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We generated a novel strain of mutant mouse with a deletion in the gene encoding metabotropic glutamate receptor 1 (mGluR1). Gross anatomy of the hippocampus, excitatory synaptic transmission, long-term depression, and short-term potentiation in the hippocampal CA1 region are all apparently normal in the mutant mice. In contrast, long-term potentiation (LTP) is substantially reduced, and a moderate level of impairment is observed in context-specific associative learning. We propose that mGluR1 is not "in line" in LTP production, but rather modulates the plasticity process, and hence affects context-specific associative learning.

The neurological mutation, staggerer , causes a severe disruption in the integrity of the olivo-cerebellar circuitry. The primary site of action is the Purkinje cell population which is reduced in cell number, with cells that are atrophic in dendritic structure, small in size and ectopic in position. This primary defect has a cascade effect on the Purkinje cell-afferent populations, leading to the target-related cell death of virtually all of the cerebellar granule cells and the majority of the neurons in the inferior olive. As part of our ongoing study of the cell-cell interactions in the cerebellar circuitry, we have studied the inferior olive of the staggerer mutant from birth to adulthood. We find that the reduction in olive neuron number does not occur until after birth in the mutants. On the day of birth, the number of cells is indistinguishable in mutants and in wild type. Similarly, we find that the four principal subnuclei of the olive are well defined at birth, but regress to a state of poor resolution during the first 3 postnatal weeks. Finally, Golgi impregnations reveal that of the two morphological classes of inferior olive neurons, only one class— the Type II or complex dendritic type survive in the mutant. These results are discussed in terms of their implications for the cell-cell interactions in the developing olivocerebellar circuit.

In lurcher--wild type mouse chimeras (lurcher chimeras), mutant Purkinje cells are transiently present and probably provide target support for afferent granule cells during the sensitive period of target-dependent cell death. Previous studies demonstrate that wild type Purkinje cells in the cerebella of mature lurcher chimeras often have atrophic dendritic morphologies, leading to the hypothesis that developmental deafferentation of wild type Purkinje cells occurs uniquely in lurcher chimeras following the period of mutant Purkinje cell loss. Other studies document the survival of a disproportionately large number of granule cells in these animals. Based on cell birthdate analyses, the hypothesis further proposes that deafferentation induces an up-regulation of trophic activity among the Purkinje cell population and the consequent rescue of late generated granule cells that might otherwise be lost to target related cell death. In the present study, we take advantage of phenotypic differences between the staggerer and lurcher mutations to test this hypothesis. While staggerer--wild type chimeras (staggerer chimeras) resemble lurcher chimeras in several respects, including extensive cell loss, they differ in that staggerer Purkinje cells never provide target support for granule cells. Hence the hypothesis predicts that Purkinje cells in these animals should not exhibit the atrophic morphologies found in lurcher chimeras. We have developed a new semiquantitative method for scoring dendritic morphology in a large number of Golgi-impregnated cells. We have used this method to characterize the distribution of wild type Purkinje cell morphologies in staggerer chimeras, and to compare these with the corresponding distributions of morphologies in lurcher chimeras and wild type--wild type chimeras. We find that morphologies in staggerer chimeras closely resemble those in control chimeras. Furthermore, Purkinje cells in both staggerer and wild type chimeras differ significantly from those in lurcher chimeras. These results confirm a direct prediction of the hypothesis.

In this paper, we continue our examination of the role of cell lineage in the development of the cerebellar Purkinje cell population of the mouse. The analysis of Purkinje cell lineage is based on counts of the number of wild-type Purkinje cells in +/Lc ↔ wild-type chimeras. +/Lc Purkinje cells undergo a cell autonomous degeneration early in post-natal development leaving variable numbers of wild-type Purkinje cells in chimeric animals. Using theoretical, statistical, and experimental approaches, we have tested various developmental models to account for the numerical development of Purkinje cell numbers in the +/Lc ↔ wild-type chimeras. We have analyzed models based on the assumption that cell lineages are irrelevant to Purkinje cell development, as well as our own previous hypothesis that Purkinje cells descend from a small number of progenitor cells selected during the early stages of neurogenesis. The theoretical approach calculates the distributions of Purkinje cell numbers in hypothetical +/Lc ↔ wild-type chimeras and inbred mice based on both clonal and nonclonal hypotheses of neuronal development. Variations of the model are compared with published cell counts from +/Lc ↔ C3H/HeJ, +/Lc ↔ C57BL/6J, +/Lc ↔ AKR/J chimeras, and C3H/HeJ inbred mice. The statistical approach assesses the significance of the fits of the observed data with different variations of the model by Monte Carlo simulation techniques. The results of the comparison suggest that our observed data is more likely to be explained by a clonal model of development than by alternate models in which cell lineages play a minor role. Our experimental approach describes a new +/Lc ↔ C3H/HeJ chimera in which all of the Purkinje cells (>7900) are found on one side of the brain. We have analyzed this chimera with respect to clonal and nonclonal models of Purkinje cell development. The extreme asymmetric distribution of Purkinje cells provides added support to the hypothesis that there is a small number of progenitor cells that generate Purkinje cells. Our findings lead to the conclusion that while not all alternate models of mammalian CNS development can be completely excluded, the early progenitor hypothesis is the most probable model of Purkinje cell development.

Most neurons undergo their last cell division within the first 1 to 2% of the lifespan of an organism. This has been interpreted to mean that adult neurons are permanently postmitotic, but Alzheimer's disease (AD) is an example of a late-onset neurodegenerative disease that challenges this concept. In AD, neurons in populations at risk for death reactivate their cell cycle and replicate their genome - but rather than complete the cycle with mitosis and cytokinesis, the neurons die. While opening new perspectives on the etiology of AD dementia, the simple linear model suggested by this description gains in complexity with the maturation of the adult brain. This complexity makes the full understanding of the relationship between cell division and cell death more difficult to achieve. The quest for understanding is worthwhile, however, as fresh avenues for therapeutic intervention are the prizes for success.

