Little is known of the molecular mechanisms whereby spermatogonia, mitotic germ cells of the testis, self-renew and differentiate into sperm^1,2. Here we show that Zfp145, encoding the transcriptional repressor Plzf, has a crucial role in spermatogenesis. Zfp145 expression was restricted to gonocytes and undifferentiated spermatogonia and was absent in tubules of W/W^v mutants that lack these cells. Mice lacking Zfp145 underwent a progressive loss of spermatogonia with age, associated with increases in apoptosis and subsequent loss of tubule structure but without overt differentiation defects or loss of the supporting Sertoli cells. Spermatogonial transplantation experiments revealed a depletion of spermatogonial stem cells in the adult. Microarray analysis of isolated spermatogonia from Zfp145-null mice before testis degeneration showed alterations in the expression profile of genes associated with spermatogenesis. These results identify Plzf as a spermatogonia-specific transcription factor in the testis that is required to regulate self-renewal and maintenance of the stem cell pool.

High throughput screening (HTS) is routinely used to identify bioactive small molecules. This requires physical compounds, which limits coverage of accessible chemical space. Computational approaches combined with vast on-demand chemical libraries can access far greater chemical space, provided that the predictive accuracy is sufficient to identify useful molecules. Through the largest and most diverse virtual HTS campaign reported to date, comprising 318 individual projects, we demonstrate that our AtomNet® convolutional neural network successfully finds novel hits across every major therapeutic area and protein class. We address historical limitations of computational screening by demonstrating success for target proteins without known binders, high-quality X-ray crystal structures, or manual cherry-picking of compounds. We show that the molecules selected by the AtomNet® model are novel drug-like scaffolds rather than minor modifications to known bioactive compounds. Our empirical results suggest that computational methods can substantially replace HTS as the first step of small-molecule drug discovery.

5′-AMP-activated protein kinase (AMPK) is an energy sensor that controls cell metabolism, and it has been related to apoptosis and cell-cycle arrest. Although its role in metabolic homeostasis is well documented, its function in cancer is much less clear. In this study, we examined the role of AMPK in a mouse model of astrocytoma driven by oncogenic H-Ras^V12 and/or with PTEN deletion based on the common constitutive activation of the Raf/MEK/ERK and PI3K/AKT cascades in human astrocytomas. We also evaluated the activity and role of AMPK in human glioblastoma cells and xenografts. AMPK was constitutively activated in astrocytes expressing oncogenic H-Ras^V12 in parallel with high cell division rates. Genetic deletion of AMPK or attenuation of its activity in these cells was sufficient to reduce cell proliferation. The levels of pAMK were always related to the levels of phosphorylated retinoblastoma (Rb) at Ser804, which may indicate an AMPK-mediated phosphorylation of Rb. We confirmed this AMPK–Rb relationship in human glioblastoma cell lines and xenografts. In clinical specimens of human glioblastoma, elevated levels of activated AMPK appeared especially in areas of high proliferation surrounding the blood vessels. Together, our findings indicate that the initiation and progression of astrocytic tumors relies upon AMPK-dependent control of the cell cycle, thereby identifying AMPK as a candidate therapeutic target in this setting. Cancer Res; 73(8); 2628–38. ©2013 AACR.

Transcription factors (TF) play a key role in certain mechanisms by which specific genes are expressed in a temporal and tissue-specific manner. Understanding those mechanisms is still a challenging question in biology. Their modular organization allows the possibility of classifying them based on the structure of the domains that bind DNA or interact with other proteins. Those domains not only define the different TF families but also provide insights into the biological functions played by them. Among these, the POK (Poxviruses and Zinc-finger (POZ) and Krüppel) family of transcription repressors is characterized by the presence in their structures of an amino-terminal POZ/Broad Complex, Tramtrack, and Bric à brac (BTB) domain and several Krüppel-type zinc fingers at the carboxy-terminal moiety. The POZ/BTB domain mediates homo- and heterodimerization as well as protein–protein interactions, allowing the recruitment of corepressor complexes. On the other hand, the specific zinc fingers mediate specific DNA sequences recognition and binding. In the last few years, several reports have highlighted the importance that this family of transcriptional repressors plays in different processes such as cancer, development and stem cell biology.