MicroRNAs, processed by the RNAase III enzyme Dicer, are ~22 nucleotide endogenous noncoding small RNAs. The function of Dicer in the mouse central nervous system (CNS) development is not well understood. Here we show that specifically deleting Dicer expression in the CNS and in the cerebral cortex using two Cre lines results in reduced progenitor numbers, abnormal neuronal differentiation and thinner cortical wall. Incomplete Dicer deletion during early embryonic stages contributes to normal development of early-born neurons in the cortex and motor neurons in the spinal cord. However, at late embryonic stages when Dicer is completely ablated in the CNS, the migration of late-born neurons in the cortex and oligodendrocyte precursor expansion and differentiation in the spinal cord are greatly affected. Our studies of different timings of Dicer deletion demonstrate the importance of the Dicer-mediated microRNA pathway in regulating distinct phases of neurogenesis and gliogenesis during the CNS development.

BackgroundOdontogenic myxoma is a benign odontogenic tumor with locally aggressive behavior, and is relatively rare in the oral cavity. There are currently no clear surgical management guidelines for odontogenic myxoma, and a variety of approaches may be used. This study evaluated the literature concerning the surgical management of odontogenic myxoma, and reports the long-term outcome of a case managed by using a more conservative surgical approach.Case presentationWe managed a 40-year-old Japanese man with odontogenic myxoma in the right mandible by enucleation and curettage, a relatively conservative approach that has proved to have been justified by a lack of recurrence over 10 years. Our strategy was compared with others reported in the literature, which was identified by a PubMed search using the term “odontogenic myxoma”. Articles without full text or with missing data were excluded. The age and sex of patients, the tumor location (maxilla/mandible), treatment (conservative/radical), recurrence, and follow-up period were compared in the reported cases that we evaluated. From the initial 211 studies identified, 20 studies qualified as mandibular cases of odontogenic myxoma. Recurrence was reported in three cases that had been treated with a more conservative surgical approach.ConclusionsEnucleation and curettage has proved an effective approach in several cases in ours there has been no recurrence more than 10 years after surgery but the risk of recurrence appears to be higher. We discuss the important factors that must be considered when determining the correct management approach to odontogenic myxoma.

The adult hippocampus consists of the dentate gyrus (DG) and the CA1, CA2 and CA3 regions and is essential for learning and memory functions. During embryonic development, hippocampal neurons are derived from hippocampal neuroepithelial cells and dentate granular progenitors. The molecular mechanisms that control hippocampal progenitor proliferation and differentiation are not well understood. Here we show that noncoding microRNAs (miRNAs) are essential for early hippocampal development in mice. Conditionally ablating the RNAase III enzyme Dicer at different embryonic time points utilizing three Cre mouse lines causes abnormal hippocampal morphology and affects the number of hippocampal progenitors due to altered proliferation and increased apoptosis. Lack of miRNAs at earlier stages causes early differentiation of hippocampal neurons, in particular in the CA1 and DG regions. Lack of miRNAs at a later stage specifically affects neuronal production in the CA3 region. Our results reveal a timing requirement of miRNAs for the formation of specific hippocampal regions, with the CA1 and DG developmentally hindered by an early loss of miRNAs and the CA3 region to a late loss of miRNAs. Collectively, our studies indicate the importance of the Dicer-mediated miRNA pathway in hippocampal development and functions.

Proper formation of the shape and size of cortical functional areas is essential for complex brain function, including sensory perception and motor control. Our previous work identified the transcription factor Lim domain only 4 (Lmo4), a regulator in calcium-dependent gene transcription, that has unique, region-specific expression in postnatal mouse cortices with high expression anteriorly and posteriorly but very low expression in between. Here we report that Lmo4 expression coincides with the timing of the development of the somatosensory barrel field. Lmo4 cortical deletion causes changes in expression patterns of cortical regional markers and results in rostro-medial shrinkage but not rostral or caudal shift of the somatosensory barrel subfield. Fine regulation of accurate shape of the barrel subfield by Lmo4, as well as Lmo4-mediated calcium-dependent gene expression, is critical for normal brain functions, as Lmo4-deficient mice display impaired sensorimotor performance. Moreover, even though Lmo4 has broad expression in the central nervous system, it plays a subtle role in the development of non-cortical regions. Our results reveal a new mechanism of cortical area formation and normal sensorimotor control that is regulated by genes with region-specific expression in the developing cortex.

BackgroundHuman dental pulp stem cells (DPSCs), which have the ability to differentiate into multiple lineages, were recently identified. DPSCs can be collected readily from extracted teeth and are now considered to be a type of mesenchymal stem cell with higher clonogenic and proliferative potential than bone marrow stem cells (BMSCs). Meanwhile, the treatment of severe bone defects, such as fractures, cancers, and congenital abnormalities, remains a great challenge, and novel bone regenerative techniques are highly anticipated. Several studies have previously shown that 4-(4-methoxyphenyl)pyrido[40,30:4,5]thieno[2,3-b]pyridine-2-carboxamide (TH), a helioxanthin derivative, induces osteogenic differentiation of preosteoblastic and mesenchymal cells. However, the osteogenic differentiation activities of TH have only been confirmed in some mouse cell lines. Therefore, in this study, toward the clinical use of TH in humans, we analyzed the effect of TH on the osteogenic differentiation of DPSCs, and the in-vivo osteogenesis ability of TH-induced DPSCs, taking advantage of the simple transplantation system using cell-sheet technology.MethodsDPSCs were obtained from dental pulp of the wisdom teeth of five healthy patients (18–22 years old) and cultured in regular medium and osteogenic medium with or without TH. To evaluate osteogenesis of TH-induced DPSCs in vivo, we transplanted DPSC sheets into mouse calvaria defects.ResultsWe demonstrated that osteogenic conditions with TH induce the osteogenic differentiation of DPSCs more efficiently than those without TH and those with bone morphogenetic protein-2. However, regular medium with TH did not induce the osteogenic differentiation of DPSCs. TH induced osteogenesis in both DPSCs and BMSCs, although the gene expression pattern in DPSCs differed from that in BMSCs up to 14 days after induction with TH. Furthermore, we succeeded in bone regeneration in vivo using DPSC sheets with TH treatment, without using any scaffolds or growth factors.ConclusionsOur results demonstrate that TH-induced DPSCs are a useful cell source for bone regenerative medicine, and the transplantation of DPSC sheets treated with TH is a convenient scaffold-free method of bone healing.Electronic supplementary materialThe online version of this article (10.1186/s13287-018-0783-7) contains supplementary material, which is available to authorized users.