MafB interacts with Gcm2 and regulates parathyroid hormone expression and parathyroid development.

Serum calcium and phosphate homeostasis is critically regulated by parathyroid hormone (PTH) secreted by the parathyroid glands. Parathyroid glands develop from the bilateral parathyroid-thymus common primordia. In mice, the expression of transcription factor Glial cell missing 2 (Gcm2) begins in the dorsal/anterior part of the primordium on embryonic day 9.5 (E9.5), specifying the parathyroid domain. The parathyroid primordium then separates from the thymus primordium and migrates to its adult location beside the thyroid gland by E15.5. Genetic ablation of gcm2 results in parathyroid agenesis in mice, indicating that Gcm2 is essential for early parathyroid organogenesis. However, the regulation of parathyroid development at later stages is not well understood. Here we show that transcriptional activator v-maf musculoaponeurotic fibrosarcoma oncogene homologue B (MafB) is developmentally expressed in parathyroid cells after E11.5. MafB expression was lost in the parathyroid primordium of gcm2 null mice. The parathyroid glands of mafB(+/-) mice were mislocalized between the thymus and thyroid. In mafB(-/-) mice, the parathyroid did not separate from the thymus. Furthermore, in mafB(-/-) mice, PTH expression and secretion were impaired; expression levels of renal cyp27b1, one of the target genes of PTH, was decreased; and bone mineralization was reduced. We also demonstrate that although Gcm2 alone does not stimulate the PTH gene promoter, it associates with MafB to synergistically activate PTH expression. Taken together, our results suggest that MafB regulates later steps of parathyroid development, that is, separation from the thymus and migration toward the thyroid. MafB also regulates the expression of PTH in cooperation with Gcm2.

Pathway-dependent modulation by P2-purinoceptors in the mouse retina.

Adenosine trisphosphate (ATP) activates purinoceptors and acts as a neurotransmitter in the nervous system. In the retina, we previously reported that the immunohistochemical distribution of the subset of P2-purinoceptors differs between the ON and OFF pathways. Here, we investigated whether ATP activates P2-purinoceptors and modulates the physiological function of the mouse retina. We also examined if signal processing by P2-purinoceptors is pathway specific. Results showed that ATP activated both ON- and OFF-cholinergic amacrine cells. However, responses in OFF-cholinergic amacrine cells were greater than those in ON-cholinergic amacrine cells. Pharmacological studies in OFF-cholinergic amacrine cells showed that the response of OFF-cholinergic amacrine cells is mediated P2X(2)-purinoceptors. Further, ATP increased gamma-aminobutyric acid (GABA)ergic inhibitory postsynaptic currents (IPSCs) in OFF- but not ON-cholinergic amacrine cells. The increase in GABAergic IPSCs was mediated by P2-purinoceptors. P2-purinoceptor-mediated signals suppressed OFF ganglion cells but activated ON ganglion cells. Our findings indicate that ATP physiologically modulates signal processing of the ON and OFF pathways in a pathway-specific manner through P2-purinoceptors.

Lumbar spinous process-splitting laminectomy for lumbar canal stenosis. Technical note.

In conventional laminectomy for lumbar canal stenosis (LCS), intraoperative damage of posterior supporting structures can lead to irreversible atrophy of paraspinal muscles. In 2001, the authors developed a new procedure for lumbar laminectomy, the lumbar spinous process-splitting laminectomy (LSPSL). In this new procedure, the spinous process is split longitudinally in the middle and then divided at its base from the posterior arch, leaving the bilateral paraspinal muscles attached to the lateral aspects. Ample working space for laminectomy is obtained by retracting the split spinous process laterally together with its attached paraspinal muscles. After successfully decompressing nerve tissues, each half of the split spinous process is reapproximated using a strong suture. Thus, the supra- and interspinous ligaments are preserved, as is the spinous process, and damage to the paraspinal muscles is minimal. Eighteen patients with LCS underwent surgery in which this new technique was used. Twenty patients in whom conventional laminectomy was undertaken were chosen as controls. At 2 years, the clinical outcomes (as determined using the Japanese Orthopaedic Association [JOA] scores and recovery rate) and the rate of measured magnetic resonance imaging-documented paravertebral muscle atrophy were evaluated and compared between the two groups. The mean JOA score recovery rates were 67.6 and 59.2%, respectively, for patients treated with LSPSL and conventional laminectomy; the mean rates of paravertebral muscle atrophy were 5.3 and 23.9%, respectively (p = 0.0005). Preservation of posterior supporting structures and satisfactory recovery rate after 2 years indicated that this technique can be a useful alternative to conventional decompression surgery for lumbar canal stenosis.

The potential to induce glial differentiation is conserved between Drosophila and mammalian glial cells missing genes.

Drosophila glial cells missing (gcm) is a key gene that determines the fate of stem cells within the nervous system. Two mouse gcm homologs have been identified, but their function in the nervous system remains to be elucidated. To investigate their function, we constructed retroviral vectors harboring Drosophila gcm and two mouse Gcm genes. Expression of these genes appeared to influence fibroblast features. In particular, mouse Gcm1 induced the expression of astrocyte-specific Ca(2+)-binding protein, S100beta, in those cells. Introduction of the mouse Gcm1 gene in cultured cells from embryonic brains resulted in the induction of an astrocyte lineage. This effect was also observed by in utero injection of retrovirus harboring mouse Gcm1 into the embryonic brain. However, cultures from mouse Gcm1-deficient mouse brains did not exhibit significant reductions in the number of astrocytes. Furthermore, in situ hybridization analysis of mouse Gcm1 mRNA revealed distinct patterns of expression in comparison with other well-known glial markers. The mammalian homolog of Drosophila gcm, mouse Gcm1, exhibits the potential to induce gliogenesis, but may function in the generation of a minor subpopulation of glial cells.

NMR and ICP spectroscopic analysis of the DNA-binding domain of the Drosophila GCM protein reveals a novel Zn2+ -binding motif.

Drosophila GCM (glial cell missing) is a novel DNA-binding protein that determines the fate of glial precursors from the neural default to glia. The GCM protein contains the functional domain that is essential for recognition of the upstream sequence of the repo gene. In the DNA-binding region of this GCM protein, there is a cysteine-rich region with which divalent metal ions such as Zn(2+) must bind and other proteins belonging to the GCM family have a corresponding region. To obtain a more detailed insight into the structural and functional features of this DNA-binding region, we have determined the minimal DNA-binding domain and obtained inductively coupled plasma atomic emission spectra and (1)H-(15)N, (1)H-(15)N-(13)C and (113)Cd(2+) NMR spectra, with or without its specific DNA molecule. Considering the results, it was concluded that the minimal DNA-binding domain includes two Zn(2+)-binding sites, one of which is adjacent to the interface for DNA binding. Systematic mutational analyses of the conserved cysteine residues in the minimal DNA-binding domain revealed that one Zn(2+)-binding site is indispensable for stabilization of the higher order structure of this DNA-binding domain, but that the other is not.