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Major depressive disorder (MDD) is a complex and devastating illness that affects people of all ages. Despite the large use of antidepressants in current medical practice, neither their mechanisms of action nor the aetiology of MDD are completely understood. Experimental evidence supports the involvement of Parvalbumin-positive GABAergic neurons (PV-neurons) in the pathogenesis of MDD. DLX5 and DLX6 (DLX5/6) encode two homeodomain transcription factors involved in cortical GABAergic differentiation and function. In the mouse, the level of expression of these genes is correlated with the cortical density of PV-neurons and with anxiety-like behaviours. The same genomic region generates the lncRNA DLX6-AS1, which, in humans, participates in the GABAergic regulatory module downregulated in schizophrenia and ASD. Here, we show that the expression levels of Dlx5/6 in the adult mouse brain are correlated with the immobility time in the forced swim test, which is used to measure depressive-like behaviours. We show that the administration of the antidepressant fluoxetine (Flx) to normal mice induces, within 24 h, a rapid and stable reduction in Dlx5, Dlx6 and Dlx6-AS1 expression in the cerebral cortex through the activation of the TrkB-CREB pathway. Experimental Dlx5 overexpression counteracts the antidepressant effects induced by Flx treatment. Our findings show that one of the short-term effects of Flx administration is the reduction in Dlx5/6 expression in GABAergic neurons, which, in turn, has direct consequences on PV expression and on behavioural profiles. Variants in the DLX5/6 regulatory network could be implicated in the predisposition to depression and in the variability of patients' response to antidepressant treatment. [ABSTRACT FROM AUTHOR]

Endothelin-A (ETA) is a G-protein-coupled receptor expressed in the neural crest-derived mesenchyme of the pharyngeal arches during craniofacial development. Targeted deletion of the [ET.sub.A] receptor or its ligand endothelin-1 (ET-1) causes cleft palate and hypoplasia of the mandible, otic cup, and tympanic ring. Previously we showed that G[[alpha].sub.q]/G[[alpha].sub.11]-null mice die around E 11.0, whereas G[[alpha].sub.q.sup.(-/-)] G[[alpha].sub.11.sup.(+/-)] mice survive to birth with hypomorphic phenotypes similar to, but less severe than, ETA or ET-1-null mice. To determine whether ET-1 signaling is transduced by G[[alpha].sub.q]/G[[alpha].sub.11] proteins, we examined the expression patterns of several ET-1 dependent and independent transcription factors in G[alpha].sub.q]/G[[alpha].sub.11]-deficient embryos. Expression of genes encoding the ET-1-dependent transcription factors D1x3, D1x6, dHAND, and eHAND was specifically downregulated in the pharyngeal arches of G[[alpha].sub.q]/G[alpha].sub.11]-deficient mice. In contrast, pharyngeal arch expression of the homeobox gene Msx1, which is not regulated by ET-1 signaling, was maintained in these embryos. We conclude that the G[[alpha].sub.q] and G[[alpha].sub.11] proteins serve as the intracellular mediators of ET-1 signaling in the pharyngeal arch mesenchyme. Keywords: G-protein; Neural crest; Pharyngeal arches; Endothelin; G[[alpha].sub.q]/G[[alpha].sub.11]; D1x3; D1x6; dHAND/HAND2; eHAND/HAND1; Craniofacial development

In the mouse embryo, Dlx5 is expressed in the otic placode and vesicle, and later in the semicircular canals of the inner ear. In mice homozygous for a null Dlx5/LacZ allele, a severe dysmorphogenesis of the vestibular region is observed, characterized by the absence of semicircular canals and the shortening of the endolymphatic duct. Minor defects are observed in the cochlea, although Dlx5 is not expressed in this region. Cristae formation is severely impaired; however, sensory epithelial cells, recognized by calretinin immunostaining, are present in the vestibular epithelium of [Dlx5.sup.-/-] mice. The maculae of utricle and saccule are present but cells appear sparse and misplaced. The abnormal morphogenesis of the semicircular canals is accompanied by an altered distribution of proliferating and apoptotic cells. In the [Dlx5.sup.-/-] embryos, no changes in expression of Nkx5.1(Hmx3), Pax2, and Lfng have been seen, while expression of bone morphogenetic protein-4 (Bmp4) was drastically reduced. Notably, BMP4 has been shown to play a fundamental role in vestibular morphogenesis of the chick embryo. We propose that development of the semicircular canals and the vestibular inner ear requires the independent control of several homeobox genes, which appear to exert their function via tight regulation of BPM4 expression and the regional, organization of cell differentiation, proliferation, and apoptosis. Key Words: Dlx; homeobox gene; transcription factor; bone morphogenetic protein-4; inner ear; apoptosis.

