Date of Award

2018

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biotechnology Science and Engineering

Committee Chair

Joseph D. Ng

Committee Member

Shawn E. Levy

Committee Member

Devin Absher

Committee Member

Eric Mendenhall

Committee Member

Luis Rogelio Cruz-Vera

Committee Member

Marcela Brissova

Subject(s)

Diabetes--Research., Nucleotide sequence., Islands of Langerhans.

Abstract

Type 1 Diabetes is chronic disease where immune moderated destruction of insulin producing β cells disrupts normal glucose homeostasis in the body. Recent findings show that few β cells remain in the pancreatic islets decades after disease onset challenging the previous understanding that β cells are completely destroyed. Overcoming the limited availability of T1D tissues, we studied functional and molecular features of pancreatic islets from individuals with T1D and investigated the nature of the remaining β cells. We found that remnant β cells have normal insulin secretory function and normally express key transcription factor that regulates β cell function. On the other hand, glucagon producing α cells, in normal physiology, counters insulin action and assist in producing glucose from liver when glucose levels fall too low. However, in T1D patients, counterregulatory response of glucagon is abnormal and exogenous insulin treatment can sometimes induce hypoglycemic shock (low glucose). We found that remaining α cells in pancreatic islets of T1D individuals had impaired glucagon secretion and expression of key transcription factor important for normal α cell function were compromised. We propose a model for disrupted α cell function based on our inspection of altered expression of genes in T1D α cells that furthers our understanding of susceptibility to hypoglycemia in T1D. We further advanced the molecular characterization of pancreatic islets from normal individuals through single cell resolution. Islets are highly multicellular where various cell types collectively contribute to proper islet function. Efforts to purify each cell type and investigate their transcriptional features has been challenging from flow cytometry approach due lack of cell type specific markers and traditional single cell RNA-sequencing approach has been low throughput compromising sensitivity. We applied a high throughput approach on single cell RNA-sequencing to profile ~40,075 single cells from pancreatic islets of healthy individuals. We obtained pure populations of all pancreatic cell types based on transcriptional similarity and further identified transcriptional heterogeneity in β and α cells highlighting their intrinsic properties of subpopulation and cellular states. With this approach and findings about α and β cells subpopulations, we can further investigate their changes at various age and diabetic state.

Share

COinS
 
 

To view the content in your browser, please download Adobe Reader or, alternately,
you may Download the file to your hard drive.

NOTE: The latest versions of Adobe Reader do not support viewing PDF files within Firefox on Mac OS and if you are using a modern (Intel) Mac, there is no official plugin for viewing PDF files within the browser window.