Biomedical subjects

I Fariñas

Publications and source records attributed to I Fariñas.

At least 19 recordsLinked to original sources

PubMed2006

Abnormal development of pacinian corpuscles in double trkB;trkC knockout mice.

Pacinian corpuscles depend on either Aalpha or Abeta nerve fibers of the large- and intermediate-sized sensory neurons for the development and maintenance of the structural integrity. These neurons express TrkB and TrkC, two members of the family of signal transducing neurotrophin receptors, and mice lacking TrkB and TrkC lost specific neurons and the sensory corpuscles connected to them. The impact of single or double targeted mutations in trkB and trkC genes in the development of Pacinian corpuscles was investigated in 25-day-old mice using immunohistochemistry and ultrastructural techniques. Single mutations on trkB or trkC genes were without effect on the structure and S100 protein expression, and caused a slight reduction in the number of corpuscles. In mice carrying a double mutation on trkB;trkC genes most of the corpuscles were normal with a reduction of 17% in trkB-/-;trkC+/- mice, and 8% in trkB +/-;trkC -/- mice. Furthermore, a subset of the remaining Pacinian corpuscles (23% in trkB-/-;trkC+/- mice; 3% in trkB+/-;trkC-/- mice) were hypoplasic or atrophic. Present results strongly suggest that the development of a subset of murine Pacinian corpuscles is regulated by the Trk-neurotrophin system, especially TrkB, acting both at neuronal and/or peripheral level. The precise function of each member of this complex in the corpuscular morphogenesis remains to be elucidated, though.

Animals↗

PubMed2003

p75NTR in the spleen: age-dependent changes, effect of NGF and 4-methylcatechol treatment, and structural changes in p75NTR-deficient mice.

In addition to their well-known actions within the nervous system, neurotrophins and their receptors are involved in immune system functioning, as demonstrated by their wide distribution in lymphoid tissues and their in vitro actions on immunocompetent cells. Nevertheless, the in vivo roles of neurotrophin-receptor systems in lymphoid tissues, as well as the scope of their influence throughout development and adulthood, are yet to be clarified. In the present study, we used combined morphological and immunohistochemical techniques to investigate the presence and cellular localization of p75NTR, the pan-neurotrophin receptor protein, in rat spleen from newborns to aging individuals, and the structural and innervation changes in the spleens of p75NTR-deficient mice. In rats, p75NTR was expressed by splenic nerve fibers and dendritic cells in an age-regulated fashion, with maximal expression detected at 2 weeks. Consistently, the spleens of newborn mice lacking this receptor protein showed no signs of ingrowing sympathetic fibers, along with an absence of defined white pulp areas. The present findings suggest a prolonged role of p75NTR in the physiology of the spleen; at least during the embryonic development period, the receptor may be critical for correct innervation and compartmentalization processes to occur.

Aging↗

PubMed2002

Development and evolution of inner ear sensory epithelia and their innervation.

The development and evolution of the inner ear sensory patches and their innervation is reviewed. Recent molecular developmental data suggest that development of these sensory patches is a developmental recapitulation of the evolutionary history. These data suggest that the ear generates multiple, functionally diverse sensory epithelia by dividing a single sensory primordium. Those epithelia will establish distinct identities through the overlapping expression of genes of which only a few are currently known. One of these distinctions is the unique pattern of hair cell polarity. A hypothesis is presented on how the hair cell polarity may relate to the progressive segregation of the six sensory epithelia. Besides being markers for sensory epithelia development, neurotrophins are also expressed in delaminating cells that migrate toward the developing vestibular and cochlear ganglia. These delaminating cells originate from multiple sites at or near the developing sensory epithelia and some also express neuronal markers such as NeuroD. The differential origin of precursors raises the possibility that some sensory neurons acquire positional information before they delaminate the ear. Such an identity of these delaminating sensory neurons may be used both to navigate their dendrites to the area they delaminated from, as well as to help them navigate to their central target. The navigational properties of sensory neurons as well as the acquisition of discrete sensory patch phenotypes implies a much more sophisticated subdivision of the developing otocyst than the few available gene expression studies suggest.

Animals↗

PubMed2002

Sensing life: regulation of sensory neuron survival by neurotrophins.

