Stefano Bertuzzi

Specification of Pituitary Cell Lineages by the LIM Homeobox Gene Lhx3

During pituitary organogenesis, the progressive differentiation of distinct pituitary-specific cell lineages from a common primordium involves a series of developmental decisions and inductive interactions. Targeted gene disruption in mice showed that Lhx3, a LIM homeobox gene expressed in the pituitary throughout development, is essential for differentiation and proliferation of pituitary cell lineages. In mice homozygous for the Lhx3 mutation, Rathkes pouch formed but failed to grow and differentiate; such mice lacked both the anterior and intermediate lobes of the pituitary. The determination of all pituitary cell lineages, except the corticotrophs, was affected, suggesting that a distinct, Lhx3-independent ontogenetic pathway exists for the initial specification of this lineage.

Disruption of fibroblast growth factor receptor 3 signaling results in defects in cellular differentiation, neuronal patterning, and hearing impairment

Deletion of fibroblast growth factor receptor 3 (Fgfr3) leads to hearing impairment in mice due to defects in the development of the organ of Corti, the sensory epithelium of the Cochlea. To examine the role of FGFR3 in auditory development, cochleae from Fgfr3−/− mice were examined using anatomical and physiological methods. Deletion of Fgfr3 leads to the absence of inner pillar cells and an increase in other cell types, suggesting that FGFR3 regulates cell fate. Defects in outer hair cell differentiation were also observed and probably represent the primary basis for hearing loss. Furthermore, innervation defects were detected consistent with changes in the fiber guidance properties of pillar cells. To elucidate the mechanisms underlying the effects of FGFR3, we examined the expression of Bmp4, a known target. Bmp4 was increased in Fgfr3−/− cochleae, and exogenous application of bone morphogenetic protein 4 (BMP4) onto cochlear explants induced a significant increase in the outer hair cells, suggesting the Fgf and Bmp signaling act in concert to pattern the cochlea. Developmental Dynamics 236:1905–1917, 2007. Published 2007 Wiley‐Liss, Inc.

Alternative promoter use in eye development: the complex role and regulation of the transcription factor MITF

During vertebrate eye development, the transcription factor MITF plays central roles in neuroepithelial domain specification and differentiation of the retinal pigment epithelium. MITF is not a single protein but represents a family of isoforms generated from a common gene by alternative promoter/exon use. To address the question of the role and regulation of these isoforms, we first determined their expression patterns in developing mouse eyes and analyzed the role of some of them in genetic models. We found that two isoforms, A- and J-Mitf, are present throughout development in both retina and pigment epithelium, whereas H-Mitf is detected preferentially and D-Mitf exclusively in the pigment epithelium. We further found that a genomic deletion encompassing the promoter/exon regions of H-, D- and B-Mitf leads to novel mRNA isoforms and proteins translated from internal start sites. These novel proteins lack the normal, isoform-specific N-terminal sequences and are unable to support the development of the pigment epithelium, but are capable of inducing pigmentation in the ciliary margin and the iris. Moreover, in mutants of the retinal Mitf regulator Chx10 (Vsx2), reduced cell proliferation and abnormal pigmentation of the retina are associated with a preferential upregulation of H- and D-Mitf. This retinal phenotype is corrected when H- and D-Mitf are missing in double Mitf/Chx10 mutants. The results suggest that Mitf regulation in the developing eye is isoform-selective, both temporally and spatially, and that some isoforms, including H- and D-Mitf, are more crucial than others in effecting normal retina and pigment epithelium development.

Measuring the Results of Science Investments

Science agencies and research institutions are building the infrastructure to evaluate results of federal funding of scientific research. Historically, federally funded basic and applied scientific research has promoted scientific knowledge, innovation, economic growth, and social well-being. However, there is increasing pressure to document the results of these research investments in a scientific manner (1, 2) and to quantify how much of the work is linked to innovation (3).

Expression of murine Lhx5 suggests a role in specifying the forebrain

A LIM homeobox gene, Lim5, is known to be expressed in the forebrain of Xenopus and zebrafish (Toyama et al. [1995] Dev. Biol. 170:583–593). Results from developmental and comparative studies of its mouse ortholog, Lhx5, indicate that this gene may play important roles in forebrain development. Lhx5 expression is detected in the most anterior portion of the neural tube at the headfold stage, overlapping partially with Otx2 expression domain. After neural tube closure, Lhx5 is expressed as a transverse stripe, covering most of the diencephalic primordium. This expression recedes to restricted areas as Dlx gene expression occurs. By midgestation, both genes, Lhx5 and Dlx5, are expressed in the diencephalon and ventral telencephalon in an alternating complementary pattern. It may be that Dlx inhibits Lhx5, and this may represent a step of early regionalization of the forebrain. Lhx5 is also expressed in midbrain, hindbrain, and spinal cord, overlapping extensively with Lhx1 starting from day E10.5 of gestation. The early, persistent, and dynamic expression of Lhx5 suggests a regulatory function in forebrain formation. Dev. Dyn. 208:266–277, 1997.