As the mature nervous system is sculpted out of its embryonic anlage, regressive events are a surprisingly common feature. As one example, the establishment of adult innervation in the CNS and PNS often involves a massive withdrawal of previously formed functional synapses. In the cerebellum, the one-to-one relationship of inferior olivary climbing fibers to Purkinje cells is preceded by a transient stage in which each Purkinje cell is multiply innervated. The regulation of this regressive event is still not fully understood; previous studies suggested that some stimulus from the maturing granule cells is necessary. We have used the lurcher (Lc) mutation as a model system in which to study this phenomenon. In lurcher mice, Purkinje cells degenerate during the first few postnatal weeks, after receiving synaptic contacts from both inferior olivary neurons and granule cells. We have recorded the climbing fiber responses both in lurcher mutants at postnatal days 14–20 (P14-P20) and in adult lurcher chimeras. In the latter, experimental genetics are used to create a situation in which untreated wild-type Purkinje cells are present in an environment that ranges from 100% wild-type to nearly mutant. We found that in P14-P16 lurcher mutants, most of the cells recorded (75%) remained polyinnervated, whereas in wild-type control mice, only 10% of the Purkinje cells retained their multiple innervation. By P18-20, it was difficult to find Purkinje cells in the lurcher mutants that would withstand an intracellular electrode. Nonetheless, in those cells that were successfully impaled, most remained multiply innervated. By this age in wild-type mice, 100% of the Purkinje cells are monoinnervated.(ABSTRACT TRUNCATED AT 250 WORDS)

Staggerer is a neurological mutation of mice that causes a severe ataxia correlated with digenesis of the cerebellar cortex. The Purkinje cell population in the homozygous mutant is reduced in size with a near total atrophy of dendritic structure. Further, the cells are ectopic and are reduced in number by about 75%. All of these phenotypes have been shown to be direct effects of the staggerer gene on the Purkinje cell itself. As an indirect consequence of gene action, virtually all of the cerebellar granule cells die as do 60% of the cells of the inferior olive. The mutation is described as recessive because of the heterozygote, +/sg, is behaviorally normal and the mature cerebellum shows none of the defects described in the homozygous mutant. We report here that, as the +/sg mouse advances in age, a syndrome of cell losses is observed. While these losses are not as severe as in the homozygote, by 12 months of age 35% of the Purkinje cells are gone, as are 35% of the granule cells and 40% of the cells in the inferior olive. We propose that these results illustrate a synergy between the aging process and the heterozygous genotype. Neither alone is sufficient to cause the cell loss. This interaction suggests that the +/sg represents a new model for the genetic contribution to regressive CNS changes during aging.

The respective roles of genetic and epigenetic factors in generation of pattern formation in the vertebrate nervous system are still poorly elucidated. The mammalian cerebellum is subdivided in parasagittal modules defined by anatomical, physiological, and biochemical criteria. Immunostaining of adult mouse cerebellum with two monoclonal antibodies, P-path, which recognizes 9-O-acetylated glycolipids, and Zebrin II, which recognizes a 36-kDa protein, reveals three classes of sagittally organized bands of Purkinje cells: two complementary groups distinctly immunoreactive to one antibody but not the other and a third group that contains double-labeled cells. No Purkinje cells could be detected that were unreactive to either antibody. The specific and reproducible topography of these three classes of Purkinje cells may be related to the compartmentation of the cerebellum into developmental genetic modules.

The V(D)J recombination activation gene RAG-1 was isolated on the basis of its ability to activate V(D)J recombination on an artificial substrate in fibroblasts. This property and the expression pattern in tissues and cell lines indicate that RAG-1 either activates or catalyzes the V(D)J recombination reaction of immunoglobulin and T cell receptor genes. We here describe the introduction of a mutation in RAG-1 into the germline of mice via gene targeting in embryonic stem cells. RAG-1-deficient mice have small lymphoid organs that do not contain mature B and T lymphocytes. The arrest of B and T cell differentiation occurs at an early stage and correlates with the inability to perform V(D)J recombination. The immune system of the RAG-1 mutant mice can be described as that of nonleaky scid mice. Although RAG-1 expression has been reported in the central nervous system of the mouse, no obvious neuroanatomical or behavioral abnormalities have been found in the RAG-1-deficient mice.

The mammalian cerebellum has long intrigued neurobiologists as an attractive model system in which to approach the study of pattern formation because of its simple, highly repetitive cytoarchitecture. Overlaid on the apparent homogeneity, however, is a large scale pattern of sagittally organized bands and clusters that is seen at all levels, from the molecular constituents of the cells to the network properties of the region. It is rapidly becoming recognized that this pattern reflects a fundamental organizing principle of the cerebellum.

Lurcher is an autosomal dominant mutation in the mouse. Heterozygote (+/Lc) animals lose 100% of their cerebellar Purkinje cells during the first postnatal month. Aggregation chimeras made between +/Lc and wild-type embryos have been used to demonstrate that this neuronal cell death is a cell autonomous property of the +/Lc Purkinje cells. In lurcher chimeras, all +/Lc PCs die while wild-type Purkinje cells survive in the numbers expected. Although they are normal in number, previous work from our laboratories has shown that when the genetically wild-type Purkinje cells are present in the mosaic environment of the lurcher chimeric mouse they develop a very unusual morphology. Their dendritic trees are small, and the caliber of their dendrites is increased. This paper examines the fine structure of these unusual cells as well as their afferent fibers. Purkinje cell somas in the lurcher chimera have an increased number of lysosomes and the rough endoplasmic reticulum is improperly configured. In the majority of the Purkinje cell dendrites the organelles are disorganized; it is not certain whether this is a cause or a consequence of the increase in dendritic caliber previously reported. Presynaptic fibers have been examined and, while all classes of expected synapses can be observed, the numbers of synaptic profiles visible in any one thin section are reduced. Climbing fiber terminations on the Purkinje cells were smaller than normal with a greatly diminished number of constituent vesicles. Unexpectedly, we found unusual morphologies among the Bergmann glial fibers and the presence of unusual (or ectopic) astrocytic like glial cells near the pial surface. These changes in turn were accompanied by an increase in the number of glial-like fibers near the pia in some parts of the chimeric cerebellar cortex. The results are discussed in light of our knowledge of other mutant mice, and a hypothesis is put forward to explain some of our results.

The two mouse genes, En-1 and En-2, that are homologs of the Drosophila segmentation gene engrailed, show overlapping spatially restricted patterns of expression in the neural tube during embryogenesis, suggestive of a role in regional specification. Mice homozygous for a targeted mutation that deletes the homeobox were viable and showed no obvious defects in embryonic development. This may be due to functional redundancy of En-2 and the related En-1 gene product during embryogenesis. Consistent with this hypothesis, the mutant mice showed abnormal foliation in the adult cerebellum, where En-2, and not En-1, is normally expressed.

