TY - JOUR

T1 - Differential expression of glutamic acid decarboxylase in rat and human islets

AU - Petersen, J S

AU - Russel, S

AU - Marshall, M O

AU - Kofod, Hans

AU - Buschard, K

AU - Cambon, N

AU - Karlsen, Alan E

AU - Boel, E

AU - Hagopian, W A

AU - Hejnaes, K R

PY - 1993/3

Y1 - 1993/3

N2 - The GABA synthesizing enzyme GAD is a prominent islet cell autoantigen in type I diabetes. The two forms of GAD (GAD64 and GAD67) are encoded by different genes in both rats and humans. By in situ hybridization analysis of rat and human pancreases, expression of both genes was detected in rat islets, whereas only GAD64 mRNA was detected in human islets. Immunocytochemical analysis of rat and human pancreatic sections or isolated islets with antibodies to GAD64 and GAD67 in combination with antibodies to insulin, glucagon, or SRIF confirmed that a GAD64 and GAD67 expression were beta-cell specific in rat islets. In contrast, only GAD64 was detected in human islets and was, in addition to beta-cells, also surprisingly localized to some alpha-cells, delta-cells, and PP-cells. In long-term (4 wk) monolayer cultures of newborn rat islet cells, GAD64 expression remained beta-cell specific as observed in vivo, whereas GAD67 was localized not only to the beta-cells but also in the alpha-cells and delta-cells. A small but distinct fraction of GAD positive cells in these monolayer cultures did not accumulate GABA immunoreactivity, which may indicate cellular heterogeneity with respect to GABA catabolism or GAD enzyme activity. In a rat insulinoma cell line (NHI-6F) producing both glucagon and insulin depending on the culture conditions, GAD64 expression was detected only in cultures in which the insulin producing phenotype dominated. In conclusion, these data demonstrate that the two GAD isoforms are differentially expressed in rat and human islets but also that the expression differs according to culture conditions. These findings emphasize the need to consider both the species and culture conditions of islets.

AB - The GABA synthesizing enzyme GAD is a prominent islet cell autoantigen in type I diabetes. The two forms of GAD (GAD64 and GAD67) are encoded by different genes in both rats and humans. By in situ hybridization analysis of rat and human pancreases, expression of both genes was detected in rat islets, whereas only GAD64 mRNA was detected in human islets. Immunocytochemical analysis of rat and human pancreatic sections or isolated islets with antibodies to GAD64 and GAD67 in combination with antibodies to insulin, glucagon, or SRIF confirmed that a GAD64 and GAD67 expression were beta-cell specific in rat islets. In contrast, only GAD64 was detected in human islets and was, in addition to beta-cells, also surprisingly localized to some alpha-cells, delta-cells, and PP-cells. In long-term (4 wk) monolayer cultures of newborn rat islet cells, GAD64 expression remained beta-cell specific as observed in vivo, whereas GAD67 was localized not only to the beta-cells but also in the alpha-cells and delta-cells. A small but distinct fraction of GAD positive cells in these monolayer cultures did not accumulate GABA immunoreactivity, which may indicate cellular heterogeneity with respect to GABA catabolism or GAD enzyme activity. In a rat insulinoma cell line (NHI-6F) producing both glucagon and insulin depending on the culture conditions, GAD64 expression was detected only in cultures in which the insulin producing phenotype dominated. In conclusion, these data demonstrate that the two GAD isoforms are differentially expressed in rat and human islets but also that the expression differs according to culture conditions. These findings emphasize the need to consider both the species and culture conditions of islets.

KW - Animals

KW - Antibodies, Monoclonal

KW - Autoantigens

KW - Base Sequence

KW - Blotting, Western

KW - Fluorescent Antibody Technique

KW - Gene Expression

KW - Glutamate Decarboxylase

KW - Humans

KW - Immunohistochemistry

KW - In Situ Hybridization

KW - Islets of Langerhans

KW - Molecular Sequence Data

KW - Rats

KW - Rats, Inbred Lew

KW - Species Specificity

M3 - Journal article

C2 - 8432419

VL - 42

SP - 484

EP - 495

JO - Diabetes

JF - Diabetes

SN - 0012-1797

IS - 3

ER -