Nitric oxide (NO) inhibits proliferation of subventricular zone (SVZ) neural precursor cells in adult mice in vivo under physiological conditions. The mechanisms underlying this NO effect have now been investigated using SVZ-derived neural stem cells, which generate neurospheres in vitro when stimulated by epidermal growth factor (EGF). In these cultures, NO donors decreased the number of newly formed neurospheres as well as their size, which indicates that NO was acting on the neurosphere-forming neural stem cells and the daughter neural progenitors. The effect of NO was cytostatic, not proapoptotic, and did not involve cGMP synthesis. Neurosphere cells expressed the neuronal and endothelial isoforms of NO synthase (NOS) and produced NO in culture. Inhibition of NOS activity by Nω-nitro-l-arginine methylester (l-NAME) promoted neurosphere formation and growth, thus revealing an autocrine/paracrine action of NO on the neural precursor cells. Both exogenous and endogenous NO impaired the EGF-induced activation of the EGF receptor (EGFR) tyrosine kinase and prevented the EGF-induced Akt phosphorylation in neurosphere cells. Inhibition of the phosphoinositide-3-kinase (PI3-K)/Akt pathway by LY294002 significantly reduced the number of newly formed neurospheres, which indicates that this is an essential pathway for neural stem cell self-renewal. Chronic administration of l-NAME to adult mice enhanced phospho-Akt staining in the SVZ and reduced nuclear p27Kip1 in the SVZ and olfactory bulb. The inhibition of EGFR and PI3-K pathway by NO explains, at least in part, its antimitotic effect on neurosphere cells and may be a mechanism involved in the physiological role of NO as a negative regulator of SVZ neurogenesis in adult mice.

Thyroid cancer, a cancerous tumor or growth located within the thyroid gland, is the most common endocrine cancer. It is one of the few cancers whereby incidence rates have increased in recent years. It occurs in all age groups, from children through to seniors. Most studies are focused on dissecting its genetic basis, since our current knowledge of the genetic background of the different forms of thyroid cancer is far from complete, which poses a challenge for diagnosis and prognosis of the disease. In this review, we describe prevailing advances and update our understanding of the molecular genetics of thyroid cancer, focusing on the main genes related with the pathology, including the different noncoding RNAs associated with the disease.

Hirschsprung disease (HSCR; OMIM 142623) is a developmental disorder characterized by aganglionosis along variable lengths of the distal gastrointestinal tract, which results in intestinal obstruction. Interactions among known HSCR genes and/or unknown disease susceptibility loci lead to variable severity of phenotype. Neither linkage nor genome-wide association studies have efficiently contributed to completely dissect the genetic pathways underlying this complex genetic disorder. We have performed whole exome sequencing of 16 HSCR patients from 8 unrelated families with SOLID platform. Variants shared by affected relatives were validated by Sanger sequencing. We searched for genes recurrently mutated across families. Only variations in the FAT3 gene were significantly enriched in five families. Within-family analysis identified compound heterozygotes for AHNAK and several genes (N = 23) with heterozygous variants that co-segregated with the phenotype. Network and pathway analyses facilitated the discovery of polygenic inheritance involving FAT3, HSCR known genes and their gene partners. Altogether, our approach has facilitated the detection of more than one damaging variant in biologically plausible genes that could jointly contribute to the phenotype. Our data may contribute to the understanding of the complex interactions that occur during enteric nervous system development and the etiopathology of familial HSCR.