Experimental aggregation chimeric mice offer a perspective on cell lineage relationships that is complementary to that of prospective tracing methods such as dye injections or recombinant retroviruses. To create a lineage map of cerebral cortex, the position and genotype of cortical neurons in three-dimensional space were reconstructed with the aid of a computer-assisted mapping system. Chi-square statistical analyses indicate that the spatial distribution of cell lineages in the cerebral cortex is highly nonrandom. When individual dimensions are analyzed separately, a high degree of order is found in the spatial distribution of neuronal genotype ratios in the anterior-posterior dimension but not in the medial-lateral dimension. This suggests an arrangement of lineage-related neurons into “slabs” or “stripes” of cells that are organized in the plane perpendicular to the neuraxis. Additionally, a highly significant variation in genotype ratios was found in the radial dimension (i.e., among cortical cell layers). These data suggest the hypothesis that separate sets of progenitor cells give rise to the superficial and deep layers of cortex. Taken together, our data are consistent with a picture of the developing nervous system in which early developmental restrictions to cell mixing set up boundaries that may be of considerable developmental genetic importance.

Contemplating Alzheimer's disease as cancer: a loss of cell-cycle controlThe nerve cells of the adult brain are born predominantly during embryogenesis, and as development proceeds, the addition of new nerve cells slows to a barely detectable trickle. By the time a human being nears the end of life most of their nerve cells have been in a post-mitotic state for seven to nine decades. The means by which cells accomplish this feat of suspended animation are unknown, but there are no apparent failures of the cell cycle arrest mechanism.During the past few years several laboratories have suggested that if a nerve cell violates the prohibition against cell division it will die rather than divide. The principle was first suggested when a powerful oncogene was expressed specifically in maturing Purkinje cells in transgenic mice. Unexpectedly, transgenic Purkinje cells began replicating their DNA but subsequently died 1xIn vivo viability of postmitotic Purkinje neurons requires pRb family member function. Feddersen, R.M. et al. Mol. Cell. Neurosci. 1995; 6: 153–167Crossref | PubMed | Scopus (58)See all References1. Next, researchers found that the activation of cell cycle processes is part of the mechanism by which developmental failure of trophic support leads to nerve cell death 2xThe induction of multiple cell cycle events precedes target-related neuronal death. Herrup, K. and Busser, J.C. Development. 1995; 121: 2385–2395PubMedSee all References, 3xAnalysis of cell cycle-related gene expression in postmitotic neurons: selective induction of Cyclin D1 during programmed cell death. Freeman, R. et al. Neuron. 1994; 12: 343–355Abstract | Full Text PDF | PubMed | Scopus (499)See all References.Now, several laboratories have explored the role of cell cycle processes in late-onset neurodegenerative disease. Our laboratory was one of several that provided immunocytochemical evidence for the presence of cell cycle activators (Fig. 1Fig. 1) as well as inhibitors in neurons of Alzheimer's disease brain. But the cell cycle is a highly regulated phenomenon.Fig. 1Immunocytochemical evidence for the re-expression of proliferating cell nuclear antigen (PCNA), a subunit of DNA polymerase. (a) Although normally found only in dividing cells, hippocampal neurons in Alzheimer's disease brain show occasional cells with significant expression of this protein. (b) Cells from a similar region of an age-matched, non-demented control show no evidence of expression.View Large Image | Download PowerPoint SlideOur laboratory adapted cytogenetics techniques such as fluorescent in situ hybridization (FISH) to analyze the DNA directly. We discovered that the chromosome complement in 4% of the hippocampal pyramidal cells in Alzheimer's disease has doubled 4xMice deficient for Rb are nonviable and show defects in neurogenesis and haematopoiesis. Yang, Y. et al. J. Neurosci. 2001; 21: 2661–2668PubMedSee all References4. Using either short centromeric FISH probes or long probes to unique sequences we were able to show that these neurons had up to four copies of each locus instead of the expected two – direct evidence that a coordinated DNA duplication had occurred (Fig. 2Fig. 2). No evidence of mitosis was found, suggesting the cells arrested at or near the G2 phase of the cell cycle.Fig. 2Fluorescence in situ hybridization for unique sites in the human genome. Neurons of the adult brain should all be diploid and display no more than two sites of hybridization. (a) In the Alzheimer's disease hippocampal neuron illustrated, four spots are found (white arrows) indicating that cells have arrested in G-phase, and that coordinated DNA duplication has occurred. (b) Cells from control subjects always have two spots or fewer.View Large Image | Download PowerPoint SlideThe implication of these findings is that the neurons in the Alzheimer's disease brain are subjected to a mitotic pressure that drives them to attempt a cell cycle they cannot complete. In most cancers, a gene mutation disrupts cell cycle suppression leading to the clonal expansion of a single dysregulated cell. If our model is correct, then the problem in Alzheimer's disease is nearly the exact opposite: although the nerve cells themselves remain genetically intact, extrinsic factors that promote cell division increase until, one by one, the most susceptible neurons divide and die.

Retrograde axonal transport of125I labeled nerve growth factor (NGF) occurs in the adrenergic neurons of the sympathetic nervous system of rats as well as mice. This transport is saturable, it can be blocked by an excess of unlabeled NGF and shows a specificity for the biologically active form of the protein. Other proteins such as serum albumin, chymotrypsin or insulin are transported in varying, but much smaller, amounts. Although the transport of albumin is blocked by an excess of NGF, the opposite is not true, again suggesting a specific mechanism. NGF antibody, injected subcutaneously, prevents retrograde transport in neonatal but not in more mature animals and the relative resistance of the latter to the action of NGF antiserum may be related to this phenomenon.

This report contains additional observations on the cell lineage relationships of the motor neurons of the facial nucleus and of the cerebellar Purkinje cells of the mouse. These cell populations were quantitatively analyzed in the mosaic brains of experimental aggregation chimeras. The cell markers used to perform the analysis were (1) staining differences in beta-glucuronidase enzyme activity due to differences at the Gus locus on chromosome 5 and (2) self-destruction of all Purkinje cells of one genotype due to the cell autonomous action of the lurcher gene on chromosome 6. Of 6 animals examined in the Purkinje cell study, 5 showed left/right differences in the clonal composition of the cerebellum. Of 4 animals examined in the facial nucleus study, all 4 showed differences in genotype ratio. These results imply that the event that defines the selection of the progenitor cells for each of these two cell types is, in fact, two bilaterally independent events. This is consistent with the pictures of the early nervous system derived from embryological observations. The implication of these findings for cell mixing during development is discussed.

