A survey of MabQ113 immunoreactivity in the adult rat brain: differential staining of the lateral and medial habenular nuclei

Structural and Molecular Compartmentation in the Cerebellum

Most descriptions treat the cerebellum as a uniform structure, and the possibility of important regional heterogeneities in either chemistry or physiology is rarely considered. However, it is now clear that such an assumption is inappropriate. Instead, there is substantial evidence that the cerebellum is composed of hundreds of distinct modules, each with a precise pattern of inputs and outputs, and expressing a range of molecular signatures. By screening a monoclonal antibody library against cerebellar polypeptides we have identified antigens – zebrins – that reveal some of the cerebellum’s covert heterogeneity. This article reviews some of these findings, relates them to the patterns of afferent connectivity, and considers some possible mechanisms through which the modular organization may arise.

Genomic sequences of aldolase C (Zebrin II) direct lacZ expression exclusively in non-neuronal cells of transgenic mice

Aldolase C is regarded as the brain-specific form of fructose-1, 6-bisphosphate aldolase whereas aldolase A is regarded as muscle-specific. In situ hybridization of mouse central nervous system using isozyme-specific probes revealed that aldolase A and C are expressed in complementary cell types. With the exception of cerebellar Purkinje cells, aldolase A mRNA is found in neurons; aldolase C message is detected in astrocytes, some cells of the pia mater, and Purkinje cells. We isolated aldolase C genomic clones that span the entire protein coding region from 1.5 kb 5' to the transcription start site to 0.5 kb 3' to the end of the last exon. The bacterial gene, lacZ, was inserted in two different locations and the constructs tested in transgenic mice. When the protein coding sequences were replaced with lacZ, three of five transgenic lines expressed beta-galactosidase only in cells of the pia mater; one line also expressed in astrocyte-like cells. When lacZ was inserted into the final exon (and all structural gene sequences were retained) transgene expression was observed in astrocytes in all regions of the central nervous system as well as in pial cells. Thus, with the exception of Purkinje cell expression, the behavior of the full-length transgene mimics the endogenous aldolase C gene. The results with the shorter transgene suggest that additional enhancer elements exist within the intragenic sequences. The absence of Purkinje cell staining suggests that the cis elements required for this expression must be located outside of the sequences used in this study.

Novel developmental boundary in the cerebellum revealed by zebrin expression in the lurcher (Lc/+) mutant mouse

The cerebellar cortex contains at least two classes of Purkinje cells, which are organized into alternating arrays of parasagittal bands. The clearest demonstration of this compartmentation is the pattern of expression of a family of polypeptide antigens, the zebrins, which are expressed selectively by Purkinje cell subsets. Furthermore, anterograde tracing experiments show that the zebrin compartments are closely correlated with both afferent and efferent projection maps. The further subdivision of long parasagittal bands into smaller modules may occur through several different mechanisms, including the intrinsic cerebellar lobulation and the selective distribution of afferent terminal fields. However, while the longitudinal subdivisions are straightforwardly shown, the mediolateral boundaries are more subtle. In this report we describe a novel mediolateral and anteroposterior compartmentation boundary in mice, running across lobule VIII, that is revealed by the consequences of the lurcher (Lc/+) allele for zebrin expression. In normal mice zebrin compartmentation develops in several discrete stages: until postnatal day 5 (PD5) there is no zebrin expression; from PD5-PD7 zebrin is found only in the posterior lobe vermis, with immunoreactive Purkinje cells in lobules X, IX, and VIII but not elsewhere; from PD7-PD12 most Purkinje cells in the vermis become zebrin+; from PD12-PD15 immunoreactivity also appears in the hemispheres so that almost all Purkinje cells now are zebrin+; and finally, from PD15-PD25 zebrin is gradually suppressed in those Purkinje cells that are zebrin- in the adult until the mature pattern of parasagittal compartments is revealed. In the Lc/+ mutant the normal developmental progression is interrupted at around PD7. As a result, the pattern of zebrin expression becomes frozen at that stage when immunoreactive Purkinje cells are confined exclusively to the posterior lobe vermis. A reproducible boundary between expressing and nonexpressing zones runs mediolaterally across the dorsal surface of lobule VIII. Apart from zebrin expression itself, there are no obvious structural correlates of this transition. This mediolateral boundary identifies a developmental unit in the posterior lobe vermis of the cerebellum, and provides further evidence that the cerebellum is a highly heterogeneous structure.

