Ingela Bergqvist

The basic helix-loop-helix transcription factor E2-2 is involved in T lymphocyte development.

E2A, HEB and E2–2 genes encode a group of basic helix‐loop‐helix (bHLH) transcription factors that are structurally and functionally similar. Deletion of the genes encoding either of these proteins leads to early lethality and a block in B lymphocyte development. Evidence for a function in T lymphocyte development has, however, only been reported for E2A and HEB. To further elucidate the role of E2–2 at developmental stages that have proven difficult to study due to the early lethality phenotype of mice defective in E2–2, we generated and analyzed mice conditionally mutated in the E2–2 gene. These mice are mosaic with respect to E2–2 expression, consisting of cells with either one functional and one null mutated E2–2 allele or two null mutated alleles. Using this experimental model, we find that cells with a homozygous null mutated E2–2 gene are under‐represented in B lymphocyte as well as T lymphocyte cell lineages as compared to other hematopoietic or non‐hematopoietic cell lineages. Our data suggests that E2–2 deficiency leads to a partial block in both B and T lymphocyte development. The block in T cell development appears to occur at an early stage in differentiation, since skewing in the mosaicism is observed already in CD4+8+ double‐positive thymocytes.

Gene array identification of Ipf1/Pdx1-/- regulated genes in pancreatic progenitor cells

BackgroundThe homeodomain transcription factor IPF1/PDX1 exerts a dual role in the pancreas; Ipf1/Pdx1 global null mutants fail to develop a pancreas whereas conditional inactivation of Ipf1/Pdx1 in β-cells leads to impaired β-cell function and diabetes. Although several putative target genes have been linked to the β-cell function of Ipf1/Pdx1, relatively little is known with respect to genes regulated by IPF1/PDX1 in early pancreatic progenitor cells.ResultsMicroarray analyses identified a total of 111 genes that were differentially expressed in e10.5 pancreatic buds of Ipf1/Pdx1-/- embryos. The expression of one of these, Spondin 1, which encodes an extracellular matrix protein, has not previously been described in the pancreas. Quantitative real-time RT-PCR analyses and immunohistochemical analyses also revealed that the expression of FgfR2IIIb, that encodes the receptor for FGF10, was down-regulated in Ipf1/Pdx1-/- pancreatic progenitor cells.ConclusionThis microarray analysis has identified a number of candidate genes that are differentially expressed in Ipf1/Pdx1-/- pancreatic buds. Several of the differentially expressed genes were known to be important for pancreatic progenitor cell proliferation and differentiation whereas others have not previously been associated with pancreatic development.

Establishment and Characterization of RAG-2 Deficient Non-Obese Diabetic Mice

The authors have established a new immunodeficient mouse strain on the genetic background of the diabetes prone non‐obese diabetic (NOD) mouse. A deletion mutant of the RAG‐2 gene was back crossed 10 generations onto the NOD/Bom strain background. The homozygous NODrag−2−/− mice lack functionally mature B and T lymphocytes and do not develop insulitis or diabetes throughout life. In contrast, heterozygous NODrag−2+/− develop both insulitis and diabetes with an incidence similar to the wild type NOD mice. In transfer experiments, spleen cells from diabetic NOD donors were found to transfer disease to NODrag−2−/− recipients similar to what has been previously observed in transfer to irradiated NOD recipients or to immunodeficient NOD‐scid/scid mice. While resembling the recently established NOD‐scid/scid mice in many respects, the NODrag−2−/− mice represents an advantageous model for reconstitution of the pathogenesis of murine IDDM as it does not produce any endogenous, mature T or B lymphocytes.

Transgenic Cre recombinase expression in germ cells and early embryogenesis directs homogeneous and ubiquitous deletion of loxP‐flanked gene segments

We report on the establishment of a transgenic mouse line expressing Cre recombinase under control of the c‐kit promoter. Expression of Cre recombinase was only observed in late spermatogenesis and oogenesis, however, Cre‐mediated deletion of floxed gene segments occurred at this stage as well as in early embryogenesis. As a consequence of this, a chimeric distribution of loxed alleles was found in a large fraction of these mice. The chimerism was very homogeneous in different organs and tissues of the same individual but varied between different individual offspring. The potential uses for this mouse line are discussed.