Genetically mosaic animals are valuable tools in the study of cell lineage relationships during development. The work described here is a quantitative analysis of large motor neurons of the facial nerve nucleus of the mouse. Aggregation chimeric mice were made from embryos which differed at the structural locus for the enzyme beta-glucuronidase. This difference is an intrinsic property of each cell and is easily detected by histochemical means. The numbers of cells in each of 10 facial nuclei from six glucuronidase chimeras were determined and each cell was scored for its embryo of origin using the glucuronidase marker. Unlike cerebellar Purkinje cells, this analysis revealed no evidence of numerical quanta of invariant size in the facial nucleus. Determination of the fraction of the total cells comprised by the descendants of each embryo, however, revealed evidence of quanta. These values suggest that the neurons of each facial nucleus descend from 12 progenitors. In agreement with similar calculations performed on Purkinje cells, the facial nucleus progenitors appear to be selected as the sole source of the facial nucleus neurons some time during the neural plate to neural groove stage of development. The absence of rigidly specified numerical quanta in the nucleus suggests that factors extrinsic to these cells contribute to the final adult number of neurons.

Leaner is an autosomal recessive mutation of the mouse which results in a severe ataxia accompanied by cellular losses in the cerebellar cortex. The purpose of this report is to construct a developmental profile of these losses. Of the three cerebellar cell types studied, the granule cells are the first to show obvious degenerative changes. Pycnotic cells are numerous in the internal granule cell layer at postnatal day 10, and, while they are found throughout the cortex, they are more concentrated in the anterior folia. Initially, there is a strong tendency for the pycnotic cells to be located in the deep half of the internal granule cell layer. By four postnatal months the rate of loss has slowed but the finding of occasional pycnotic cells in animals up to one year old suggests it continues for the life of the animal. Quantitative analysis of Purkinje and Golgi cells in leaner cerebella reveals a progressive loss of these cells as well. The number of Golgi cells falls uniformly to around half of the wild-type number. By contrast, the Purkinje cells show much more extensive degeneration. Further, the rate of cell death shows a regional variation; it is significantly more rapid in anterior folia. Overall, the number of Purkinje cells in leaner falls to about one-fifth of the wild-type number. The loss of both Purkinje and Golgi cells occurs late relative to the major events of cerebellar maturation. Significant cell loss is not observed until the end of the first postnatal month. For the next 4 to 6 weeks there is extensive cell death but, rather than abating, it appears to continue at a low rate for the life of the animal. It is hoped that this developmental sketch of the leaner defect will stimulate others to approach leaner and its alleles, tottering and rolling, as models for heterogeneity of disease expression.

The enzymes coded for by two alleles at the glucuronidase structural locus (Gus) were compared in their response to pH, buffering anion, buffer molarity, ionic strength, and temperature. The heat-labile Gush gene product responded in a qualitatively similar but quantitatively reduced manner compared to the relatively heat-stable Gusb gene product. In all buffers tested, the enzyme was most heat stable at pH 5.0. Ranking of the various buffer anions tested, according to increasing heat stabilization, was water less than acetate less than or equal to phosphate less than citrate. Varying the molarity of the buffers from 0.01 to 0.6 M at pH 5.0 revealed further differences among the buffers. Increasing ionic strength exerted a destabilizing force on the protein. The half-life of the enzyme decreased by as much as a hundredfold between 71 and 75 C. The Gush/Gush genotype also results in decreased activity levels in all tissues, reportedly because of decreased synthesis. The heat inactivation curves of Gusb/Gush heterozygotes were incompatible with any theoretical curve based on the assumption that the Gusb and Gush chromosomes in the heterozygote behave in a manner similar to that seen in the homozygotes.

Heterozygous lurcher (+/Lc) mutant mice lose 100% of their Purkinje cells (PCs), 90% of their granule cells, and 75 % of their inferior olivary neurons. In order to determine the primary site of Lc gene action, lurcher ↔ wild-type aggregation chimaeras were produced. The cerebella of the three chimaeras examined were intermediate or normal in size compared to + /Lc and wild-type cerebella. The PCs were reduced in number. Using the β-glucuronidase locus (Gus) as a cell marker, all of the PCs present were identified as having descended from the wild-type embryo. It appears that all of the + /Lc PCs degenerated. Hence, the Lc gene acts directly on PCs to cause their degeneration. The inferior olivary nuclei of the chimaeras seemed to have fewer neurons than wild-type but more than + /Lc animals. As revealed by β-glucuronidase histochemistry, both + /+ and + /Lc cells were present, and the ratio of genotypes was similar to the ratio seen in other regions of the brain. The evidence suggests that the death of olivary neurons in lurcher is secondary to another defect, probably the loss of PCs. β-glucuronidase is not an accurate cell marker for granule cells, and so no conclusion concerning the action of the Lc gene on granule cells could be made with these chimaeras.

The site of gene action of the Staggerer mutation of mice was investigated with Staggerer in equilibrium or formed from wild-type chimeras. Homozygous Staggerer mice show severe locomotor difficulties due to cerebellar abnormalities which include degeneration of virtually all granule cells and cytological defects in Purkinje cells. Although the locomotor deficits of the mutant were not present in the chimeras, the presence of Staggerer cells affected cerebellar structure. The size and the extent of foliation of the chimeric cerebella were intermediate between wile-type and homozygous Staggerer. A normally proportioned granule cell layer was present. Using beta-glucuronidase as an independent determinant of a cell's genotype, it was found that the genotypically Staggerer medium-to-large neurons expressed all of the light microscopic defects observable in these cells in the homozygous mutant. These defects include: (1) smaller size; (2) usually ectopic location; and (3) regional variation in the cytological appearance of the perikaryon. By contrast, all Purkinje cells which were genotypically wild-type appeared normal in size, in location and in their cytological appearance. Their density, however, was much reduced from wild-type. The effects of the Staggerer mutation on the granule, stellate and basket cells could not be directly assessed as the glucuronidase marker is not suitable for use with these cells. The Staggerer gene thus acts directly on Purkinje cells rather than via extracellular environmental changes. The findings are discussed in terms of their implications for normal cerebellar development.

In an attempt to use mouse metallothionein-I (mMT-I) regulatory sequences to direct expression of human ornithine transcarbamylase in the liver of transgenic animals, fusion genes joining either 1.6 kilobases or 185 base pairs of the mMT-I regulatory region to the human ornithine transcarbamylase protein-coding sequence were used to produce transgenic mice. In mice carrying the fusion gene with 1.6 kilobases of the mMT-I 5'-flanking sequences, transgene expression was observed in a wide range of tissues, but, unexpectedly, expression in liver was never observed. Surprisingly, in mice carrying the fusion gene regulated by only 185 base pairs of the mMT-I 5'-flanking sequences, the transgene was expressed exclusively in male germ cells during the tetraploid, pachytene stage of meiosis.

