Nasal Placode Development, GnRH Neuronal Migration and Kallmann Syndrome.

The development of Gonadotropin releasing hormone-1 (GnRH) neurons is important for a functional reproduction system in vertebrates. Disruption of GnRH results in hypogonadism and if accompanied by anosmia is termed Kallmann Syndrome (KS). From their origin in the nasal placode, GnRH neurons migrate along the olfactory-derived vomeronasal axons to the nasal forebrain junction and then turn caudally into the developing forebrain. Although research on the origin of GnRH neurons, their migration and genes associated with KS has identified multiple factors that influence development of this system, several aspects still remain unclear. This review discusses development of the olfactory system, factors that regulate GnRH neuron formation and development of the olfactory system, migration of the GnRH neurons from the nose into the brain, and mutations in humans with KS that result from disruption of normal GnRH/olfactory systems development.

Suppression of Red Blood Cell Autofluorescence for Immunocytochemistry on Fixed Embryonic Mouse Tissue.

Autofluorescence is a problem that interferes with immunofluorescent staining and complicates data analysis. Throughout the mouse embryo, red blood cells naturally fluoresce across multiple wavelengths, spanning the emission and excitation spectra of many commonly used fluorescent reporters, including antibodies, dyes, stains, probes, and transgenic proteins, making it difficult to distinguish assay fluorescence from endogenous fluorescence. Several tissue treatment methods have been developed to bypass this issue with varying degrees of success. Sudan Black B dye has been commonly used to quench autofluorescence, but can also introduce background fluorescence. Here we present a protocol for an alternative called TrueBlack Lipofuscin Autofluorescence Quencher. The protocol described in this unit demonstrates how TrueBlack efficiently quenches red blood cell autofluorescence across red and green wavelengths in fixed embryonic tissue without interfering with immunofluorescent signal intensity or introducing background staining. We also identify optimal incubation, concentration, and multiple usage conditions for routine immunofluorescence microscopy. © 2017 by John Wiley & Sons, Inc.

Sox21 regulates the progression of neuronal differentiation in a dose-dependent manner.

Members of the SoxB transcription factor family play critical roles in the regulation of neurogenesis. The SoxB1 proteins are required for the induction and maintenance of a proliferating neural progenitor population in numerous vertebrates, however the role of the SoxB2 protein, Sox21, is less clear due to conflicting results. To clarify the role of Sox21 in neurogenesis, we examined its function in the Xenopus neural plate. Here we report that misexpression of Sox21 expands the neural progenitor domain, and represses neuron formation by binding to Neurogenin (Ngn2) and blocking its function. Conversely, we found that Sox21 is also required for neuron formation, as cells lacking Sox21 undergo cell death and thus are unable to differentiate. Together our data indicate that Sox21 plays more than one role in neurogenesis, where a threshold level is required for cell viability and normal differentiation of neurons, but a higher concentration of Sox21 inhibits neuron formation and instead promotes progenitor maintenance.