiv2020

Single cell analysis of human site-specific melanocyte differentiation and the decoding of developmental programs in melanoma

In humans, epidermal melanocytes are responsible for skin pigmentation, defense against ultraviolet radiation, and the deadliest common skin cancer, melanoma. While there is substantial overlap in melanocyte development pathways between different model organisms, species dependent differences are frequent and the conservation of these processes in human skin remains unresolved1-3. Thus, the biology of developing and adult human melanocytes remains largely uncharacterized. Here, we used a single-cell enrichment and RNA-sequencing pipeline to study human epidermal melanocytes derived directly from skin, capturing transcriptomes across different anatomic sites, developmental age, sexes, and multiple skin tones. Using donor-matched skin from distinct volar and non-volar anatomic locations, we uncovered subpopulations of melanocytes exhibiting site-specific enrichment that occurs during gestation and persists through adulthood. In addition, we identified human melanocyte differentiation transcriptional programs that are distinct from gene signatures generated from model systems. Finally, we use these programs to define patterns of dedifferentiation that are predictive of melanoma prognosis. Overall, the characterization of human melanocytes fresh from skin revealed new subpopulations, human-specific transcriptional programs, and valuable insights into melanoma dedifferentiation.

cancer biology↗

bioRxiv2019

A Single-Cell Atlas and Lineage Analysis of the Adult Drosophila Ovary

The Drosophila ovary is a widely used model for germ cell and somatic tissue biology. We have used single-cell RNA-sequencing to build a comprehensive cell atlas of the adult Drosophila ovary containing unique transcriptional profiles for every major cell type in the ovary, including the germline and follicle stem cells. Using this atlas we identify novel tools for identification and manipulation of known and novel cell types and perform lineage tracing to test cellular relationships of previously unknown cell types. By this we discovered a new form of cellular plasticity in which inner germarial sheath cells convert to follicle stem cells in response to starvation.\n\nGraphical Abstract\n\nO_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=162 SRC=\"FIGDIR/small/798223v1_ufig1.gif\" ALT=\"Figure 1\">\nView larger version (60K):\norg.highwire.dtl.DTLVardef@b4c486org.highwire.dtl.DTLVardef@1d24e4aorg.highwire.dtl.DTLVardef@1217adorg.highwire.dtl.DTLVardef@1d09a63_HPS_FORMAT_FIGEXP M_FIG C_FIG

developmental biology↗

bioRxiv2019

Development of mouse and human cochlea at single cell resolution

Hearing loss is a common and disabling condition, yet our understanding of the physiologic workings of the inner ear has been limited by longstanding difficulty characterizing the function and characteristics of the many diverse, fragile, and rare cell types in the cochlea. Using single-cell RNA-sequencing and a novel clustering algorithm, CellFindR, we created a developmental map of the mouse and human cochlea, identifying multiple previously undescribed cell types, progenitor populations, and predicted lineage relationships. We additionally associated the expression of known hearing loss genes to the cell types and developmental timepoints in which they are expressed. This work will serve as a resource for understanding the molecular basis of hearing and designing therapeutic approaches for hearing restoration.

bioinformatics↗

bioRxiv2019

A hierarchy of migratory keratinocytes maintains the tympanic membrane

Although the conductive function of the tympanic membrane (TM) is critical for hearing, it is unknown how the organ maintains cellular homeostasis. Using a combination of single-cell RNA sequencing, lineage tracing, whole-organ explant, and live-cell imaging, we demonstrate that the stem cells of the TM epidermis reside in a distinct location at the superior portion of the TM and, as progeny migrate inferiorly, Pdgfra+ fibroblasts maintain a niche supporting proliferation of committed progenitors, while keratinocytes distal from the niche differentiate. Thus, the TM has a three dimensional differentiation hierarchy of keratinocytes distinct from that at other epidermal sites. The TM represents a physiological context where, in the absence of injury, keratinocytes both transit through a proliferative committed progenitor state and exhibit directional lateral migration. This work forms a foundation for understanding common disorders of the TM and introduces a new model system for the understanding of keratinocyte biology.

cell biology↗