Hassan Marzban

Patterned Purkinje cell degeneration in mouse models of Niemann‐Pick type C disease

Niemann Pick disease type C1 (NPC1) is an inherited, autosomal recessive, lipid‐storage disorder with major neurological involvement. Purkinje cell death is a prominent feature of the neuropathology of NPC. We have investigated Purkinje cell death in two murine models of NPC1, BALB/c npcnih and C57BLKS/J spm. In both cases, extensive Purkinje cell death was found in the cerebellum. The pattern of Purkinje cell death is complex. First, zebrin II‐negative Purkinje cells disappear, to leave survivors aligned in stripes that closely resemble the pattern revealed by using zebrin II immunocytochemistry. Subsequently, as the disease progresses, additional Purkinje cells die. At the terminal stages of the disease, the surviving Purkinje cells are concentrated in lobules IX and X of the posterior lobe vermis. Purkinje cell degeneration is accompanied by the ectopic expression of tyrosine hydroxylase and the small heat shock protein HSP25, both associated preferentially with the surviving cells. The pattern of cell death thus reflects the fundamental compartmentation of the cerebellum into zones and stripes. J. Comp. Neurol. 456:279–291, 2003.

Complementary stripes of phospholipase Cβ3 and Cβ4 expression by Purkinje cell subsets in the mouse cerebellum

Transverse boundaries divide the cerebellar cortex into four transverse zones, and within each zone the cortex is further subdivided into a symmetrical array of parasagittal stripes. Several molecules believed to mediate long‐term depression at the parallel fiber–Purkinje cell synapse are known to be expressed in stripes. We have therefore explored the distributions of phospholipase Cβ3 and phospholipase Cβ4, key components in the transduction of type 1 metabotropic glutamate receptor‐mediated responses. The data reveal that both phospholipase Cβ isotypes are expressed strongly in the mouse cerebellum in subsets of Purkinje cells. The two distributions are distinct and largely nonoverlapping. The pattern of phospholipase Cβ3 expression is unique, revealing stripes in three of the four transverse zones and a uniform distribution in the fourth. In contrast, phospholipase Cβ4 appears to be confined largely to the Purkinje cells that are phospholipase Cβ3‐negative. PLCβ3 is restricted to the zebrin II‐immunopositive Purkinje cell subset. Not all zebrin II‐immunoreactive Purkinje cells express PLCβ3: in lobules IX and X it is restricted to that zebrin II‐immunopositive subset that also expresses the small heat shock protein HSP25. PLCβ4 expression is restricted to, and coextensive with, the zebrin II‐immunonegative Purkinje cell subset. These nonoverlapping expression patterns suggest that long‐term depression may be manifested differently between cerebellar modules. J. Comp. Neurol. 496:303–313, 2006.

Conservation of the architecture of the anterior lobe vermis of the cerebellum across mammalian species.

Publisher Summary Within the mammalia, the morphology of the cerebellum varies dramatically both in form and size; however, despite numerous anatomical differences, the mammalian cerebellum is classified into 10 lobules, and there is a more fundamental compartmentation of the cerebellum into transverse zones and parasagittal stripes. This chapter focuses on the conserved nature of cerebellar compartmentation, with a specific focus on the anterior vermis, which has a very characteristic appearance in rats and mice. The highly conserved antigen zebrin II has proven useful in comparative studies of cerebellar compartmentation. The results presented in the chapter suggest that regardless of cerebellar size, a characteristic set of stripes is present in the anterior lobe vermis of the mammalian cerebellum, and the topography of zebrin II expression is well conserved. The restriction of the zebrin II epitope to Purkinje cells and the molecular weight of the zebrin II/aldolase C antigen are highly conserved from fish to primates, except amphibia. Differences in the molecular architecture of the cerebellum among phylogenetic groups of mammals are minor, but consistent, such as the pattern of zebrin II expression in the anterior vermis of ferrets resembles that of cats. Several investigations have shown evidence that stripes are determined early in development and are not a response to usage, and several hundred distinct cerebellar modules have been identified based upon expression patterns and afferent terminal fields; however, the function of stripes in the adult cerebellum is a matter of speculation.

Phospholipase cβ4 expression reveals the continuity of cerebellar topography through development