Neurotrophins are a family of structurally and functionally related neurotrophic factors which, in mammals, include: nerve growth factor, brain-derived neurotrophic factor, neurotrophin-3 (NT-3), and NT-4/5. In addition to their canonical role in promoting neuronal survival, these molecules appear to regulate multiple aspects of the development of the nervous system in vertebrates, including neuronal differentiation, axon elongation and target innervation, among others. Actions of neurotrophins and of their receptors in vivo are being analyzed by loss-of-function or gain-of-function experiments in mice. Here, we review the phenotypes of the primary sensory system in these mutant mouse strains and the different strategies specifically involved in the regulation of neuronal survival by neurotrophins in this portion of the nervous system.

Animals↗

PubMed2001

Spatial shaping of cochlear innervation by temporally regulated neurotrophin expression.

Previous work suggested qualitatively different effects of neurotrophin 3 (NT-3) in cochlear innervation patterning in different null mutants. We now show that all NT-3 null mutants have a similar phenotype and lose all neurons in the basal turn of the cochlea. To understand these longitudinal deficits in neurotrophin mutants, we have compared the development of the deficit in the NT-3 mutant to the spatial-temporal expression patterns of brain-derived neurotrophic factor (BDNF) and NT-3, using lacZ reporters in each gene and with expression of the specific neurotrophin receptors, trkB and trkC. In the NT-3 mutant, almost normal numbers of spiral ganglion neurons form, but fiber outgrowth to the basal turn is eliminated by embryonic day (E) 13.5. Most neurons are lost between E13.5 and E15.5. During the period preceding apoptosis, NT-3 is expressed in supporting cells, whereas BDNF is expressed mainly in hair cells, which become postmitotic in an apical to basal temporal gradient. During the period of neuronal loss, BDNF is absent from the basal cochlea, accounting for the complete loss of basal turn neurons in the NT-3 mutant. The spatial gradients of neuronal loss in these two mutants appear attributable to spatial-temporal gradients of neurotrophin expression. Our immunocytochemical data show equal expression of their receptors, TrkB and TrkC, in spiral sensory neurons and thus do not relate to the basal turn loss. Mice in which NT-3 was replaced by BDNF show a qualitative normal pattern of innervation at E13.5. This suggests that the pattern of expression of neurotrophins rather than their receptors is essential for the spatial loss of spiral sensory neurons in NT-3 null mutants.

Afferent Pathways↗

PubMed2000

Mice lacking alpha-synuclein display functional deficits in the nigrostriatal dopamine system.

alpha-Synuclein (alpha-Syn) is a 14 kDa protein of unknown function that has been implicated in the pathophysiology of Parkinson's disease (PD). Here, we show that alpha-Syn-/- mice are viable and fertile, exhibit intact brain architecture, and possess a normal complement of dopaminergic cell bodies, fibers, and synapses. Nigrostriatal terminals of alpha-Syn-/- mice display a standard pattern of dopamine (DA) discharge and reuptake in response to simple electrical stimulation. However, they exhibit an increased release with paired stimuli that can be mimicked by elevated Ca2+. Concurrent with the altered DA release, alpha-Syn-/- mice display a reduction in striatal DA and an attenuation of DA-dependent locomotor response to amphetamine. These findings support the hypothesis that alpha-Syn is an essential presynaptic, activity-dependent negative regulator of DA neurotransmission.

Amphetamine↗

PubMed1999

Wnt3a-/--like phenotype and limb deficiency in Lef1(-/-)Tcf1(-/-) mice.

Members of the LEF-1/TCF family of transcription factors have been implicated in the transduction of Wnt signals. However, targeted gene inactivations of Lef1, Tcf1, or Tcf4 in the mouse do not produce phenotypes that mimic any known Wnt mutation. Here we show that null mutations in both Lef1 and Tcf1, which are expressed in an overlapping pattern in the early mouse embryo, cause a severe defect in the differentiation of paraxial mesoderm and lead to the formation of additional neural tubes, phenotypes identical to those reported for Wnt3a-deficient mice. In addition, Lef1(-/-)Tcf1(-/-) embryos have defects in the formation of the placenta and in the development of limb buds, which fail both to express Fgf8 and to form an apical ectodermal ridge. Together, these data provide evidence for a redundant role of LEF-1 and TCF-1 in Wnt signaling during mouse development.

Animals↗

PubMed1999

Expression of Trk receptors in the developing mouse trigeminal ganglion: in vivo evidence for NT-3 activation of TrkA and TrkB in addition to TrkC.