The interaction of nerve growth factor (NGF) with its receptor on cells of the PC 12 cell line was studied. All experiments were done at 0.5 °C to minimize degradation and processes requiring membrane mobility. Under these conditions, a single class of high affinity binding sites with a dissociation constant of 2.9 × 10 −9 M was observed. The number of receptors per cell was 58000. The binding was linear with the number of cells in the assay and was not displaced by proteins other than native nerve growth factor. Trypsin treatment of the cells destroyed the specific binding. The removal of divalent cations had no effect on the binding. Culturing the cells for 2 weeks in NGF prior to assay did not change the receptor number or receptor affinity and there was a similar lack of effect of the density of the culture from which the cells were taken for assay. The present findings are compared with previous studies on the dorsal root ganglia and sympathetic ganglia neurons, and the implication for the use of PC 12 as a model for the study of NGF action are discussed.

This paper examines the structure and cytoarchitecture of the cerebellum of the weaver mutant mouse with particular emphasis on regional differences along the mediolateral and anterior-posterior axes. We have uncovered several, previously undescribed features of the weaver cerebellar phenotype. Perhaps the most dramatic example of our findings is the severe disruption of the folial structure of the hemispheres of the weaver cerebellum. A dorsal overgrowth of tissue occurs in the hemispheres that forms a finger-like projection superficial to an atrophie but structurally more normal cerebellar mass underneath. While this folial abnormality is most evident in the homozygote ( wv/wv ) the antecedents of its appearance are already apparent in the heterozygote ( +/wv ). At the level of the cytoarchitectonics of the mutant brain, we find substantial variation in the positioning, numbers and density of both Purkinje and granule cells. As a whole, Purkinje plus Golgi II cell numbers are down by over 40%, but this reduction occurs almost exclusively in the medial half of the cerebellum. The hemispheric region contains a nearly normal number of cells per sagittal section (although their positions are predominantly incorrect). The granule cells also show numerical variation; they are nearly absent at the midline, but a substantial number of them survive in the lateral cerebellar cortex. In the paraflocculus, for example, granule cells can be observed in a modest internal granule cell layer as late as 38 postnatal days. These results are discussed in terms of a model of wv gene action in which we propose that the effect of the mutation is a general disruption of cellular distribution in the cerebellar cortex, affecting both Purkinje and granule cells and beginning prenatally.

Staggerer (sg) is a mutation in mice which causes severe cerebellar atrophy. Virtually all of the granule cells degenerate by the end of the first postnatal month. The Purkinje cells are also affected. They are reduced in number, ectopic in location, reduced in size and show a regional variation in their cytological appearance. The appearance of the cerebellar cortex of Staggerer in equilibrium wild-type chimeric mice has demonstrated that the reduced size, ectopia, and regional variation are always traits of cells whose nucleus is of sg/sg genotype and thus are due to factors intrinsic to the affected cell. This report is a quantitative analysis of the cerebellar cortex of two Staggerer chimeras. Sections were chosen from serially sectioned half cerebella. Using beta-glucuronidase activity as an independent marker of a cell's genotype, cells were scored as belonging to 1 of 3 cell classes: wild-type Purkinje cell, wild-type Golgi cell, and Staggerer medium-to-large neuron. The results confirm that the total number of cells in the chimera (all 3 classes) is greater than that found in a homozygous Staggerer but less than that found in a wild-type. Further, the distribution of the two genotypes strongly suggests that the decreased number of cells in Staggerer and in the chimera is due to an intrinsic defect in the Staggerer cells and not to a general (extrinsic) compromising of cerebellar development. Possible implications for normal cerebellar development are discussed.

Recent quantitative studies of lurcher chimeric mice have shown that the adult population of cerebellar Purkinje cells can properly be described as a small number of developmental clones of cells. The clones are not seen as patches of contiguous neurons; rather, the cells of any one clone distribute throughout the half-cerebellum that contains them, intermingling extensively with the Purkinje cells of other linkages. Lurcher ⇌ wild-type chimeras were analyzed using the cell autonomous Purkinje-cell-lethal mutant, lurcher ( + L ), as a cell marker. Cell counts from these chimeras revealed that the number of surviving Purkinje cells was always an integral multiple of a unit clone size. These numerical quanta are the evidence for the existence of Purkinje cell developmental clones. When two different inbred strains of mouse were compared (C3H/HeJ and C57BL/6), the resulting clonal analysis showed that the unit clone size (i.e., the number of Purkinje cells in one quantum) is an autonomous property of the lineage and hence, presumably, intrinsic to the progenitor cell that founded it. The current study uses the lurcher chimeric mouse system to examine the cell lineage relationships among the Purkinje cells of a third inbred strain of mouse, AKR/J. The data both support and extend our previous studies. Quantitative analysis reveals that the Purkinje cells of this strain also exist in clones, and the size of these clones is also strain-specific. The number of cells in a single clone (7850), however, is different from either C3H/HeJ (10,200) or C57BL/6 (9200). The fact that this value is so highly polymorphic among the inbred strains of mouse makes it likely that, rather than being a function of different alleles at a single genetic locus, clone size may well represent a multifactorial (but still cell-autonomous) property of developing Purkinje cells. Additional results from a single chimeric animal suggest strongly that clone number (i.e., the number of progenitors selected to found the population) is not strain-specific but results instead from cell:cell interactions during early central nervous system formation.

The cell surface receptor for beta-nerve growth factor was used as a probe to study the development of embryonic chick sensory ganglia. The ganglia were shown to lose their responsiveness to nerve growth factor in vitro between 14 and 16 days of embryonic age. This loss occurred by a decrease in the magnitude of the maximum biological response, not by a shifting of the response to higher concentrations. Binding assays for the beta-nerve growth factor receptor, using 125I-radiolabelled beta-nerve growth factor, were performed with cells from sensory ganglia 8, 12, 14, 16, 18, and 21 days of age. The assays revealed a twofold increase in the number of receptor sites per ganglion between 8 and 14 days and a sixfold drop between 14 and 16 days of embryonic life. Neither increase nor decrease was accompanied by a large change in the affinity of the receptor for the protein. Together with the results of the bioassay, the data show that the loss of biological responsiveness is correlated with and may be due to a loss of the cells' ability to bind beta-nerve growth factor. Correlation of the results of the binding assays with the known ontogeny of the chick embryo provides a hint at the role of nerve growth factor in normal development.