Zebrin II: a polypeptide antigen expressed selectively by Purkinje cells reveals compartments in rat and fish cerebellum

Monoclonal antibody mab-zebrin II was generated against a crude homogenate of cerebellum and electrosensory lateral line lobe from the weakly electric fish Apteronotus leptorhynchus. On Western blots of fish cerebellar proteins, mab-zebrin II recognizes a single polypeptide antigen of apparent molecular weight 36 kD. Immunocytochemistry of apteronotid brains reveals that zebrin II immunoreactivity is confined exclusively to Purkinje cells in the corpus cerebelli, lateral valvula cerebelli, and the eminentia granularis anterior. Other Purkinje cells, in the medial valvula cerebelli and eminentia granularis posterior, are not zebrin II immunoreactive. Immunoreactive Purkinje cells are stained completely, including dendrites, axons, and somata. The antigen seems to be absent only from the nucleus. A similar distribution is seen in catfish, goldfish, and a mormyrid fish. Zebrin II immunoreactivity is also found in the rat cerebellum. Western blotting of rat cerebellar proteins reveals a single immunoreactive polypeptide, with apparent molecular weight 36 kD, as in the fish. Also as in the fish, staining in the adult rat cerebellum is confined to a subset of Purkinje cells. Peroxidase reaction product is deposited throughout the immunoreactive Purkinje cells with the exception of the nucleus. No other cells in the cerebellum express zebrin II. At higher antibody concentrations, a weak glial cross reactivity is seen in most other brain regions: we believe that this is probably nonspecific. Zebrin II+ Purkinje cells are clustered together to form roughly parasagittal bands interposed by similar nonimmunoreactive clusters. In all there are 7 zebrin II+ and 7 zebrin II- compartments in each hemicerebellum. One immunoreactive band is adjacent to the midline; two others are disposed laterally to each side in the vermis; there is a paravermal band; and finally three more bands are identified in each hemisphere. Both in number and position, these compartments correspond precisely to the bands revealed by using another antibody, mabQ113 (anti-zebrin I). In both fish and rat the compartmentation revealed by zebrin II immunocytochemistry is related to the organization of cerebellar afferent and efferent projections and may provide clues as to the fundamental architecture of the vertebrate cerebellum.

Organization and postnatal development of zebrin II antigenic compartmentation in the cerebellar vermis of the grey opossum, Monodelphis domestica

The mammalian cerebellar cortex consists of a number of parasagittal Purkinje cell compartments that can be demonstrated cytochemically. The afferent inputs to the cerebellum are also compartmentalized, and a complex but reproducible relationship exists between the afferents and the intrinsic maps. Developmental studies in the rat have shown that many of the main features of compartmentation are already established at birth, and are therefore not easily manipulated experimentally. The compartmentation antigen zebrin II is expressed selectively by Purkinje cell subsets in a range of species, including fish and primates. In this study, zebrin II immunoreactivity has been studied in the grey opossum, Monodelphis domestica, in order to develop a marsupial model of compartment formation in which the early developmental events are more readily accessible. A monoclonal antibody to zebrin II from the weakly electric fish Apteronotus recognizes a 36 kD polypeptide in homogenates of Monodelphis cerebellum that appears to be identical to the antigen in the rat. Immunocytochemistry reveals that zebrin II in adult Monodelphis is confined exclusively to the cerebellum, where it is expressed by a subset of Purkinje cells. All regions of the cell, except the nucleus, are stained. The zebrin II+ Purkinje cells are arranged in a set of parasagittal compartments interposed by similar zebrin II- compartments. In each hemicerebellum there is one zebrin II+ band abutting the midline (P1+), and two others laterally in the vermis (P2+, P3+). A fourth zebrin II+ compartment straddles the paravermian region (P4+). Three other compartments have been identified in the hemisphere (P5+, P6+, P7+). This arrangement is very similar to that found in the rat. During postnatal development, zebrin II is first expressed between P14 and P21 in Purkinje cells of the posterior lobe vermis, and spreads throughout the cerebellar cortex by P28. As in rat, there is a stage at which all Purkinje cells are zebrin II+, including those destined to be zebrin II- in the adult. The mature pattern of expression emerges after P35 as immunoreactivity gradually disappears from the cells destined to become zebrin II-. The adult appearance is attained only after P56. The developmental timetable is therefore similar to that in rat, but is rather more protracted. Monodelphis should prove to be a valuable experimental model in which to study the early events leading to the formation of cerebellar compartments.