Animals lacking neurotrophin-3 (NT-3) are born with deficits in almost all sensory ganglia. Among these, the trigeminal ganglion is missing 70% of the normal number of neurons, a deficit which develops during the major period of neurogenesis between embryonic stages (E) 10.5 and E13.5. In order to identify the mechanisms for this deficit, we used antisera specific for TrkA, TrkB, and TrkC to characterize and compare the expression patterns of each Trk receptor in trigeminal ganglia of wild type and NT-3 mutants between E10.5 and E15.5. Strikingly, TrkA, TrkB, and TrkC proteins appear to be exclusively associated with neurons, not precursors. While some neurons show limited co-expression of Trk receptors at E11.5, by E13. 5 each neuron expresses only one Trk receptor. Neuronal birth dating and cell counts show that in wild-type animals all TrkB- and TrkC-expressing neurons are generated before E11.5, while the majority of TrkA-expressing neurons are generated between E11.5 and E13.5. In mice lacking NT-3, the initial formation of the ganglion, as assessed at E10.5, is similar to that in wild-type animals. At E11.5, however, the number of TrkC-expressing neurons is dramatically reduced and the number of TrkC-immunopositive apoptotic profiles is markedly elevated. By E13.5, TrkC-expressing neurons are virtually eliminated. At E11.5, compared to wild type, the number of TrkB-expressing neurons is also reduced and the number of TrkB immunoreactive apoptotic profiles is increased. TrkA neurons are also reduced in the NT-3 mutants, but the major deficit develops between E12.5 and E13.5 when elevated numbers of TrkA-immunoreactive apoptotic profiles are detected. Normal numbers of TrkA- and TrkB-expressing neurons are seen in a TrkC-deficient mutant. Therefore, our data provide evidence that NT-3 supports the survival of TrkA-, TrkB- and TrkC-expressing neurons in the trigeminal ganglion by activating directly each of these receptors in vivo.

Animals↗

PubMed1998

GFRalpha1 is an essential receptor component for GDNF in the developing nervous system and kidney.

Glial cell line-derived neurotrophic factor (GDNF) is a distant member of the TGFbeta protein family that is essential for neuronal survival and renal morphogenesis. We show that mice who are deficient in the glycosyl-phosphatidyl inositol (GPI) -linked protein GFRalpha1 (GDNFRalpha) display deficits in the kidneys, the enteric nervous system, and spinal motor and sensory neurons that are strikingly similar to those of the GDNF- and Ret-deficient mice. GFRalpha1-deficient dopaminergic and nodose sensory ganglia neurons no longer respond to GDNF or to the structurally related protein neurturin (NTN) but can be rescued when exposed to GDNF or neurturin in the presence of soluble GFRalpha1. In contrast, GFRalpha1-deficient submandibular parasympathetic neurons retain normal response to these two factors. Taken together with the available genetic and biochemical data, these findings support the idea that GFRalpha1 and the transmembrane tyrosine kinase Ret are both necessary receptor components for GDNF in the developing kidney and nervous system, and that GDNF and neurturin can mediate some of their activities through a second receptor.

Aging↗

PubMed1998

Characterization of neurotrophin and Trk receptor functions in developing sensory ganglia: direct NT-3 activation of TrkB neurons in vivo.

Spinal sensory ganglia have been shown to contain neuronal subpopulations with different functions and neurotrophin dependencies. Neurotrophins act, in large part, through Trk receptor tyrosine kinases: nerve growth factor (NGF) via TrkA, brain-derived neurotrophic factor (BDNF) and neurotrophin-4/5 (NT-4/5) via TrkB, and neurotrophin-3 (NT-3) via TrkC. In the present paper, we use antibodies to TrkA, TrkB, and TrkC to characterize their expression patterns and to determine which subpopulations of cells are lost in mice lacking individual neurotrophins or Trk receptors. Despite previous reports of Trk receptor mRNAs in neural crest cells, we detect Trk receptor proteins only in neurons and not in neural crest cells or neuronal precursors. Comparisons of neonatal mice deficient in NT-3 or its cognate receptor TrkC have shown that there is a much greater deficiency in spinal sensory neurons in the former, suggesting that NT-3 may activate receptors in addition to TrkC. Using the same antibodies, we show that, during the major period of neurogenesis, NT-3 is required to maintain neurons that express TrkB in addition to those that express TrkC but is not essential for neurons expressing TrkA. Results also indicate that survival of cells expressing both receptors can be maintained by activation of either one alone. NT-3 can thus activate more than one Trk receptor in vivo, which when coexpressed are functionally redundant.

Animals↗

PubMed1997

Lack of neurotrophin 3 causes losses of both classes of spiral ganglion neurons in the cochlea in a region-specific fashion.