Mediolateral boundaries divide the mouse cerebellar cortex into four transverse zones, and within each zone the cortex is further subdivided into a symmetrical array of parasagittal stripes. Various expression markers reveal this complexity, and detailed maps have been constructed based on the differential expression of zebrin II/aldolase C in a Purkinje cell subset. Recently, phospholipase (PL) Cβ4 expression in adult mice was shown to be restricted to, and coextensive with, the zebrin II‐immunonegative Purkinje cell subset. The Purkinje cell expression of PLCβ4 during embryogenesis and postnatal development begins just before birth in a subset of Purkinje cells that are clustered to form a reproducible array of parasagittal stripes. Double label and serial section immunocytochemistry revealed that the early PLCβ4‐immunoreactive clusters in the neonate are complementary to those previously identified by neurogranin expression. The PLCβ4 expression pattern can be traced continuously from embryo to adult, revealing the continuity of the topographical map from perinatal to adult cerebella. The only exception, as has been seen for other antigenic markers, is that transient PLCβ4 expression (which subsequently disappears) is seen in some Purkinje cell stripes during the second postnatal week. Furthermore, the data confirm that some adult Purkinje cell stripes are composite in origin, being derived from two or more distinct embryonic clusters. Thus, the zone and stripe topography of the cerebellum is conserved from embryo to adult, confirming that the early‐ and late‐antigenic markers share a common cerebellar topography. J. Comp. Neurol. 502:857–871, 2007.

Purkinje Cell Compartmentation as Revealed by Zebrin II Expression in the Cerebellar Cortex of Pigeons (Columba livia)

Purkinje cells in the cerebellum express the antigen zebrin II (aldolase C) in many vertebrates. In mammals, zebrin is expressed in a parasagittal fashion, with alternating immunopositive and immunonegative stripes. Whether a similar pattern is expressed in birds is unknown. Here we present the first investigation into zebrin II expression in a bird: the adult pigeon (Columba livia). Western blotting of pigeon cerebellar homogenates reveals a single polypeptide with an apparent molecular weight of 36 kDa that is indistinguishable from zebrin II in the mouse. Zebrin II expression in the pigeon cerebellum is prominent in Purkinje cells, including their dendrites, somata, axons, and axon terminals. Parasagittal stripes were apparent with bands of Purkinje cells that strongly expressed zebrin II (+ve) alternating with bands that expressed zebrin II weakly or not at all (−ve). The stripes were most prominent in folium IXcd, where there were seven +ve/−ve stripes, bilaterally. In folia VI–IXab, several thin stripes were observed spanning the mediolateral extent of the folia, including three pairs of +ve/−ve stripes that extended across the lateral surface of the cerebellum. In folium VI the zebrin II expression in Purkinje cells was stronger overall, resulting in less apparent stripes. In folia II–V, four distinct +ve/−ve stripes were apparent. Finally, in folia I (lingula) and X (nodulus) all Purkinje cells strongly expressed zebrin II. These data are compared with studies of zebrin II expression in other species, as well as physiological and neuroanatomical studies that address the parasagittal organization of the pigeon cerebellum. J. Comp. Neurol. 501:619–630, 2007.

Cellular commitment in the developing cerebellum

The mammalian cerebellum is located in the posterior cranial fossa and is critical for motor coordination and non-motor functions including cognitive and emotional processes. The anatomical structure of cerebellum is distinct with a three-layered cortex. During development, neurogenesis and fate decisions of cerebellar primordium cells are orchestrated through tightly controlled molecular events involving multiple genetic pathways. In this review, we will highlight the anatomical structure of human and mouse cerebellum, the cellular composition of developing cerebellum, and the underlying gene expression programs involved in cell fate commitments in the cerebellum. A critical evaluation of the cell death literature suggests that apoptosis occurs in ~5% of cerebellar cells, most shortly after mitosis. Apoptosis and cellular autophagy likely play significant roles in cerebellar development, we provide a comprehensive discussion of their role in cerebellar development and organization. We also address the possible function of unfolded protein response in regulation of cerebellar neurogenesis. We discuss recent advancements in understanding the epigenetic signature of cerebellar compartments and possible connections between DNA methylation, microRNAs and cerebellar neurodegeneration. Finally, we discuss genetic diseases associated with cerebellar dysfunction and their role in the aging cerebellum.

On the Architecture of the Posterior Zone of the Cerebellum

The mammalian cerebellum is histologically uniform. However, underlying the simple laminar architecture is a complex arrangement of parasagittal stripes and transverse zones that can be revealed by the expression of many molecules, in particular, zebrin II/aldolase C. By using a combination of Purkinje cell antigenic markers and afferent tracing, four transverse zones have been identified: in mouse, these are the anterior zone (∼lobules I–V), the central zone (∼lobules VI–VII), the posterior zone (PZ: ∼lobules VIII–dorsal IX), and the nodular zone (∼ventral lobule IX + lobule X). A fifth transverse zone—the lingular zone (∼lobule I)—is found in birds and bats. Within the anterior and posterior zones, parasagittal stripes of Purkinje cells expressing zebrin II alternate with those that do not. To explore this model further and to broaden our understanding of the evolution of cerebellar patterning, stripes in the PZ have been compared in multiple mammalian species. We conclude that a posterior zone with a conserved stripe organization is a common feature of the mammalian and avian cerebellar vermis and that zonal boundaries are independent of cerebellar lobulation.