Loss of Cytokine-STAT5 Signaling in the CNS and Pituitary Gland Alters Energy Balance and Leads to Obesity

Signal transducers and activators of transcription (STATs) are critical components of cytokine signaling pathways. STAT5A and STAT5B (STAT5), the most promiscuous members of this family, are highly expressed in specific populations of hypothalamic neurons in regions known to mediate the actions of cytokines in the regulation of energy balance. To test the hypothesis that STAT5 signaling is essential to energy homeostasis, we used Cre-mediated recombination to delete the Stat5 locus in the CNS. Mutant males and females developed severe obesity with hyperphagia, impaired thermal regulation in response to cold, hyperleptinemia and insulin resistance. Furthermore, central administration of GM-CSF mediated the nuclear accumulation of STAT5 in hypothalamic neurons and reduced food intake in control but not in mutant mice. These results demonstrate that STAT5 mediates energy homeostasis in response to endogenous cytokines such as GM-CSF.

Characterization of Lhx9, a novel LIM/homeobox gene expressed by the pioneer neurons in the mouse cerebral cortex

In order to explain the phenotype observed in Lhx2 mutant embryos, we previously proposed that an Lhx2 related gene might exist. We now have cloned a new LIM/homeobox gene called Lhx9. Lhx9 is closely related to Lhx2 and is expressed in the developing central nervous system (CNS). Lhx9 and Lhx2 have expression patterns that overlap in some areas but are distinct in others. Thus, in some developmental domains these two highly related proteins may be functionally redundant. Lhx9 is expressed in the pioneer neurons of the cerebral cortex, while Lhx2 is expressed throughout the cortical layers. Postnatally, Lhx9 is expressed in the inner nuclei of the cerebellum, while Lhx2 is in the granular layer. In the developing limbs, both genes are highly expressed in a similar pattern. Based on the expression pattern and the developmental regulation of Lhx9, we propose that Lhx9 may be involved in the specification or function of the pioneer neurons of the cerebral cortex. We show that both Lhx9 and Lhx2 bind the LIM domain binding protein Ldb1/Nli1/Clim2.

Compromised generation of GABAergic interneurons in the brains of Vax1-/- mice.

The subcortical telencephalon is the major source of GABAergic interneurons that, during development, tangentially migrate to the cerebral cortex, where they modulate the glutamatergic excitatory action of pyramidal cells. The transcription factor Vax1, an intracellular mediator of both Shh and Fgf signaling, is expressed at high levels in the medial and lateral ganglionic eminences (MGE and LGE, respectively), in the septal area (SA), in the anterior entopeduncular area (AEP) and in the preoptic area (POA). We show that Vax1 expression in the neuroepithelium is graded: low in the ventricular zone (VZ) and high in the subventricular zone (SVZ), in a pattern that closely reproduces that of several members of the Dlx and Gsh family of homeobox transcription factors. We provide evidence that Vax1 plays an important role in proliferation and differentiation of MGE, POA/AEP and septum, and that the last structure is completely absent in Vax1-/- mice. We show that the absence of Vax1 causes a severe depletion of GABAergic neurons in the neocortex, ranging from 30% to 44%, depending on the cortical areas considered. Taken together, our data indicate that a loss of function mutation in the Vax1 gene generates abnormalities in basal ganglia subventricular zone development and that it prevents the formation of the septum, impairing GABAergic interneuron generation.

Lack of the ventral anterior homeodomain transcription factor VAX1 leads to induction of a second pituitary

The pituitary gland is an endocrine organ that is developmentally derived from a fold in the oral ectoderm and a juxtaposed fold in the neural ectoderm. Here, we show that the absence of Vax1, a homeodomain transcription factor known for its role in eye and optic chiasm development, causes the rostral oral ectoderm to form an ectopic fold that eventually develops into a separate second pituitary with all the pituitary cell types and neuronal fibers characteristic of the normal pituitary. The induction of the second pituitary is associated with a localized ectopic expression of Fgf10, a gene encoding a growth factor known to recruit oral ectodermal cells into the pituitary. Interestingly, there are rare cases of pituitary duplications in humans that are also associated with optic nerve dysplasia, suggesting that VAX1 might be involved in the pathogenesis of this disorder.

Future perspectives in melanoma research. Meeting report from the "Melanoma Research: a bridge Naples-USA. Naples, December 6th-7 th2010"

Progress in understanding the molecular basis of melanoma has made possible the identification of molecular targets with important implications in clinical practice. In fact, new therapeutic approaches are emerging from basic science and it will be important to implement their rapid translation into clinical practice by active clinical investigation.The first meeting of Melanoma Research: a bridge Naples-USA, organized by Paolo A. Ascierto (INT, Naples, Italy) and Francesco Marincola (NIH, Bethesda, USA) took place in Naples, on 6-7 December 2010.This international congress gathered more than 30 international and Italian faculty members and was focused on recent advances in melanoma molecular biology, immunology and therapy, and created an interactive discussion across Institutions belonging to Government, Academy and Pharmaceutical Industry, in order to stimulate new approaches in basic, translational and clinical research. Four topics of discussion were identified: New pathways in Melanoma, Biomarkers, Clinical Trials and New Molecules and Strategies.