The Transcription Factor Cux1 Regulates Dendritic Morphology of Cortical Pyramidal Neurons

In the murine cerebral cortex, mammalian homologues of the Cux family transcription factors, Cux1 and Cux2, have been identified as restricted molecular markers for the upper layer (II-IV) pyramidal neurons. However, their functions in cortical development are largely unknown. Here we report that increasing the intracellular level of Cux1, but not Cux2, reduced the dendritic complexity of cultured cortical pyramidal neurons. Consistently, reducing the expression of Cux1 promoted the dendritic arborization in these pyramidal neurons. This effect required the existence of the DNA-binding domains, hence the transcriptional passive repression activity of Cux1. Analysis of downstream signals suggested that Cux1 regulates dendrite development primarily through suppressing the expression of the cyclin-dependent kinase inhibitor p27Kip1, and RhoA may mediate the regulation of dendritic complexity by Cux1 and p27. Thus, Cux1 functions as a negative regulator of dendritic complexity for cortical pyramidal neurons

DNA Methyltransferase Protein Synthesis Is Reduced in CXXC Finger Protein 1–Deficient Embryonic Stem Cells

CXXC finger protein 1 (CFP1) binds to unmethylated CpG dinucleotides and is required for embryogenesis. CFP1 is also a component of the Setd1A and Setd1B histone H3K4 methyltransferase complexes. Murine embryonic stem (ES) cells lacking CFP1 fail to differentiate, and exhibit a 70% reduction in global genomic cytosine methylation and a 50% reduction in DNA methyltransferase (DNMT1) protein and activity. This study investigated the underlying mechanism for reduced DNMT1 expression in CFP1-deficient ES cells. DNMT1 transcript levels were significantly elevated in ES cells lacking CFP1, despite the observed reduction in DNMT1 protein levels. To address the posttranscriptional mechanisms by which CFP1 regulates DNMT1 protein activity, pulse/chase analyses were carried out, demonstrating a modest reduction in DNMT1 protein half-life in CFP1-deficient ES cells. Additionally, global protein synthesis was decreased in ES cells lacking CFP1, contributing to a reduction in the synthesis of DNMT1 protein. ES cells lacking CFP1 were found to contain elevated levels of phosphorylated eIF2α, and an accompanying reduction in translation initiation as revealed by a lower level of polyribosomes. These results reveal a novel role for CFP1 in the regulation of translation initiation, and indicate that loss of CFP1 function leads to decreased DNMT1 protein synthesis and half-life

Africa Insight

Africa Insight is an independent publication which endeavours to promote insight into the process of change and development in Africa.This journal focuses on contemporary issues of Afric

Africa Insight

Africa Insight is an independent publication which endeavours to promote insight into the process of change and development in Africa.This journal focuses on contemporary issues of Afric

Human CCAAT displacement protein is homologous to the Drosophila homeoprotein, cut.

Human CCAAT displacement protein (CDP), a putative repressor of developmentally regulated gene expression, was purified fron HeLa cells by DNA binding-site affinity chromatography. cDNA encoding CDP was obtained by immunoscreening a lambda gt11 library with antibody raised against purified protein. The deduced primary amino acid sequence of CDP reveals remarkable homology to Drosophila cut with respect to the presence of a unique homeodomain and "cut repeats". As cut participates in determination of cell fate in several tissues in Drosophila, the similarity predicts a broad role for CDP in mammalian development