Article Distribution of parkin in the adult rat brain Velia D’Agata a,b, *, Weiqin Zhao b , Alessia Pascale b , Ofer Zohar b , Giovanni Scapagnini b , Sebastiano Cavallaro a,b a Institute of Bioimaging and Pathophysiology of the Central Nervous System, Italian National Research Council, Catania, Italy b Blanchette Rockefeller Neurosciences Institute, West Virginia University, Rockville, MD, USA Abstract A mutation in the parkin gene has been identified as the cause for an autosomal recessively inherited form of Parkinson’s disease (PD). The authors have recently isolated the mRNA coding for the rat homolog of parkin and showed its widespread expression in the central nervous system (CNS) by in situ hybridization. In the present study, we investigated the distribution of parkin in the rat CNS with a polyclonal antibody that reacts with a  52-kDa protein, mainly localized in the cytoplasm and corresponding to the predicted molecular mass of parkin. Immunohistochemistry on adult rat brain sections showed a widespread distribution of parkin. This included labeling of cell bodies, nuclei as well as processes in the hippocampus, cerebral cortex, cerebellum, and several nuclei in the brainstem. The regional expression of parkin-immunoreactivity (IR) correlated well with the parkin-mRNA levels assessed by real-time quantitative reverse transcription –polymerase chain reaction (RT-PCR). This study provides the detailed analysis of the regional and cellular distribution of parkin in the rat brain and may be useful in elucidating its pathophysiological role. D 2001 Elsevier Science Inc. All rights reserved. Keywords: Autosomal recessive juvenile parkinsonism; Parkinson’s disease; Central nervous system; Distribution; Immunohistochemistry 1. Introduction Parkinson’s disease (PD) is the most common neurodege- nerative movement disorder, with a prevalence of 1–2% among persons older than 65 years of age (De Rijk et al., 1997). The clinical phenotype of PD includes resting tremor, muscular rigidity, bradykinesia, and postural instability. The cause of the disease is still unknown, but four disease gene loci have been localized within the human genome and named PARK1, PARK2, PARK3, and PARK4, respectively, depending on their sequence of discovery (Riess et al., 2000). The PARK2 gene locus has been mapped to chromosome 6q25.2–q27 (Matsumine et al., 1997), and a gene has been identified which has been named parkin. Mutations of this gene have recently been found in several families with autosomal recessive juvenile parkinsonism (ARJP) (Abbas et al., 1999; Hattori et al.,1998a,b; Klein et al., 2000; Leroy et al.,1998; Lucking et al., 1998, 2000). In addition, a specific polymorphism (R/W366) in the parkin gene has been asso- ciated with a decreased risk of PD (Wang et al., 1999). The frequency of parkin mutations and the associated phenotype has not been clearly established. In Japanese patients with parkin mutations, the disease is characterized by early onset, levodopa (L-dopa) responsiveness, sleep benefit, motor fluctuations after L-dopa therapy, and a slow progression of the disease (Ishikawa and Tsuji, 1996; Yamamura et al., 1973, 1993). In contrast, the clinical characteristics of some European and North African patients with parkin mutations were indistinguishable from those patients with idiopathic PD, with an age of onset of up to 58 years (Abbas et al., 1999; Klein et al., 2000; Lucking et al., 1998, 2000). Neuropathological features from the patients studied include selective degeneration of dopami- nergic neurons in the substantia nigra pars compacta (SNc) without Lewy bodies (Takahashi et al., 1994). In addition, the partial hypogenesis in cerebral hemispheres, midbrain, or cerebellum have also been reported in some cases (Yamamura et al., 1994). 0278-5846/01/$ – see front matter D 2001 Elsevier Science Inc. All rights reserved. PII:S0278-5846(01)00301-3 Abbreviations: ARJP, autosomal recessive juvenile parkinsonism; CNS, central nervous system; IBR, in between ring fingers; IR, immunoreactivity; L-dopa, levodopa; PD, Parkinson’s disease; SNc, substantia nigra pars compacta; SNr, substantia nigra pars reticulata * Corresponding author. Blanchette Rockefeller Neurosciences Insti- tute, West Virginia University, Academic and Research Building, 9601 Medical Center Drive, Rockville, MD 20850, USA. Tel.: +1-301-2947176; fax: +1-301-2947007. E-mail address: vdagata@brni-jhu.org (V. D’Agata). Progress in Neuro-Psychopharmacology & Biological Psychiatry 26 (2002) 519 – 527