Quantitative morphological techniques have revealed several new aspects of the action of the Staggerer mutant gene. Staggerer is an autosomal recessive gene which causes ataxia and severe malformation of the cerebellar cortex in mice. The Purkinje cells of the cerebellar cortex are small, abnormal in morphology and reduced in numbers. The close synaptic and developmental relationship of Purkinje cells with the cells of the deep cerebellar nuclei (dcn) lead us to look for effects of the Staggerer mutation on the dcn neurons. The volume of the deep nuclear region is shrunken in Staggerer and there is a reduction in the volume of the white matter. These findings account for the reduced wet weights and protein concentration found by Roffler-Tarlov and Sidman. In contrast to the cells of the cortex, where 75% of the medium-to-large neurons are missing, the number of cells present in Staggerer dcn is identical to wild-type. The dcn neurons are not completely spared, however. Measurements of cross-sectional cell area revealed a 30% shrinkage of neurons in Staggerer dcn. The most likely interpretation of previous work and the current findings is that the Staggerer gene acts early in development but exerts its effects directly only on those derivatives of the ventricular zone in the roof of the fourth ventricle which are destined to become Purkinje and Golgi cells.

Recent genetic and biochemical studies indicate that lipoprotein receptors are components of the neuronal receptor for Reelin, mediating the glycoprotein's essential function in cortical development. At least eight cadherin-related neuronal receptors may also play a part in this signalling system.

Lurcher in equilibrium ichthyosis chimeric mice were constructed to determine whether the death of cerebellar granule cells in lurcher mutants is caused by intrinsic or extrinsic factors. Quantitative analysis demonstrates that more lurcher granule cells survive in the chimeras than would have in the mutants themselves. Thus the granule cell death is an indirect consequence of the lurcher gene acting on some other cell type, probably the cerebellar Purkinje cells.

In comparing strategies used to control neuron number, we find it useful to view nervous system development as occurring in three phases. The phases overlap--each is a process, not an event. The first phase is the development of a genetic nervous system. This is a nervous system of simple genetic intention, not a blueprint or pile of bricks. Its characteristics are abstract: How many neurons in this stem cell destined to produce, which cells are programmed to die, how much target does this cell need to survive. At the level of the individual, the genetic nervous system is essentially fixed, but over generations it is fluid. As this genetic intent interacts within a world of cells, a real brain appears. A new set of rules only tacitly present in the genome is expressed--the embryonic nervous system emerges. The interaction of its parts defines the shape and size of the nervous system. Neuron numbers are adjusted interactively by changes in proliferative potential and the severity of cell death. Cell fates are established in part through interactions with other cells and with hormones. Glial cell numbers are adjusted to match the neuron populations. This phase of brain development is what the embryologist sees under the microscope. The third and final phase of development begins when the brain starts to function and the animal starts to deal with its world. Small changes in neuron number may occur during this period, but these changes are generally of minor functional importance. At this point, the smaller elements of neuronal organization are refined in shape, number, and distribution. Axons are lost or rearranged; dendrites grow, branch, and retract; synapses are fine-tuned; and finally, receptor densities and transmitter titres are adjusted. Some of these interactions and numerical adjustments continue until the animal dies.

This study quantitatively examines the developmental relationship between Purkinje cell and granule cell neurons in the cerebellum. Lurcher chimeric mice were used as a model system since target size (i.e. the number of Purkinje cells) can be varied genetically and its effect on granule cell number can be examined. The validity of this model is supported by our previous studies showing that the death of all the Purkinje cells in +/Lc mice is a direct effect of Lc gene action while the loss of 90% of the granule cells is a secondary consequence of some defect extrinsic to the granule cells, most likely the Purkinje cell loss. In the present study of 3 +/Lc mice, 4 strains of wild-type mice and 4 lurcher chimeras, the number of granule cells was directly correlated with the number of Purkinje cells. In wild-type mice, there is a constant ratio of about 175 granule cells for each Purkinje cell. These findings provide suggestive evidence that 'numerical matching' occurs between the presynaptic granule cell population and its postsynaptic target, the Purkinje cell. The quantitative relationships revealed in the chimeric animals compared with the non-chimeric values lead us to propose a model in which the number of granule cells is a function of at least two factors: the initial number of Purkinje cells and the length of time each Purkinje cell is present during a 'critical period' of granule cell development.

Publisher Summary This chapter explores the roles that cell lineage plays in the development of the mammalian central nervous system (CNS). The discussion focuses on mammals, which means, of necessity, a focus on the mouse as the experimental animal and on genetic mosaics as the analytical tool. The chapter discusses the concepts and definitions of cell lineage and provides an overview of what has been gleaned thus far from the combination of concepts and methodology. It is axiomatic that cell lineage relationships exist during the development of any multicellular organism. All creatures are essentially a single clone of cells by virtue of the fact that all of the cells of an organism are descended from a single founder cell: the fertilized egg. In the mammal, this can be extended since all cells in the adult are (poly) clonal descendants of the few cells that form the inner cell mass of the preimplantation embryo and, later, from the cells of the embryonic ectoderm of the early postimplantation embryo. The chapter describes how to study cell lineage and mentions cell markers and strategies for their use.

The nerve growth factors (NGF's) isolated from cobra venom (Naja naja) and mouse submaxillary gland are closely related proteins. They are structurally similar in that about 60% of their amino acid residues are identical (Hogue-Angeletti, R. A., Frazier, W. A., Jacobs, J. W., Niall, H.D., and Bradshaw, R. A. (1976), Biochemistry, preceding paper in this issue). They are functionally similar in that they both elicit maximum neurite outgrowth from chick embryonic dorsal root ganglia at the same protein concentration. However, the extent of the response is not as great with Naja naja NGF. The cobra NGF has an affinity close to that of mouse NGF for a major proportion of the specific NGF receptors on cells from dissociated embryonic dorsal root ganglia. Despite these similarities there are differences which can be detected between the two proteins. High concentrations of Naja naja NGF will not displace approximately 20% of the binding of mouse NGF to specific NGF receptors. Moreover, Naja naja NGF shows limited cross-reactivity with antiserum to mouse NGF in a competition radioimmunoassay, consistent with the extent of its amino acid sequence homology with mouse NGF. Naja naja NGF does not interact with the alpha- and gamma-subunits of 7S NGF to form a high molecular weight complex. In this behavior it resembles a modified form of mouse NGF which, like Naja naja NGF, lacks COOH-terminal arginine residues.

