Diabetes mellitus affects nearly 300 million people in the world. The development of diabetes is caused by dysfunction or by reduction of insulin-producing β-cells that are part of the endocrine pancreas. Therefore, the most critical step for understanding the pathophysiology of diabetes and for restoring lost β cells is the identification of molecular cues that specify the cellular phenotype in the pancreas. This work is based on the hypothesis that the transcription factor NEUROD1 is a key factor for the development of the pancreas and for the maintenance of endocrine tissue function. Neurod1 conditional KO mutants (Neurod1CKO) were generated using the Cre-loxP system by crossing floxed Neurod1 mice with Isl1-Cre line. Immunohistochemical analyses of the pancreas at embryonic day 17.5 and postnatal day 0 showed that the deletion of Neurod1 negatively affected the development, organization of endocrine tissue, and total mass of pancreatic endocrine cells. To better understand molecular changes, quantitative PCR was used to analyse mRNA expression in the developing pancreas at the age of embryonic day 14.5 and postnatal day 1. Genes important for the development and function of the pancreas have been selected for the study of expression changes. These analyses showed changes in expression of genes...

Detailed knowledge of the role that particular genes and factors play during the development and in the normal function of the auditory system is necessary to develop successful regenerative inner ear therapies. Islet1 transcription factor and brain derived neurothrophic factor (BDNF) have great potential to play a role in regenerative inner ear therapy as both have been shown to be sufficient for self-repair regeneration in cochlea in animal studies. In this study we looked at the roles these two factors play in the development and function of the auditory system. In the transgenic mice used in the study, overexpression of Isl1 affected cell specification during embryonic development, leading to enlargement of the cochleovestibular ganglion and accelerated nerve fiber extension and branching in mutant embryos. The hearing of young transgenic mice was not affected. However, it started to decline in 1-month-old animals. This early onset of age-related hearing loss was found to be a consequence of the neurodegeneration of the olivocochlear system caused by Pax2-driven Isl1 misexpression in the hindbrain. Our data provide the first evidence that the alternation of the olivocochlear system efferent system accelerates the age-related functional decline of hearing without the loss of OHCs. The functional role of...

Detailed knowledge of the role that particular genes and factors play during the development and in the normal function of the auditory system is necessary to develop successful regenerative inner ear therapies. Islet1 transcription factor and brain derived neurothrophic factor (BDNF) have great potential to play a role in regenerative inner ear therapy as both have been shown to be sufficient for self-repair regeneration in cochlea in animal studies. In this study we looked at the roles these two factors play in the development and function of the auditory system. In the transgenic mice used in the study, overexpression of Isl1 affected cell specification during embryonic development, leading to enlargement of the cochleovestibular ganglion and accelerated nerve fiber extension and branching in mutant embryos. The hearing of young transgenic mice was not affected. However, it started to decline in 1-month-old animals. This early onset of age-related hearing loss was found to be a consequence of the neurodegeneration of the olivocochlear system caused by Pax2-driven Isl1 misexpression in the hindbrain. Our data provide the first evidence that the alternation of the olivocochlear system efferent system accelerates the age-related functional decline of hearing without the loss of OHCs. The functional role of...

1 Abstract Diabetes mellitus is characterized by the dysfunction and reduction of insulin-producing cells, resulting in hyperglycemia, which in long term harms the organism. For future therapy, it is crucial to understand the function of various factors participating in the differentiation and maturation of endocrine pancreatic cells. The aim of this study was to unravel the functional role of ISL1 during the development of the pancreas. ISL1 is expressed in all endocrine cells of the islets of Langerhansbut its function remains unclear, especially during early pancreatogenesis. As the global deletion of this gene is embryonically lethal, we used the tissue specific deletion of Isl1 in Neurod1 possitive cells using the Cre-loxP system. In this work we studied the effect of this deletion on the structure of islets of Langerhans, the formation of endocrine cell types and relative expression of genes during early pancreatic development. A defective achitecture of islets together with postnatal absence of α-cells was found in the Isl1 deletion mutant. Also, the expression of genes important for the specification of α-cell lineage and their subsequent function was decreased. The secondary outcome was the optimalization of a protocol for effective sorting of endocrine cells using fluorescent flow cytometry, which...

The ophthalmic trigeminal placode (opV) is the birth place of one cell type of sensory neurons contributing to the trigeminal ganglion. Signals from the neural tube induce placodal identity within the surface ectoderm. Specified opV placode cells then up-regulate neuron differentiation markers and migrate to the ganglion. Several molecular pathways have been shown to act in opV placode cell development. Despite this, signals that specify individual neurons from within the opV placode remain unknown. However, it is known that components of the Notch signaling pathway are expressed in the opV placode. I tested the role of Notch signaling in opV placode development by separately inhibiting and over-activating the pathway. Using DAPT, an inhibitor of gamma-secretase, I inhibited Notch signaling in 13-15 somite stage chick embryo heads. Attenuated Notch signaling caused increased neuronal differentiation of opV cells at 13-15 somites. I also observed an increase in migratory opV placode (Pax3+) cells in the mesenchyme and expression of neuronal marker Islet1 in the ectoderm. Further, I activated Notch signaling by misexpressing the Notch intracellular domain (NICD) by in ovo electroporation of 10-12 somite stage chick embryos. This resulted in Pax3+ targeted cells failing to differentiate and remain instead in the ectoderm. Thus, Notch/Delta signaling plays an important role in selecting ophthalmic trigeminal cells to differentiate and migrate to the trigeminal ganglion.