Recent studies suggest that physiological and tumorigenic proliferation of mammalian cells is controlled by multiple cyclin-dependent kinases (CDKs) largely in tissue-specific manners. We and others previously demonstrated that adult mice deficient for the Cyclin D partner CDK4 (Cdk4-/- mice) exhibit hypoplasia in the pituitary and pancreatic islet due to primary postnatal defects in proliferation

Mouse knockouts of Cdk2 and Cdk4 are individually viable whereas the double knockouts are embryonic lethal due to heart defects, and this precludes the investigation of their overlapping roles in definitive hematopoiesis. Here we use a conditional knockout mouse model to investigate the effect of combined loss of Cdk2 and Cdk4 in hematopoietic cells. Cdk2fl/flCdk4-/-vavCre mice are viable but disp

In mitosis, the Greatwall kinase (called microtubuleassociated serine/threonine kinase like [Mastl] in mammals)is essential for prometaphase entry or progression by suppressing protein phosphatase 2A (PP2A) activity. PP2A suppression in turn leads to high levels of Cdk1 substrate phosphorylation. We have used a mouse model with an oocyte-specific deletion of Mastl to show that Mastl-null oocytes r

Cell-cycle inhibition has yet to offer a generally effective approach to cancer treatment, but a full evaluation of different combinations of cell-cycle inhibitors has not been evaluated. Cyclin A2, a core component of the cell cycle, is often aberrantly expressed in cancer where it may impact cell proliferation. In this study, we investigated the role of cyclin A2 in tumorigenesis using a conditi

In this issue of Blood, Matsumoto et al report that T cell-specific deletion of the cyclin-dependent kinase inhibitor p57Kip2(p57) in mice leads to a block in T-cell development as a result of hyperactivation of the E2F-p53 pathway and demonstrate that the loss of p57 accelerates lymphomagenesis in the absence of p53.

The initiation of DNA replication requires two protein kinases: cyclin-dependent kinase (Cdk) and Cdc7. Although S phase Cdk activity has been intensively studied, relatively little is known about how Cdc7 regulates progression through S phase. We have useda Cdc7 inhibitor, PHA-767491, todissect the role of Cdc7 in Xenopus egg extracts. We show that hyperphosphorylation of mini-chromosome maintena

The liver acts as a hub for metabolic reactions to keep a homeostatic balance during development and growth. The process of liver cancer development, although poorly understood, is related to different etiologic factors like toxins, alcohol, or viral infection. At the molecular level, liver cancer is characterized by a disruption of cell cycle regulation through many molecular mechanisms. In this

Cyclin-dependent kinase 2 (Cdk2) is dispensable for mitotic cell cycle progression and Cdk2 knockout mice are viable due to the compensatory functions of other Cdks. In order to assess the role of Cdk2 under limiting conditions, we used Skp2 knockout mice that exhibit increased levels of Cdk inhibitor, p27Kip1, which is able to inhibit Cdk2 and Cdk1. Knockdown of Cdk2 abrogated proliferation of Sk

Cyclin-dependent kinases (Cdks) are serine/threonine kinases and their catalytic activities are modulated by interactions with cyclins and Cdk inhibitors (CKIs). Close cooperation between this trio is necessary for ensuring orderly progression through the cell cycle. In addition to their well-established function in cell cycle control, it is becoming increasingly apparent that mammalian Cdks, cycl

Successful completion of the cell cycle relies on the precise activation and inactivation of cyclindependent kinases (Cdks) whose activity is mainly regulated by binding to cyclins. Recently, a new family of Cdk regulators termed Speedy/RINGO has been discovered, which can bind and activate Cdks but shares no apparent amino acid sequence homology with cyclins. All Speedy proteins share a conserved

During neurogenesis, cell cycle regulators play a pivotal role in ensuring proper proliferation, cell cycle exit, and differentiation of neural precursors. However, the precise role of cyclin-dependent kinases (Cdks) in these processes is not well understood. We generated Cdk2 and Cdk4 double knockout (DKO) mice and found a striking ablation of the intermediate zone and cortical plate in mouse emb

Mammalian oocytes are arrested at the prophase of meiosis I during fetal or postnatal development, and the meiosis is resumed by the preovulatory surge of luteinizing hormone. The in vivo functional roles of cyclin-dependent kinases (Cdks) during the resumption of meiosis in mammalian oocytes are largely unknown. Previous studies have shown that deletions of Cdk3, Cdk4 or Cdk6 in mice result in vi

Cyclin-dependent kinase 1 (Cdk1) is an archetypical kinase and a central regulator that drives cells through G2 phase and mitosis. Knockouts of Cdk2, Cdk3, Cdk4, or Cdk6 have resulted in viable mice, but the in vivo functions of Cdk1 have not been fully explored in mammals. Here we have generated a conditional-knockout mouse model to study the functions of Cdk1 in vivo. Ablation of Cdk1 leads to a

Orbital magnetization is known empirically to play an important role in several magnetic phenomena, such as permanent magnetism and ferromagnetic superconductivity. Within the recently developed "modern theory of orbital magnetization," theoretical insight has been gained into the nature of this often neglected contribution to magnetism but is based on an underlying mean-field approximation. From

Identification of the factors critical to the tumor-initiating cell (TIC) state may open new avenues in cancer therapy. Here we show that the metabolic enzyme glycine decarboxylase (GLDC) is critical for TICs in non-small cell lung cancer (NSCLC). TICs from primary NSCLC tumors express high levels of the oncogenic stem cell factor LIN28B and GLDC, which are both required for TIC growth and tumorig

The recent Company of Biologists workshop 'Growth, Division and Differentiation: Understanding Developmental Control', which was held in September 2011 at Wiston House, West Sussex, UK, brought together researchers aiming to understand cell proliferation and differentiation in various metazoans, ranging from flies to mice. Here, we review the common themes that emerged from the meeting, highlighti

The identification of new members in the Cdk and cyclin families, functions for many of which are still emerging, has added new facets to the cell cycle regulatory network. With roles extending beyond the classical regulation of cell cycle progression, these new players are involved in diverse processes such as transcription, neuronal function, and ion transport. Members closely related to Cdks an