Development of parasagittal zonation in the rat cerebellar cortex: MabQ113 antigenic bands are created postnatally by the suppression of antigen expression in a subset of Purkinje cells

Monoclonal antibody mabQ113 recognizes a polypeptide antigen that, in the adult cerebellum, is confined to a subset of Purkinje cells that are clustered together to form parasagittal bands interposed by similar nonimmunoreactive bands. The Purkinje cell compartments are congruent with bands of climbing fibers projecting from subregions of the inferior olivary complex (IOC). The array of mabQ113 parasagittal bands appears late in the development of the cortex. Weak mabQ113 immunoreactivity is first seen at postnatal day 6 (P6) in the Purkinje cells of the posterior lobe of the vermis. From the earliest stages there are signs of differential expression of the mabQ113 antigen in clusters of Purkinje cells: four mabQ113+ clusters are clearly present in the posterior lobe of the vermis at P6-P7. Their relation to the adult band display remains uncertain. During the next few days immunoreactivity spreads rostrally throughout the rest of the vermis and laterally to include the Purkinje cells in the hemispheres, until by P12 all the Purkinje cells in the cerebellum are mabQ113+. Nevertheless, signs of the adult band display are seen already in the vermis where the cells destined to become the vermal mabQ113+ bands (P1+, P2+ and P3+) stain more intensely than their neighbours. Following the stage of global mab113 epitope expression, bands are created by the selective suppression of immunoreactivity by Purkinje cells in the P- regions. By P15 the mabQ113+ and mabQ113- bands are clearly differentiated in the vermis and selective staining has begun to appear in the hemispheres also. The band pattern matures gradually during the third and fourth postnatal weeks until the adult appearance is attained by P30. The cerebellar afferent projections were lesioned to explore the interplay of cerebellar input and mabQ113 expression. The olivocerebellar projection was lesioned bilaterally by using 3-acetylpyridine in the adult and unilaterally in the newborn by electrolytic lesion and unilateral inferior cerebellar pedunculectomy. Mossy fibers from the dorsal and ventral spinocerebellar tracts were lesioned surgically both in adults and in newborn and trigeminal projections to the cerebellum were removed in the newborn by unilateral ablation of the spinal trigeminal nucleus. The consequences of total blockage of vibrissal and hindlimb inputs were also explored in both adults and neonates. None of these treatments led to a modification in the pattern of mabQ113 epitope expression.(ABSTRACT TRUNCATED AT 400 WORDS)

Expression of monoclonal antibody Q113 immunoreactivity in the rat cerebral cortex: unique differential sublayering of layer I: staining of radial glia

Monoclonal antibody mabQ113 recognizes a 120-kilodalton polypeptide which, in the cerebellar cortex, is confined exclusively to a subset of Purkinje cells which are organized in parasagittal bands (Hawkes et al.: Brain Research 333:359-365, 1985). In all other areas of the adult rat brain examined the localization of the mabQ113 epitope was marked by regional neuronal and glial co-expression (Plioplys and Hawkes: Brain Research 375:1-12, 1986). Similar neuronal-glial co-expression was characteristic of the adult rat cerebral cortex. Intriguingly, mabQ113 revealed a unique differential sublamination of layer I. In the neocortex, layer I was split into two sublayers, with the more superficial sublayer weakly stained and the deeper sublayer stained more intensely, whereas in the pyriform cortex, layer I was split into three. These sublaminations do not correspond to previously described subdivisions of layer I. In the developing cortex, the mabQ113 epitope is found in radial glial fibers. Stained radial fibers are first seen beginning at E17, reach a maximum at P4 and finally disappear between P12 and P14. The laminar distribution of mabQ113-immunoreactivity emerges earlier in the pyriform cortex than the neocortex: the sublamination of layer I is seen at P4 in the pyriform cortex but not until P8 in the neocortex. The significance of these observations is discussed.

Zonation in the rat cerebellar cortex: patches of high acetylcholinesterase activity in the granular layer are congruent with Purkinje cell compartments