MFng Is Dispensable for Mouse Pancreas Development and Function

ABSTRACT Notch signaling regulates pancreatic cell differentiation, and mutations of various Notch signaling components result in perturbed pancreas development. Members of the Fringe family of β1,3-N-acetylglucosaminyltransferases, Manic Fringe (MFng), Lunatic Fringe (LFng), and Radical Fringe (RFng), modulate Notch signaling, and MFng has been suggested to regulate pancreatic endocrine cell differentiation. We have characterized the expression of the three mouse Fringe genes in the developing mouse pancreas between embryonic days 9 and 14 and show that the expression of MFng colocalized with the proendocrine transcription factor Ngn3. In contrast, the expression of LFng colocalized with the exocrine marker Ptf1a, whereas RFng was not expressed. Moreover, we show that expression of MFng is lost in Ngn3 mutant mice, providing evidence that MFng is genetically downstream of Ngn3. Gain- and loss-of-function analyses of MFng by the generation of mice that overexpress MFng in early pancreatic progenitor cells and mice with a targeted deletion of MFng provide, however, evidence that MFng is dispensable for pancreas development and function, since no pancreatic defects in these mice were observed.

Functional expression of Cre recombinase in sub-regions of mouse CNS and retina

We describe a strategy for generating CNS and retina sub‐region‐specific mutations using the Cre/loxP system. Transgenic mice expressing Cre recombinase under the control of the c‐kit promoter were established. Functional Cre expression was predominantly found to be restricted to the CA1, CA2 and CA3 regions of the hippocampus, the anterior region of the dentate gyrus, and to the ganglion cell layer of the retina.

A role for E2-2 at the DN3 stage of early thymopoiesis.

Roles for the E-proteins E2A and HEB during T lymphocyte development have been well established. Based on our previous observations of counter selection against T cells lacking E2-2, it seemed reasonable to assume that there would be a function also for E2-2 in thymocyte development. Aiming at assigning such a role for E2-2, we analyzed the expression of E2-2, E2A, HEB as well as Id mRNA during T cell development. Interestingly, whereas all three E-proteins were expressed during early thymocyte development, significant expression beyond the DP stage was detected only for E2A. Among the Id proteins, Id2 displayed a prominent expression exclusively in DN1, whereas Id3 showed some expression in DN1, followed by a down regulation and then a prominent induction, peaking in the DP stage. E2-2 was expressed during the DN stages, as well as in the DP stage, suggesting that E2-2 operates in concert with the other E-proteins during early thymocyte development. We found that E2-2 null thymocytes displayed a partial block at the DN3 stage of development, as well as a reduced expression of pre-T alpha, known to be regulated also by E2A and HEB. The fact that E2-2 deficient thymocytes develop without gross abnormalities is likely to stem from redundancy due to the co-expression of E2A and HEB.

PAN-AMPK activator O304 improves glucose homeostasis and microvascular perfusion in mice and type 2 diabetes patients

AMPK activated protein kinase (AMPK), a master regulator of energy homeostasis, is activated in response to an energy shortage imposed by physical activity and caloric restriction. We here report on the identification of PAN-AMPK activator O304, which - in diet-induced obese mice - increased glucose uptake in skeletal muscle, reduced β cell stress, and promoted β cell rest. Accordingly, O304 reduced fasting plasma glucose levels and homeostasis model assessment of insulin resistance (HOMA-IR) in a proof-of-concept phase IIa clinical trial in type 2 diabetes (T2D) patients on Metformin. T2D is associated with devastating micro- and macrovascular complications, and O304 improved peripheral microvascular perfusion and reduced blood pressure both in animals and T2D patients. Moreover, like exercise, O304 activated AMPK in the heart, increased cardiac glucose uptake, reduced cardiac glycogen levels, and improved left ventricular stroke volume in mice, but it did not increase heart weight in mice or rats. Thus, O304 exhibits a great potential as a novel drug to treat T2D and associated cardiovascular complications.