Essential functions of neurotrophin 3 (NT-3) in regulating afferent and efferent innervation of the cochlea have been characterized by comparison of normal and NT-3 mutant mice. NT-3 deficiency has striking, region-specific effects, with complete loss of sensory neurons in the basal turn and dramatic but incomplete neuronal loss in the middle and apical turns. The sensory innervation of inner and outer hair cells was reorganized in mutant animals. Instead of a strictly radial pattern of innervation, the axons of remaining sensory neurons projected spirally along the row of inner hair cells to innervate even the most basal inner hair cells. Innervation of outer hair cells was strongly reduced overall and was not detected in the basal turn. The presence of fibers extending to both inner and outer hair cells suggests that subsets of types I and II sensory neurons survive in the absence of NT-3. Likewise, projections of the cochlea to auditory nuclei of the brainstem were attenuated but otherwise present. Equally striking changes in efferent innervation were observed in mutant animals that closely mimicked the abnormal sensory innervation pattern. Despite these impressive innervation deficiencies, the morphology of the organ of Corti and the development of inner and outer hair cells appeared comparatively normal.

Animals↗

PubMed1997

Effects of neurotrophin and neurotrophin receptor disruption on the afferent inner ear innervation.

Two neurotrophins and their two receptors appear to regulate the survival of vestibular and cochlear neurons in the developing ear. Mice lacking either brain derived neurotrophic factor (BDNF) or its associated receptor, Trk B, show a severe reduction in the number of vestibular neurons and a loss of all innervation to the semicircular canals. Mice lacking NT-3 or its receptor, Trk C, show a severe reduction of spiral neurons in the basal turn of the cochlea. Mice lacking both BDNF and NT-3 or Trk B and Trk C, reportedly lose all innervation to the inner ear. These two neurotrophins and their associated receptors are necessary for the normal afferent innervation of the inner ear.

Journal Article↗

PubMed1997

The role of neurotrophic factors in regulating the development of inner ear innervation.

Several neurotrophins and their receptors regulate the survival of vestibular and cochlear neurons and probably also the efferent and autonomic neurons that innervate the inner ear. Mice lacking either brain-derived neurotrophic factor (BDNF) or its associated receptor, TrkB, lose all innervation to the semicircular canals and have reduced innervation of the outer hair cells in the apical and middle turns of the cochlea. Mice lacking neurotrophin-3 (NT-3) or its receptor, TrkC, lose many spiral ganglion cells predominantly in the basal turn of the cochlea. Nerve fibers from spiral ganglion cells in the middle turn extended to inner hair cells of the base. In mice lacking both BDNF and NT-3, or both TrkB and TrkC, there is a complete loss of innervation to the inner ear. Thus, these two neurotrophins and their associated receptors have been shown to be absolutely necessary for the normal development of afferent innervation of the inner ear. Current research efforts are testing the therapeutic potential for neurotrophins to treat hearing loss.

Animals↗

PubMed1997

Brain-derived neurotrophic factor regulates maturation of the DARPP-32 phenotype in striatal medium spiny neurons: studies in vivo and in vitro.

The medium spiny neuron is the predominant striatal neuronal subtype. The striatum, a participant in motor and cognitive functions, is a site of pathophysiology in prevalent neuropsychiatric diseases and is the target of many currently utilized pharmacologic agents. DARPP-32, a dopamine and cyclic AMP-regulated phosphoprotein, is a widely-used marker of mature striatal medium-sized neurons, but the molecules regulating DARPP-32 transcription have not been identified. We show that a null mutation in the mouse brain-derived neurotrophic factor gene leads to decreased DARPP-32 immunoreactivity in striatal medium spiny neurons at birth and postnatal day 10. Striatal DARPP-32 messenger RNA and protein are decreased relative to wild-type littermate controls. In densely plated (1 x 10(6) cells/cm2) primary cultures derived from the ganglionic eminences, addition of brain-derived neurotrophic factor (100 ng/ml) to defined media results in a greater than 3-fold increase in the number of DARPP-32-immunopositive cells after 12 h and greater than 4-fold (P<0.005) after 24 h. The increase in DARPP-32-immunopositivity is abolished by the addition of 2 microg/ml actinomycin D without a significant effect on cell viability. These data suggest that brain-derived neurotrophic factor directly or indirectly regulates DARPP-32 transcription in medium spiny neurons. This is the first demonstration of transcriptional regulation of DARPP-32, and the first evidence of a forebrain abnormality in a newborn neurotrophin "knockout" mouse.

Animals↗

PubMed1996

Neurotrophin-3 is a survival factor in vivo for early mouse trigeminal neurons.

