Basket cell development in the normal and hypothyroid rat cerebellar cortex studied with a monoclonal anti-neurofilamentantibody NICOLE LECLERC, CLAUDE GRAVEL, AND ANDRIUS PLIOPLYS Laboratory of Neurobiology, Laval Universiv, QuPbec. (QuP. ), Cancld(l AND RICHARD HAWKES' Laboratory of Neurobiology, Laval University, QuPbec. (QuP.), Concld(1 nnd Department of Biochemistry, Laval University, QuPbec (QuP.),Cnnad(l Received September 14, 1984 Leclerc, N., Gravel, C., Plioplys, A. & Hawkes, R. (1985) Basket cell development in the normal and hypothyroid rat cerebellar cortex studied with a monoclonal anti-neurofilament antibody. Can. J. Bioc-hem. Cell Biol. 63, 564-576 We have used a monoclonal antibody against an antigenic determinant of the 2 10-kdalton neurofilament protein to study basket cell maturation in rat cerebellar cortex. Neurofilament immunoreactivity first appears in basket cells at postnatal day 12 and mature axonal "pinceaux" are present at postnatal day 17. There are large differences in the rate of maturation from lobe to lobe which do not fully correspond to the rate of Purkinje cell differentiation. In hypothyroid rats the expression of the neuro- filament antigen by basket cells is almost completely suppressed. Leclerc, N., Gravel, C., Plioplys, A. & Hawkes, R. (1985) Basket cell development in the normal and hypothyroid rat cerebellar cortex studied with a monoclonal anti-neurofilament antibody. Can. J. Bioc-hem. Cell Biol. 63, 564-576 Nous avons utilise un anticorps monoclonal dirige contre la sous-unite de 21 0 kdalton des neurofilaments afin d'itudier la maturation des cellules a corbeilles du cortex ceribelleux de rat blanc. L'immunoreactivite apparait dans les axones des cellules a corbeilles au jour 12 post-partum, et des pinceaux d'apparence mature sont visibles au jour 17 post-partum. De grandes varia- tions apparaissent dans la vitesse de maturation des differents lobes, ne correspondant pas complhtement avec celles constatees pour la vitesse de differenciation des cellules de Purkinje. Chez les rats hypothyroi'diens. I'expression de I'antighne par les cellules a corbeilles est presque nulle. Introduction From a developmental viewpoint the neurons of the cerebellar cortex can be divided into two broad classes. One class, comprising the Purkinje cells and the Golgi cells, is primarily formed prenatally (1) and the cells do not normally divide in the postnatal animal. The other neuronal class, the stellate, basket, and granule cells, is formed during the 1 st month postnatally from a transient germinal epithelium at the surface of the cerebellar cortex, the external granular layer. The small fraction of the postmitotic neuroblasts which are destined to be- come basket cells are formed early in cortical develop- ment. They do not undergo the migratory descent into the granular layer, which is characteristic of the majority of their progenitors which are destined to become granule cells. Instead, they remain close to the Purkinje cell layer where they form a highly specialized axonal plexus enveloping the Purkinje cell somata. ABBREVIATIONS: SPM, synaptosomal plasma membrane(s); P15, postnatal day 15; HAT, hypoxanthine-aminopterin-thy- midine; PBS, phosphate-buffered saline; PTU, n-propyl-2- thiouracil. '~uthor to whom all correspondence should be sent at the following address: Laboratoires de Neurobiologie, Pavillon Notre-Dame, 2075, ave. de Vitre, Quebec (Que.), Canada G1J 5B3. Immunocytochemical studies of the cells derived from the external granular layer, using polyclonal antisera to neurofilaments, has shown that basket cells are the only ones which are immunoreactive (2, 3). This corresponds well with the high concentration of neuro- filaments seen in basket cell axons by electron micros- copy (4). Anti-neurofilament antibodies are therefore valuable tools to study cell differentiation in the cerebel- lum. Isolated neurofilaments consist of three polypep- tide subunits, apparent molecular weights 210000, 160 000, and 68 000 (5) (but see Ref. 6). We have produced a monoclonal antibody, mabN2 10, which specifically binds to the 210-kdalton subunit only. We have used mabN210 to study the expression of neurofila- ment antigens in the developing rat cerebellar cortex. We have also begun to explore the consequences of experimental disturbances of corticogenesis for basket cell differentiation. The relative timing of different development events is crucial to the formation of a normal adult cerebellar cortex and perturbations in the chronology tend to produce cortical abnormalities (7, 8). Thyroid hormone has been demonstrated to play a crucial role in regulating the rate of development of the cerebellum. In hypothyroidism there is an overall slowing of cerebellar maturation which leads to deve- lopmental asynchronies amongst the various compo- nents and ultimately to permanent damage (9). The Can. J. Biochem. Cell Biol. Downloaded from www.nrcresearchpress.com by 74.121.191.133 on 06/07/13 For personal use only.