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

Grafts of dissociated cerebellar cells containing Purkinje cell precursors organize into zebrin I defined compartments

A prominent feature of the mammalian cerebellum is its organization into parasagittal compartments. One marker of such compartments is the zebrin I molecule that is expressed by bands of Purkinje cells (PC). In order to understand better the basis for the development of this organization, we have transplanted dissociated rat cerebellar anlage, taken during the period of proliferation of PC precursors, into kainic acid lesioned adult rat cerebellum. As previously observed, the resultant grafts exhibited trilaminar structures reminiscent of the normal cerebellum. In every case, the PC in the resultant grafts were organized into zebrin I+ and - compartments. In one case, most of the grafted PC were integrated into a region of PC deficient host molecular layer that was induced by pretreatment with kainic acid. Clear bands defined by zebrin I reactivity were seen where groups of the grafted PC had entered the host molecular layer. These bands did not correlate in distribution or size with host bands. Hypotheses compatible with these findings that involve specific and non-specific aggregation of PC are discussed.

Expression of compartmentation antigen zebrin I in cerebellar transplants

The mammalian cerebellum is divided into multiple parasagittal compartments as defined by the organization of afferent and efferent projections and by the pattern of expression of several biochemical markers. One such marker is the antigen zebrin I, a 120 kD polypeptide of unknown function that is expressed differentially by a subset of Purkinje cells. Zebrin I+ Purkinje cells are grouped into an array of 14 parasagittal bands interposed by zebrin I- compartments. This Purkinje cell compartmentation corresponds to compartments in the olivocerebellar projection. The afferent axon compartments are present prior to the expression of the mature zebrin I phenotype, thus raising the possibility that differential afferent input regulates the zebrin I phenotype of the target of that input. Lesion studies in the neonate preclude a role for afferent inputs in the regulation of zebrin I expression postnatally, but a prenatal role in commitment still remains open. To explore this possibility, cerebellar anlagen were dissected from embryos at embryonic days 12-15, that is, prior to any contact with afferents, and transplanted ectopically into adult hosts. In the first series of experiments, the grafts were placed into the anterior chamber of the eye, and in the second series, into cavities prepared in the neocortex. Grafts were allowed to mature and then were immunoperoxidase or immunofluorescence stained for zebrin I immunoreactivity. Zebrin I was expressed by grafted Purkinje cells in cortico and in oculo. Double-labelling experiments confirmed that both the zebrin I+ and the zebrin I- phenotypes were present. The zebrin I immunoreactivity revealed that the zebrin I+ Purkinje cells resemble those in situ with an extensive dendritic arborization that extends through the molecular layer perpendicular to the long axes of the folia. In conclusion, the present data suggest that afferent input does not play a role in the determination of the zebrin I phenotype of Purkinje cells.

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.

The compartmentalization of the monkey and rat cerebellar cortex: zebrin I and cytochrome oxidase

The cerebellar cortex of mammals is composed of parasagittal zones that encompass the afferent inputs, the efferent corticonuclear and corticovestibular projections, and a number of intrinsic molecular markers. One such marker is the polypeptide antigen zebrin I that is recognized by monoclonal antibody (mab) Q113. In rodents, zebrin I immunocytochemistry reveals an array of parasagittal Purkinje cell compartments. In the present study, zebrin I has been used to reveal the molecular heterogeneity of the cerebellar cortex in the squirrel monkey (Saimiri sciureus). As in rodents, zebrin I is Purkinje cell specific in the primate cerebellum and not all Purkinje cells are immunoreactive. Immunocytochemistry on frontal or horizontal sections reveals a system of bands of zebrin I+ cells extending through the vermis of both anterior and posterior lobes. A midline (P1+) band and two more lateral bands (P2+ and P3+) are found in all lobules. The situation in the paravermis and hemispheres is similar, with alternating zebrin I+ and zebrin I- compartments, but the complex lobulation obscures the precise band pattern: it seems probable that 4 additional bands are present in the hemispheres, as in rodents. Comparison of rat and monkey cerebellums suggests that the cortex has expanded in primates by the growth of the same individual bands found in rats rather than by the addition of supplementary compartments. The zebrin I compartmentalization revealed by using mab Q113 is reproducible from individual and thus provides a stable frame of reference that has been used to compare the different chemoarchitectonic patterns found in the cerebellar cortex.(ABSTRACT TRUNCATED AT 250 WORDS)

Parasagittal organization of the rat cerebellar cortex: direct comparison of Purkinje cell compartments and the organization of the spinocerebellar projection

Retrograde and anterograde transport of tracers, electrophysiological recording, somatotopic mapping, and histochemical and immunological techniques have all revealed a parasagittal parcellation of the cerebellar cortex, including its efferent and many of its afferent connections. In order to establish whether the different compartments share a common organizational plan, a systematic comparative analysis of the patterns of parasagittal zonation in the cerebellar cortex of the rat has been undertaken, by using the parasagittal compartmentation of zebrin I+ and zebrin I- Purkinje cells as revealed by monoclonal antibody Q113 as a reference frame. The distribution of mossy fiber terminals originating from the lower thoracic-higher lumbar spinal cord was compared to the distribution of zebrin I bands. Three-dimensional reconstructions from alternate frontal sections processed either for the anterograde transport of tracer or for zebrin I immunoreactivity reveal that the limits of the spinocerebellar terminal fields in the granular layer correlate well with the boundaries of some, but not all, zebrin I compartments in the molecular layer above. This leads to a subdivision of the zebrin I compartments into spinal receiving and spinal nonreceiving portions. In lobules II and VIII, the spinocerebellar terminal fields assume different positions relative to the zebrin I compartments in the ventral compared to the dorsal faces. Thus, each longitudinal compartment may be further divided transversely into subzones, each receiving a specific combination of mossy fiber afferents. The further subdivision of zebrin I compartments by mossy fiber terminal fields increases the resolution of the topography to such a point that anatomical compartment widths become compatible with the width of the microzones and the patches identified by electrophysiological methods.

Purkinje cell axon collateral distributions reflect the chemical compartmentation of the rat cerebellar cortex

Monoclonal antibody mabQ113 has been used to study the distribution of Purkinje cell axon collaterals in the rat cerebellar cortex. MabQ113 recognizes a polypeptide antigen, zebrin I, that is confined to a subset of Purkinje cells. Antigenic Purkinje cells are arranged in parasagittal compartments running throughout the cortex. No other cerebellar cells are immunoreactive. Immunoreactive axon collaterals are confined principally to the infraganglionic plexus with only a few extending into the molecular layer. Three probable target cells for the axon collaterals have been identified: Golgi cells, Lugaro cells, and other Purkinje cells. About 90% of immunoreactive axon collaterals in the anterior lobe are located beneath the mabQ113+ Purkinje cell compartment in which they originate but some do invade the neighboring mabQ113- territory. In the anterior lobe vermis, the distribution of invading mabQ113+ collaterals is not symmetrical, such that the probability of an invading collateral from the P2+ compartment is greater at the medial boundary into P1- than at the lateral into P2-. The distribution of immunoreactive collaterals is consistent with their playing a role in synchronizing the firing of Purkinje cells within the same compartment.

5'-Nucleotidase and the mabQ113 antigen share a common distribution in the cerebellar cortex of the mouse

The parasagittal distribution patterns in the mouse cerebellar cortex for 5'-nucleotidase and the antigen for the Purkinje cell specific antibody mabQ113 are identical and thus suggestive of a common organizational schema for cerebellar cortical compartments.