Haploinsufficiency of phosphodiesterase 10A activates PI3K/AKT signaling independent of PTEN to induce an aggressive glioma phenotype.

Glioblastoma is universally fatal and characterized by frequent chromosomal copy number alterations harboring oncogenes and tumor suppressors. In this study, we analyzed exome-wide human glioblastoma copy number data and found that cytoband 6q27 is an independent poor prognostic marker in multiple data sets. We then combined CRISPR-Cas9 data, human spatial transcriptomic data, and human and mouse RNA sequencing data to nominate PDE10A as a potential haploinsufficient tumor suppressor in the 6q27 region. Mouse glioblastoma modeling using the RCAS/tv-a system confirmed that Pde10a suppression induced an aggressive glioma phenotype in vivo and resistance to temozolomide and radiation therapy in vitro. Cell culture analysis showed that decreased Pde10a expression led to increased PI3K/AKT signaling in a Pten-independent manner, a response blocked by selective PI3K inhibitors. Single-nucleus RNA sequencing from our mouse gliomas in vivo, in combination with cell culture validation, further showed that Pde10a suppression was associated with a proneural-to-mesenchymal transition that exhibited increased cell adhesion and decreased cell migration. Our results indicate that glioblastoma patients harboring PDE10A loss have worse outcomes and potentially increased sensitivity to PI3K inhibition.

Deletion of Siah-interacting protein gene in Drosophila causes cardiomyopathy.

Drosophila is a useful model organism in which the genetics of human diseases, including recent advances in identification of the genetics of heart development and disease in the fly, can be studied. To identify novel genes that cause cardiomyopathy, we performed a deficiency screen in adult Drosophila. Using optical coherence tomography to phenotype cardiac function in awake adult Drosophila, we identified Df(1)Exel6240 as having cardiomyopathy. Using a number of strategies including customized smaller deletions, screening of mutant alleles, and transgenic rescue, we identified CG3226 as the causative gene for this deficiency. CG3226 is an uncharacterized gene in Drosophila possessing homology to the mammalian Siah-interacting protein (SIP) gene. Mammalian SIP functions as an adaptor protein involved in one of the ß-catenin degradation complexes. To investigate the effects of altering ß-catenin/Armadillo signaling in the adult fly, we measured heart function in flies expressing either constitutively active Armadillo or transgenic constructs that block Armadillo signaling, specifically in the heart. While, increasing Armadillo signaling in the heart did not have an effect on adult heart function, decreasing Armadillo signaling in the fly heart caused the significant reduction in heart chamber size. In summary, we show that deletion of CG3226, which has homology to mammalian SIP, causes cardiomyopathy in adult Drosophila. Alterations in Armadillo signaling during development lead to important changes in the size and function of the adult heart.

Tissue distribution of fetal liver cells following in utero transplantation in mice.

Transplantation of hepatic stem cells in utero has been advanced as a potential clinical approach to a variety of diseases, including deficiencies of coagulation factors. Although syngeneic transplantation has met with some success, consideration needs to be given to the potential for transplanted cells to colonize nontarget tissues. Liver cells were harvested from Rosa26 embyros at embryonic age 12.5 days postconception (pc) and transplanted into the peritoneal cavity of syngeneic recipients in utero. Tissues were harvested from tissue recipients at various time points ranging from 1 to 328 days pc, and tissues were stained for beta-galactosidase to identify the existence of cells derived from Rosa26 donors. Beta-galactosidase-positive cells were found in the lung, liver, and brain as early as 20 days pc and through 328 days pc. Positive cells in these tissues existed as islands of cells that were morphologically similar to hepatocytes. In the spleen, individual beta-galactosidase-positive cells of both leukocytic and erythrocytic lineages were present, and suggest that hematopoietic cells were transferred to recipients along with hepatocytes. The lack of an inflammatory response to the beta-galactosidase-positive cells suggests that the donor cells were immunologically tolerated. In summary, the possibility that cells administered in utero may inadvertently colonize nontarget tissues suggests that clinical application of this method will need to be approached with diligence.

Cardiomyopathy is associated with ribosomal protein gene haplo-insufficiency in Drosophila melanogaster.

The Minute syndrome in Drosophila melanogaster is characterized by delayed development, poor fertility, and short slender bristles. Many Minute loci correspond to disruptions of genes for cytoplasmic ribosomal proteins, and therefore the phenotype has been attributed to alterations in translational processes. Although protein translation is crucial for all cells in an organism, it is unclear why Minute mutations cause effects in specific tissues. To determine whether the heart is sensitive to haplo-insufficiency of genes encoding ribosomal proteins, we measured heart function of Minute mutants using optical coherence tomography. We found that cardiomyopathy is associated with the Minute syndrome caused by haplo-insufficiency of genes encoding cytoplasmic ribosomal proteins. While mutations of genes encoding non-Minute cytoplasmic ribosomal proteins are homozygous lethal, heterozygous deficiencies spanning these non-Minute genes did not cause a change in cardiac function. Deficiencies of genes for non-Minute mitochondrial ribosomal proteins also did not show abnormal cardiac function, with the exception of a heterozygous disruption of mRpS33. We demonstrate that cardiomyopathy is a common trait of the Minute syndrome caused by haplo-insufficiency of genes encoding cytoplasmic ribosomal proteins. In contrast, most cases of heterozygous deficiencies of genes encoding non-Minute ribosomal proteins have normal heart function in adult Drosophila.

Cardiac copper deficiency activates a systemic signaling mechanism that communicates with the copper acquisition and storage organs.

Copper (Cu) is an essential cofactor for a variety of metabolic functions, and the regulation of systemic Cu metabolism is critical to human health. Dietary Cu is absorbed through the intestine, stored in the liver, and mobilized into the circulation; however, systemic Cu homeostasis is poorly understood. We generated mice with a cardiac-specific knockout of the Ctr1 Cu transporter (Ctr1(hrt/hrt)), resulting in cardiac Cu deficiency and severe cardiomyopathy. Unexpectedly, Ctr1(hrt/hrt) mice exhibited increased serum Cu levels and a concomitant decrease in hepatic Cu stores. Expression of the ATP7A Cu exporter, thought to function predominantly in intestinal Cu acquisition, was strongly increased in liver and intestine of Ctr1(hrt/hrt) mice. These studies identify ATP7A as a candidate for hepatic Cu mobilization in response to peripheral tissue demand, and illuminate a systemic regulation in which the Cu status of the heart is signaled to organs that take up and store Cu.