Angus M. Sinclair

Kidney-specific inactivation of the KIF3A subunit of kinesin-II inhibits renal ciliogenesis and produces polycystic kidney disease

Polycystic kidney disease (PKD) is the most common genetic cause of renal failure in humans. Several proteins that are encoded by genes associated with PKD have recently been identified in primary cilia in renal tubular epithelia. These findings have suggested that abnormalities in cilia formation and function may play a role in the pathogenesis of PKD. To directly determine whether cilia are essential to maintain tubular integrity, we conditionally inactivated KIF3A, a subunit of kinesin-II that is essential for cilia formation, in renal epithelia. Constitutive inactivation of KIF3A produces abnormalities of left–right axis determination and embryonic lethality. Here we show that tissue-specific inactivation of KIF3A in renal tubular epithelial cells results in viable offspring with normal-appearing kidneys at birth. Cysts begin to develop in the kidney at postnatal day 5 and cause renal failure by postnatal day 21. The cyst epithelial cells lack primary cilia and exhibit increased proliferation and apoptosis, apical mislocalization of the epidermal growth factor receptor, increased expression of β-catenin and c-Myc, and inhibition of p21CIP1. These results demonstrate that the absence of renal cilia produces both the clinical and cell biological findings associated with PKD. Most generally, the phenotype of Kif3a mutant mice suggests a role for primary cilia in the maintenance of lumen-forming epithelial differentiation.

Connection Between B Lymphocyte and Osteoclast Differentiation Pathways

Osteoclasts differentiate from the hemopoietic monocyte/macrophage cell lineage in bone marrow through cell-cell interactions between osteoclast progenitors and stromal/osteoblastic cells. Here we show another osteoclast differentiation pathway closely connected with B lymphocyte differentiation. Recently the TNF family molecule osteoclast differentiation factor/receptor activator of NF-κB ligand (ODF/RANKL) was identified as a key membrane-associated factor regulating osteoclast differentiation. We demonstrate that B-lymphoid lineage cells are a major source of endogenous ODF/RANKL in bone marrow and support osteoclast differentiation in vitro. In addition, B-lymphoid lineage cells in earlier developmental stages may hold a potential to differentiate into osteoclasts when stimulated with M-CSF and soluble ODF/RANKL in vitro. B-lymphoid lineage cells may participate in osteoclastogenesis in two ways: they 1) express ODF/RANKL to support osteoclast differentiation, and 2) serve themselves as osteoclast progenitors. Consistent with these observations in vitro, a decrease in osteoclasts is associated with a decrease in B-lymphoid cells in klotho mutant mice (KL−/−), a mouse model for human aging that exhibits reduced turnover during bone metabolism, rather than a decrease in the differentiation potential of osteoclast progenitors. Taken together, B-lymphoid lineage cells may affect the pathophysiology of bone disorders through regulating osteoclastogenesis.

A novel colonic repressor element regulates intestinal gene expression by interacting with Cux/CDP.

ABSTRACT Intestinal gene regulation involves mechanisms that direct temporal expression along the vertical and horizontal axes of the alimentary tract. Sucrase-isomaltase (SI), the product of an enterocyte-specific gene, exhibits a complex pattern of expression. Generation of transgenic mice with a mutated SI transgene showed involvement of an overlapping CDP (CCAAT displacement protein)-GATA element in colonic repression of SI throughout postnatal intestinal development. We define this element as CRESIP (colon-repressive element of the SI promoter). Cux/CDP interacts with SI and represses SI promoter activity in a CRESIP-dependent manner. Cux/CDP homozygous mutant mice displayed increased expression of SI mRNA during early postnatal development. Our results demonstrate that an intestinal gene can be repressed in the distal gut and identify Cux/CDP as a regulator of this repression during development.

Erythropoietin Receptor in Ovarian Cancer Cells – Letter

A recent article by Solar et al. ([1][1]) reported that erythropoietin (Epo) inhibits apoptosis induced by photodynamic therapy in ovarian cells. The conclusion was based on tumor immunohistochemistry data generated with anti-EpoR antibodies and in vitro studies with ovarian cell lines, SKOV3 and