The visual system homeobox 2 (Vsx2/Chx10) gene is required for proper eye development in vertebrates. In mouse, mutations in Vsx2 cause micro-ophthalmia, optic nerve aplasia, and failed retinal development, as well as aberrant retinal lamination. GDF11, a member of the TGF-β superfamily of signaling molecules known to function as an autocrine negative regulator of sensory neuron neurogenesis, has also been shown to have dramatic effects on retinal development: Absence of Gdf11 results in an increase in numbers of retinal ganglion cells, resulting from changes in the fates of retinal stem/progenitor cells in Gdf11 null retinas. In the present study, we performed genetic manipulations of the GDF11 signaling system to determine whether alterations in Gdf11 activity levels can improve retinal development in Vsx2-null mice. We found that removal of Gdf11 alleles in Vsx2 orJ/orJ mice can rescue retinal development and thickness to a substantial extent, and partially restores the expression of genes important for the development of specific types of retinal neurons. The molecular mechanism(s) by which reduction of Gdf11 activity enables rescue of retinal development in Vsx2 mutant animals is currently being investigated, and should provide important insights for potential treatment of retinal dystrophies. © 2012 Springer Science+Business Media, LLC.

Abiotic stresses such as drought, heat or salinity are a major cause of yield loss worldwide. Recent studies revealed that the acclimation of plants to a combination of different environmental stresses is unique and cannot be directly deduced from studying the response of plants to each of the different stresses applied individually. Here we report on the response of Arabidopsis thaliana to a combination of salt and heat stress using transcriptome analysis, physiological measurements and mutants deficient in abscisic acid, salicylic acid, jasmonic acid or ethylene signaling. Arabidopsis plants were found to be more susceptible to a combination of salt and heat stress compared to each of the different stresses applied individually. The stress combination resulted in a higher ratio of Na+/K+ in leaves and caused the enhanced expression of 699 transcripts unique to the stress combination. Interestingly, many of the transcripts that specifically accumulated in plants in response to the salt and heat stress combination were associated with the plant hormone abscisic acid. In accordance with this finding, mutants deficient in abscisic acid metabolism and signaling were found to be more susceptible to a combination of salt and heat stress than wild type plants. Our study highlights the important role abscisic acid plays in the acclimation of plants to a combination of two different abiotic stresses.

Stem cell therapies to treat central nervous system (CNS) injuries and diseases face many obstacles, one of which is the fact that the adult CNS often presents an environment hostile to the development and differentiation of neural stem and progenitor cells. Close examination of two regions of the nervous system – the olfactory epithelium (OE), which regenerates, and the neural retina, which does not – have helped identify endogenous signals, made by differentiated neurons, which act to inhibit neurogenesis by stem/progenitor cells within these tissues. In this chapter, we provide background information on these systems and their neurogenic signaling systems, with the goal of providing insight into how manipulation of endogenous signaling molecules may enhance the efficacy of stem cell neurotherapeutics.