Congenital diarrheal disorder linked to a mutation in DGAT1
Congenital diarrheal disorders (CDD) are a group of rare intestinal diseases that are caused by genetic mutations. In a study published in the Journal of Clinical Investigation, Robert Farese and colleagues at the University of California, San Francisco, identified a family with two of three children affected by CDD. The affected children both carried a rare mutation in the DGAT1 gene. DGAT1 mediates the formation of triglycerides and is being assessed as a therapeutic target in the treatment of obesity. The study by Farese’s group suggests that targeting of DGAT1 could cause a severe diarrheal disorder.
TITLE: DGAT1 mutation is linked to a congenital diarrheal disorder
Feel the burn: natriuretic peptides enhance human skeletal muscle metabolism
Cardiac natiuretic peptides (NP) are proteins secreted by the heart muscle that help regulate different aspects of metabolism. In a study published in the Journal of Clinical Investigation, researchers led by Cedric Moro at the Institute of Metabolic and Cardiovascular Diseases in Toulouse, France investigated the role of NPs in human skeletal muscle metabolism. Expression of the NP receptor NPRA was correlated with several other metabolism related genes. Additionally, aerobic exercise training enhanced their expression and increased fat oxidation. These results demonstrate that NP signaling in human skeletal muscle increases metabolism and might contribute to exercise-induced improvement in skeletal muscle metabolism in humans.
TITLE: Natriuretic peptides enhance the oxidative capacity of human skeletal muscle
Improved detection of polyomavirus in Merkel cell carcinoma
Merkel cell carcinoma (MCC) is a rare, aggressive skin cancer. A virus known as the Merkel cell polyomavirus (MCPyV) can be detected in 80% of cases. In this issue of the Journal of Clinical Investigation, researchers led by James DeCaprio at the Dana Farber Institute in Boston described the development of new antibodies to detect MCPyV. Using these new antibodies, DeCaprio and colleagues found MCPyV in 56 of 58 tumors tested. Additionally, they identified mutations in the gene TP53 in the two tumors that lacked detectable MCPyV. This study suggests that MCPyV is present in MCC tumors more frequently than previously reported.
TITLE: Improved detection suggests all Merkel cell carcinomas harbor Merkel polyomavirus
Pumping iron to develop red blood cells
Erythropoiesis (the formation of red blood cells) is regulated by the induction of the hormone erythropoietin (EPO) and the suppression of hepcidin, a small molecule that prevents iron uptake. While EPO synthesis is known to be directly regulated by the protein HIF1, HIF1′s role in hepcidin suppression is unclear. In a study published in the Journal of Clinical Investigation, researchers led by Volker Haase at Vanderbilt University found that HIF-mediated suppression of hepcidin required induction of EPO; however, EPO did not directly regulate hepcidin expression. These data suggest that the HIF1 pathway may be a suitable therapeutic target for the treatment of iron-associated orders such as anemia.
TITLE: Hypoxia-inducible factor regulates hepcidin via erythropoietin-induced erythropoiesis
Finding the inflammatory culprit in a mouse model of multiple sclerosis
Multiple sclerosis is an autoimmune disorder in which the body’s immune cells invade and inflame the tissues of the central nervous system (CNS). In a mouse model of multiple sclerosis (EAE mice), a particular type of immune cell, known as Th17 cells, are responsible for CNS inflammation, but the cellular mechanisms that promote inflammation are currently unknown. In a study published in the Journal of Clinical Investigation, researchers led by Tak Mak at the Princess Margaret Hospital in Toronto found that EAE mice lacking the protein MALT1 do not develop CNS inflammation even though the immune cells still invade the CNS. MAK and colleagues found that the Th17 cells in mice lacking MALT1 do not express proteins that mediate inflammation. This study identified MALT1 as an important regulator of inflammatory Th17 cells in a mouse model of multiple sclerosis and suggest that MALT1 may be an attractive target for the treatment of human MS.
TITLE: The NF-κB-regulator MALT1 determines the encephalitogenic potential of Th17 cells
Skeletal muscle deficiencies underlie ATR-X syndrome
ATR-X syndrome is a severe intellectual disability disorder caused by mutations in the ATRX gene. Patients with these mutations suffer from decreased muscle tone, spinal curvature (kyphosis), and delayed ability to walk, suggesting that there is an underlying skeletal muscle defect. In a study published in the Journal of Clinical Investigation, researchers led by David Picketts at the Ottawa Hospital Research Institute in Ottawa, Ontario, determined that Atrx is required for postnatal muscle growth and regeneration in mice. Mice with a skeletal muscle-specific Atrx deficiency had reduced muscle tone, spinal curvature, reduced muscle regeneration, and a significantly lower body mass compared to normal mice. Picketts and colleagues found that Atrx was required to stabilize chromosomes during the rapid cell division that takes place during muscle development. These findings demonstrate that many ATR-X symptoms are due to a skeletal muscle defect.
TITLE: Compromised genomic integrity impedes muscle growth following Atrx inactivation
Integrin mutation linked to lung and kidney disease
Integrins are proteins that connect the extracellular matrix to the cellular cytoskeleton. The integrin α3β1, encoded by the gene ITGA3, is expressed in the lungs and kidneys and must modified by a sugar molecule (glycosylated) in order to function properly. In a study published in the Journal of Clinical Investigation, researchers led by Arnoud Sonnenberg at the Netherlands Cancer Institute report on a mutation in ITGA3 in a patient with lung disease and kidney failure. The mutation in ITGA3 caused excessive glycosylation and degradation of integrin α3, leading to severe kidney and lung defects. This study identifies a mutation that could be screened for in newborns presenting with respiratory distress or nephrotic syndrome of unknown origin.
TITLE: Gain-of-glycosylation in integrin α3 causes lung disease and nephrotic syndrome
Researchers identify osteoclast precursors associated with rheumatoid arthritis
Rheumatoid arthritis (RA) is an autoimmune disease that causes inflammation of the joints and surrounding tissues and is associated with increased bone resorption and osteoporosis. The cells that break down bone, known as osteoclasts, have been shown to arise from a population of precursor cells, but the role of this population in RA is unknown. In a study published in the Journal of Clinical Investigation, researchers led by Julia Charles at Harvard Medical School identified a population of bone marrow cells that develop into osteoclasts. This population of precursor cells expands in mouse models of RA. Charles and colleagues also determined that these cells block some immune cell functions and could potentially reduce inflammation in RA. These results suggest that therapeutics that prevent the development of these cells into osteoclasts could help reduce bone resorption and inflammation in RA.
TITLE: Inflammatory arthritis increases mouse osteoclast precursors with myeloid suppressor function