The rat cerebellar cortex is built from parasagittally arranged modules with topographically ordered afferent and efferent projections. The intrinsic organization of the cerebellum is revealed by immunocytochemical staining with monoclonal antibody, mabQ113. In the cerebellum, mabQ113 recognizes a polypeptide epitope that is restricted to a subset of Purkinje cells. Antigenic Purkinje cells are clustered to form a complex pattern of parasagittal compartments. Several biochemical markers reveal a superficially similar organization of the cortex, and so it is important to determine how many independent maps are present. This report compares the mabQ113 antigen display to the patchy distribution of acetylcholinesterase (AChE). In the granular layer and the white matter of the adult cerebellar cortex there is a patchy AChE staining that includes both the hemispheres and the vermis. The staining is often not sharply resolved cytologically, but seems to be associated primarily with the synaptic glomeruli. The boundaries of these granular layer patches in the vermis correspond to the mabQ113+/mabQ113- boundaries of the overlying Purkinje cell compartments. Thus, AChE and mabQ113 antigen share a common compartmentation both in the vermis, and in the hemispheres. Both mabQ113 and AChE distributions develop postnatally in the cerebellar cortex. At birth (PO) there is neither AChE activity nor mabQ113 immunoreactivity. Both staining patterns emerge during the second postnatal week. In the vermis at P10, there is AChE activity in the granular layer and white matter, and the distribution is already patchy despite the absence of synaptic glomeruli. At the same age the mabQ113 immunoreactivity is found in all Purkinje cells rather than a subset, and the band pattern has yet to mature. There is also transient AChE staining of Purkinje cell somata and dendrites. The AChE patches clarify between P10 and P20 along with the appearance of the synaptic glomeruli and the development of differential mabQ113 staining, but there is no reason to believe that the two are causally linked. In contrast to the cerebellar cortex, AChE staining in the cerebellar nuclei matures very early and at P0 the activity is already high. Zones of high and low AChE activity are seen in all the cerebellar nuclei and may be related to the distribution of the terminal fields of the different Purkinje cell populations.(ABSTRACT TRUNCATED AT 400 WORDS)

Parasagittal organization of the rat cerebellar cortex: direct correlation between antigenic Purkinje cell bands revealed by mabQ113 and the organization of the olivocerebellar projection

The Purkinje cells of the cerebellar cortex and the cortical afferent and efferent projections are organized into parallel parasagittal zones. The parasagittal organization is clearly revealed by immunocytochemistry with a monoclonal antibody, mabQ113. The mabQ113 antigen is confined to a subset of Purkinje cells that are clustered together to form an elaborate, highly reproducible pattern of bands and patches, interspersed with similar mabQ113- regions. The mabQ113+ territories have been classified into seven parasagittal bands (P1+-P7+) in each hemicerebellum. The degree of correspondence between the compartments revealed by the anterograde labeling of the olivocerebellar projection and by mabQ113 immunocytochemistry has been explored in the adult rat. Horseradish peroxide-wheat germ agglutinin conjugate was injected as an anterograde tracer into the inferior olivary complex. When the injection site did not encompass all the olive, an incomplete, patchy labeling of the molecular layer was seen in the cerebellar cortex. Labeled zones of the molecular layer were interrupted by unlabeled regions to give a pattern of parasagittal cortical bands. The positions of these bands were compared with the distribution of the mabQ113+ antigenic bands as seen on the two adjacent sections. Labeled climbing fibers were found to terminate on both mabQ113+ and mabQ113- Purkinje cell zones. The mabQ113+/mabQ113- boundaries and the bands of climbing fibers seen by using the anterograde tracer typically coincide. The one consistent exception is the midline band of mabQ113+ Purkinje cells, P1+. The normal olivocerebellar projection is exclusively contralateral and the climbing fiber projection to the paramedian vermis splits P1+ down the middle, implying that it consists of two adjacent mabQ113+ bands not separated by mabQ113-territory. It is likely that the climbing fiber projection to the cerebellar cortex and the distribution of the two Purkinje cell phenotypes share a common compartmental organization.

The development of differential mabQ113-immunoreactivity in the rat habenular complex

Monoclonal antibody mabQ113 selectively labels a subset of Purkinje cells which are arranged in parasagittal bands throughout the vermis and hemispheres of the rat cerebellar cortex. No other cerebellar cell types are immunoreactive. By contrast, in the remainder of the brain the mabQ113 epitope is located primarily in glial cells. In general, the glial immunoreactivity is not differentially distributed. An exception is that mabQ113 densely and uniformly stains the lateral habenula (LHb) but gives no labelling of the medial habenula (MHb). During cerebellar development, the mabQ113 epitope is expressed in three stages. Before postnatal day 7 (P7) all Purkinje cells are negative. Secondly, all Purkinje cells become mabQ113+ between P7 and P12. The parasagittal bands are created between P12 and P30 by selective suppression of epitope expression. To explore whether epitope suppression is also responsible for differential staining patterns in other brain regions the ontogenic development of mabQ113 immunoreactivity has been mapped in the habenular complex. Neither the MHb nor the LHb express the mabQ113 epitope prenatally. P1 is the first age at which the LHb is stained. During the next few days the intensity of staining within the LHb steadily increases until the adult pattern is attained at P6. At no time is there expression of the mabQ113 antigen in the MHb. This also confirms that the two classes of habenular astrocytes, mabQ113-/GFAP+ and mabQ113+/GFAP+, are intrinsically different throughout postnatal life.