This report continues our studies of the cell lineage relationships among the cells of the cerebellar Purkinje cell population. It examines the question of whether there are cell autonomous factors that regulate cell number during mammalian CNS development. Experimental aggregation chimeras were made by the joining of two embryos, one wild-type, one lurcher in genotype; both embryos were of C57BL 6 genetic background. Since all Purkinje cells of + Lc genotype will degenerate, only wild-type Purkinje cells remain in the cerebellar cortex of the adult chimeras. The number of remaining cells does not vary uniformly from zero (the lurcher value) to wild-type (92,000 for C57BL 6 ). Rather the cells occur in numerical quanta that represent developmental clones of cells. In an earlier work, the Purkinje cell population of the C3H HeJ inbred strain was shown to consist of eight such clones in each cerebellar half. Each C3H HeJ clone contains 10,200 Purkinje cells. Evidence is presented in the present study that the Purkinje cells of the C57BL 6 strain, exist in 10 clones, of 9200 cells per half cerebellum. The findings suggest (1) that a clonal organization exists in the Purkinje cell population of at least two inbred strains of mice, (2) that differences in adult neuronal number can be due to either the number of clones present or the size of each individual clone (i.e., the number of cells per clone), and (3) that the number of cells in a clone appears to be an autonomous property of the lineage itself and hence, presumably, of the progenitor cell that founded the clone.

Mouse chimeras were made by aggregating two embryos at the 8-cell stage of development. These experimental mosaic animals are useful in assessing whether the effect of a mutant gene in a given cell type is direct (intrinsic) or indirect (extrinsic). The results reported are an analysis of the involvement of the staggerer gene in the phenotype of granule cell death observed in staggerer mutant mice. The ichthyosis mutation has been used as an independent cell marker. This mutation produces no known neurological defects but does cause a characteristic clumping of heterochromatin, especially in small cells. Analysis of two staggerer in equilibrium ichthyosis chimeras leads to the conclusion that staggerer granule cells, that would have died in the mutant, are rescued in the mosaic cerebella. The death of granule cells in the homozygous staggerer mutant is thus an indirect, epigenetic consequence of direct gene action in other cells. The implications and limitations of this conclusion are discussed.

Staggerer mice (sg/sg) have a severe ataxia correlated with cerebellar Purkinje cell anomalies and granule cell death. Previous studies of adult staggerer ⇹ wild-type chimeric mice have revealed that the mutant Purkinje cell defects visible in the light microscope (small size, ectopia and reduced number) are intrinsic properties of sg/sg Purkinje cells, while the granule cell death observed in the mutant is not an intrinsic property of sg/sg granule cells. In this report we continue the study of granule cell death and examine the phenotype, observed in staggerer mutants, of the developmental persistence of the external granular layer (EGL). Four staggerer ⇹ wild-type mouse chimeras were examined at 16 or 17 days of postnatal age. Most showed intermediate amounts of granule cell pycnosis and all showed intermediate expression of EGL persistence. There was little correlation observed between the amount of granule cell pycnosis and either the genotype of the immediately underlying Purkinje cells, or the proportion of staggerer cells in the chimera as a whole (determined by the genotype ratio of other brain regions and by coat melanocytes). While the presence or absence of an EGL did not correlate with the genotype of the immediately adjacent Purkinje cells, there was good agreement between the extent of persistence of the EGL and the overall contribution of staggerer cells to the chimera. The results suggest that the intermediate numbers of granule cells observed in adult staggerer chimeras are the result of both reduced granule cell genesis and increased pruning by cell death. The findings are further discussed in terms of two possible models of staggerer gene action.

Iodination of the β nerve growth factor protein up to 4.1 iodines per mole of nerve growth factor was achieved with no loss of biological activity. At this level of incorporation no native or monoiodo nerve growth factor remained, the major species being the tri- and tetraiodo derivatives. An 125 I-labeled β nerve growth factor of high specific activity containing 0.5 iodine per mole of β nerve growth factor was used to determine the specific binding of nerve growth factor to dorsal root ganglion cells of 8-day-old embryonic chicks. The specific binding of 125 I-labeled nerve growth factor reached saturation at 30-50 ng/ml and half-saturation at 7-8 ng/ml (0.26 nM). The number of receptors per responsive medio-dorsal cell was calculated to be about 2 × 10 4 . The pattern of displacement of bound 125 I-labeled β nerve growth factor by native β nerve growth factor showed that the two proteins had identical affinities for the receptor. The specificity of the binding for β nerve growth factor was demonstrated by the fact that only native β nerve growth factor displaced the bound 125 I-labeled form. Partially inactivated derivatives of β nerve growth factor retained the same fraction of their specific-binding capacity as of their biological activity. The specificity of the binding for cell type was shown by the lack of any specific component of 125 I-labeled β nerve growth factor binding to liver or brain cells. The rate constant for association of β nerve growth factor with its receptor, k 1 , was 1.0 × 10 7 mol -1 sec -1 and the rate constant for dissociation, k -1 , 1.2 × 10 -8 sec -1 .

Previous analysis of lurcher in equilibrium wild type aggregation chimeras revealed that the degeneration of cerebellar Purkinje cells (PCs) in lurcher mutants is due to a defect intrinsic to the PCs themselves. Thus, all of the PCs remaining in lurcher chimeric mice are descended from only the wild type embryo. In this study, we have determined the number of PCs in four lurcher chimeras and three wild type mice. The low number of wild type PCs (10,200) in half of the cerebellum of one chimera (chi 11) suggested that these cells might be descended from a single progenitor. This idea is strongly supported by the quantitative analysis of the PCs in the other animals. These numbers are integral multiples of the number of PCs in chi 11. We believe that each stepwise increase in the number of PCs in the chimeras is due to the addition of a single wild type cell to the progenitor pool. The existence of integral multiples implies that no other cells can contribute to the PC population after the progenitors become committed to forming PCs. We cannot know, however, whether the PC progenitors also give rise to other cell populations. The values of the integrals in wild type mice indicate that the entire PC population descends from a small number of progenitors (8 in C3H/HeJ mice). We calculate that these progenitors are committed during the neural plate to neural fold stage of development. Thus, the fate of the progenitors of the cerebellar PCs is restricted very early in neural development.

