ap20187 and Glucose-Intolerance

Most degenerative diseases begin with a gradual loss of specific cell types before reaching a threshold for symptomatic onset. However, the endogenous regenerative capacities of different tissues are difficult to study, because of the limitations of models for early stages of cell loss. Therefore, we generated a transgenic mouse line (Mos-iCsp3) in which a lox-mismatched Cre/lox cassette can be activated to produce a drug-regulated dimerizable caspase-3. Tissue-restricted Cre expression yielded stochastic Casp3 expression, randomly ablating a subset of specific cell types in a defined domain. The limited and mosaic cell loss led to distinct responses in 3 different tissues targeted using respective Cre mice: reversible, impaired glucose tolerance with normoglycemia in pancreatic β cells; wound healing and irreversible hair loss in the skin; and permanent moderate deafness due to the loss of auditory hair cells in the inner ear. These mice will be important for assessing the repair capacities of tissues and the potential effectiveness of new regenerative therapies.

Topics: Alopecia; Animals; Apoptosis; Caspase 3; Cell Lineage; Dimerization; Disease Models, Animal; Epidermis; Gene Expression Regulation; Gene Knockdown Techniques; Genes, Transgenic, Suicide; Glucose Intolerance; Hair Cells, Auditory, Inner; Hearing Loss, Bilateral; Hearing Loss, Sensorineural; Homeodomain Proteins; Insulin; Islets of Langerhans; Keratin-14; Mice; Mice, Inbred C57BL; Mice, Transgenic; Mosaicism; Organ Specificity; Phenotype; Tacrolimus; Transcription Factor Brn-3C; Transgenes; Wound Healing

We describe the generation and characterization of the first inducible 'fatless' model system, the FAT-ATTAC mouse (fat apoptosis through targeted activation of caspase 8). This transgenic mouse develops identically to wild-type littermates. Apoptosis of adipocytes can be induced at any developmental stage by administration of a FK1012 analog leading to the dimerization of a membrane-bound, adipocyte-specific caspase 8-FKBP fusion protein. Within 2 weeks of dimerizer administration, FAT-ATTAC mice show near-knockout levels of circulating adipokines and markedly reduced levels of adipose tissue. FAT-ATTAC mice are glucose intolerant, have diminished basal and endotoxin-stimulated systemic inflammation, are less responsive to glucose-stimulated insulin secretion and show increased food intake independent of the effects of leptin. Most importantly, we show that functional adipocytes can be recovered upon cessation of treatment, allowing the study of adipogenesis in vivo, as well as a detailed examination of the importance of the adipocyte in the regulation of multiple physiological functions and pathological states.

Topics: Adipocytes; Adipose Tissue; Animals; Apoptosis; Caspase 8; Caspases; Dimerization; Eating; Enzyme Activation; Glucose Intolerance; Inflammation; Insulin; Insulin Secretion; Leptin; Lipodystrophy; Lipopolysaccharides; Mice; Mice, Transgenic; Recombinant Fusion Proteins; Tacrolimus; Tacrolimus Binding Proteins