Expression of Runx2 transcription factor in non-skeletal tissues, sperm and brain

Runx transcription factors: lineage-specific regulators of neuronal precursor cell proliferation and post-mitotic neuron subtype development

Runt-related (RUNX) genes encode evolutionarily conserved transcription factors that play essential roles during development and adult tissue homeostasis. RUNX proteins regulate the transition from proliferation to differentiation in a variety of cell lineages. Moreover, they control the diversification of distinct cellular phenotypes in numerous tissues. Alterations of RUNX functions are associated with several cancers and other human pathologies, underscoring the vital roles of these transcription factors in adult organs. Insights into the functions and regulations of mammalian RUNX proteins have been provided mostly by studies of RUNX involvement in mechanisms of hematopoietic and skeletal development and disease. A growing number of recent investigations are revealing new functions for RUNX family members during the development of the mammalian nervous system. This review will discuss recent progress in the study of RUNX protein involvement in mammalian neural development, with emphasis on the differentiation of olfactory, sensory, and motor neuron lineages.

The expression of Usp26 gene in mouse testis and brain

Deubiquitinating enzymes (DUBs) play an important role in ubiquitin-dependent processes as negative regulators of protein ubiquitination. Ubiquitin-specific protease 26 (USP26) is a member of this family. The expression of Usp26 in mammalian testis and in other tissues has yet to be fully elucidated. To study the expression of Usp26 mRNA and protein in various murine tissues, reverse transcription (RT)-PCR and immunohistochemistry analyses were carried out. The RT-PCR analysis showed that the Usp26 transcript was expressed in all of the tested tissues. USP26 protein localization was examined by immunohistochemistry, and it was shown that USP26 was not detectable at 20 days postpartum, with the expression restricted to the cytoplasm of condensing spermatids (steps 9-16), Leydig cells and nerve fibers in the brain. In addition, the USP26 protein was detected at moderate levels in myocardial cells, the corpus of epidydimis, epithelium of the renal tubules and the seminal gland of postnatal day 35 mice. Its spatial and temporal expression pattern suggests that Usp26 may play an important role in development or function of the testis and brain. Further research into these possibilities is in progress.

'Runxs and regulations' of sensory and motor neuron subtype differentiation: implications for hematopoietic development

Runt-related (RUNX) transcription factors are evolutionarily conserved regulators of a number of developmental mechanisms. RUNX proteins often control the balance between proliferation and differentiation and alterations of their functions are associated with different types of cancer and other human pathologies. Moreover, RUNX factors control important steps during the developmental acquisition of mature phenotypes. A number of investigations are beginning to shed light on the involvement of RUNX family members in the development of the nervous system. This review summarizes recent progress in the study of the roles of mammalian RUNX proteins during the differentiation of sensory and motor neurons in the peripheral and central nervous system, respectively. The implications of those findings for RUNX-mediated regulation of hematopoietic development will also be discussed.

The osteogenic transcription factor runx2 controls genes involved in sterol/steroid metabolism, including CYP11A1 in osteoblasts

Steroid hormones including (1,25)-dihydroxyvitamin D3, estrogens, and glucocorticoids control bone development and homeostasis. We show here that the osteogenic transcription factor Runx2 controls genes involved in sterol/steroid metabolism, including Cyp11a1, Cyp39a1, Cyp51, Lss, and Dhcr7 in murine osteoprogenitor cells. Cyp11a1 (P450scc) encodes an approximately 55-kDa mitochondrial enzyme that catalyzes side-chain cleavage of cholesterol and is rate limiting for steroid hormone biosynthesis. Runx2 is coexpressed with Cyp11a1 in osteoblasts as well as nonosseous cell types (e.g. testis and breast cancer cells), suggesting a broad biological role for Runx2 in sterol/steroid metabolism. Notably, osteoblasts and breast cancer cells express an approximately 32-kDa truncated isoform of Cyp11a1 that is nonmitochondrial and localized in both the cytoplasm and the nucleus. Chromatin immunoprecipitation analyses and gel shift assays show that Runx2 binds to the Cyp11a1 gene promoter in osteoblasts, indicating that Cyp11a1 is a direct target of Runx2. Specific Cyp11a1 knockdown with short hairpin RNA increases cell proliferation, indicating that Cyp11a1 normally suppresses osteoblast proliferation. We conclude that Runx2 regulates enzymes involved in sterol/steroid-related metabolic pathways and that activation of Cyp11a1 by Runx2 may contribute to attenuation of osteoblast growth.

Assessment of transmission distortion on chromosome 6p in healthy individuals using tagSNPs

The best-documented example for transmission distortion (TD) to normal offspring are the t haplotypes on mouse chromosome 17. In healthy humans, TD has been described for whole chromosomes and for particular loci, but multiple comparisons have presented a statistical obstacle in wide-ranging analyses. Here we provide six high-resolution TD maps of the short arm of human chromosome 6 (Hsa6p), based on single-nucleotide polymorphism (SNP) data from 60 trio families belonging to two ethnicities that are available through the International HapMap Project. We tested all approximately 70,000 previously genotyped SNPs within Hsa6p by the transmission disequilibrium test. TagSNP selection followed by permutation testing was performed to adjust for multiple testing. A statistically significant evidence for TD was observed among male parents of European ancestry, due to strong and wide-ranging skewed segregation in a 730 kb long region containing the transcription factor-encoding genes SUPT3H and RUNX2, as well as the microRNA locus MIRN586. We also observed that this chromosomal segment coincides with pronounced linkage disequilibrium (LD), suggesting a relationship between TD and LD. The fact that TD may be taking place in samples not selected for a genetic disease implies that linkage studies must be assessed with particular caution in chromosomal segments with evidence of TD.

Radiosynthesis and evaluation of 5-[125I]iodoindol-3-yl-beta-D-galactopyranoside as a beta-galactosidase imaging radioligand

The synthesis and investigation of 5-[125I]iodoindol-3-yl-beta-d-galactopyranoside ([125I]IBDG) as a radioligand for single-photon emission computed tomography (SPECT) imaging of b-galactosidase expression are described. No-carrier-added [125I]IBDG was synthesized by a radioiododestannylation approach in > 75% overall radiochemical yield and > 99% radiochemical purity. [125I]IBDG was evaluated as a substrate using beta-galactosidase-expressing (D54L) and nonexpressing (D54) human glioma cell lines. A 24-hour incubation of this substrate with cultured cells revealed a 6.5-fold greater intracellular trapping of radioactivity in D54L cells compared with D54 cells. Systemic delivery of [125I]IBDG in nude mice bearing D54L tumors failed to show significant trapping of radioactivity within these tumors by SPECT imaging. In contrast, intratumoral injection of the substrate resulted in efficient trapping of radioactivity in D54L tumors but not D54 tumors, resulting in clear SPECT visualization of the former tumor. Based on dynamic SPECT imaging and blood metabolite analysis, we conclude that although [125I]IBDG is an efficient in vivo substrate for beta-galactosidase, its rapid renal clearance hampers its intratumoral availability on systemic administration.