RESUMO
Islet-1 (Isl-1) is essential for the survival and ensuing differentiation of pancreatic endocrine progenitors. Isl-1 remains expressed in all adult pancreatic endocrine lineages; however, its specific function in the postnatal pancreas is unclear. Here we determine whether Isl-1 plays a distinct role in the postnatal ß-cell by performing physiological and morphometric analyses of a tamoxifen-inducible, ß-cell-specific Isl-1 loss-of-function mouse: Isl-1(L/L); Pdx1-CreER(Tm). Ablating Isl-1 in postnatal ß-cells reduced glucose tolerance without significantly reducing ß-cell mass or increasing ß-cell apoptosis. Rather, islets from Isl-1(L/L); Pdx1-CreER(Tm) mice showed impaired insulin secretion. To identify direct targets of Isl-1, we integrated high-throughput gene expression and Isl-1 chromatin occupancy using islets from Isl-1(L/L); Pdx1-CreER(Tm) mice and ßTC3 insulinoma cells, respectively. Ablating Isl-1 significantly affected the ß-cell transcriptome, including known targets Insulin and MafA as well as novel targets Pdx1 and Slc2a2. Using chromatin immunoprecipitation sequencing and luciferase reporter assays, we found that Isl-1 directly occupies functional regulatory elements of Pdx1 and Slc2a2. Thus Isl-1 is essential for postnatal ß-cell function, directly regulates Pdx1 and Slc2a2, and has a mature ß-cell cistrome distinct from that of pancreatic endocrine progenitors.
Assuntos
Resistência à Insulina/genética , Células Secretoras de Insulina/metabolismo , Proteínas com Homeodomínio LIM/genética , Elementos Reguladores de Transcrição/genética , Fatores de Transcrição/genética , Animais , Apoptose/genética , Linhagem Celular Tumoral , Imunoprecipitação da Cromatina , Perfilação da Expressão Gênica , Teste de Tolerância a Glucose , Transportador de Glucose Tipo 2/genética , Transportador de Glucose Tipo 2/metabolismo , Proteínas de Homeodomínio/genética , Proteínas de Homeodomínio/metabolismo , Insulina/genética , Insulina/metabolismo , Proteínas com Homeodomínio LIM/metabolismo , Fatores de Transcrição Maf Maior/genética , Fatores de Transcrição Maf Maior/metabolismo , Camundongos , Camundongos Knockout , Transativadores/genética , Transativadores/metabolismo , Fatores de Transcrição/metabolismoRESUMO
Se utilizó un paradigma de elección para evaluar la distribución del comportamiento entrelazado de dos grupos de dos participantes entre respuestas que tenían solo consecuencias operantes y respuestas con consecuencias culturales. En un diseño BABABAB de ensayo discreto, cada participante podría seleccionar una de tres opciones, que entregaba 3 o 5 puntos. En las condiciones B (consecuencia cultural), dos de las opciones tenían efectos adicionales: la opción de tres puntos también sumaba 3 puntos a las ganancias del otro participante, y una de las opciones de 5 puntos quitaba esa cantidad de las ganancias del otro participante. La tercera opción era igual en ambas condiciones y le entregaba 5 puntos al participante que la elegía. Los resultados indicaron que los participantes en ambos grupos inicialmente produjeron combinaciones de respuestas que ganaban 8 puntos para un individuo u otro frecuentemente (y 0 o 3 para el otro), pero la distribución de respuesta cambió hacia combinaciones de 6 puntos para cada individuo. Este paso de refuerzo máximo individual hacia máximo refuerzo grupal indica que las contingencias culturales no actuaron de acuerdo con las contingencias operantes, lo que sugiere la presencia de diferentes mecanismos de selección.
A choice paradigm was used to evaluate allocation of interlocking behavior of two groups of two participants between responses having operant consequences only, and responses having cultural consequences. In a discrete trial BABABAB design, each participant could select one of three options, which delivered either 3 or 5 points. In B (cultural consequence) condition, two of the options had additional effects: the 3-point option also added 3 points to the other participant's earnings, and one of the 5-point options also subtracted 5 points from the other participant's earnings. The third option was unchanged in both conditions and delivered 5 points to the participant who selected it. Results indicated that participants in both groups initially frequently produced response combinations that earned 8 points for one or the other individual (and 0 or 3 points for the other), but allocation of responding increasingly changed to combinations that produced 6 points for each individual. This shift in performances away from maximum individual reinforcement towards maximum group reinforcement indicates cultural contingencies did not act in concert with operant contingencies, suggesting they are different mechanisms of selection.