Cyclin D1 belongs to the core cell cycle machinery, and it is frequently overexpressed in human cancers 1,2 . The full repertoire of cyclin D1 functions in normal development and in oncogenesis is currently unclear. Here we developed FLAG-and HA-tagged cyclin D1 knock-in mouse strains that allowed high-throughput mass spectrometry approach to search for cyclin D1-binding proteins in different mouse organs. In addition to cell cycle partners, we observed several proteins involved in transcription. Genome-wide location (ChIP-chip) analyses revealed that during mouse development cyclin D1 occupies promoters of abundantly expressed genes. In particular, we found that in developing mouse retinas -an organ that critically requires cyclin D1 function 3,4 -cyclin D1 binds the upstream regulatory region of the Notch1 gene where it serves to recruit CBP histone acetyltransferase. Genetic ablation of cyclin D1 resulted in decreased CBP recruitment, decreased histone acetylation of the Notch1 promoter region, and led to decreased levels of the Notch transcript and protein in cyclin D1-null retinas. Transduction of an activated allele of Notch1 into cyclin D1 −/− retinas increased proliferation of retinal progenitor cells, indicating that upregulating Notch1 signaling alleviates the phenotype of cyclin D1-deficiency. These studies reveal that in addition to its well-established cell cycle roles, cyclin D1 plays an in vivo transcriptional function in mouseCorrespondence and request for materials should be addressed to P.S. (Peter_Sicinski@dfci.harvard.edu). * These authors contributed equally to this work. 8 Current address: Stanford University School of Medicine, Stanford, CA 94305, USA.Supplementary Information is linked to the online version of the paper at www.nature.com/nature Author Contributions F.B. and PS designed the study, analyzed the data and wrote the manuscript. F.B. performed the experiments with the help of co-authors as detailed below. S.J. performed protein purifications. J.E.E. performed and together with S.P.G. Author InformationThe complete ChIP-chip and expression datasets have been submitted to the online data repository GEO, record GSE13636 (http://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?token=zvuhbiaakuwumxa&acc=GSE13636). Reprints and permissions information is available at www.nature.com/reprints. NIH Public Access Author ManuscriptNature. Author manuscript; available in PMC 2010 September 22. NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript development. Our approach, which we term "genetic-proteomic" can be used to study the in vivo function of essentially any protein.To study the molecular functions of cyclin D1 during development and in cancer formation, we generated knock-in mouse strains in which tandem (FLAG-and HA-) tags were inserted into the endogenous cyclin D1 locus through homologous recombination in embryonal stem cells. Tags were introduced into N-terminus of cyclin D1 (D1 Ntag allele) or into C-terminus (D1 Ctag ) and homozygous D1 Ntag/Ntag and D1 C...

SUMMARYSeveral models of cell fate determination can be invoked to explain how single retinal progenitor cells (RPCs) produce different cell types in a terminal division. To gain insight into this process, the effects of the removal of a cell fate regulator, Notch1, were studied in newly postmitotic cells using a conditional allele of Notch1 (N1-CKO) in mice. Almost all newly postmitotic N1-CKO cells became rod photoreceptors, whereas wild-type (

The Bone morphogenetic proteins (BMPs) mediate a wide range of diverse cellular behaviors throughout development. Previous studies implicated an important role for BMP signaling during the differentiation of the definitive mammalian kidney, the metanephros. In order to examine whether BMP signaling also plays an important role during the patterning of earlier renal systems, we examined the development of the earliest nephric system, the pronephros. Using the amphibian model system Xenopus laevis, in combination with reagents designed to inhibit BMP signaling during specific stages of nephric development, we revealed an evolutionarily conserved role for this signaling pathway during renal morphogenesis. Our results demonstrate that conditional BMP inhibition after specification of the pronephric anlagen is completed, but prior to the onset of morphogenesis and differentiation of renal tissues, results in the severe malformation of both the pronephric duct and tubules. Importantly, the effects of BMP signaling on the developing nephron during this developmental window are specific, only affecting the developing duct and tubules, but not the glomus. These data, combined with previous studies examining metanephric development in mice, provide further support that BMP functions to mediate morphogenesis of the specified renal field during vertebrate embryogenesis. Specifically, BMP signaling is required for the differentiation of two types of nephric structures, the pronephric tubules and duct. Developmental Dynamics 237:132-144, 2008.

The authors have declared no conflicts of interest for this article.