Method For Detecting And Purifying Pancreatic Beta Cells

Abstract

The invention is based, in part, on the discovery that a polypeptide, referred to herein as Betacam, is selectively expressed on the surface of pancreatic islet cells, Thus, in one aspect, the invention is directed to compositions comprising Betacam or that can be used to detect Betacam. In another aspect, the invention provides methods of detecting (e.g., non-invasively) pancreatic beta cells from a mammalian cell source. Another aspect of the invention is directed to cellular purification of pancreatic beta cells from a heterogeneous cell source of multiple kinds. In another aspect, the invention provides methods of identifying agents that modulate activity of Betacam-In yet another aspect, the invention provides for improved treatment and diagnosis of diabetes.

What is claimed is: 
     
         1 . An isolated nucleic acid that encodes an amino acid sequence of Betcam wherein the amino acid sequence consists essentially of amino acids 31 through 462 of SEQ ID NO: 1, amino acids 19 through 450 of SEQ ID NO: 2 or amino acids 30 through 463 of SEQ ID NO: 3. 
     
     
         2 . An isolated nucleic acid that encodes an amino acid sequence of an extracellular domain of Betacam, wherein the amino acid sequence consists essentially of SEQ ID NO: 14, SEQ ID NO: 15, an amino acid sequence that has at least 50% identity to SEQ ID NO: 14 or an amino acid sequence that has at least 50% identity to SEQ ID NO: 15. 
     
     
         3 . An isolated nucleic acid consisting essentially of SEQ ID NO: 26. 
     
     
         4 . An isolated polypeptide that consists essentially of amino acids 31 through 462 of SEQ ID NO: 1, amino acids 19 through 450 of SEQ ID NO:2 or amino acids 30 through 463 of SEQ ID NO: 3. 
     
     
         5 . An isolated polypeptide that consists essentially of SEQ ID NO: 14, SEQ ID NO: 15, an amino acid sequence that has at least 50% identity to SEQ ID NO: 14 or an amino acid sequence that has at least 50% identity to SEQ ID NO: 15. 
     
     
         6 . An antibody that has binding specificity for the polypeptide of  claim 4  or  5 . 
     
     
         7 . A method of detecting beta cells in a mixture of pancreatic cells comprising detecting the presence of a polypeptide on the surface of the cells, wherein the polypeptide comprises SEQ ID NO: 14, SEQ ID NO: 15, an amino acid sequence that has at least 50% identity to SEQ ID NO: 14 or an amino acid sequence that has at least 50% identity to SEQ ID NO: 15, and detection of expression of the polypeptide on the surface of the cells indicates that the cells are pancreatic beta cells. 
     
     
         8 . The method of  claim 7  further comprising isolating the pancreatic beta cells from the mixture of cells. 
     
     
         9 . The method of  claim 8  wherein the pancreatic beta cells are isolated from a biological sample. 
     
     
         10 . The method of  claim 7  wherein the biological sample is pancreatic tissue. 
     
     
         11 . The method of  claim 10  wherein the pancreatic tissue is obtained from a cadaver. 
     
     
         12 . The method of  claim 7  wherein expression of the polypeptide is detected using an antibody that has binding affinity for the polypeptide. 
     
     
         13 . A method of detecting pancreatic beta cells in an individual in need thereof, comprising administering to the individual an agent that detects the presence of a polypeptide on the surface of the pancreatic beta cells, wherein the polypeptide comprises SEQ ID NO: 14, SEQ ID NO: 15, an amino acid sequence that has at least 50% identity to SEQ ID NO: 14 or an amino acid sequence that has at least 50% identity to SEQ ID NO: 15. 
     
     
         14 . The method of  claim 13  wherein the individual is being screened for a risk of developing diabetes. 
     
     
         15 . The method of  claim 13  wherein the individual has diabetes. 
     
     
         16 . The method of  claim 15  wherein the diabetes is Type I diabetes or Type II diabetes. 
     
     
         17 . The method of  claim 13  wherein the individual has had an islet cell transplantation. 
     
     
         18 . A method of isolating pancreatic beta cells from a mixture of pancreatic cells comprising:
 a) contacting the mixture with a reagent that specifically binds to a polypeptide present on the surface of pancreatic beta cells, wherein the polypeptide comprises SEQ ID NO: 14, SEQ ID NO: 15, an amino acid sequence that has at least 50% identity to SEQ ID NO: 14 or an amino acid sequence that has at least 50% identity to SEQ ID NO: 15, thereby producing a combination;   b) maintaining the combination under conditions in which the reagent binds to the polypeptide present on the surface of the pancreatic beta cells, thereby producing a complex of pancreatic beta cells bound to the reagent; and   c) separating the complex from the combination,   thereby isolating pancreatic beta cells from the mixture of pancreatic cells.   
     
     
         19 . The method of  claim 18  further comprising d) separating the pancreatic beta cells from the reagent. 
     
     
         20 . The method of  claim 18  wherein the mixture of pancreatic beta cells is pancreatic tissue. 
     
     
         21 . The method of  claim 20  wherein the pancreatic tissue is obtained from a cadaver. 
     
     
         22 . The method of  claim 18  wherein the reagent is an antibody that has binding affinity for the polypeptide. 
     
     
         23 . A method of identifying an agent that modulates the biological activity of betacam comprising:
 a) contacting a composition comprising a polypeptide, wherein the polypeptide has an amino acid sequence comprising SEQ ID NO: 14, SEQ ID NO: 15, an amino acid sequence that has at least 50% identity to SEQ ID NO: 14 or an amino acid sequence that has at least 50% identity to SEQ ID NO: 15 with an agent to be assessed;   b) measuring the biological activity of the polypeptide in the presence of the agent compared to a suitable control,   wherein if the polypeptide modulates the activity of the polypeptide in the presence of the agent compared to the control, then the agent modulates the biological activity of betacam.   
     
     
         24 . The method of  claim 23  wherein the composition is one or more pancreatic beta cells. 
     
     
         25 . The method of  claim 24  wherein the biological activity measured is homotypic cell adhesion between betacam-expressing pancreatic beta cells. 
     
     
         26 . The method of  claim 24  wherein the control comprises pancreatic beta cells which have not been contacted with the agent to be assessed.