Amyotrophic lateral sclerosis (ALS) is a devastating human neurodegenerative disease. The causes of ALS are poorly understood, although the protein TDP-43 has been suggested to play a critical role in disease pathogenesis. Here we show that Ataxin-2, a polyglutamine (polyQ) protein mutated in spinocerebellar ataxia type 2 (SCA2), is a potent modifier of TDP-43 toxicity in animal and cellular models. The proteins associate in a complex that depends on RNA. Ataxin-2 is abnormally localized in spinal cord neurons of ALS patients. Likewise, TDP-43 shows mislocalization in SCA2. To assess a role in ALS, we analyzed the Ataxin-2 gene (ATXN2) in 915 ALS patients. We found intermediate-length polyQ expansions (27–33 Qs) in ATXN2 significantly associated with ALS. These data establish ATXN2 as a relatively common ALS disease susceptibility gene. Further, these findings indicate that the TDP-43/Ataxin-2 interaction may be a promising target for therapeutic intervention in ALS and other TDP-43 proteinopathies.

Background-Microcomputed tomography (micro-CT) has been used extensively in research to generate high-resolution 3D images of calcified tissues in small animals nondestructively. It has been especially useful for the characterization of skeletal mutations but limited in its utility for the analysis of soft tissue such as the cardiovascular system. Visualization of the cardiovascular system has been largely restricted to structures that can be filled with radiopaque intravascular contrast agents in adult animals. Recent ex vivo studies using osmium tetroxide, iodinated contrast agents, inorganic iodine, and phosphotungstic acid have demonstrated the ability to stain soft tissues differentially, allowing for high intertissue contrast in micro-CT images. In the present study, we demonstrate the application of this technology for visualization of cardiovascular structures in developing mouse embryos using Lugol solution (aqueous potassium iodide plus iodine). Methods and Results-We show the optimization of this method to obtain ex vivo micro-CT images of embryonic and neonatal mice with excellent soft-tissue contrast. We demonstrate the utility of this method to visualize key structures during cardiovascular development at various stages of embryogenesis. Our method benefits from the ease of sample preparation, low toxicity, and low cost. Furthermore, we show how multiple cardiac defects can be demonstrated by micro-CT in a single specimen with a known genetic lesion. Indeed, a previously undescribed cardiac venous abnormality is revealed in a PlexinD1 mutant mouse. Conclusions-Micro-CT of iodine-stained tissue is a valuable technique for the characterization of cardiovascular development and defects in mouse models of congenital heart disease. (Circ Cardiovasc Imaging. 2010;3:314-322.)Key Words: micro-CT Ⅲ iodine Ⅲ mouse Ⅲ development Ⅲ PlexinD1 Ⅲ congenital heart disease T he ability to genetically manipulate the mouse has resulted in a powerful model system for the investigation of many disease processes. In particular, genetic studies in the mouse have enhanced our understanding of embryonic development, and by extension, of congenital defects. In humans, cardiac defects are the most common serious anomalies among live births with an estimated frequency of 0.6%. 1 Numerous mouse models of congenital heart disease have been generated and characterized, adding greater insight into the molecular and cellular origins of these defects. 2 In addition, current research in the area of targeted gene deletions holds great promise to further elucidate mechanisms of cardiac development. Editorial see p 228 Clinical Perspective on p 322Although structurally similar to the human, the significantly reduced size of the murine cardiovascular system presents a number of technical challenges when attempting to stage anatomic features such as vascular structures. Identification and characterization of the phenotype of cardiovascular defects in mice traditionally has relied on histological analysis of sectioned specimens. Histology,...

The plasticity of differentiated cells in adult tissues undergoing repair is an area of intense research. Pulmonary alveolar Type II cells produce surfactant and function as progenitors in the adult, demonstrating both self-renewal and differentiation into gas exchanging Type I cells. In vivo, Type I cells are thought to be terminally differentiated and their ability to give rise to alternate lineages has not been reported. Here, we show that Hopx becomes restricted to Type I cells during development. However, unexpectedly, lineage-labeled Hopx+ cells both proliferate and generate Type II cells during adult alveolar regrowth following partial pneumonectomy. In clonal 3D culture, single Hopx+ Type I cells generate organoids composed of Type I and Type II cells, a process modulated by TGFβ signaling. These findings demonstrate unanticipated plasticity of Type I cells and a bi-directional lineage relationship between distinct differentiated alveolar epithelial cell types in vivo and in single cell culture.