The RNA-binding protein DND1 acts Sequentially as a negative regulator of pluripotency and a positive regulator of epigenetic modifiers required for germ cell reprogramming.

The Keene Laboratory has a long-term interest in the structure and function of viral and mammalian genomes. Having determined the first genomic sequences for rabies, Ebola, Marburg and vesicular stomatitis virus, and discerned the origins of defective interfering viruses, interests shifted to the cloning of six human genes involved in autoimmune reactivity. This resulted in the identification of numerous autoimmune RRM-type RNA-binding proteins the discovery of the RRM, and the RNA targets to which they bind. The current interests of the lab surround the functions of the human RRM-ELAV/Hu proteins that are bound to a subset of cellular mRNAs involved in growth regulation neuronal plasticiyt and cancer. The laboratory demonstrated that ELAV/Hu proteins bind and regulate the expression of early response gene transcripts such as those encoding the protooncogene and cytokine proteins.

In addition, it was shown that while stabilizing these mRNAs and/or activating their translation, the ELAV/Hu proteins participate in cellular , differentiation and carcinogenesis. More recently, the laboratory has examined dozens of RNA-binding proteins in order to identify large numbers of structurally
and/or functionally related mRNAs that cluster in vivo based upon their binding to these proteins. This has been termed ribonomics because it involves parallel analysis of mRNA subsets en masse based upon their presence in messenger ribonucleoprotein complexes. This new approach to functional genomics is being applied to virus-infected cells, tumors and cells treated with various agents. Ribonomics has led to the identification of mRNA clusters that are posttranscriptionally regulated, and represent the organizational state of genetic information between the genome and the proteome. Dr. Keen has propsed the existence of post-transcriptional operons based upon the association of structurally and functionally-linked mRNAs in vivo.

In mammals, the primary step in male sex determination is the initiation of testis development in the bipotential gonad primordium. This step depends on the Y-linked male sex-determining gene, Sry. Expression of Sry in the XY gonad, or as a transgene in an XX gonad, leads to the differentiation of Sertoli cells. Failures in Sertoli cell differentiation in the XY gonad result in sex reversal and ovary formation. In addition to Sertoli cell differentiation, we are studying the signaling pathways between Sry expression and early steps in testis organogenesis using mouse as a model system. Using genetic and cell biology approaches, we determined the origin of several key cell types of the testis. We also identified two pathways, proliferation and cell migration, that are controlled by Sry and lead to the architectural patterning of the testis. Currently we are investigating the novel hypothesis that reciprocal signals between the vasculature and Sertoli cells are involved in patterning testis cords. Testis organogenesis is an ideal model system to study the integration of vasculature during development of organ structure. In addition, we are investigating critical signals between Sertoli cells and germ cells during testis cord formation. Defects in these signals result in teratomas and gonadal blastomas, common neoplasias in young boys. Experimental approaches include the use of molecular and biochemical techniques, mutant mice, transgenics, organ culture assays, differential screens, immunocytochemistry imaging techniques, and classic mouse genetics.