The intermediary role of Dlx6 in regulating an endothelin-1-dependent dHAND branchial arch enhancer has been studied. An evolutionarily conserved dHAND enhancer that must have endothelin-1 (ET-1) signaling for activity is described. The basic helix-loop-helix transcription factor dHAND is necessary for craniofacial development and its expression in the branchial arches is downregulated in ET-1 mutant embryos.

Myelination in the outer nervous system is prevented by the activation of Krox-20 in Schwann cells. Krox-20 activation occurs before the initiation of myelination, blocking the differentiation in the Schwann cells at an early stage. Krox-20 controls the genes essential for myelination, and inhibits myelination despite the expression of the early myelin marker and other associated proteins in Krox-20.

Abstract Background The DLX gene family encodes for homeobox transcription factors involved in the control of morphogenesis and tissue homeostasis. Their expression can be regulated by Endothelin1 (ET1), a peptide associated with breast cancer invasive phenotype. Deregulation of DLX gene expression was found in human solid tumors and hematologic malignancies. In particular, DLX4 overexpression represents a possible prognostic marker in ovarian cancer. We have investigated the role of DLX genes in human breast cancer progression. Methods MDA-MB-231 human breast carcinoma cells were grown in vitro or injected in nude mice, either subcutaneously, to mimic primary tumor growth, or intravenously, to mimic metastatic spreading. Expression of DLX2, DLX5 and DLX6 was assessed in cultured cells, either treated or not with ET1, tumors and metastases by RT-PCR. In situ hybridization was used to confirm DLX gene expression in primary tumors and in lung and bone metastases. The expression of DLX2 and DLX5 was evaluated in 408 primary human breast cancers examining the GSE1456 and GSE3494 microarray datasets. Kaplan-Meier estimates for disease-free survival were calculated for the patients grouped on the basis of DLX2/DLX5 expression. Results Before injection, or after subcutaneous growth, MDA-MB-231 cells expressed DLX2 but neither DLX5 nor DLX6. Instead, in bone and lung metastases resulting from intravenous injection we detected expression of DLX5/6 but not of DLX2, suggesting that DLX5/6 are activated during metastasis formation, and that their expression is alternative to that of DLX2. The in vitro treatment of MDA-MB-231 cells with ET1, resulted in switch from DLX2 to DLX5 expression. By data mining in microarray datasets we found that expression of DLX2 occurred in 21.6% of patients, and was significantly correlated with prolonged disease-free survival and reduced incidence of relapse. Instead, DLX5 was expressed in a small subset of cases, 2.2% of total, displaying reduced disease-free survival and high incidence of relapse which was, however, non-significantly different from the other groups due to the small size of the DLX+ cohort. In all cases, we found mutually exclusive expression of DLX2 and DLX5. Conclusions Our studies indicate that DLX genes are involved in human breast cancer progression, and that DLX2 and DLX5 genes might serve as prognostic markers.

Abstract Background Understanding and manipulating gene function in physiological conditions is a major objective for both fundamental and applied research. In contrast to other experimental settings, which use either purely genetic or gene delivery (viral or non-viral) strategies, we report here a strategy based on direct protein delivery to central nervous system (CNS) tissues. We fused Cre recombinase with cell-penetrating peptides and analyzed the intracellular biological activity of the resulting chimerical proteins when delivered into cells endowed with Cre-mediated reporter gene expression. Results We show that active Cre enzymatic conjugates are readily internalized and exert their enzymatic activity in the nucleus of adherent cultured cells. We then evaluated this strategy in organotypic cultures of neural tissue explants derived from reporter mice carrying reporter "floxed" alleles. The efficacy of two protocols was compared on explants, either by direct addition of an overlying drop of protein conjugate or by implantation of conjugate-coated beads. In both cases, delivery of Cre recombinase resulted in genomic recombination that, with the bead protocol, was restricted to discrete areas of embryonic and adult neural tissues. Furthermore, delivery to adult brain tissue resulted in the transduction of mature postmitotic populations of neurons. Conclusion We provide tools for the spatially restricted genetic modification of cells in explant culture. This strategy allows to study lineage, migration, differentiation and death of neural cells. As a proof-of-concept applied to CNS tissue, direct delivery of Cre recombinase enabled the selective elimination of an interneuron subpopulation of the spinal cord, thereby providing a model to study early events of neurodegenerative processes. Thus our work opens new perspectives for both fundamental and applied cell targeting protocols using proteic cargoes which need to retain full bioactivity upon internalisation, as illustrated here with the oligomeric Cre recombinase.