A novel TCIRG1 gene mutation leads to severe osteopetrosis with altered content of monocytes/macrophages in several organs

Circulating inflammatory monocytes oppose microglia and contribute to cone cell death in retinitis pigmentosa

Retinitis pigmentosa (RP) is an intractable inherited disease that primarily affects the rods through gene mutations followed by secondary cone degeneration. This cone-related dysfunction can lead to impairment of daily life activities, and ultimately blindness in patients with RP. Paradoxically, microglial neuroinflammation contributes to both protection against and progression of RP, but it is unclear which population(s) - tissue-resident microglia and/or peripheral monocyte-derived macrophages (mφ) - are implicated in the progression of the disease. Here we show that circulating blood inflammatory monocytes (IMo) are key effector cells that mediate cone cell death in RP. Attenuation of IMo and peripherally engrafted mφ by Ccl2 deficiency or immune modulation via intravenous nano-particle treatment suppressed cone cell death in rd10 mice, an animal model of RP. In contrast, the depletion of resident microglia by a colony-stimulating factor 1 receptor inhibitor exacerbated cone cell death in the same model. In human patients with RP, IMo was increased and correlated with disease progression. These results suggest that peripheral IMo is a potential target to delay cone cell death and prevent blindness in RP.

The V-ATPase a3 Subunit: Structure, Function and Therapeutic Potential of an Essential Biomolecule in Osteoclastic Bone Resorption

This review focuses on one of the 16 proteins composing the V-ATPase complex responsible for resorbing bone: the a3 subunit. The rationale for focusing on this biomolecule is that mutations in this one protein account for over 50% of osteopetrosis cases, highlighting its critical role in bone physiology. Despite its essential role in bone remodeling and its involvement in bone diseases, little is known about the way in which this subunit is targeted and regulated within osteoclasts. To this end, this review is broadened to include the three other mammalian paralogues (a1, a2 and a4) and the two yeast orthologs (Vph1p and Stv1p). By examining the literature on all of the paralogues/orthologs of the V-ATPase a subunit, we hope to provide insight into the molecular mechanisms and future research directions specific to a3. This review starts with an overview on bone, highlighting the role of V-ATPases in osteoclastic bone resorption. We then cover V-ATPases in other location/functions, highlighting the roles which the four mammalian a subunit paralogues might play in differential targeting and/or regulation. We review the ways in which the energy of ATP hydrolysis is converted into proton translocation, and go in depth into the diverse role of the a subunit, not only in proton translocation but also in lipid binding, cell signaling and human diseases. Finally, the therapeutic implication of targeting a3 specifically for bone diseases and cancer is discussed, with concluding remarks on future directions.

Differential proteomic analysis of tibial subchondral bone from male and female guinea pigs with spontaneous osteoarthritis

A proteomic study on the tibial subchondral bone in guinea pigs with spontaneous osteoarthritis was performed to investigate the molecular alterations that occur in early osteoarthritis. A total of 132 healthy Hartley guinea pigs (aged 1 month; 66 female and 66 male) were randomly divided into 11 groups of six. Changes in articular cartilage and tibial subchondral bone were assessed using macroscopic examinations and micro-computed tomography. iTRAQ-integrated liquid chromatography-tandem mass spectrometry was used to identify differentially altered proteins in the tibial subchondral bone between 1- and 3-month-old guinea pigs, which were then validated using western blotting. A gradual progression of cartilage degeneration was observed in the knee joints of the subject animals from 5-11 months. With aging, the tibial subchondral trabecular bone acquired more plate-like and less anisotropic properties, with increased bone mineral density, bone volume, trabecular thickness and numbers. The proteomic study identified 138 and 113 proteins significantly differentially expressed between 3- and 1-month old guinea pigs in both the male and female animals, respectively. Western blotting confirmed the increased expression of osteoblast-associated protein S100 calcium-binding protein A8 (S100A8) and the deregulated expression of osteoclast-associated proteins coronin 1A (CORO1A) and T-cell immune regulator 1 (TCIRG1) in the 3-month old guinea pigs in comparison to the 1-month old guinea pigs. Spontaneous cartilage degeneration in the knee joints of male Hartley guinea pigs tended to be more serious compared with the females during the development of osteoarthritis. Together, the results suggest that osteoblast-associated protein S100A8 and osteoclast-associated proteins CORO1A and TCIRG1 are potentially key regulators of early osteoarthritic development in tibial subchondral bone.

Osteopetrosis mimicking juvenile myelomonocytic leukemia

A 5-month-old boy developed splenomegaly, anemia, thrombocytopenia with elevated white cells, monocytosis and immature granulocytes in the peripheral blood. Bone marrow showed dysplasia without blastosis. Increased colony-forming unit-granulocyte-macrophage was found in the peripheral blood, mimicking granulocyte-macrophage colony-stimulating factor hypersensitivity. These findings fulfilled the diagnosis criteria for juvenile myelomonocytic leukemia (JMML), but no mutations in the CBL, NRAS, KRAS, or PTPN11 genes were detected. In addition to these findings severe hypogammaglobulinemia and elevated alkaline phosphatase were present. Bone X-ray showed dense and radiopaque bones with a bone-in-bone appearance characteristic of infantile malignant osteopetrosis (IMO). Genetic mutation in T-cell, immune regulator 1 (TCIRG1) was identified, confirming the diagnosis of IMO. Careful differential diagnosis including osteopetrosis, is therefore recommended in patients with clinical features and hematologic findings consistent with JMML.