Mice lacking neurotrophin-3 (NT-3) have been shown previously to be born with severe sensory deficits. This study characterizes the developmental course of this deficit in the trigeminal sensory ganglion, which in NT-3 homozygous mutants contains only 35% of the normal number of neurons at birth. At embryonic day 10.5 (E10.5), normal numbers of neurons, as assessed by expression of neurofilament protein and of total cells, are present in the ganglia of mutant homozygotes. During the next 3 d (E10.5-E13.5), virtually all of the deficit develops, after which mutant animals retain only approximately 30% the normal number of neurons. Quantification of neuronal and neuronal precursor numbers in normal and mutant animals reveals that neurons are specifically depleted in the absence of NT-3. A deficiency in precursor proliferation is only seen after most of the neuronal deficit has developed. Numbers of apoptotic cells in the ganglia of mutant animals are elevated during this same interval, indicating that the neuronal deficit is caused, in large part, by increased cell death of embryonic neurons. To determine sources of NT-3 in the trigeminal system, we examined the expression pattern of beta-galactosidase in mice, in which lacZ has replaced the NT-3 coding exon. E10.5-E11.5 embryos exhibit intense reporter expression throughout the mesenchyme and epithelia of the first branchial arch. Beta-galactosidase expression in E13.5 embryos is largely confined to the oral epithelium and the mesenchyme underlying the skin. Throughout the E10.5-E13.5 interval, the trigeminal ganglion and its targets in the CNS do not express reporter activity. We conclude that NT-3 acts principally as a peripherally derived survival factor for early trigeminal neurons.

Animals↗

PubMed1996

Renal and neuronal abnormalities in mice lacking GDNF.

Glial cell-line derived neurotrophic factor (GDNF) is a potent survival factor for embryonic midbrain dopaminergic, spinal motor, cranial sensory, sympathetic, and hindbrain noradrenergic neurons, and is available to these cells in vivo. It is therefore considered a physiological trophic factor and a potential therapeutic agent for Parkinson's disease, amyotrophic lateral sclerosis, and Alzheimer's disease. Here we show that at postnatal day 0 (P0), GDNF-deficient mice have deficits in dorsal root ganglion, sympathetic and nodose neurons, but not in hindbrain noradrenergic or midbrain dopaminergic neurons. These mice completely lack the enteric nervous system (ENS), ureters and kidneys. Thus GDNF is important for the development and/or survival of enteric, sympathetic and sensory neurons and the renal system, but is not essential for catecholaminergic neurons in the central nervous system (CNS).

Animals↗

PubMed1996

A reciprocal cell-cell interaction mediated by NT-3 and neuregulins controls the early survival and development of sympathetic neuroblasts.

Neurotrophin 3 (NT-3) can support the survival of some embryonic sympathetic neuroblasts before they become nerve growth factor dependent. We show that NT-3 is produced in vivo by nonneuronal cells neighboring embryonic sympathetic ganglia. NT-3 mRNA is produced by these nonneuronal cells in vitro and is up-regulated by platelet-derived growth factor, ciliary neurotrophic factor, and glial growth factor 2 (a neuregulin). Nonneuronal cell-conditioned medium promotes survival and induces TrkA expression in isolated sympathetic neuroblasts, and this activity is blocked by anti-NT-3 antibody. Neuroblasts also enhance NT-3 production by nonneural cells. Neuroblasts synthesize several forms of neuregulin, and antibodies to neuregulin attenuate the effect of the neuroblasts on the nonneuronal cells. These data suggest a reciprocal cell-cell interaction, in which neuroblast-derived neuregulins promote NT-3 production by neighboring nonneuronal cells, which in turn promotes neuroblast survival and further differentiation.

Animals↗

PubMed1996

Lack of neurotrophin-3 results in death of spinal sensory neurons and premature differentiation of their precursors.

To understand mechanisms resulting in the absence of two-thirds of spinal sensory neurons in mice lacking NT-3, we have compared dorsal root ganglia development in normal and mutant embryos. The reduction in neurons, achieved by E13, results from several deficits: first, elevated neuronal apoptosis significantly reduces neuronal numbers; second, elevated neurogenesis between E11 and E12, without changes in rates of precursor proliferation or apoptosis, depletes the precursor pool; consequently, the reduced precursor pool prevents increases in neuronal numbers between E12 and E13, when most neurons are born in normal animals. Although deficits occur before final target innervation, we show that NT-3 is expressed at all stages in regions accessible to these neurons or their axons and is only restricted to final targets after innervation.

Animals↗