Journal of Chemical Neuroanatomy 17 (1999) 1 – 12 Calbindin immunoreactivity in the developing and adult human cerebellum Tapas C. Nag, Shashi Wadhwa * Department of Anatomy, All India Institute of Medical Sciences, New Delhi 110029, India Received 19 August 1998; received in revised form 3 February 1999; accepted 22 May 1999 Abstract Calbindin (CALB), a calcium-binding protein, is known to be expressed in the embryonic nervous system. In this study, we have examined its distribution in the cerebellum of human fetuses (11 – 25 weeks of gestation) and adult by immunohistochemistry. At the gestational age of 11 – 12 weeks, CALB immunoreactivity was present in granule and Purkinje cells throughout the cerebellum. By 16 – 21 weeks of gestation, immunoreactive Purkinje cells were well-differentiated in the vermis and flocculus, and their axons ran towards the deep cerebellar nuclei area, while the axon collaterals were seen to be distributed into adjacent folia. At the gestational period of 24–25 weeks, most Purkinje cells of the flocculus and vermis were arranged in one to two rows, while those of the hemispheres were still undifferentiated. A few Golgi cells of the vermis showed immunoreactivity. The neurons of the deep nuclei were immunonegative right from the gestational age of 11 weeks although a fine stippled staining of fibers was present throughout the body of all nuclei. The fibers lying close to the hilum of the dentate nucleus were strongly CALB-positive. The vestibulocerebellar fibers, being traced at the level of lower pons and upper medulla oblongata were stained as early as 11 weeks of gestation, whereas the olivocerebellar fibers were stained from 16 weeks onward. In the adult cerebellum, Purkinje cells were moderately immunopositive while granule cells were faintly stained; no other cells, including those of the deep nuclei were stained. In the medulla oblongata, the inferior olivary nucleus and olivocerebellar fibers were strongly CALB-positive. Our results indicate that CALB is expressed in early migratory Purkinje cells, and their maturation occurs in a vermal-to-hemisphere gradient. It is likely that CALB plays a significant role in the regulation of Ca 2 + -dependent activities in the developing cerebellum. © 1999 Elsevier Science B.V. All rights reserved. Keywords: Calcium-binding protein; Purkinje cells; Golgi cells; Vestibulocerebellar fibers; Olivocerebellar fibers; Immunohistochemistry www.elsevier.com/locate/jchemneu 1. Introduction The EF-hand family of calcium-binding proteins (CBPs, viz., calbindin (CALB), parvalbumin and calre- tinin) represent useful neurochemical markers for sub- populations of neurons as well as interneurons of the central nervous system (CNS, Jande et al., 1981; Gar- cia-Segura et al., 1984; Celio, 1990; Baimbridge et al. 1982; Andressen, et al., 1993). In the neocortex of most mammals, CALB is found in a sub-group of GABAer- gic neurons, the double bouquet cells (Celio, 1990; Ferrer et al., 1992; del Rio and DeFelipe, 1996), whereas parvalbumin is found in basket neurons and chandelier cells (DeFelipe et al., 1989; Hendry et al., 1989; Anderson et al., 1995). Although the various roles of CBPs in the CNS are not yet understood completely, several workers have proposed that they are primarily involved in the physiological buffering and transport of Ca 2 + inside cytosol. In the absence of these proteins, there is an accumulation of high Ca 2 + inside cytosol, causing hyperexcitability which often leads to neurode- generation (Jande et al., 1981; Heizmann and Braun, 1995). The distribution of CBPs in the CNS of lower mam- mals, especially rats, is now known in detail (Jande et al., 1981; Baimbridge et al., 1982; Garcia-Segura et al., 1984; Rogers, 1989; Celio, 1990). Recent studies have shown calretinin expression in the human thalamus (Cicchetti et al., 1998; Fortin et al., 1998a,b) and the distribution of CALB, parvalbumin and calretinin in the primate basal ganglia (Parent et al., 1996) and * Corresponding author. Fax: +91-11-6862663. E-mail address: shashiwadhwa@hotmail.com (S. Wadhwa) 0891-0618/99/$ - see front matter © 1999 Elsevier Science B.V. All rights reserved. PII:S0891-0618(99)00016-2