Antigenic compartmentation of the cerebellar cortex in the chicken (Gallus domesticus)

The chick is a well‐understood developmental model of cerebellar pattern formation,but we know much less about the patterning of the adult chicken cerebellum. Therefore an expression study of two Purkinje cell stripe antigens—zebrin II/aldolase C and phospholipase Cβ4 (PLCβ4)—has been carried out in the adult chicken (Gallus domesticus). The mammalian cerebellar cortex is built around transverse expression domains (“transverse zones”), each of which is further subdivided into parasagittally oriented stripes. The results from the adult chicken reveal a similar pattern. Five distinct transverse domains were identified. In the anterior lobe a uniformly zebrin II‐immunopositive/PLCβ4‐immunonegative lingular zone (LZ; lobule I) and a striped anterior zone (AZ; lobules II–VIa) were distinguished. A central zone (CZ; ∼lobules VIa–VIIIa,b) and a posterior zone (PZ; ∼lobules VIIIa,b–IXc,d) were distinguished in the posterior lobe. Finally, the nodular zone (NZ; lobule X) is uniformly zebrin II‐immunoreactive and is innervated by vestibular mossy fibers. Lobule IXc,d is considered as a transitional region between the PZ and the NZ, because the vestibular mossy fiber projection extends into these lobules and because they receive optokinetic mossy and climbing fiber input. It is proposed that the zebrin II‐immunonegative P3‐ stripe corresponds to the lateral vermal B zone of the mammalian cerebellum and that the border between the avian homologs of the mammalian vermis and hemispheres is located immediately lateral to P3−. Thus, there seem to be transverse zones in chicken that are plausible homologs of those identified in mammals, together with an LZ that is characteristic of birds. J. Comp. Neurol. 518:2221–2239, 2010.

Expression of the immunoglobulin superfamily neuroplastin adhesion molecules in adult and developing mouse cerebellum and their localisation to parasagittal stripes

Neuroplastin (np) 55 and 65 are immunoglobulin superfamily members that arise by alternative splicing of the same gene and have been implicated in long‐term activity‐dependent synaptic plasticity. Both biochemical and immunocytochemical data suggest that np55 is the predominant isoform (>95% of total neuroplastin) in cerebellum. Neuroplastin immunoreactivity is concentrated in the molecular layer and synaptic glomeruli in the granule cell layer. Expression in the molecular layer appears to be postsynaptic. First, neuroplastin is associated with Purkinje cell dendrites in two mouse granuloprival cerebellar mutants, disabled and cerebellar deficient folia. Second, in an acid sphingomyelinase knockout mouse with widespread protein trafficking defects, neuroplastin accumulates in the Purkinje cell somata. Finally, primary cerebellar cultures show neuroplastin expression in Purkinje cell dendrites and somata lacking normal histotypic organization and synaptic connections, and high‐magnification views indicate a preferential association with dendritic spines. In the molecular layer, differences in neuroplastin expression levels present as a parasagittal array of stripes that alternates with that revealed by the expression of another compartmentation antigen, zebrin II/aldolase c. Neuroplastin immunoreactivity is first detected weakly at postnatal day 3 (P3) in the anterior lobe vermis. By P5, parasagittal stripes are already apparent in the immature molecular layer. At this stage, punctate deposits are also localised at the perimeter of the Purkinje cell perikarya; these are no longer detected by P15. The data suggest a role for neuroplastins in the development and maintenance of normal synaptic connections in the cerebellum. J. Comp. Neurol. 462:286–301, 2003.

Compartmentation of the cerebellar cortex of hummingbirds (Aves: Trochilidae) revealed by the expression of zebrin II and phospholipase Cβ4

The parasagittal organization of the mammalian cerebellar cortex into zones has been well characterized by immunohistochemical, hodological and physiological studies in recent years. The pattern of these parasagittal bands across the cerebellum is highly conserved across mammals, but whether a similar conservation of immunohistochemically defined parasagittal bands occurs within birds has remained uncertain. Here, we examine the compartmentation of the cerebellar cortex of a group of birds with unique cerebellar morphology-hummingbirds (Trochilidae). Immunohistochemical techniques were used to characterize the expression of zebrin II (aldolase C) and phospholipase C beta 4 (PLC beta 4) in the cerebellar cortex of two hummingbird species. A series of zebrin II immunopositive/immunonegative parasagittal stripes was apparent across most folia representing three major transverse zones: an anterior zone with a central stripe flanked by three lateral stripes on either side; a central zone of high/low immunopositive stripes; and a posterior zone with a central stripe flanked by four to six lateral stripes on either side. In addition, both folia I and X were uniformly immunopositive. The pattern of PLC beta 4 immunoreactivity was largely complementary-PLC beta 4 positive stripes were zebrin II negative and vice versa. The similarity of zebrin II expression between the hummingbirds and the pigeon indicates that the neurochemical compartmentation of the cerebellar cortex in birds is highly conserved, but species differences in the number and width of stripes do occur.