Disruption of the CNTF gene results in motor neuron degeneration

Abstract

CNTF is a cytosolic molecule expressed postnatally in myelinating Schwann cells and in a subpopulation of astrocytes. Although CNTF administration prevents lesion-mediated and genetically determined motor neuron degeneration, its physiological function remained elusive. Here it is reported that abolition of CNTF gene expression by homologous recombination results in a progressive atrophy and loss of motor neurons in adult mice, which is functionally reflected by a small but significant reduction in muscle strength.CILIARY neurotrophic factor (CNTF) has many activities in vitro U , acting as a very potent survival factor for cultured parasympathetic' , sympathetic', sensory' and spinal motor neurons~· 4, and hippocampal neurons 5 . Moreover, CNTF is a cholinergic differentiation factor (increasing choline acetyltransferase ( ChAT) and reducing tyrosine hydroxylase (TH) levels) for primary cultures of rat sympathetic neurons 6 . It also promotes the survival of 0ligodendrocytes 7 and the differentiation ofO-2A glial precursor cells into type-II astrocytes in vitro8.Furthermore, the local administration of CNTF in vivo prevents the degeneration of facial nerve motor neurons after axotomy in the early postnatal period 9 and also markedly interferes with the degenerative changes in progressive motor neuronopathy (pmn) mutant mice'o . Although these observations provide promising perspectives for the therapeutic use of CNTF, the physiological function of CNTF remains elusive. CNTF is expressed postnatally in myelinating Schwann cells and in a subpopulation of astrocytes" . The structure of the molecule (lack of leader sequence) '2.13, its immunohistochemical localization in the cytosol" ·'4 and the absence of release of substantial quantities of CNTF into the culture medium of primary cultures of astrocytes'5 and transfected Cos or HeLa cells'2.13 characterize CNTF as a typical non-secreted cytosolic molecule. These characteristics strongly suggest that CNTF is not a physiological survival factor for motor neurons during embryonic development, because the period of naturally occurring motor neuron cell death in mice and rats is over at birth'6. But the cytosolic localization of CNTF and the evidence against its secretion along the classic endoplasmic reticulum (ER)-Golgi pathway does not exclude the possibility of an unconventional, regulated release, for example, as suggested for basic fibroblast growth factor (FGF)'7.'8 . The localization of CNTF in myelinating Schwann cells and its relatively high quantities in the cytosol"·'4.' 9 in comparison to its very high potency as a neurotrophic factorl.3 suggests that only a very small proportion of the cytosolic CNTF needs to reach the axons of the responsive neurons and that CNTF might have a maintenance function in postnatal neurons, in particular motor neurons. The site of synthesis and expected site of action of CNTF, together with its postnatal expression, invited an evaluation of its function by elimination of its expression by gene targeting.. Here we report on the...

Trophic Support of Motoneurons: Physiological, Pathophysiological, and Therapeutic Implications

“…To address this issue, we used gene-targeting techniques to produce transgenic mice in which the CNTF gene was disrupted (60). As expected, CNTF null mutants obtained by gene targeting resulting in a complete absence of CNTF protein and corresponding biological activity did not show a reduction of the number of motoneurons during embryonic development (60).…”

“…However, morphometric analysis of spinal motoneurons demonstrated a gradually increasing atrophy and degeneration of motoneurons accompanied by reactive gliosis, starting at the eighth postnatal week. By 28 weeks, a 22% reduction of the number of motoneurons in the facial nucleus was detectable (60). Although the motor func-tion from plain inspection did not indicate clear-cut signs of motoneuron impairment, measurement of grip strength as a parameter for motor function revealed a small but statistically significant reduction in 28-weekold CNTF null mutants (60) .…”

“…By 28 weeks, a 22% reduction of the number of motoneurons in the facial nucleus was detectable (60). Although the motor func-tion from plain inspection did not indicate clear-cut signs of motoneuron impairment, measurement of grip strength as a parameter for motor function revealed a small but statistically significant reduction in 28-weekold CNTF null mutants (60) . The fact that the clinical manifestation of impaired function in degenerative motoneuron diseases does not occur before 50% of the motoneurons have degenerated (67) and the statistically significant (P < 0.05) reduction in grip strength not only reflects the number of neurons lost but also an impaired function of at least part of the atrophic motoneurons.…”

Hypothalamic CNTF volume transmission shapes cortical noradrenergic excitability upon acute stress

“…BainsCat#012704 cfos ‐Cre ERT2 mouseJAX LabsCat#021882 ROSA26‐stop‐ZsGreen1 f / f mouse ( Ai6 )JAX LabsCat#007906 Scgn − /− miceMMRRC for authorsMalenczyk et al (2017) Cntf − / − mice A. GiordanoMasu et al (1993) Scgn‐ Cre mouseG. SzabóDeveloped for this studyAAV8‐EF1a‐double floxed‐hChR2(H134R)‐mCherry‐WPRE‐HGHpAAddgene Viral ServiceCat#20297AAV8‐hSyn‐DIO‐hM3D(Gq)‐mCherryAddgene Viral ServiceCat#44361AAV8‐hSyn‐DIO‐hM4D(Gi)‐mCherryAddgene Viral ServiceCat#44362AAV8‐hSyn‐DIO‐hM3D(Gq)‐mCherryAddgene Viral ServiceCat#44361pAAV‐hSyn‐DIO‐mCherryAddgene Viral ServiceCat#50459AAV‐hSyn1‐GCaMP6f‐P2A‐nls‐dTomatoAddgene Viral ServiceCat#51085 Sequence‐based reagents Primers for CNTFIDTRef#72797892‐3Control siRNASanta CruzCat#sc‐37007SCGN siRNASanta CruzCat#sc‐153255Accell SMARTpool CNTF siRNAGE DharmaconCat#A‐091086Accell SMARTpool SCGN siRNA…”

The lack of cardiotrophin-1 alters expression of interleukin-6 and leukemia inhibitory factor mRNA but does not impair cardiac injury response

“…The gp130 cytokine family is characterized by functional redundancy, and the phenotypes of mice lacking individual cytokines [12,17,28,29,45] are much less severe than the phenotypes of mice lacking their shared receptors [10,30,46]. Nonetheless, the early and robust expression of CT-1 in the developing heart tube, and the sustained expression of CT-1 in the adult heart, suggested that CT-1 played a unique role in promoting cardiac myocyte survival and hypertrophy during development and after injury.…”