In this report we use postnatal 3H-thymidine injections to test whether granule cells that are generated early in postnatal cerebellar development and whose axons have access to their Purkinje cell target beginning in the first postnatal week have an advantage over granule cells generated 9 days later in the competition for target-related stabilization. In the wild-type mouse, 3-5% of the adult granule cell population is labeled by injection of 3H-thymidine at either postnatal day 4 (P4) or P13. In the lurcher mutant, however, over 40% of the surviving granule cells are labeled by P4 injection while less than 1% are labeled after a P13 injection. Together, these results suggest that time of target contact is a critical factor in the competition for neuronal survival. The results from the lurcher chimeras, however, reveal that the situation is likely to be more complicated. In all chimeras examined, with target sizes ranging from 3 to 108% of wild type, equivalent numbers of granule cells were labeled at P4 and P13. These data lead to the contradictory conclusion that, in this experimental situation, early generated granule cells do not have a competitive advantage over later-generated granule cells. The results are discussed in terms of various models of target stabilization. We propose that, of the various hypotheses, our results are best explained by postulating two distinct mechanisms for developmental cell death. Supporting evidence for this hypothesis from other neuronal systems is also briefly reviewed.

Staggerer (sg) is a neurological mutant mouse in which the cerebellar granule cells degenerate after migration to the internal granule cell layer. In addition, the Purkinje cells are abnormal, being ectopic, smaller in size and without tertiary branchlet spines. In this study we report two new observations on this mutant: (1) the effects of the mutation show a regional variation in severity along the mediolateral axis. This variation is seen in the cross-sectional size of the tissue, the extent of cortical folding, as well as the density and cytological appearance of the medium-to-large cortical neurons (MLNs); (2) cell counts were done of 30-day-old mutants and of wild-type controls. The counts revealed that three-quarters of the MLNs of the cerebellar cortex are missing in staggerer. These findings cannot exclude the possibility that Golgi as well as Purkinje cells are absent since the two cannot be distinguished in staggerer. Depending on the number of Golgi cells present, between 60% and 90% of the wild-type number of Purkinje cells is missing in staggerer. The results are discussed in terms of their implications for other studies and for locating the site of staggerer gene action.

Cell death is a common yet puzzling feature of the development of many populations of neurons in the CNS. In the invertebrate phyla, such death is often preprogrammed; by contrast, in vertebrates, the best studied examples of histogenetic cell death are influenced by interactions among the neurons and their target. One attempt to explain this seemingly wasteful scheme of development has led to the hypothesis that this target-related cell death allows 2 populations of cells, which develop in isolation, to come into numerical and functional balance and hence to provide an epigenetic “buffer” mechanism to accommodate developmental variations. In the current study we have examined the extent to which the cell death observed in the cerebellar granule cell population serves to numerically match these neurons with their primary postsynaptic target, the Purkinje cell. Staggerer chimeras were made by aggregating 8-cell staggerer embryos with embryos of wild-type genotype. The cerebella of the resulting animals developed with widely varying numbers of normal (wild-type) Purkinje cell targets. Although staggerer Purkinje cells were present in the chimeric brains, these cells are intrinsically deficient in their normal developmental program (in the mutant, because of this deficiency, 100% of the granule cells die). Both granule cells and Purkinje cells were counted in chimeras and several wild-type mice. The results reveal that the number of granule cells present in these brains has a linear relationship with the number of Purkinje cells, and that the line connecting the points intersects the Y-axis close to the origin. These observations suggest that numerical matching is an important function of target-related cell death in the granule cell population.(ABSTRACT TRUNCATED AT 250 WORDS)

Previous studies of wild-type mice or mutant-wild-type mouse chimeras using the neurological mutant staggerer have supported a numerical matching hypothesis for target-related cell death. However, analyses of chimeras of a second neurological mutant, lurcher, have suggested that there may be significant flexibility in the relationship between the numbers of pre- and postsynaptic neurons. Whereas in staggerer chimeras there is a strict proportionality between the number of cerebellar granule cells and their postsynaptic target, the Purkinje cells, in lurcher chimeras, Wetts and Herrup (1983) report a relative increase in granule cell survival. We have reexamined the numerical matching between Purkinje and granule cells in an additional 5 lurcher----wild- type and 4 wild-type----wild-type chimerase. Our findings confirm and extend the results of the previous study to show that there is a close correlation between the number of granule and Purkinje cells in +/Lc chimeras, but for any given number of Purkinje cells in the +/Lc chimeras, more granule cells survive than in staggerer chimeras or inbred mouse strains. Whereas the ratio of granule to Purkinje cells in staggerer chimeras or inbred mouse strains is constant across all target sizes, in +/Lc chimeras the ratio of granule cells to Purkinje cells increases as the number of target neurons decreases. It seems likely that the increased granule cell survival is somehow related to the delayed degeneration of the +/Lc fraction of target cells in the +/Lc chimeras. Among the possible explanations for the observed results, we favor the hypothesis that a trophic factor is produced in +/Lc chimeras in response to the deafferentation of Purkinje cells that is capable of rescuing granule cells from target-related cell death. Our preference is based, in part, on observations of the state of the dendritic tree of the wild-type Purkinje cells that survive in +/Lc chimeras (Caddy et al., 1986).

Background Our previous studies of Alzheimer’s disease (AD) suggested that glutamine broadly improves cellular readiness to respond to stress and acts as a neuroprotectant both in vitro and in AD mouse models. We now expand our studies to a second neurodegenerative disease, ataxia-telangiectasia (A-T). Unlike AD, where clinically significant cognitive decline does not typically occur before age 65, A-T symptoms appear in early childhood and are caused exclusively by mutations in the ATM (A-T mutated) gene. Results Genetically ATM-deficient mice and wild type littermates were maintained with or without 4 % glutamine in their drinking water for several weeks. In ATM mutants, glutamine supplementation restored serum glutamine and glucose levels and reduced body weight loss. Lost neurophysiological function assessed through the magnitude of hippocampal long term potentiation was significantly restored. Glutamine supplemented mice also showed reduced thymus pathology and, remarkably, a full one-third extension of lifespan. In vitro assays revealed that ATM-deficient cells are more sensitive to glutamine deprivation, while supra-molar glutamine (8 mM) partially rescued the reduction of BDNF expression and HDAC4 nuclear translocation of genetically mutant Atm−/− neurons. Analysis of microarray data suggested that glutamine metabolism is significantly altered in human A-T brains as well. Conclusion Glutamine is a powerful part of an organism’s internal environment. Changes in its concentrations can have a huge impact on the function of all organ systems, especially the brain. Glutamine supplementation thus bears consideration as a therapeutic strategy for the treatment of human A-T and perhaps other neurodegenerative diseases.